Liquid plant growth regulating composition

Abstract

The present invention relates to a liquid plant growth regulating composition comprising macronutrients at least in the form of nitrogen (N), sulphur (S) and optionally phosphorus (P) in mixture with an inhibitor of nitrogen-metabolizing bacteria, wherein said inhibitor is substantially non-toxic to the plant. Advantageously, the composition has a predefined ratio between sulphur (S) and organic nitrogen (Norg), which promotes growth of a part of the plant, such as shoots or roots. Thus, the invention also relates to the use of the composition for root, shoot or overall growth of a plant, as well as to a method of manufacturing said composition.

Description

[0001] LIQUID PLANT GROWTH REGULATING COMPOSITION

[0002] Technical field

[0003] The present invention relates to a liquid composition capable of controlling several aspects of plant growth by providing for efficient utilization of nitrogen while promoting plant growth.

[0004] More specifically, the invention relates to a liquid growth regulating composition, which enables to regulate the growth of the whole plant and / or certain parts thereof, such as roots or shoots. Further, the invention also relates to a method of manufacture of the composition of the invention.

[0005] Background

[0006] Cultivation of plants requires input of nutrients and traditionally, this input has been in the form of inorganic nitrogen, phosphorus and potassium. This focus on inorganic nitrogen has dominated the field of plant nitrogen nutrition research and development for decades while the importance of organic nitrogen compounds for plant growth was more recently recognized. Organic nitrogen is a large and chemically diverse group of compounds with some representatives having strong negative effects on plants and others that display clear advantages as nitrogen carriers compared to the traditionally recognized mineral nitrogen compounds. In this latter group, basic amino acids, in particular L-arginine and L-lysine have been identified as having unique properties for plant cultivation.

[0007] WO 2001 / 087804 (Holmen Aktiebolag) relates to a nitrogen-containing fertilizer for plant growth intended for application to a growth substrate, either alone or in mixture with other fertilizers. The fertilizer concerned can be used very effectively in raising (tree) seedlings from the seeds of various tree species, including both hardwoods and softwoods, said seedlings being planted out in a growth site, for instance in woodland, at a later stage.More specifically, the object of WO 01 / 87804 is to provide a source of nitrogen which whilst providing the nutrition needed for plant growth also has the maximum immobility in the growth substrate, such that substantially all of the nitrogen applied will remain in the growth substrate for future absorption by the plant. This is provided by a fertilizer comprised of the L-form of a basic amino acid or its salt.

[0008] WO 2009 / 082351 (SweTree Technologies) relates to a fertilizer affecting plant biomass allocation. More specifically, the fertilizer stimulates root growth, fine root development, increase the number of root tips and mycorrhiza development.

[0009] Furthermore, a method for using the fertilizer for modulation of the root fraction of the biomass is described. More specifically, the fertilizer described in WO 2009 / 082351 comprises naturally occurring L-amino acid chosen from the group of L-arginine, L-asparagine, glycine, L-glutamic acid and L-glutamine as its nitrogen source for stimulating root growth and mycorrhiza development.

[0010] Liquid nutrition products designed to specifically stimulate root growth or shoot growth are available from Arevo AB. The benefits of the products are according to its marketing material obtained ground-breaking in terms of how plants absorb nutrients, based on how plants can use basic amino acid as a natural source of nitrogen - the nutrient most important to plants. It is stated that arginine is very efficiently taken up by forest plants and stimulates the growth of roots and mycorrhiza.

[0011] WO 2024 / 055079 (RLF Agtech Ltd) relates to a method for improving plant growth and yield by providing a method of treating plant material with a nutrient solution containing one or more amino acids and plant nutrients.

[0012] The amino acid(s) may be aspartic acid, threonine, serine, glutamic acid, glycine, alanine, cysteine, valine, methionine, leucine, isoleucine, tyrosine, phenylalanine, lysine, histidine, arginine and proline, glycine being the preferred one.Plant nutrients may be nitrogen, phosphorus, potassium and mixtures thereof (NPK nutrients), and optionally also other elements, such as trace elements selected from the group consisting of sulphur, magnesium, zinc, manganese, copper, iron, boron, molybdenum, calcium, silicon and mixtures thereof.

[0013] Whether a fertilizer contains inorganic nitrogen or organic nitrogen, a well-known issue to manage relates to the leakage of nitrogen.

[0014] Inorganic nitrogen-based fertilizers have been identified as a potential contribution in global warming, and an excess of leaked nitrogen may lead to several issues such as soil acidification, loss of base cations such as magnesium and calcium in turn leading nutrient deficiencies of cultivated plants.

[0015] Organic nitrogen-based fertilizers and other growth regulating compositions have been introduced as an alternative, since they will release nitrogen more slowly, hence allowing for plants to benefit from a larger proportion of the fertilizer nitrogen content.

[0016] However, a specific problem of nitrogen loss may occur in liquid organic nitrogenbased fertilizers when they are diluted to salt concentrations and pH-values suitable for plant growth:

[0017] The more dilute conditions will allow for growth of anaerobic microbes, such as bacteria, that feed on the organic nitrogen source, hence constituting a source of nitrogen eakage' and efficiency loss. As the organic nitrogen is consumed, NH3 will be produced raising the pH further, whereby a vicious circle or loop is created.

[0018] In addition to the loss of nitrogen, this mechanism may result in the formation of H2S, creating unpleasant odours and also contributing to the formation of biofilms.

[0019] The latter becomes a problem e.g. in greenhouses, when pipes or hoses are used to transport and distribute diluted fertilizer, since flow therein may be restricted, corrugation may appear in metal pipes and as a worst case scenario, pipes or hoses may be clogged. This problem is not restricted to organic-based fertilizers and compositions, but may also occur with inorganic nitrogen-based fertilizers.In conclusion, there is an ongoing need for new and further improved fertilizers that improve plant growth according to predefined criteria, while minimizing any negative impact on the environment in terms of leakage of nutrients and / or loss of organic material.

[0020] Summary of the invention

[0021] In a first aspect, the present invention relates to a liquid plant growth regulating composition comprising macronutrients at least in the form of nitrogen (N), sulphur (S) and optionally phosphorus (P) in mixture with an inhibitor of nitrogenmetabolizing bacteria, wherein said inhibitor is substantially non-toxic to the plant. Advantageously, at least part of the nitrogen (N) is present in the form of organic nitrogen (Norg); and the ratio (weight / weight) of sulphur (S):organic nitrogen (Norg) is at least about 0.13.

[0022] In a second aspect, the present invention relates to a liquid plant growth regulating composition according to the invention used in a method to promote shoot, root or overall growth of a plant.

[0023] In a third aspect, the present invention relates to a method of manufacturing a liquid plant growth regulating composition as described herein.

[0024] Further details and embodiments of the invention will appear from the detailed description below and the appended dependent claims.

[0025] Definitions

[0026] The terms "sulphur (S)", "sulphur" and "S" may be used interchangeably in the present context, and refer to the element sulphur which may be free ions or complexed to other ions in the liquid composition.The terms "chloride (Cl)", "chloride" and "Cl" may be used interchangeably in the present context, and refer to the element chloride which may be in the form of free ions or complexed.

