A method for precise fertilization of banana based on concentration of nitrate nitrogen in soil solution

Abstract

The application discloses a banana precise fertilization method based on nitrate nitrogen concentration in soil solution, and specific steps are as follows: collecting soil solution, immediately determining the concentration of nitrate nitrogen in the soil solution on site by ion meter, or carrying out cold storage treatment, and determining the concentration of nitrate nitrogen in the laboratory; comparing the determined concentration of nitrate nitrogen with the range of the concentration of nitrate nitrogen in the soil solution suitable for banana growth; and determining a fertilization scheme according to the comparison result. The application determines the content of nitrate nitrogen in the soil solution, takes the nitrogen level in the soil solution as a reference index for banana nitrogen fertilizer application, accurately judges the nitrogen level of banana plants, and precisely adjusts fertilization, so that the problems of large workload, serious lag and poor precision of the traditional fertilization method are solved. The application also accurately gives the range of the concentration of nitrate nitrogen in the soil solution suitable for banana growth, i.e. 70-280 mg / L ‑1 , which provides a clear basis for banana nitrogen fertilizer application.

Description

Technical Field

[0001] This invention belongs to the field of agricultural production technology, specifically relating to a method for precise fertilization of bananas based on the concentration of nitrate nitrogen in the soil solution. Background Technology

[0002] Bananas are a typical "water and fertilizer intensive" crop, requiring 623-760 kg / hm² of nitrogen fertilizer throughout their entire growth period. 2 Potassium fertilizer 748-851 kg / hm 2 Therefore, bananas require nitrogen fertilizer second only to potassium fertilizer. The rational application of nitrogen fertilizer is a key link in improving nitrogen fertilizer utilization and reducing investment and environmental problems caused by nitrogen fertilizer loss, while maintaining high and stable banana yields.

[0003] Currently, the main methods for guiding banana fertilization include empirical fertilization, fertilization based on soil testing and formulating fertilizer recommendations according to the nutrient requirements of the growth stage, fertilization based on the number of leaves, and fertilization based on leaf nutrient diagnosis. Empirical fertilization lacks scientific rigor and is prone to over-fertilization and nutrient deficiency later in the growing season. Fertilization based on soil testing and formulating fertilizer recommendations is labor-intensive, requires sophisticated equipment and highly specialized personnel, making it difficult for farmers to implement on their own. Fertilization based on leaf nutrient diagnosis is highly delayed, which is a major reason for the difficulty in its practical application and promotion. Moreover, nutrient deficiency symptoms are easily confused with disease symptoms, leading to misdiagnosis. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for precise fertilization of bananas based on the concentration of nitrate nitrogen in the soil solution, which avoids the problems of large workload, poor accuracy and strong lag in fertilization.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for precise fertilization of bananas based on the concentration of nitrate nitrogen in the soil solution, the specific steps of which are as follows:

[0007] (1) Collect soil solution and determine the concentration of nitrate nitrogen in the soil solution;

[0008] (2) The measured concentration of nitrate nitrogen was compared with the concentration range of nitrate nitrogen in the soil solution suitable for banana growth, which is 70–280 mg·L⁻¹. -1 ;

[0009] (3) Determine the fertilizer application rate based on the comparison results. When the measured nitrate nitrogen concentration is below 70 mg·L⁻¹ -1 At that time, apply 60-70 kg / hm² of nitrogen fertilizer (N). 2 When the concentration of nitrate nitrogen obtained by measurement is between 70 and 100 mg·L⁻¹ -1At that time, apply a small amount of nitrogen fertilizer (N) 30-35 kg / hm. 2 When the measured concentration of nitrate nitrogen is higher than 100 mg·L⁻¹ -1 At this time, no fertilizer is needed.

[0010] Preferably, the soil solution is soil pore water containing dissolved solutes.

[0011] Preferably, the specific steps for collecting the soil solution in step (1) are as follows:

[0012] Before planting, a soil solution collector is buried in the soil according to the depth of the main root system of the crop, and the soil solution is collected under negative pressure conditions of -60 to -80 kPa.

