Irrigation method and device for improving bio-availability of phosphorus in soil in root zone in crop growth period

Abstract

The invention belongs to the field of agricultural production and environmental protection, and particularly relates to an irrigation method and device for improving bio-availability of phosphorus in soil in a root zone in a crop growth period, in the crop growth period, oxalic acid is periodically irrigated to the soil in the root zone of the crop at intervals in a low dosage mode, and a phosphorus-containing water-soluble fertilizer is irrigated to the soil in the root zone of the crop at the same time or within 0-30 minutes later. The bio-availability of exogenous and endogenous phosphorus in root zone soil is safely, moderately and continuously improved, the phosphorus application demand is reduced, and the adverse effect of excess phosphorus in the soil is reduced.

Description

Technical Field

[0001] The present invention belongs to the fields of agricultural production and environmental protection, and particularly relates to an irrigation method and device for improving the biological availability of soil phosphorus in the root zone during the growth period of crops. Background Art

[0002] In agricultural production, especially in protected agriculture production, the input of phosphate fertilizer is excessive, the utilization rate is low, and the surplus of soil phosphorus is relatively common, resulting in the imbalance of soil nutrients, aggravating soil degradation, and being unfavorable to the sustainable development of agriculture.

[0003] The application of phosphorus efficiency-enhancing products can improve the biological availability of soil phosphorus, reduce the demand for phosphate fertilizer, and reduce the risk of soil phosphorus surplus. Typical phosphorus efficiency-enhancing products include phosphate-solubilizing bacteria agents, humic acid substances, and small molecule organic acids. Phosphate-solubilizing bacteria agents are mostly used in the early growth stage of crops by dipping roots and irrigating roots. Humic acid substances are mostly applied to open-field and protected soil in the form of base fertilizer together with organic fertilizer.

[0004] Exogenous addition of small molecule organic acids can improve the biological availability of soil phosphorus within a certain period of time by affecting the soil pH value and the content of calcium ions. Among small molecule organic acids, oxalic acid has a relatively significant effect on soil available phosphorus and has great application potential. However, a one-time high-dose application of oxalic acid is likely to cause large changes in the physical and chemical properties such as the soil pH value in a short period of time, and the risk during the crop growth period is relatively high; a one-time low-dose application of oxalic acid has relatively little impact on the physical and chemical properties such as the soil pH value, and the risk during the crop growth period is small, but the effect or duration of soil available phosphorus may not be sufficient. More importantly, there are difficulties in applying oxalic acid during the crop growth period: when applying by root irrigation in the root zone soil of crops, the labor intensity is large and the operation cost is high; when applying by furrow irrigation / flood irrigation, the dosage of oxalic acid is large and the efficiency of soil available phosphorus in the root zone is low; when applying by drip irrigation, oxalic acid is easily precipitated with calcium ions in conventional irrigation water, blocking the drip irrigation system.

[0005] The combined application of oxalic acid and phosphorus-containing fertilizers is likely to be beneficial to improving the biological availability of both endogenous and exogenous phosphorus in the soil (after phosphate fertilizer enters the soil). However, considering the difficulty in applying oxalic acid during the crop growth period, the combined application of oxalic acid and phosphorus-containing fertilizers during the crop growth period is also not easy to implement.

[0006] Therefore, there is an urgent need for a suitable method to safely and conveniently apply oxalic acid, especially the combined application of oxalic acid and phosphorus-containing fertilizers, on phosphorus-rich soils during the crop growth period, gently regulate the soil physical and chemical properties, safely, moderately, and continuously improve the biological availability of exogenous and endogenous phosphorus in the soil, reduce the phosphorus application demand, and promote the sustainable development of agriculture. Summary of the Invention

[0007] The purpose of the present invention is to provide an irrigation method and device for improving the biological availability of soil phosphorus in the root zone during the growth period of crops.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] The irrigation method for improving the biological availability of phosphorus in the root zone soil during the growth period of the crops of the present invention is that during the growth period of the crops, oxalic acid is applied to the root zone soil of the crops by intermittent, low-dose and periodic irrigation, and at the same time or within 0-30 minutes thereafter, a water-soluble phosphorus fertilizer is applied by irrigation, continuously improving the biological availability of exogenous and endogenous phosphorus in the root zone soil.

[0010] Among them: the intermittent irrigation application of oxalic acid means that oxalic acid is added once or multiple times during each irrigation process, and the proportion of the irrigation duration in the addition of oxalic acid period to the total irrigation duration is <30%, or the proportion of the irrigation amount in the addition of oxalic acid period to the total irrigation amount is <30%; the mass concentration of oxalic acid in the irrigation water during the addition of oxalic acid period is more than 8 times the mass concentration of calcium ions in the irrigation water before the addition of oxalic acid.