[0027] The term "nitrogen (N)", "nitrogen" and "N" may be used interchangeably in the present context, and refer to the element nitrogen which may be in form of inorganic or organic nitrogen, in the form of free ions or complexed. In the present context, the term does not include molecular nitrogen (N2).

[0028] The terms "organic nitrogen", "organic nitrogen (N)" and Norgmay be used interchangeably in the present application.

[0029] The terms "inorganic nitrogen", "inorganic nitrogen (N)" and Njnorg may be used interchangeably in the present context.

[0030] Brief description of the drawings

[0031] Figures 1A and B are photographs of seedlings of Scots pine (Pinus sylvestris) grown from seeds for five months using a commercial composition with low sulphur:organic N ratio (left) or the composition with high sulphur:organic N ratio of the invention (right).

[0032] Figure 2 shows the development of height of Scots pine seedlings at the early-mid phases of seedling cultivation using either an inorganicorganic N composition with low sulphur:organic N ratio (dashed bars) or an inorganic:organic N composition with high sulphur:organic N ratio (black bars).

[0033] Figures 3A and B show the final harvest of Scots pine seedlings displaying shoot and root dry weight biomasses and root:shoot ratios of seedlings using either an organic N composition with low sulphur:organic N ratio (dashed bars) for four weeks at the end of the cultivation period or an organic N composition with high sulphunorganic N ratio (black bars) for four weeks at the end of the cultivation period.

[0034] Figures 4A and B show the final harvest of Lodgepole pine (Pinus contorta) seedlings displaying shoot and root dry weight biomasses and root : shoot ratio of seedlingsusing either an organic N composition with low sulphur:organic N ratio (dashed bars) for four weeks at the end of the cultivation period or an organic N composition with high sulphurorganic N ratio (black bars) for four weeks at the end of the cultivation period.

[0035] Figure 5 shows the growth (fresh weight biomass of clippings) of lawn grass using either an organic N composition with low sulphunorganic N ratio (dashed bar) for four weeks or an organic N composition with high sulphurorganic N ratio (solid bar). Figure 6 shows the greenness of lawn grass either an organic N composition with low sulphurorganic N ratio (dashed bar) for four weeks or an organic N composition with high sulphurorganic N ratio (solid bar).

[0036] Figures 7A and B illustrate the root development of grass 33 days after sowing (DAS). Figure 8 illustrates the amount of organic nitrogen (Norg) remaining in liquid growth regulating compositions according to the invention after storage for 14 days.

[0037] The content of added inhibitor of nitrogen-metabolizing bacteria (as Fe(lll)) is gradually increased from left to right, starting with a control (no added Fe(lll)).

[0038] Figure 9 shows how pH varies in liquid growth regulating compositions according to the invention with increased content of Fe(lll), increasing from the left (Control) to the right.

[0039] Figure 10 shows how the sulfide content of water decreases with an increased addition of Fe(lll), illustrating how sulfide formed as a result of bacterial metabilization of sulfate can be controlled by adding an inhibitor of said metabolism. Figure 11 illustrates the amount of organic nitrogen (Norg) remaining in liquid growth regulating compositions according to the invention after storage for 14 days.

[0040] The content of citrate (as citric acid) is gradually increased from left to right, starting with a control (no added citrate).

[0041] Figure 12 shows how pH varies in liquid growth regulating compositions according to the invention with increased content of citrate (as citric acid), increasing from the left (Control) to the right.Figure 13 shows the effects on pH of diluted liquid growth regulating compositions according to the invention when citrate (as citric acid); or citrate (as citric acid) and Fe(lll) are added, as compared to a control of the same composition without said additions.

[0042] Detailed description of the invention

[0043] As appears from the above, the present invention relates to a liquid growth regulating composition capable of controlling several aspects of plant growth while providing for efficient utilization of nitrogen while promoting plant growth.

[0044] An efficient utilization of nitrogen may be obtained by providing a composition which eliminates or at least reduces bacterial degradation of the nitrogen supplied to plants. Such bacterial degradation is known to happen primarily after dilution of growth regulating compositions comprising a substantial proportion of organic nitrogen, since the lower salt concentration in ready-for use solutions is more beneficial to bacterial growth than the salt concentrations normally found in concentrates of such compositions. Ready-for use i.e. diluted solutions are therefore more prone to degradation by bacteria and during such degradation processes, additional problems may occur such as rapidly changing pH due to bacterial exudation of ammonia (NH3). Furthermore, under conditions of rapid bacterial growth, oxygen concentrations may decline, leading to promotion of anaerobic bacteria and such bacteria may use sulfate as an alternative electron acceptor to oxygen, leading to the formation of the toxic gas hydrogen sulfide (H2S).

[0045] The control of several aspects of plant growth is obtained by providing a composition, wherein the proportion of sulphur (S) is be used to promote the growth of a plant, such as to upregulate or downregulate growth of part of a plant, such as root, as compared to other parts, such as shoot. If desired, the root:shoot ratio as such maybe increased or decreased. This may be achieved by adjusting the sulphur (S) supply to a plant in view of the nitrogen (N) supply, i.e. the S:N (weightweight) ratio, usually provided as a growth regulating composition.

[0046] The invention may advantageously be used during certain growth phases, when it is desired to enhance a certain characteristic of a plant. For example, when plants cultivated in nurseries are to be transferred to free land beds or planted in forest clear cuts, a sensitive step is the removal of the cultivated plant from its nursery pot, as roots are easily damaged in that process, leading to loss of organic material and negative impact of the plant growth after transfer.

[0047] At this stage, well developed roots, preferably grown to a dense or collected 'lump', will be easier to transfer without losses. Plants with an intact root lump will have a higher probability of survival and rapid establishment compared to those with a damaged root lump.

[0048] The advantage of extensive root growth may also be utilized where plants are required to withstand external pressures, such as intense wear and tear e.g., on golf courses, race courses, soccer fields etc.

[0049] The invention may also be used in certain climate zones with environmentally challenging conditions. For example, in dry growth zones, it may be desired to keep the shoot growth relatively limited, especially during early phases of the growth of a crop but at the same time stimulate growth of roots, fine roots, root hairs and mycorrhiza. Further, in agriculture, the root:shoot ratio may advantageously be tuned to a desired level depending on if the product of interest for the yield is above or below ground.

[0050] Thus, the present invention provides means for adjusting root:shoot ratios of plants by adjusting the proportion of sulphur (S) available for growth. The sulphur (S) proportion is advantageously determined based on the nitrogen (N) content.More specifically, in a first aspect, the present invention relates to a liquid plant growth regulating composition comprising macronutrients at least in the form of nitrogen (N), sulphur (S) and optionally phosphorus (P) in mixture with an inhibitor of nitrogen-metabolizing bacteria, wherein said inhibitor is substantially non-toxic to the plant. Nitrogen-metabolizing bacteria includes (i) ammonifying bacteria; (ii) ammonium-oxidizing bacteria; (iii) nitrite-oxidizing bacteria; and (iv) denitrifying bacteria.

[0051] In an illustrative example, the composition according to the invention comprises inhibitors of ammonifying bacteria and ammonium-oxidizing bacteria, i.e. bacteria that convert ammonia to nitrite, including genera such as Nitrosomonas, Nitrosococcus and Nitrosovibrio.