[0013] Preferably, when collecting the soil solution, the matric potential of the soil is -5 to -20 kPa.

[0014] Preferably, the depth is 15-20 cm.

[0015] Preferably, before collecting the soil solution, if the soil matrix potential is already at -5 to -20 kPa, the soil solution is collected directly under negative pressure conditions of -60 to -80 kPa; if the soil matrix potential is below -20 kPa, the soil is first irrigated to bring the soil matrix potential to the above range, and the soil solution is collected under negative pressure conditions of -60 to -80 kPa after 12 to 24 hours.

[0016] Preferably, the determination of the concentration of nitrate nitrogen in the soil solution in step (1) includes the following specific steps:

[0017] The concentration of nitrate nitrogen in the soil solution was measured in the field using an ion meter or by collecting the soil solution and refrigerating it, and then measured in the laboratory after refrigeration.

[0018] More preferably, the specific steps for determining the concentration of nitrate nitrogen in the soil solution are to use an ion meter to measure it on-site.

[0019] Preferably, the temperature for the refrigeration treatment is 0–4°C.

[0020] Preferably, the laboratory determination method is the phenol disulfonic acid colorimetric method or the ultraviolet spectrophotometric method.

[0021] Preferably, the specific steps for determining the suitable concentration range of nitrate nitrogen in the soil solution for banana growth are as follows:

[0022] Bananas were planted under different nitrate nitrogen concentrations, and the biomass of the aboveground and underground parts of the plants at different growth stages was measured. At the same time, the nitrogen, phosphorus, potassium, calcium and magnesium contents of the plants were measured, and the banana yield was measured at maturity. Finally, the range of nitrate nitrogen concentration in the soil solution suitable for banana growth was determined based on the highest biomass and yield, and the optimal ratio of nitrogen, phosphorus, potassium, calcium and magnesium contents in the plant.

[0023] Preferably, the steps for measuring the aboveground and underground biomass of the banana plant are as follows:

[0024] After separating the above-ground and underground parts of the plant and removing dust and soil, the plant is blanched at 100℃~110℃ for 30 minutes, and then dried at 60℃ to constant weight. The dry weight is the biomass.

[0025] Preferably, the steps for determining the total calcium and total magnesium content of the banana plant are as follows:

[0026] The plant powder was treated with a mixed acid, and then the total calcium and total magnesium content in the banana plant was determined by atomic absorption spectrophotometry.

[0027] Preferably, the mixed acid is nitric acid and perchloric acid.

[0028] Preferably, the total potassium content in the banana plant is determined by flame photometry.

[0029] Preferably, the total nitrogen content in the banana plant is determined using the Kjeldahl method.

[0030] Preferably, the total phosphorus content in the banana plant is determined using the molybdenum-antimony colorimetric method.

[0031] The present invention has the following advantages and beneficial effects compared with the prior art:

[0032] (1) This invention uses the nitrogen level in the soil solution as a reference indicator for applying nitrogen fertilizer to banana plants by measuring the nitrate nitrogen content in the soil solution. This allows for accurate assessment of the nitrogen level in banana plants and precise adjustment of fertilization, solving the problems of large workload, severe lag, and poor accuracy associated with traditional fertilization methods. Furthermore, this invention accurately provides the suitable nitrate nitrogen concentration range for banana growth in the soil solution as 70–280 mg·L⁻¹. -1 This provides a clear basis for the application of nitrogen fertilizer to bananas. When the measured nitrate nitrogen concentration is below 70 mg·L⁻¹... -1 This indicates a nitrogen deficiency in the soil, which will significantly affect plant growth, requiring immediate application of more nitrogen fertilizer; when the measured nitrate nitrogen concentration is between 70 and 100 mg / L... -1 This indicates that the soil is about to enter a nitrogen-deficient state. Timely fertilization will not affect normal plant growth. When the measured nitrate nitrogen concentration is between 100 and 280 mg / L... -1This indicates that the soil has sufficient nitrogen, plants are growing normally, and no fertilization is needed; when the measured nitrate nitrogen is higher than 280 mg·L⁻¹, the soil is considered to have sufficient nitrogen. -1 This indicates that there is excessive nitrogen fertilizer in the soil, which inhibits plant growth, and no further fertilization is needed.