[0011] The low-dose irrigation application of oxalic acid means that the dosage of oxalic acid per mu of soil each time is 1-10 kg of oxalic acid.

[0012] The time interval of the periodic irrigation application of oxalic acid is 7-21 days, and the application frequency during the growth period of the crops is 3-9 times.

[0013] When the water-soluble phosphorus fertilizer forms a precipitate with oxalic acid, the water-soluble phosphorus fertilizer is applied by irrigation within 0-30 minutes after the irrigation application of oxalic acid; when the water-soluble phosphorus fertilizer does not form a precipitate with oxalic acid, the water-soluble phosphorus fertilizer is applied by irrigation at the same time or within 0-30 minutes after the irrigation application of oxalic acid.

[0014] An irrigation device for implementing the irrigation method for improving the biological availability of phosphorus in the root zone soil during the crop growth period according to the present invention includes a conventional irrigation water tank, a low-calcium irrigation water tank, an oxalic acid solution tank, a phosphorus-containing fertilizer tank, an irrigation pump, an irrigation main pipe, an acid suction pump, a fertilizer suction pump, a conventional irrigation water valve, a low-calcium irrigation water valve, an acid suction valve, a fertilizer suction valve, and a drip irrigation belt. The water inlet of the irrigation pump is respectively connected to the conventional irrigation water tank and the low-calcium irrigation water tank, and a conventional irrigation water valve is provided on the pipeline between the irrigation pump and the conventional irrigation water tank, and a low-calcium irrigation water valve is provided on the pipeline between the irrigation pump and the low-calcium irrigation water tank. Alternatively, the water inlet of the irrigation pump is respectively connected to one end of the conventional irrigation water valve and the low-calcium irrigation water valve, and the other ends of the conventional irrigation water valve and the low-calcium irrigation water valve are respectively connected to the conventional irrigation water tank and the low-calcium irrigation water tank. The water outlet of the irrigation pump is connected to one end of the irrigation main pipe, and the other end of the irrigation main pipe is connected with a drip irrigation belt. The water inlets of the acid suction pump and the fertilizer suction pump are respectively connected to the oxalic acid solution tank and the phosphorus-containing fertilizer tank, and the water outlets of the acid suction pump and the fertilizer suction pump are respectively connected to the irrigation main pipe through an acid suction pipeline and a fertilizer suction pipeline, and an acid suction valve is provided on the acid suction pipeline, and a fertilizer suction valve is provided on the fertilizer suction pipeline. Alternatively, the water outlet of the acid suction pump is connected to one end of the acid suction valve, the water outlet of the fertilizer suction pump is connected to one end of the fertilizer suction valve, and the other ends of the acid suction valve and the fertilizer suction valve are respectively connected to the irrigation main pipe through the acid suction pipeline and the fertilizer suction pipeline.

[0015] The water inlet of the irrigation pump is communicated with the first interface of the three-way joint A, the second interface and the third interface of the three-way joint A are respectively connected to the conventional irrigation water tank and the low-calcium irrigation water tank, the conventional irrigation water valve is provided on the pipeline between the three-way joint A and the conventional irrigation water tank, and the low-calcium irrigation water valve is provided on the pipeline between the three-way joint A and the low-calcium irrigation water tank. Alternatively, the water inlet of the irrigation pump is communicated with the first interface of the three-way joint A, the second interface of the three-way joint A is connected to one end of the conventional irrigation water valve, the other end of the conventional irrigation water valve is connected to the conventional irrigation water tank, the third interface of the three-way joint A is connected to one end of the low-calcium irrigation water valve, and the other end of the low-calcium irrigation water valve is connected to the low-calcium irrigation water tank.

[0016] A tee joint B is provided between the acid suction pipe and the fertilizer suction pipe and the main irrigation pipe. The first interface of the tee joint B is connected to the main irrigation pipe. The second interface of the tee joint B is connected to the water outlet of the acid suction pump through the acid suction pipe, and an acid suction valve is arranged on the acid suction pipe. The third interface of the tee joint B is connected to the water outlet of the fertilizer suction pump through the fertilizer suction pipe, and a fertilizer suction valve is arranged on the fertilizer suction pipe; or, the first interface of the tee joint B is connected to the main irrigation pipe, the second interface of the tee joint B is connected to one end of the acid suction valve through the acid suction pipe, and the other end of the acid suction valve is connected to the water outlet of the acid suction pump. The third interface of the tee joint B is connected to one end of the fertilizer suction valve through the fertilizer suction pipe, and the other end of the fertilizer suction valve is connected to the water outlet of the fertilizer suction pump.