[0052] The inhibitor of nitrogen-metabolizing bacteria will control, preferably inhibit or at least substantially reduce, bacterial nitrification of nitrogen intended for plant nutrition, making the composition of the invention an efficient provider of nitrogen with low overall nitrogen losses.

[0053] The inhibitor of nitrogen-metabolizing bacteria may comprise ferric iron, i.e. Fe(lll), optionally coordinated with other molecules.

[0054] Thus, as will appear from the below, such ferric iron may for example originate from added ferric chloride, or any other suitable source.

[0055] The composition according to the invention may comprise inorganic nitrogen (Ninorg), organic nitrogen (Norg) or a mixture of inorganic nitrogen (Ninorg), organic nitrogen (Norg).

[0056] More specifically, the fraction, i.e. proportion, of nitrogen (N) present as organic nitrogen (Norg) is at least about 20%, such as at least about 30%, e.g. at least about 50%, of the total amount of nitrogen (N) in the composition.As the skilled person will appreciate, the proportion of organic vs. inorganic nitrogen (N) may be decided based on commonly known effects of the different forms of nitrogen, such as the slow release of nitrogen (N) from basic L-amino acids. Thus, the gist of the invention resides at least in the fact that a higher sulphur (S) content than previously used in view e.g. of the total nitrogen (N) content enables an intentional fine tuning of the proportion between root and shoot growth.

[0057] Said organic nitrogen (N) may originate from one or more basic L-amino acids.

[0058] In this context, the term "originate" means that the amino acids are ionized, fully or partly, in the composition of the invention. As the skilled person will appreciate, such ions formed by adding amino acids may or may not coordinate with other components of the composition, depending on its pH and other constituents.

[0059] The composition according to the invention will advantageously comprise organic nitrogen (Norg) originating from basic L-amino acids, i.e. one or more selected from the group consisting of L-arginine, L-lysine and L-histidine.

[0060] In an advantageous example, the organic nitrogen (Norg) originates from L-arginine or L-lysine, preferably arginine, or a mixture of the two, in the above-discussed proportion. The balance of the nitrogen (N) content may be other forms of organic nitrogen, or inorganic nitrogen. In an illustrative example, the balance of nitrogen (N) is in the form of nitrate (NO3 ).

[0061] More specifically, in a liquid plant growth regulating composition according to the invention, the ratio (weight:weight) of sulphur (S):nitrogen (N) is set to a pre-defined value, which promotes the growth of a selected part of the plant, such as roots, shoots or overall growth.

[0062] The said ratio may be at least about 0.13, such as at least about 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, or 2.0.More specifically, the ratio may be above about 2,0, such as above 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0.

[0063] For other applications, the ratio may be above 3.0, such as 3.25, 3.50, 3.75 or 4.00. Higher ratios are also encompassed by the invention.

[0064] Ranges of ratios may be between 1.30 and 1.50, e.g 1.50-1.75 or to 1.75.

[0065] Upper limits of said ranges may be 2.00, 2.50, 2.75, 3.00, 3.50, 3.75 or 4.00.

[0066] Alternatively, the upper limit is set to 4.50, 5.00, 5.5, 6.0, 6.5 or 7.0.

[0067] More specifically, the ratio of sulphur (S):nitrogen (N) may be at least about 0.24, e.g. at least about 0.4 or at least about 0.50.

[0068] As appears from the experiments below, the present inventors have found that the ratio of sulphur (S) to organic nitrogen (N) in a growth regulating composition may exert a strong control of a composition's growth stimulating effect. As discussed above, it is known (WO 2009 / 082351) that inclusion of certain amino acids, in particular basic amino acids, promotes the growth of roots. The present inventors have now found (Examples 2-5) that effects of organic and inorganic N on growth of shoots and roots may be significantly enhanced by sulphur (S). In view of the prior art, a certain ratio of S:l\l in a growth stimulating composition containing organic N was surprisingly found to enable the effects of organic and inorganic N on root vs shoot growth.

[0069] Other macronutrients may be included in the composition of the invention, such as macronutrients selected from the group consisting of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg).

[0070] In an advantageous example, the composition according to the invention comprises phosphorus (P).Further, the composition may comprise citrate, such as citrate originating from citric acid or a salt thereof, such as potassium citrate. As will appear from the experimental part below, the citrate has several advantageous effects, such as reducing the nitrogen loss caused by certain bacteria and by exerting a buffering effect. Citrate may hence both reduce growth rates of bacteria through a direct inhibitory effect but also through an indirect effect, due to its buffer capacity which leads to a reduction of pH increase from bacteria I ly produced ammonia during decomposition of nitrogen compounds.

[0071] Further, micronutrients may be included in the composition of the invention, such as micronutrients selected from the group consisting of boron (B), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni) and zinc (Zn).

[0072] The liquid plant growth regulating composition of the invention is advantageously an aqueous solution, wherein the pH is in the range of about 3.2 to about 3.8, such as 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0 or 4.5 or 5.0 as an undiluted concentrate. As the skilled person will appreciate, the pH may change with dilution, depending e.g. on its content of phosphate ions and other components having a buffering or pH stabilizing effect. Common pH values for use may vary within wide ranges, depending on plant and soil conditions, such as pH 5-7, e.g. 6 or 7.

[0073] Further, the plant growth regulating composition may include other additives, such as benzoic acid, enhancing the stability of the solution by preventing growth of certain microorganisms in the concentrated product.

[0074] The liquid plant growth regulating composition according to the invention may be used as a fertilizer as such, or alternatively be combined, mixed or in any other way used with one or more other additives such as herbicides, pesticides and fertilizers.Thus, an illustrative fertilizer preparation capable of regulation root, shoot and / or root:shoot growth may comprise a liquid growth regulating composition as described in the present invention together with any wetting agent, carrier, thickener etc. conventionally used to this end.

[0075] The liquid plant growth regulating composition of the invention is advantageously manufactured as a concentrate, as will be described in more detail below in the context of the third aspect of the invention.

[0076] In a second aspect, the invention relates to a method of use of a composition as defined in the present application to promote shoot growth, wherein a composition as described above is used. All details regarding the first aspect of the invention apply equally well to this second aspect of use.

[0077] Thus, a ratio of sulphur (S):nitrogen (N) of at least about 0.20 may be used, or any ratio defined above in relation to the first aspect of the invention. At this level, the shoot growth will be enhanced on behalf of the root growth. Illustrative examples of promoted shoot growth will be described in further detail in the section Experimental below, as well as in the context of the appended drawings.

[0078] Alternatively, the invention relates to the use of a composition as defined in the present application to promote root growth, wherein a composition is used in which the ratio of sulphur (S):nitrogen (N) is at least about 0.40. At this level, the root growth will be enhanced on behalf of the shoot growth. Examples of promoted root growth will be described in further detail in the section Experimental below, as well as in the context of the appended drawings where the increased density, appearing as more compact lumps' of roots as compared to plants supplied with fertilizer having a lower content of sulphur (S).The invention also relates to the use of a composition as defined in the present application to promote the root:shoot ratio, i.e. to promote overall total growth. Alternatively, the invention relates to the use of a composition as defined in the present application to promote turf growth, wherein a composition is used in which the ratio (weight:weight) of sulphur (S):nitrogen (N) is at least about 0.50.