[0033] (2) The fertilization method, instruments and professional requirements of the present invention are not high, the measurement method is simple, the professional requirements of the implementer are small, and it is easy for agricultural technicians or growers to carry out on their own and to promote it on a large scale.

[0034] Soil solution is not only the material basis for plant survival and growth and the primary source of crop water, but also the most direct source of plant nutrients. Negatively charged nitrate nitrogen is not easily adsorbed by negatively charged soil colloids, making it a highly available form of nitrogen in the soil, far exceeding the availability of positively charged ammonium nitrogen. Furthermore, nitrate nitrogen can dissolve in the soil solution and be absorbed by plants; therefore, its concentration directly determines the intensity of nitrogen absorption by plants. Using the concentration of nitrate nitrogen in the soil solution to guide the application of nitrogen fertilizer will be more timely and accurate. Detailed Implementation

[0035] The invention objective will be further described in detail below with reference to specific embodiments. The embodiments cannot be repeated one by one here, but the implementation of the invention is not limited to the following embodiments.

[0036] Example 1

[0037] Set N1 (0 mg·L) -1 N2 (<70 mg·L) -1 ), N3 (70~280mg·L) -1 ) and N4 (>280 mg·L -1Four nitrate nitrogen concentration levels and conventional fertilization (N5) were tested, with three replicates for each nitrate nitrogen concentration level. During the entire pot cultivation period, no nitrogen fertilizer was applied to treatments N1 and N2; treatment N3 received nitrogen four times on days 62, 85, 94, and 114, with a total nitrogen application of 5.60 g / pot; treatment N4 received nitrogen six times on days 53, 62, 73, 85, 94, and 114, with a total nitrogen application of 9.57 g / pot; treatment N5 received nitrogen four times, as basal fertilizer and top dressing (on days 30, 85, and 114), with a total nitrogen application of 6.00 g / pot. Bananas were planted in plastic pots with a diameter of 30 cm and a height of 30 cm, each pot containing 10 kg of the tested soil. The banana seedlings used were Zhanjiang pink bananas, purchased from the Guangdong Provincial Fruit and Vegetable Research Institute. The tested fertilizers were pure urea (N content 46.67%), superphosphate (P2O5 content 32.06%), and potassium chloride (K2O content 63.21%). While filling the soil, three ceramic heads with silicone tubing were evenly buried 20 cm below the soil surface. The three silicone tubing were connected by two T-joints. The outlet of the T-joints was connected to the inlet of the sample collection bottle via a silicone tubing. The outlet of the sample collection bottle was connected to an air pump via a silicone tubing. A soil tensiometer was also installed for soil moisture monitoring.

[0038] Before collecting soil solution, the soil was irrigated once to bring the soil tensiometer value to -20 kPa. Soil solution was extracted starting the next day and stored in a 4°C refrigerator. The nitrate nitrogen concentration in the soil solution was determined within 24 hours. Soil solution was extracted every 10 days and the nitrate nitrogen concentration was determined by ultraviolet spectrophotometry.

[0039] Nitrogen fertilizer was applied to ensure that the concentration of nitrate nitrogen remained within the range specified in the experimental design. After harvest, the aboveground parts and roots of the banana plants were separated, dried to constant weight, and the dry weight was measured to determine the plant biomass. The dried plants were then pulverized, and the total nitrogen, total phosphorus, total potassium, total calcium, and total magnesium contents were determined. Total nitrogen was determined using the Kjeldahl method, total phosphorus using the molybdenum-antimony colorimetric method, and total potassium using the flame photometry method. The results are shown in Table 3. For the determination of total calcium and magnesium, nitric acid-perchloric acid digestion was performed first, followed by atomic absorption spectrophotometry. The results are shown in Table 4.