[0017] The irrigation device includes five operation modes.

[0018] Mode 1: Open the conventional irrigation water valve, power on the irrigation pump, and conduct conventional irrigation water irrigation.

[0019] Mode 2: Open the conventional irrigation water valve and the acid suction valve simultaneously, power on the irrigation pump and the acid suction pump simultaneously, and conduct conventional irrigation water irrigation with the application of oxalic acid.

[0020] Mode 3: Open the conventional irrigation water valve, the acid suction valve, and the fertilizer suction valve simultaneously, power on the irrigation pump, the acid suction pump, and the fertilizer suction pump simultaneously, and conduct conventional irrigation water irrigation with the application of oxalic acid and phosphorus-containing fertilizers.

[0021] Mode 4: Open the low-calcium irrigation water valve, power on the irrigation pump, and conduct low-calcium irrigation water irrigation.

[0022] Mode 5: Open the conventional irrigation water valve and the fertilizer suction valve simultaneously, power on the irrigation pump and the fertilizer suction pump simultaneously, and conduct conventional irrigation water irrigation with the application of phosphorus-containing fertilizers.

[0023] Operate in the order of Mode 1, Mode 2, Mode 4, and Mode 5 or in the order of Mode 1, Mode 3, and Mode 4 for one to three cycles, and finally operate Mode 1 once. Among them, the total operation duration of Mode 2 or Mode 3 accounts for less than 30% of the total operation duration of all modes, and the operation duration of Mode 4 meets the requirement of flushing the residual oxalic acid in the irrigation device.

[0024] The advantages and positive effects of the present invention are as follows:

[0025] The intermittent irrigation of the present invention uses oxalic acid, significantly reducing the formation amount of calcium oxalate precipitation in irrigation and its adverse effects on the drip irrigation system, making the application of oxalic acid during crop growth convenient and economically feasible; intermittent, periodic, and low-dose irrigation with oxalic acid, and simultaneously or within 0-30 minutes thereafter, irrigating with a phosphorus-containing water-soluble fertilizer can gently regulate the physical and chemical properties of the root zone soil of crops, and safely, moderately, and continuously improve the biological availability of endogenous and exogenous phosphorus in the root zone soil. The present invention is very suitable for facility soils where phosphorus surplus is relatively common, reducing the phosphorus application requirement and promoting the sustainable production of facility agriculture. Brief Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the irrigation device of the present invention;

[0027] Wherein: 1 is a conventional irrigation water tank, 2 is a low-calcium irrigation water tank, 3 is an oxalic acid solution tank, 4 is a phosphorus-containing fertilizer tank, 5 is an irrigation pump, 6 is an irrigation main pipe, 7 is an acid suction pump, 8 is a fertilizer suction pump, 9 is a conventional irrigation water valve, 10 is a low-calcium irrigation water valve, 11 is an acid suction valve, 12 is a fertilizer suction valve, 13 is a drip irrigation tape, 14 is a tee A, and 15 is a tee B. Detailed Embodiment

[0028] The present invention will be further described in detail below with reference to the drawings.

[0029] The irrigation method for improving the biological availability of phosphorus in the root zone soil during the growth period of crops of the present invention is: during the growth period of crops, intermittently, at a low dose, and periodically irrigate the root zone soil of crops with oxalic acid, and simultaneously or within 0-30 minutes thereafter, irrigate with a phosphorus-containing water-soluble fertilizer, safely, moderately, and continuously improving the biological availability of exogenous and endogenous phosphorus in the root zone soil.

[0030] The intermittent irrigation with oxalic acid in this embodiment is to add oxalic acid once or multiple times during each irrigation process, and the irrigation duration of the oxalic acid addition period accounts for less than 30% (preferably 15%-25%) of the total irrigation time, or the irrigation amount of the oxalic acid addition period accounts for less than 30% (preferably 15%-25%) of the total irrigation amount; the mass concentration of oxalic acid in the irrigation water during the oxalic acid addition period is more than 8 times the mass concentration of calcium ions in the irrigation water before adding oxalic acid.

[0031] The low-dose irrigation with oxalic acid in this embodiment is 1-10 kg (preferably 1.5-4.5 kg) of oxalic acid per mu of soil each time.

[0032] The time interval for the periodic irrigation with oxalic acid in this embodiment is 7-21 days (preferably 10-15 days), and the application frequency during the growth period of crops is 3-9 times.

[0033] When the phosphorus-containing water-soluble fertilizer in this embodiment forms a precipitate with oxalic acid, the phosphorus-containing water-soluble fertilizer is irrigated and applied within 0 to 30 minutes after the irrigation and application of oxalic acid; when the phosphorus-containing water-soluble fertilizer does not form a precipitate with oxalic acid, the phosphorus-containing water-soluble fertilizer is irrigated and applied simultaneously with or within 0 to 30 minutes after the irrigation and application of oxalic acid.