[0079] For shipping and storage purposes, and as customary in the area of liquid fertilizers, the plant growth regulating composition may be prepared as a liquid concentrate. The skilled person will be aware of suitable dilution protocols depending on the intended use.

[0080] The liquid composition of the invention may be prepared as a complete fertilizer, including all nutrients required for its purpose.

[0081] Alternatively, the composition of the invention may be prepared as an additive to a preparation including the supplemental nutrients required for its purpose.

[0082] Thus, the invention also relates to a method of manufacturing a concentrated liquid plant growth-regulating composition. The method of the invention may be based on any conventional method for preparing a liquid composition from free base or salt of basic L-amino acid, advantageously wherein the pH regulation uses sulphuric acid (H2SO4) resulting in the levels of sulphur (S):organic nitrogen (N) described herein. As the skilled person will appreciate, the favourable composition may be achieved by alternative and / or additional sources, as long as the result is the herein described ability to intentionally impact the shoot or root growth, or the overall growth.

[0083] Thus, referring back to the above-discussed WO 2009 / 082351, the principles of the method described therein for manufacture may be used here, while exchanging the hydrochloric acid (HCI) for sulphuric acid (H2SO4) addition.Since the concentrated HCI used in the prior art is known to be problematic to use because of its high vapor pressure, which may cause corrosion of the mucous membranes, oesophagus, and stomach of individuals involved in the manufacture, exchanging the HCI for H2SO4 was expected to result in an improvement in conditions during manufacture.

[0084] However, the present inventors found unexpectedly that the consequence of increasing the sulphur (S) content of the composition enabled promoting growth features such as shoot, root or turf. As explained in the present application, this effect was also possible to use to choose a desired effect, depending on the level of sulphur (S). As the skilled person will appreciate, not all of this sulphur (S) must originate from the manufacture - sulphur (S) may also be added as an optional nutrient, in order to increase the total level.

[0085] In a third aspect, the invention relates to a method of manufacturing a concentrated liquid plant growth regulating composition, the method comprising the steps of a) adding water, such as purified water, to a reactor;

[0086] b) heating said water to a temperature in the range of 50-70°C, such as 60°C;

[0087] c) dissolving basic L-amino acid in said heated water;

[0088] d) dissolving citrate in the form of citric acid or citrate salts

[0089] e) dissolving ferric iron ( Fe( 111 )) in the form of for example FeCh or Fe2(SO4)3 f) optionally, adding nutrients, anti-foaming agent, a density agent, pH buffer etc; g) adjusting the pH by addition of acid, such as H2SO4; and

[0090] h) mixing the contents of the reactor to obtain a concentrated liquid plant growth regulating composition.

[0091] The nutrients added may be selected from the group consisting of monopotassium phosphate, dipotassium sulphate and magnesium sulphate heptahydrate. Morespecifically, the optional other nutrients may be selected from the group consisting of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg).

[0092] Alternatively, or additionally, the optional other nutrients are selected from the group consisting of boron (B), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni) and zinc (Zn). The skilled person can easily decide at what step, in what amount and in what form such addition is made.

[0093] Advantageously, an inhibitor of nitrogen-metabolizing bacteria may be added, as discussed above in relation to the first and second aspects of the invention.

[0094] Furthermore, or alternatively, citrate may be added.

[0095] Additional nitrogen (N) in the form of inorganic nitrogen, such as ammonium nitrate, may be added. Other forms of inorganic nitrogen are well known for nutrient purposes, and may be added if desired.

[0096] Further, a preservative conventionally used in this area, such as sodium benzoate; and / or a chelating agent conventionally used in this area, such as Fe-DTPA, may be added. The skilled person can easily decide at what step, in what amount and in what form such addition is made.

[0097] As appears from other parts of the present application, specifically in relation to the first aspect of the invention, the ratio (weight:weight) of sulphur (S):organic nitrogen (N) in the composition is advantageously preset to a desired value, such as at least about 0.13, such as at least about 0.24, e.g. at least about 0.4 or at least about 0.5, or any other value or ratio as defined above in relation to the first aspect of the invention.

[0098] Further, the fraction of nitrogen (N) present as basic L-amino acid may be at least about 20%, such as about 50% of the total amount of nitrogen (N) in the composition.The concentrate so prepared may be a composition according to the invention. Thus, the basic L-amino acid may be one or more selected from the group consisting of L-arginine, L-lysine and L-histidine, such as L-arginine or L-lysine.

[0099] The basic L-amino acid dissolved in step c) is in free base or salt form.

[0100] In a more specific example, the method of the invention comprises the steps of i. adding water to a reactor,

[0101] ii. dissolving a preservative in said water,

[0102] iii. dissolving salts containing potassium, phosphorus and / or magnesium, iv. adding at least one basic L-amino acid,

[0103] v. adding sulphuric acid (H2SO4) such that a pH of 3.4 is achieved, vi. adding iron under stirring,

[0104] vii. allowing the solution to equilibrate at ambient temperature, and viii. adjusting the pH by adding additional sulphuric acid, if needed.

[0105] Detailed description of the drawings

[0106] Figures 1A and B show results obtained as described below (Example 2), specifically Pinus sylvestris seedlings treated with a low sulphur to organic nitrogen ratio (1A) and the liquid growth stimulating composition of the invention with a high sulphur to organic nitrogen ratio (IB). The unexpected strong effect on growth of roots by the invention is clearly visible comparing the two treatments. The root lumps for seedlings treated with the high sulphur to nitrogen ratio are intact, while the root lumps of the reference seedlings (1A) are damaged.

[0107] It appears clearly from this figure that the seedlings treated according to the invention have a substantially intact root lump and hence will have a significantly greater chance of survival and establishment when planted in a forest clear-cut area.Figure 2 shows results obtained as described below (Example 3), specifically the development of height of Scots pine seedlings at the early-mid phases of seedling cultivation using either an inorganicorganic N composition with low sulphurorganic N ratio (dashed bars) or an inorganicorganic N composition with high sulphurorganic N ratio (black bars).

[0108] More specifically, Pinus sylvestris seedlings treated with a liquid growth stimulating composition to enhance shoot growth in which nitrogen was present as a mixture between organic and inorganic nitrogen and a low or high sulphur to organic nitrogen ratio. The strong effect on growth of shoots by the invention is clearly visible comparing the two treatments.

[0109] The rapid extension of shoots of seedlings treated with the growth stimulating composition of the invention is beneficial when producing seedlings as this allows for reaching the target height earlier and by that less resources needs to be used for the production.

[0110] Figures 3A and B show results obtained as described below (Example 4), specifically Pinus sylvestris seedlings treated with a liquid growth stimulating composition to enhance shoot growth in which nitrogen was present as a mixture between organic and inorganic nitrogen and a low or high sulphur to organic nitrogen ratio for the first five months followed by treatment for one month with a liquid growth stimulating composition in which all nitrogen was present as organic N and a low or high sulphur to organic nitrogen ratio.

[0111] The strong effect on growth of roots and on root:shoot ratio by the invention is clearly visible comparing the two treatments.

[0112] Figures 4A and B show results obtained as described below (Example 5), specifically Pinus contorta seedlings treated with a liquid growth stimulating composition to enhance shoot growth in which nitrogen was present as a mixture between organic and inorganic nitrogen and a low or high sulphur to organic nitrogen ratio for the firstfive months followed by treatment for one month with a liquid growth stimulating composition in which all nitrogen was present as organic N and a low or high sulphur to organic nitrogen ratio.

[0113] The strong effect on growth of roots and of root:shoot ratio by the invention is clearly visible comparing the two treatments.

[0114] Figure 5 shows results obtained as described below (Example 6), specifically the average biomass accumulation of grass clippings in grams fresh weight 33 days after sowing (DAS). Treatment 1 displays a low sulphur:organic nitrogen ratio (sulphur making up 14% relative to the amount of organic nitrogen) whereas treatment 2 displays a high sulphur:organic nitrogen ratio (sulphur making up 42% relative to the amount of organic nitrogen), which is in accordance with the invention.

[0115] It is clear from this figure that the increase in sulphur according to the invention leads to an increased biomass of grass clippings by 30.24% in treatment 2.

[0116] Figure 6 shows results obtained as described below (Example 7), specifically the green leaf index (GLI) of grass 29 days after sowing (DAS). Treatment 1 displays a sulphur:organic N ratio (sulphur making up 14% relative to the amount of organic nitrogen) whereas treatment 2 displays a high sulphur : organic N ratio (sulphur making up 42% relative to the amount of organic nitrogen), which is in accordance with the invention.

[0117] It is obvious that the increase in sulphur leads to an increased green leaf index of 64.16% in treatment 2.

[0118] Figures 7A and B show results obtained as described below (Example 8), specifically the root development of grass 33 days after sowing (DAS). Treatment 1 displays a low sulphur:organic N ratio (sulphur making up 14% relative to the amount of organic nitrogen) whereas treatment 2 displays a high sulphur:organic N ratio (sulphur making up 42% relative to the amount of organic nitrogen), which is in accordancewith the invention. It is obvious that the increase in sulphur (S):organic nitrogen (N) ratio leads to an increased root density and biomass in treatment 2.

[0119] Figure 8 illustrates the results as described below (Example 9), i.e. the amount of arginine (Y axis), here representative of metabolization of organic nitrogen (Norg) remaining in 1:90 diluted, ready-to-use liquid growth regulating compositions according to the invention after storage for 14 days (solid bars), compared to the starting point 0 days (white bars).

[0120] More specifically, the concentrated compositions were supplemented either with nothing (Control), or with 1, 10 or 100 mg / L Fe3+. ND= not detected.

[0121] The content of added inhibitor of nitrogen-metabolizing bacteria (as Fe( 111 )) is gradually increased from left to right of the X axis, starting with a control (no added Fe(lll)) to 1 mg / L, 10 mg / L and 100 mg / L.

[0122] As appears from this Figure, while no arginine could be detected in the ready-to-use control after 14 days (ND), the 1 mg / L addition reduced the arginine degradation with about 40%. An almost complete protection of the arginine was obtained at an addition of 10 mg / L, while no arginine was degraded when 100 mg / L was added. The somewhat higher value of arginine concentration for the 100 mg / L treatment after 14 days is not indicative of an increase in arginine concentration but explained by a ±10% precision in arginine analysis method using ion chromatography.

[0123] Figure 9 is an alternative representation of the results obtained as described below (Example 9), showing how pH varies in ready-to-use liquid growth regulating compositions according to the invention with increased content of Fe(lll), increasing from the left (Control) to the right. As appears from the present application, the increased pH in a liquid composition is an indication of bacterial degradation of the organic nitrogen, leading to release of NH3.As appears from this Figure, the pH remains approximately at the starting level with the smaller addition of 1 mg / L, while 10 mg / L appears to be sufficient to keep the pH steady.

[0124] Figure 10 illustrates the results obtained as described below (Example 10), and shows how the sulfide content of water decreases with an increased addition of Fe(lll). This illustrates how sulfide formed as a result of bacterial metabolization of sulfate present in the organic N fertilizer can be controlled by adding an inhibitor of said metabolism.

[0125] More specifically, Figure 10 shows, from left to right, compositions supplemented with Fe(lll) in concentrations of 1 mg / L, 10 mg / L and 100 mg / L.

[0126] Note that the sulfide value of the control solution and that of the solution containing 1 mg / L Fe3+is higher than the maximum value of detection.

[0127] As appears from this Figure, 10 mg / L efficiently reduces the sulfide content (and hence the metabolization of nitrogen), while lOOmg / L almost eliminates said sulfide.

[0128] Figure 11 illustrates the results obtained as described below (Example 11), i.e. the amount of arginine (Y axis), here representative of metabolization of organic nitrogen (NOr ) remaining in ready-to-use liquid growth regulating compositions according to the invention after storage for 14 days, compared to the starting point 0 days.

[0129] More specifically, the concentrated compositions were supplemented either with nothing (Control), or with 9 or 90 g / L of citric acid. ND= not detected.

[0130] As appears from this Figure, while no arginine could be detected in the control after 14 days (ND), the 9 g / L addition and 90 g / L addition of citrate inhibited the decomposition of arginine in the ready-to-use solution.

[0131] Figure 12 illustrates the results obtained as described below (Example 12), and shows how pH varies in ready-to-use liquid growth regulating compositions according to the invention with increased content of citrate (as citric acid), increasing from the left(Control) to the right showing 9g / L and 90 g / L. pH is presented at day 0 (white bars) and 14 (black bars).

[0132] As appears from this Figure, 9 g / L provides a fully satisfactory control of the pH in the ready-to-use liquid growth regulating composition.

[0133] Figure 13 illustrates the results obtained as described below (Example 13), and shows the effects on pH of ready-to-use liquid growth regulating compositions according to the invention when citrate (as citric acid); or a combination of citrate (as citric acid) and Fe(lll) are added, as compared to a control of the same composition without said additions. From left to right, the control Norg(control) is presented followed by a first combination of 45 g / L citric acid, 10 mg / L Fe3+; and a second combination of 45 g / L citric acid and 10 mg / L Fe3+in the concentrated Norg.

[0134] As appears from this Figure, combining citrate (as citric acid) and Fe(lll) in a ready-to-use liquid growth regulating composition has a positive synergistic effect on the preservation of the quality of the composition.

[0135] EXPERIMENTAL

[0136] The present examples are provided for illustrative purposes and are not intended as limiting the invention as defined by the appended claims. Any reference included below or elsewhere in the present application are hereby included herein via reference.

[0137] Example 1: Preparation of a liquid composition with high sulphur:organic nitrogen ratio and in which all nitrogen is present in form of the basic amino acid L-arginine 1. Screw on an air-pressure driven stirrer with driving shaft and IBC lid to a 1000 L mixing IBC and add a metal funnel to a cut-out hole.

[0138] 2. Add the requested amount of water, using the 100L increments on the mixing IBC and the digital caliper.Connect the air pressure driven stirrer to a compressor, using air pressure hose with air preparation unit. Set the air preparation unit to c. 4 bars.

[0139] Add a 15 L plastic bucket to a balance and tare it. Weigh up the requested amount of sodium benzoate. Then add all the sodium benzoate to the mixing IBC. Allow all of it to dissolve before continuing to the next step.