[0034] As Figure 1 shown, the irrigation device of the present invention includes a conventional irrigation water tank 1, a low-calcium irrigation water tank 2, an oxalic acid solution tank 3, a phosphorus-containing fertilizer tank 4, an irrigation pump 5, an irrigation main pipe 6, an acid suction pump 7, a fertilizer suction pump 8, a conventional irrigation water valve 9, a low-calcium irrigation water valve 10, an acid suction valve 11, a fertilizer suction valve 12 and a drip irrigation tape 13. The water inlet of the irrigation pump 5 is respectively connected to the conventional irrigation water tank 1 and the low-calcium irrigation water tank 2, and a conventional irrigation water valve 9 is provided on the pipeline between the irrigation pump 5 and the conventional irrigation water tank 1, and a low-calcium irrigation water valve 10 is provided on the pipeline between the irrigation pump 5 and the low-calcium irrigation water tank 2. Alternatively, the water inlet of the irrigation pump 5 is respectively connected to one end of the conventional irrigation water valve 9 and the low-calcium irrigation water valve 10, and the other ends of the conventional irrigation water valve 9 and the low-calcium irrigation water valve 10 are respectively connected to the conventional irrigation water tank 1 and the low-calcium irrigation water tank 2. The water outlet of the irrigation pump 5 is connected to one end of the irrigation main pipe 6, and the other end of the irrigation main pipe 6 is connected with a drip irrigation tape 13. The water inlets of the acid suction pump 7 and the fertilizer suction pump 8 are respectively connected to the oxalic acid solution tank 3 and the phosphorus-containing fertilizer tank 4, and the water outlets of the acid suction pump 7 and the fertilizer suction pump 8 are respectively connected to the irrigation main pipe 6 through an acid suction pipeline and a fertilizer suction pipeline, and an acid suction valve 11 is provided on the acid suction pipeline and a fertilizer suction valve 12 is provided on the fertilizer suction pipeline. Alternatively, the water outlet of the acid suction pump 7 is connected to one end of the acid suction valve 11, the water outlet of the fertilizer suction pump 8 is connected to one end of the fertilizer suction valve 12, and the other ends of the acid suction valve 11 and the fertilizer suction valve 12 are respectively connected to the irrigation main pipe 6 through an acid suction pipeline and a fertilizer suction pipeline.

[0035] The water inlet of the irrigation pump 5 is connected to the first interface of the three-way pipe A14. The second interface and the third interface of the three-way pipe A14 are respectively connected to the conventional irrigation water tank 1 and the low-calcium irrigation water tank 2. The conventional irrigation water valve 9 is arranged on the pipeline between the three-way pipe A14 and the conventional irrigation water tank 1, and the low-calcium irrigation water valve 10 is arranged on the pipeline between the three-way pipe A14 and the low-calcium irrigation water tank 2. Or, the water inlet of the irrigation pump 5 is connected to the first interface of the three-way pipe A14. The second interface of the three-way pipe A14 is connected to one end of the conventional irrigation water valve 9, and the other end of the conventional irrigation water valve 9 is connected to the conventional irrigation water tank 1; the third interface of the three-way pipe A14 is connected to one end of the low-calcium irrigation water valve 10, and the other end of the low-calcium irrigation water valve 10 is connected to the low-calcium irrigation water tank 2. In this embodiment, the second interface and the third interface of the three-way pipe A14 are respectively connected to the conventional irrigation water tank 1 and the low-calcium irrigation water tank 2. The conventional irrigation water valve 9 is arranged on the pipeline between the three-way pipe A14 and the conventional irrigation water tank 1, and the low-calcium irrigation water valve 10 is arranged on the pipeline between the three-way pipe A14 and the low-calcium irrigation water tank 2.