[0140] Add the 15 L plastic bucket to the balance and tare it. Weigh up the requested amount of mono potassium phosphate and add it to the mixing IBC. Allow all of it to dissolve before continuing to the next step.

[0141] Add the 15 L plastic bucket to the balance and tare it. Weigh up the requested amount of potassium sulphate and add it to the mixing IBC. Allow all of it to dissolve before continuing to the next step.

[0142] Add the 15 L plastic bucket to the balance and tare it. Weigh up the requested amount of magnesium sulphate heptahydrate and add it to the mixing IBC. Allow all of it to dissolve before continuing to the next step.

[0143] Add the 15 L plastic bucket to the balance and tare it. Weigh up the requested amount of L-arginine free base and add it to the mixing IBC.

[0144] Add the portable pH meter probe to the mixing IBC.

[0145] Equip acid handling PPE. Use 20 L cans of sulphuric acid. Place the 20 L sulphuric acid can on top of it. Connect a membrane pump to the air preparation unit and slowly add acid. The pH must be lower than 6.0.

[0146] Equip acid handling PPE. Use the 20 L plastic can and 1000 mL measuring cylinder to add the requested amount of micronutrient solution

[0147] Add the 15 L plastic bucket to the balance and tare it. Weigh up the requested amount of iron-DTPA base and add it to the mixing IBC.

[0148] Equip acid handling PPE. Place the 5 L plastic beaker on top of it. Add ~3 L of acid to the beaker. Use the 1000 mL measuring cylinder to keep track of how much acid is being used. Slowly pour the acid into the mixing IBC until the requested pH is achieved. Note the final amount of acid added.

[0149] Note down the final amount of sulphuric acid used (step 8 + 12).15. Adjust the final volume to the requested volume with water.

[0150] 16. Let the solution equilibrate for at least two (2) hours and take a reading of the pH. Adjust pH with additional sulphuric acid if needed.

[0151] 17. Measure the total volume and make any adjustments with water if needed.

[0152] Further, a plant growth regulating composition with improved efficiency, i.e. reduced loss of organic nitrogen in ready-to-use liquid solutions, may be prepared by starting from a liquid composition prepared as described above.

[0153] Alternatively, any full nutrient mixture containing macronutrients and micronutrients may be used as the starting point, in which case the content of organic nitrogen (Norg) is advantageously provided by adding the basic amino acid L-arginine.

[0154] pH of the fertilizer is adjusted to about 4 with 25% H2SO4, in accordance with above. An inhibitor of nitrogen-metabolizing bacteria in the form of Fe3+may be provided in the composition by adding FeCh, here to concentrations within the range of 1-100 mg / L.

[0155] Citric acid may be added to provide citrate to the composition, here in concentrations within the range of 9-90 g / L.

[0156] Example 2: Enhancing root growth of Scots pine seedlings

[0157] Pinus sylvestris seedlings were treated with a liquid growth stimulating composition in which all nitrogen was present as L-arginine, and the sulphur to organic nitrogen ratio was 0.14 and the liquid growth stimulating composition of the invention in which all nitrogen was present as the basic amino acid L-arginine and a sulphur to organic nitrogen ratio of 0.5. Plants were grown from seeds in cassettes for five months. The first five weeks in a greenhouse and the rest of the time outside.

[0158] Seedlings were fertilized with liquid fertilizer once per week. Fertilizer was administered as a mixture of inorganic nitrogen (nitrate) and organic nitrogen (L-arginine and L-lysine) for five months. During the last four weeks of cultivation seedlings were treated with a composition in which all nitrogen was administered in the form of basic amino acid (L-arginine).

[0159] Example 3: Enhancing shoot growth of Scots pine seedlings

[0160] Seedlings treated with a liquid growth stimulating composition in which nitrogen was present as a mixture between L-arginine and L-lysine and nitrate and a sulphur to organic nitrogen ratio of 0.1 (dashed bars) and the liquid growth stimulating composition of the invention in which nitrogen was present as a mixture between the basic amino acids L-arginine and L-lysine and nitrate and a sulphur to organic nitrogen ratio of 0.13 (solid bars). Plants were grown from seeds in cassettes and height measurements were taken every week during the growth phase of shoot elongation.

[0161] Example 4: Production of Scots pine seedling with a high root:shoot ratio

[0162] Pinus sylvestris seedlings treated with a liquid growth stimulating composition in which nitrogen was present as a mixture between the basic amino acids L-arginine and L-lysine and nitrate and a sulphur to organic nitrogen ratio of 0.1 (dashed bars) and the liquid growth stimulating composition of the invention in which nitrogen was present as a mixture between the basic amino acids L-arginine and L-lysine and nitrate and a sulphur to organic nitrogen ratio of 0.13 (solid bars) for the first five months followed by treatment for one month with a liquid growth stimulating composition in which all nitrogen was present as the basic amino acid L-arginine and a sulphur to nitrogen ratio of 0.14 (dashed bars) and the liquid growth stimulating composition of the invention in which all nitrogen was present as the basic amino acid L-arginine and a sulphur to nitrogen ratio of 0.5 (solid bars).Example 5: Production of Lodgepole pine seedling with a high root:shoot ratio Pinus contorta seedlings treated with a liquid growth stimulating composition in which nitrogen was present as a mixture between the basic amino acids L-arginine and L-lysine and nitrate and a sulphur to organic nitrogen ratio of 0.1 (dashed bars) and the liquid growth stimulating composition of the invention in which nitrogen was present as a mixture between the basic amino acids L-arginine and L-lysine and nitrate and a sulphur to organic nitrogen ratio of 0.13 (solid bars) for the first five months followed by treatment for one month with a liquid growth stimulating composition in which all nitrogen was present as the basic amino acid L-arginine and a sulphur to organic nitrogen ratio of 0.14 (dashed bars) and the liquid growth stimulating composition of the invention in which all nitrogen was present as the basic amino acid L-arginine and a sulphur to organic nitrogen ratio of 0.5 (solid bars).

[0163] Example 6: Cultivation of lawn grass

[0164] Four cultivation trays (Vefi; 0,15 m2) were filled each with a blend of pre-fertilized cultivation substrate (Hasselfors, S-jord) and cultivation sand (Hasselfors) in a ratio of 7 liters:0.125 liters. In each tray, 3 g of grass seeds were evenly added (Plantagen, Grasfro Premium). The seeds represent a mix of red fescue (80%) and meadow grass (20%). The trays were placed in a greenhouse with 22 degrees Celsius, in a 16 / 8 hrs light regime with about 60% humidity. Trays were rotated regularly to avoid edge effects.

[0165] During the first days of germination, the trays were covered with plastic foil to maintain an increased humidity. After 4 DAS, the germination process was active and hence, the plastic foil was removed.

[0166] The first application of fertilizer was 7 days after sowing (DAS). Four trays each received a liquid fertilizer from Arevo AB that either has a low sulphunarginine nitrogen (low S : organic N) ratio or a sulphur:organic N ratio, whereas the same arginine nitrogen amount was applied. The low sulphur:organic N ratio is characterized by sulphur making up 14% relative to the amount of arginine nitrogen.The high sulphur:organic N ratio is characterized by sulphur making up 42% relative to the amount of arginine nitrogen. The fertilizer application was executed with a portable hand pressure sprayer pump and was applied as liquid foliar application. Every seven days, the trays were fertilized.

[0167] Above-ground biomass was recorded after 33 DAS. For this, the grass was cut with a grass trimmer at a standardized distance from the soil. All cut grass from one tray was then weighed and the fresh weight recorded. This was done for all four trays per treatment (n=4) to be able to compare the low sulphur:organic N ratio treatment (Treatment 1) with the high sulphurorganic N ratio treatment (Treatment 2).

[0168] Averaged values per treatment are presented in Figure 5.

[0169] Example 7: Analysis of turf grass colour

[0170] Four cultivation trays (Vefi; 0,15 m2) were filled each with a blend of pre-fertilized cultivation substrate (Hasselfors, S-jord) and cultivation sand (Hasselfors) in a ratio of 7 liters:0,125 liters. In each tray, 3 g of grass seeds were evenly added (Plantagen, Grasfro Premium). The seeds represent a mix of red fescue (80%) and meadow grass (20%). The trays were placed in a greenhouse with 22 degrees Celsius, in a 16 / 8 hrs light regime with about 60% humidity. Trays were rotated regularly to avoid edge effects.

[0171] During the first days of germination, the trays were covered with plastic foil to maintain an increased humidity. After 4 DAS, the germination process was active and hence, the plastic foil was removed.

[0172] The first application of fertilizer was 7 days after sowing (DAS). Four trays each received a liquid fertilizer from Arevo AB that either has a low sulphur:organic N ratio or a high sulphurorganic N ratio, whereas the same arginine nitrogen amount was applied. The low sulphurorganic N ratio is characterized by sulphur making up 14% relative to the amount of arginine nitrogen. The high sulphurorganic N ratio is characterized by sulphur making up 42% relative to the amount of arginine nitrogen. The fertilizer application was executed with a portable hand pressure sprayer pump

[0173] T1and was applied as liquid foliar application. Every seven days, the trays were fertilized.

[0174] To analyse the grass colour, the green leaf index was measured 29 DAS. For this, several photos (between 5 and 8 photos) for one representative tray per treatment were taken capturing the full tray from above. To normalize for light fluctuations during the photography, a white reference card was placed on the lower right corner of the photo. To be able to assess the greenness of the grass only, both, the background and the edges of the trays were cut out of the photograph.

[0175] Additionally, the Green Leaf Index (GLI) was calculated for all photos. A Python script was used to apply the formula:

[0176] 2G - R - B

[0177] GLI = - 2G + R + B

[0178] where R, G and B represent the red, green and blue channels of an image, respectively. The Python libraries scikit-image (to load images), NumPy (for image processing incl. RGB image work) and Matplotlib (for GLI image production) were used.

[0179] The GLI was calculated for each pixel to assess vegetation greenness. The average of the GLI values of all pictures per treatment was calculated and the averaged GLI values for both, the low sulphur:organic N ratio treatment (Treatment 1) and high sulphurorganic N ratio treatment (Treatment 2), were recorded.

[0180] Example 8: Analysis of root system development in grass

[0181] Four cultivation trays (Vefi; 0,15 m2) were filled each with a blend of pre-fertilized cultivation substrate (Hasselfors, S-jord) and cultivation sand (Hasselfors) in a ratio of 7 liters: 0,125 liters. In each tray, 3 g of grass seeds were evenly added (Plantagen, Grasfro Premium). The seeds represent a mix of red fescue (80%) and meadow grass (20%). The trays were placed in a greenhouse with 22 degrees Celsius, in a 16 / 8 hrs light regime with about 60% humidity. Trays were rotated regularly to avoid edge effects.During the first days of germination, the trays were covered with plastic foil to maintain an increased humidity. After 4 DAS, the germination process was active and hence, the plastic foil was removed.

[0182] The first application of fertilizer was 7 days after sowing (DAS). Four trays each received a liquid fertilizer from Arevo AB that either has a low sulphur : organic nitrogen (low S:organic N) ratio or a high sulphur:organic N ratio, whereas the same arginine nitrogen amount was applied. The low sulphur:organic N content is characterized by sulphur making up 14% relative to the amount of arginine nitrogen. The high sulphur:organic N ratio is characterized by sulphur making up 42% relative to the amount of organic nitrogen. The fertilizer application was executed with a portable hand pressure sprayer pump and was applied as liquid foliar application. Every seven days, the trays were fertilized.

[0183] To analyse the development of the root systems, two trays per treatment were flipped upside down and a photo was taken of the lower surface of the soil displaying the root system. One representative photo of the low sulphur:organic N ratio treatment (Treatment 1) was compared to the high sulphur:organic N treatment (Treatment 2), which is displayed in Figure 7.

[0184] Example 9: Effects of Fe3+on the stability of ready-to-use organic composition The compositions were prepared according to Example 1 above, with a S:N ratio (weight / weight) of 0.4, and supplemented either with nothing (control: Arginex® Forest Root from Arevo AB), or with 1, 10 or 100 mg / L Fe3+provided as FeCh.

[0185] They were then diluted to 1:90 in non-sterile water in a 10 ml falcon tube. Incubation for 14 days at 20°C followed. A subsample was taken for arginine analysis at day 0 and day 14, see Example 13 below. pH of the diluted fertilizer solution was measured with a pH electrode (XS Instruments) at day 0 and at day 14.

[0186] The results of this example are presented in Figures 8 and 9.Example 10: Effects of Fe3+on the concentration of sulfide in ready-to-use organic composition

[0187] The concentrated compositions prepared according to the invention were supplemented either with nothing (control), or with 1, 10 or 100 mg / L Fe3+after which water with high sulfide concentration was used to dilute them to 1:90 in a 10 ml Falcon tube. The so diluted compositions were incubated at 20°C for 10 min.

[0188] After incubation, the sulfide concentration was measured (mg / L) with the methylene blue method at a wavelength of X=665 nm.

[0189] The results of this example are presented in Figure 10.

[0190] Example 11: Effects of citric acid on the stability of ready-to-use organic composition The tested compositions were prepared according to Example 1 above, with a S:N ratio (weight / weight) of 0.4. The concentrated fertilizer was complemented with either nothing (Control), with 9 or with 90 g / L citric acid. The solutions were then diluted to 1:90 in non-sterile water in a 10 ml Falcon tube and incubated for 14 days at 20°C. pH was measured with a pH electrode (XS Instruments) at day 0 and day 14.

[0191] The concentration of arginine remaining in the diluted fertilizer was analysed after 14 days of incubation, see Example 13.

[0192] The results of this example are presented in Figure 11.

[0193] Example 12: Effects of citrate on the stability of the ready-to-use organic composition The tested compositions were prepared according to Example 1 above, with a S:N ratio (weight / weight) of 0.4. The concentrated fertilizer was complemented with either nothing (Control), with 9 or with 90 g / L citric acid. The solutions were then diluted to 1:90 in non-sterile water in a 10 ml Falcon tube and incubated for 14 days at 20°C. pH was measured with a pH electrode (XS Instruments) at day 0 and day 14.