[0036] There is a three-way pipe B15 between the acid suction pipeline and the fertilizer suction pipeline and the irrigation main pipe 6. The first interface of the three-way pipe B15 is connected to the irrigation main pipe 6. The second interface of the three-way pipe B15 is connected to the water outlet of the acid suction pump 7 through the acid suction pipeline, and an acid suction valve 11 is arranged on the acid suction pipeline. The third interface of the three-way pipe B15 is connected to the water outlet of the fertilizer suction pump 8 through the fertilizer suction pipeline, and a fertilizer suction valve 12 is arranged on the fertilizer suction pipeline. Or, the first interface of the three-way pipe B15 is connected to the irrigation main pipe 6. The second interface of the three-way pipe B15 is connected to one end of the acid suction valve 11 through the acid suction pipeline, and the other end of the acid suction valve 11 is connected to the water outlet of the acid suction pump 7. The third interface of the three-way pipe B15 is connected to one end of the fertilizer suction valve 12 through the fertilizer suction pipeline, and the other end of the fertilizer suction valve 12 is connected to the water outlet of the fertilizer suction pump 8. In this embodiment, the second interface of the three-way pipe B15 is connected to the water outlet of the acid suction pump 7 through the acid suction pipeline, and an acid suction valve 11 is arranged on the acid suction pipeline. The third interface of the three-way pipe B15 is connected to the water outlet of the fertilizer suction pump 8 through the fertilizer suction pipeline, and a fertilizer suction valve 12 is arranged on the fertilizer suction pipeline.

[0037] The irrigation device of the present invention includes five operation modes:

[0038] Mode 1: Open the conventional irrigation water valve 9, power on the irrigation pump 5, and conduct conventional irrigation water irrigation;

[0039] Mode 2: Open the conventional irrigation water valve 9 and the acid suction valve 11 simultaneously, power on the irrigation pump 5 and the acid suction pump 7 simultaneously, and conduct conventional irrigation water irrigation with the application of oxalic acid;

[0040] Mode 3: Open the conventional irrigation water valve 9, the acid suction valve 11, and the fertilizer suction valve 12 simultaneously, power on the irrigation pump 5, the acid suction pump 7, and the fertilizer suction pump 8 simultaneously, and conduct conventional irrigation water irrigation with the application of oxalic acid and phosphorus-containing fertilizers;

[0041] Mode 4: Open the low-calcium irrigation water valve 10, power on the irrigation pump 5, and irrigate with low-calcium irrigation water.

[0042] Mode 5: Open the conventional irrigation water valve 9 and the fertilizer suction valve 12 simultaneously, power on the irrigation pump 5 and the fertilizer suction pump 8 simultaneously, and irrigate with conventional irrigation water and apply phosphorus-containing fertilizer.

[0043] Run one to three cycles in the order of Mode 1, Mode 2, Mode 4, and Mode 5 or in the order of Mode 1, Mode 3, and Mode 4, and finally run Mode 1 once. Among them, the total running duration of Mode 2 or Mode 3 accounts for less than 30% of the total running duration of all modes, and the running duration of Mode 4 meets the requirement of flushing the residual oxalic acid in the irrigation device.

[0044] Experimental Example 1

[0045] Intermittent and low-dose irrigation application of oxalic acid during the growth period of greenhouse cucumbers:

[0046] On a 2-acre greenhouse soil with an Olsen phosphorus content of 86 mg / kg, plant 6,000 autumn cucumber seedlings at a plant spacing of 33 cm. Among them, 1 acre of cucumbers is used as a control treatment (without applying oxalic acid; reducing phosphorus fertilizer application), and 1 acre of cucumbers is used as the treatment with oxalic acid application (reducing phosphorus fertilizer application by the same amount).

[0047] On the 40th day after cucumber seedlings are planted, carry out intermittent irrigation application of oxalic acid. The calcium ion contents in the conventional irrigation water tank 1 and the low-calcium irrigation water tank 2 are 116.4 mg / L and 8.3 mg / L respectively; the oxalic acid concentration in the oxalic acid solution tank 3 is 100 g / L; the concentration of ammonium dihydrogen phosphate in the phosphorus-containing fertilizer tank 4 is 150 g / L; the water outflow rates (L / minute) of the irrigation pump 5, the acid suction pump 7, and the fertilizer suction pump 8 are 240, 2.5, and 2.5 respectively; the irrigation main pipe 6 for each treatment (1 acre of cucumbers) is 50 meters long and 90 mm in diameter; the drip irrigation tape 13 is 13.2 meters long, 16 mm wide, and the drip hole spacing is 15 cm.

[0048] For the treatment with oxalic acid application, run for 14, 6, and 2 minutes respectively in the order of Mode 1, Mode 3, and Mode 4, and finally run Mode 1 for 8 minutes, with a total running time of 30 minutes. The total irrigation volume is 7.2 cubic meters per acre. Among them, the irrigation volume with added oxalic acid accounts for 20.0% of the total irrigation volume; the average oxalic acid content of the irrigation water with added oxalic acid is 1.03 g / L, which is 8.6 times the calcium ion content in the conventional irrigation water; the oxalic acid dosage is 1.5 kg per acre; the ammonium dihydrogen phosphate dosage is 2.2 kg per acre.

[0049] For the control treatment, run in the order of Mode 1, Mode 5, and Mode 4 for 14, 6, and 2 minutes respectively, and finally run Mode 1 for 8 minutes, for a total of 30 minutes. The total irrigation volume is 7.2 cubic meters per mu, and the amount of ammonium dihydrogen phosphate used is 2.2 kg per mu.

[0050] Experimental Example 2

[0051] The device for applying oxalic acid during the growth period of greenhouse cucumbers and the two cucumber treatments are the same as those in Experimental Example 1.

[0052] Intermittent and low-dose irrigation application of oxalic acid during the growth period of greenhouse cucumbers:

[0053] On the 50th day after the autumn cucumber seedlings were planted in Experimental Example 1, continue to carry out intermittent irrigation with oxalic acid. The oxalic acid concentration in the oxalic acid solution pool 3 is 125 g / L; the concentration of potassium dihydrogen phosphate in the phosphorus-containing fertilizer pool 4 is 135 g / L; other parameters of the irrigation device are the same as those in Experimental Example 1.

[0054] For the treatment with oxalic acid application, run in the order of Mode 1, Mode 3, and Mode 4 in 2 cycles, running for 7, 4, and 2 minutes respectively each time, and finally run Mode 1 for 7 minutes, for a total of 33 minutes. The total irrigation volume is 7.9 cubic meters per mu, among which the irrigation volume with added oxalic acid accounts for 24.2% of the total irrigation volume; the oxalic acid content in the irrigation water with added oxalic acid is 1.30 g / L, which is 11.2 times the calcium ion content in conventional irrigation water; the amount of oxalic acid used is 2.5 kg per mu; the amount of potassium dihydrogen phosphate used is 2.7 kg per mu.

[0055] For the control treatment, run in the order of Mode 1, Mode 5, and Mode 4 in 2 cycles, running for 7, 4, and 2 minutes respectively each time, and finally run Mode 1 for 7 minutes, for a total of 33 minutes. The total irrigation volume is 7.9 cubic meters per mu, and the amount of potassium dihydrogen phosphate used is 2.7 kg per mu.

[0056] Experimental Example 3

[0057] The device for applying oxalic acid during the growth period of greenhouse cucumbers and the two cucumber treatments are the same as those in Experimental Example 1.

[0058] Intermittent, low-dose, and periodic irrigation application of oxalic acid during the growth period of greenhouse cucumbers:

[0059] On the 60th day after the autumn cucumber seedlings were planted in Experimental Example 1, continue to carry out intermittent irrigation with oxalic acid. The oxalic acid concentration in the oxalic acid solution pool 3 is 125 g / L; the concentration of potassium dihydrogen phosphate in the phosphorus-containing fertilizer pool 4 is 135 g / L; other parameters of the irrigation device are the same as those in Experimental Example 1.

[0060] For the treatment with oxalic acid, it is cycled 2 times in the order of Mode 1, Mode 2, Mode 4, and Mode 5, running for 4, 4, 2, and 4 minutes respectively each time, and finally Mode 1 runs for 4 minutes, with a total running time of 32 minutes. The total irrigation volume is 7.7 cubic meters per mu. Among them, the irrigation volume with added oxalic acid accounts for 25.0% of the total irrigation volume; the oxalic acid content of the irrigation water with added oxalic acid is 1.30 g / L, which is 11.2 times the calcium ion content in conventional irrigation water; the oxalic acid dosage is 2.5 kg per mu; the dosage of potassium dihydrogen phosphate is 2.7 kg per mu.

[0061] For the control treatment, it is cycled 2 times in the order of Mode 1, Mode 4, and Mode 5, running for 8, 2, and 4 minutes respectively each time, and finally Mode 1 runs for 4 minutes, with a total running time of 32 minutes. The total irrigation volume is 7.7 cubic meters per mu, and the dosage of potassium dihydrogen phosphate is 2.7 kg per mu.

[0062] On the 70th and 80th days after cucumber transplantation, repeat the practices on the 60th day after cucumber transplantation. For the treatment with oxalic acid, including the application of oxalic acid on the 40th and 50th days after cucumber transplantation, oxalic acid is applied a total of 5 times; each time when applying oxalic acid (1.5 - 2.5 kg per mu) for irrigation, or 2 minutes after that, apply phosphate fertilizer in the form of ammonium dihydrogen phosphate or potassium dihydrogen phosphate (P 2 O 5 ) 1.6 kg per mu; a total of 8.0 kg of phosphate fertilizer (P 2 O 5 ) is applied throughout the cucumber growth period, which is 55% less than the recommended dosage of phosphate fertilizer (P 2 O 5 ) (18 kg per mu) for the target cucumber yield (9000 kg per mu).