[0194] The results of this example are presented in Figure 12.Example 13: Combination of Fe3+and citric acid on the stability of the ready-to-use organic composition

[0195] The tested compositions were prepared according to Example 1 above, with a S:N ratio (weight / weight) of 0.4 . Arginex® Forest Root from Arevo AB was used as control. Fertilizer without, and with either just 45 g / L citric acid or a combination of 10 mg / L Fe3+and 45 g / L citric acid was diluted 1:90 in non-sterile water in a 10 ml Falcon tube and incubated for 6 days. The pH was measured at day 0 and day 6.

[0196] Solutions were incubated at 20°C, and pH was measured at day 0 and 14.

[0197] The results of this example are presented in Figure 13.

[0198] Example 14: Analyses - Arginine

[0199] Arginine was analyzed on an ion chromatograph with conductivity detection on an ECO-IC (Metrohm, Switzerland) connected to a ProfIC Conductivity Detector MF (Metrohm, Switzerland). The separation was achieved by injecting 10 pL of a sample on a Metrosep C 6 (250 x 4.0 mm; Metrohm, Switzerland) column connected to a guard columns Metrosep C 6 Guard / 4.0 (Metrohm, Switzerland). The mobile phase is delivered on the column by a flow rate of 0.9 mL min1with isocratic elution. The cation eluent is composed of 1.7 mmol L1nitric acid (HNOs, CAS: 7697-37-2, 65%, for analysis EMSURE® Reag. Ph Eur,ISO, Supleco) and 1.7 mmol L'12,6-Pyridinedicarboxylic acid (CAS: 499-83-2, suitable for ion chromatography, Supleco). Column and autosampler is kept at room temperature. A calibration curve is constructed using arginine (L-arginine, >98%, CAS: 74-79-3, Sigma-Aldrich) in the range of 100-800 mg L1and used for quantification of arginine in each sample.

[0200] Example 15: Analyses - Sulfide

[0201] Sulfide was measured photometrically by measuring Dimethyl-p-phenylenediamine with a sulfide test kit (Sulfide Test, 0.020-1.50 mg / L (S2), Spectroquant*, Merck) on a Vis spectrometer (Prove 100, Spectroquant®, Merck) at a wavelength of = 665 nm.

Claims

CLAIMS1. A liquid plant growth regulating composition comprising macronutrients at least in the form of nitrogen (N), sulphur (S) and optionally phosphorus (P) in mixture with an inhibitor of nitrogen-metabolizing bacteria, wherein said inhibitor is substantially non-toxic to the plant.2 A composition according to claim 1, wherein said inhibitor is selected from the group consisting of (i) inhibitors of ammonifying bacteria; (ii) inhibitors of ammoniumoxidizing bacteria; (iii) inhibitors of nitrite-oxidizing bacteria; and (iv) inhibitors of denitrifying bacteria.3 A composition according to claim 1 or 2, wherein the inhibitor is Fe(lll), or a composition comprising Fe(lll).4 A composition according to any one of the preceding claims, which comprises inorganic nitrogen (N inorg)- 5 A composition according to any one of the preceding claims, which comprises organic nitrogen (Norg).6 A composition according to claim 5, wherein the fraction of nitrogen (N) present as organic nitrogen organic is at least about 20%, such as at least about 50%, of the total amount of nitrogen (N) in the composition.7 A composition according to claim 5 or 6, wherein the organic nitrogen (N) originates from one or more basic L-amino acids.8 A composition according to any one of claims 7, wherein the basic L-amino acid is one or more selected from the group consisting of L-arginine, L-lysine and L-histidine. 9 A composition according to claim 8, wherein the basic L-amino is L-arginine or L- lysine.10 A composition according to any one of claims 5-9, wherein the ratio (weight / weight) of sulphur (S):organic nitrogen (N) is at least about 0.13.11 A composition according to claim 10, wherein the ratio (weight / weight) of sulphur (S): organic nitrogen (N) is at least about 0.24, such as at least about 0.4 or at least about 0.5.

12. A composition according to any one of the preceding claims, which comprises phosphorus (P).

13. A composition according to claim 12, which comprises citrate.

14. A composition according to any one of the preceding claims, wherein the macronutrients are nitrogen (N), sulphur (S), phosphorus (P) in mixture with one or more of potassium (K), calcium (Ca) and magnesium (Mg).

15. A composition according to any one of the preceding claims, further comprising micronutrients selected from the group consisting of boron (B), chloride (Cl), copper (Cu), manganese (Mn), molybdenum (Mo), nickel (Ni) and zinc (Zn).

16. Use of a composition according to any one of claims 1-15 to promote plant shoot growth, wherein a composition is used in which the ratio (weight / weight) of sulphur (S):organic nitrogen (N) is at least about 0.2.

17. Use of a composition according to any one of claims 1-15 to promote plant root growth, wherein a composition is used in which the ratio (weight / weight) of sulphur (S):organic nitrogen (N) is at least about 0.4.

18. Use of a composition according to any one of claims 1-15 for turf grass growth, wherein a composition is used in which the ratio (weight / weight) of sulphur (S):organic nitrogen (N) is at least about 0.5.

19. Use of a composition according to any one of claims 1-15 to promote the overall growth of a plant.

20. A method of manufacturing a concentrated liquid plant growth regulating composition, the method comprising the steps ofa) adding water to a reactor;b) heating said water to a temperature in the range of 50-70°C;c) dissolving basic L-amino acid in said heated water;d) optionally, adding nutrients, anti-foaming agent, a density agent, pH buffer etc; e) adjusting the pH, such as by addition of H2SO4; andf) mixing the contents of the reactor to obtain a concentrated liquid plant growth regulating composition.

21. A method according to claim 20, wherein the nutrients added in step d) are selected from the group consisting of monopotassium phosphate, dipotassium sulphate and magnesium sulphate heptahydrate.

22. A method according to claim 20 or 21, wherein, an inhibitor of nitrogen-metabolizing bacteria is added.

23. A method according to claim 22, where the inhibitor is ferric iron Fe(lll).

24. A method according to any one of claims 20-23, wherein citrate is added.

25. A method according to any one of claims 20-24, wherein inorganic nitrogen, such as ammonium nitrate, is added.

26. A method according to any one of claims 20-25, wherein a preservative, such as sodium benzoate, is added.

27. A method according to any one of claims 20-26, wherein a chelating agent, such as Fe-DTPA, is added.

28. A method according to any one of claims 20-27, wherein the ratio (weight / weight) of sulphur (S):organic nitrogen (N) in the so prepared composition is at least about 0.13, such as at least about 0.24, e.g. at least about 0.4 or at least about 0.5.

29. A method according to any one of claims 20-28, wherein the fraction of nitrogen (N) present as basic L-amino acid is at least about 20%, such as about 50% of the total amount of nitrogen (N) in the composition.

30. A method according to any one of claims 20-29, wherein the optional other nutrients are selected from the group consisting of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg).

31. A method according to any one of claims 20-30, wherein the optional other nutrients are selected from the group consisting of boron (B), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni) and zinc (Zn).

32. A method according to any one of claims 20-31, wherein the basic L-amino acid is one or more selected from the group consisting of L-arginine, L-lysine and L-histidine.

33. A method according to claim 32, wherein the basic L-amino acid is L-arginine or L- lysine, such as L-arginine.

34. A method according to any one of claims 20-33, wherein the basic L-amino acid dissolved in step c) is in free base or salt form.

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