[0063] Compared with the control treatment, the single - time phosphate fertilizer dosage and the frequency of phosphate application in the treatment with oxalic acid are the same. However, on the fifth day after the third and fifth applications of oxalic acid, the content of water - soluble inorganic phosphorus (the form of phosphorus available to roots) in the surface soil (0 - 5 cm) increased from 7.0 ± 0.6 and 7.3 ± 1.3 mg / kg to 10.1 ± 0.7 and 9.6 ± 0.9 mg / kg respectively (increased by 44.3% and 31.5% respectively). The cucumber yield throughout the growth period increased from 7600 kg per mu to 8800 kg per mu (a 15.7% increase), and it is only 2.3% different from the target yield (9000 kg per mu) without reducing the application of phosphate fertilizer. Intermittent, low - dose, and periodic irrigation with oxalic acid achieved a good effect of reducing phosphate application and maintaining stable yield in greenhouse cucumbers.

Claims

1. An irrigation method for improving the biological availability of phosphorus in the root zone soil during the growth period of crops, characterized in that: During the growth period of the crops, oxalic acid is applied to the root zone soil of the crops by intermittent, low-dose, and periodic irrigation, and a phosphorus-containing water-soluble fertilizer is applied by irrigation simultaneously or within 0-30 minutes afterwards, continuously improving the biological availability of exogenous and endogenous phosphorus in the root zone soil.

2. The irrigation method for improving the biological availability of phosphorus in the root zone soil during the growth period of crops according to claim 1, characterized in that: The intermittent irrigation application of oxalic acid is to add oxalic acid once or multiple times during each irrigation process, and the proportion of the irrigation duration of the oxalic acid addition period in the total irrigation duration < 30%, or the proportion of the irrigation amount of the oxalic acid addition period in the total irrigation amount < 30%; the mass concentration of oxalic acid in the irrigation water during the oxalic acid addition period is more than 8 times the mass concentration of calcium ions in the irrigation water before the addition of oxalic acid.

3. The irrigation method for improving the biological availability of phosphorus in the root zone soil during the growth period of crops according to claim 1, characterized in that: The low-dose irrigation application of oxalic acid is 1-10 kg of oxalic acid per mu of soil each time.

4. The irrigation method for improving the biological availability of phosphorus in the root zone soil during the growth period of crops according to claim 1, characterized in that: The time interval for the periodic irrigation application of oxalic acid is 7-21 days, and the application frequency during the growth period of the crops is 3-9 times.

5. The irrigation method for improving the biological availability of phosphorus in the root zone soil during the growth period of crops according to claim 1, characterized in that: When the phosphorus-containing water-soluble fertilizer forms a precipitate with oxalic acid, the phosphorus-containing water-soluble fertilizer is applied by irrigation within 0-30 minutes after the irrigation application of oxalic acid; when the phosphorus-containing water-soluble fertilizer does not form a precipitate with oxalic acid, the phosphorus-containing water-soluble fertilizer is applied by irrigation simultaneously or within 0-30 minutes after the irrigation application of oxalic acid.

6. An irrigation device for implementing the irrigation method for improving the biological availability of phosphorus in the root zone soil during the growth period of crops according to any one of claims 1 to 5, characterized in that: It includes a conventional irrigation water tank (1), a low-calcium irrigation water tank (2), an oxalic acid solution tank (3), a phosphorus-containing fertilizer tank (4), an irrigation pump (5), an irrigation main pipe (6), an acid suction pump (7), a fertilizer suction pump (8), a conventional irrigation water valve (9), a low-calcium irrigation water valve (10), an acid suction valve (11), a fertilizer suction valve (12) and a drip irrigation tape (13). The water inlet of the irrigation pump (5) is respectively connected to the conventional irrigation water tank (1) and the low-calcium irrigation water tank (2), and a conventional irrigation water valve (9) is provided on the pipeline between the irrigation pump (5) and the conventional irrigation water tank (1), and a low-calcium irrigation water valve (10) is provided on the pipeline between the irrigation pump (5) and the low-calcium irrigation water tank (2). Or, the water inlet of the irrigation pump (5) is respectively connected to one end of the conventional irrigation water valve (9) and the low-calcium irrigation water valve (10), and the other ends of the conventional irrigation water valve (9) and the low-calcium irrigation water valve (10) are respectively connected to the conventional irrigation water tank (1) and the low-calcium irrigation water tank (2). The water outlet of the irrigation pump (5) is connected to one end of the irrigation main pipe (6), and the other end of the irrigation main pipe (6) is connected with a drip irrigation tape (13). The water inlets of the acid suction pump (7) and the fertilizer suction pump (8) are respectively connected to the oxalic acid solution tank (3) and the phosphorus-containing fertilizer tank (4), and the water outlets of the acid suction pump (7) and the fertilizer suction pump (8) are respectively connected to the irrigation main pipe (6) through an acid suction pipeline and a fertilizer suction pipeline, and an acid suction valve (11) is provided on the acid suction pipeline, and a fertilizer suction valve (12) is provided on the fertilizer suction pipeline. Or, the water outlet of the acid suction pump (7) is connected to one end of the acid suction valve (11), the water outlet of the fertilizer suction pump (8) is connected to one end of the fertilizer suction valve (12), and the other ends of the acid suction valve (11) and the fertilizer suction valve (12) are respectively connected to the irrigation main pipe (6) through an acid suction pipeline and a fertilizer suction pipeline.

7. The irrigation device for the irrigation method of improving the biological availability of phosphorus in the root zone soil during the crop growth period according to claim 6, characterized in that: The water inlet of the irrigation pump (5) is communicated with the first interface of a tee A (14), the second interface and the third interface of the tee A (14) are respectively connected to the conventional irrigation water tank (1) and the low-calcium irrigation water tank (2), the conventional irrigation water valve (9) is provided on the pipeline between the tee A (14) and the conventional irrigation water tank (1), and the low-calcium irrigation water valve (10) is provided on the pipeline between the tee A (14) and the low-calcium irrigation water tank (2). Or, the water inlet of the irrigation pump (5) is communicated with the first interface of a tee A (14), the second interface of the tee A (14) is connected to one end of the conventional irrigation water valve (9), the other end of the conventional irrigation water valve (9) is connected to the conventional irrigation water tank (1), the third interface of the tee A (14) is connected to one end of the low-calcium irrigation water valve (10), and the other end of the low-calcium irrigation water valve (10) is connected to the low-calcium irrigation water tank (2).

8. The irrigation device for the irrigation method of improving the biological availability of phosphorus in the root zone soil during the crop growth period according to claim 6, characterized in that: a tee B (15) is provided between the acid suction pipe and the fertilizer suction pipe and the irrigation main pipe (6), the first interface of the tee B (15) is connected to the irrigation main pipe (6), the second interface of the tee B (15) is connected to the water outlet of the acid suction pump (7) through the acid suction pipe and an acid suction valve (11) is arranged on the acid suction pipe, the third interface of the tee B (15) is connected to the water outlet of the fertilizer suction pump (8) through the fertilizer suction pipe and a fertilizer suction valve (12) is arranged on the fertilizer suction pipe; or, the first interface of the tee B (15) is connected to the irrigation main pipe (6), the second interface of the tee B (15) is connected to one end of the acid suction valve (11) through the acid suction pipe, the other end of the acid suction valve (11) is connected to the water outlet of the acid suction pump (7), the third interface of the tee B (15) is connected to one end of the fertilizer suction valve (12) through the fertilizer suction pipe, and the other end of the fertilizer suction valve (12) is connected to the water outlet of the fertilizer suction pump (8).

9. The irrigation device for the irrigation method of improving the biological availability of phosphorus in the root zone soil during the crop growth period according to claim 6, characterized in that: the irrigation device includes five operation modes, Mode 1, open the conventional irrigation water valve (9), the irrigation pump (5) is powered on, and conventional irrigation water is irrigated; Mode 2, the conventional irrigation water valve (9) and the acid suction valve (11) are opened simultaneously, the irrigation pump (5) and the acid suction pump (7) are powered on simultaneously, and oxalic acid is applied during the conventional irrigation water irrigation; Mode 3, the conventional irrigation water valve (9), the acid suction valve (11) and the fertilizer suction valve (12) are opened simultaneously, the irrigation pump (5), the acid suction pump (7) and the fertilizer suction pump (8) are powered on simultaneously, and oxalic acid and phosphorus-containing fertilizer are applied during the conventional irrigation water irrigation; Mode 4, open the low-calcium irrigation water valve (10), the irrigation pump (5) is powered on, and low-calcium irrigation water is irrigated; Mode 5, the conventional irrigation water valve (9) and the fertilizer suction valve (12) are opened simultaneously, the irrigation pump (5) and the fertilizer suction pump (8) are powered on simultaneously, and phosphorus-containing fertilizer is applied during the conventional irrigation water irrigation; Run one to three cycles in the order of Mode 1, Mode 2, Mode 4 and Mode 5 or in the order of Mode 1, Mode 3 and Mode 4, and finally Mode 1 runs once, wherein the total operation duration of Mode 2 or Mode 3 accounts for less than 30% of the total operation duration of all modes, and the operation duration of Mode 4 meets the requirement of flushing the residual oxalic acid in the irrigation device.

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