[0040] Table 1 Effects of different soil solution nitrate nitrogen concentrations on apparent growth parameters of bananas

[0041]

[0042] Note: Data in the table are mean ± standard deviation, n = 3. Different lowercase letters in the same column indicate significant differences between different treatments, p < 0.05.

[0043] Table 2 Effects of different soil solution nitrogen concentrations on banana biomass

[0044]

[0045]

[0046] Note: Data in the table are mean ± standard deviation, n = 3. Different lowercase letters in the same column indicate significant differences between different treatments, p < 0.05.

[0047] Table 3. Effects of different soil solution nitrogen concentrations on nitrogen, phosphorus, and potassium uptake in different parts of banana plants.

[0048]

[0049] Note: Data in the table are mean ± standard deviation, n = 3. Different lowercase letters in the same column indicate significant differences between different treatments, p < 0.05.

[0050] Table 4. Effects of different soil solution nitrogen concentrations on calcium and magnesium uptake in different parts of banana plants.

[0051]

[0052] Note: Data in the table are mean ± standard deviation, n = 3. Different lowercase letters in the same column indicate significant differences between different treatments, p < 0.05.

[0053] Table 1-4 shows the effect of different nitrate nitrogen concentration levels in soil solutions on bananas. As can be seen from Table 1-4, the optimal range of nitrate nitrogen concentration in the soil solution for banana growth is 70–280 mg·L⁻¹. -1 Banana plants grown within this range exhibit better growth indicators and higher absorption of nitrogen, phosphorus, potassium, calcium, and magnesium compared to plants grown under conventional fertilization conditions.

[0054] Example 2

[0055] Potted bananas were planted in plastic pots with a diameter of 30cm and a height of 30cm, with 10kg of test soil in each pot. While filling the pots, three ceramic heads with silicone tubing were evenly buried 20cm below the soil surface. The three silicone tubing were connected by two T-joints. The outlet of the T-joints was connected to the inlet of a sample collection bottle via a silicone tubing, and the outlet of the sample collection bottle was connected to a vacuum pump via a silicone tubing. A soil tensiometer was also installed therefor for soil moisture monitoring.

[0056] Before collecting soil solution, the soil was irrigated once to bring the soil tensiometer value to -20 kPa. Soil solution was extracted starting the next day and stored in a 4°C refrigerator. The nitrate nitrogen concentration in the soil solution was measured within 24 hours. Soil solution was extracted on days 16, 36, 43, 51, 66, 77, 87, 97, and 107, and the nitrate nitrogen concentration in the soil solution was measured using an ion meter.

[0057] The measured nitrate nitrogen content was compared with the optimal range of soil solution nitrate nitrogen concentration for banana growth obtained in Example 1, and fertilization was adjusted accordingly. Table 5 shows that the soil solution nitrate nitrogen concentration was below 70 mg·L⁻¹ on days 43, 51, 66, and 87. -1 Therefore, urea was applied at 2g, 4g, 4g and 2g on the 48th, 71st, 91st and 110th days respectively. Nitrogen was applied 4 times during the planting period, and a total of 12g of urea was applied per pot.

[0058] Table 5. Soil solution NO3--N concentration at different times

[0059]

[0060] Comparative Example 1

[0061] At 0, 35, 70, 140, 210, 280, and 420 mg·L⁻¹ respectively -1 Potted bananas were grown at nitrogen concentration levels, with each treatment replicated five times. The planting containers were cylindrical PVC pipe pots, 16 cm in diameter and 40 cm high, filled with 10-20 mesh quartz sand to a depth of 30 cm. The nutrient solution was adjusted from 1 / 2 Hoagland nutrient solution, with all element concentrations kept the same except for nitrogen levels. The banana seedlings used were Zhanjiang pink bananas, purchased from the Guangdong Provincial Fruit and Vegetable Research Institute.

[0062] After harvest, the above-ground parts and roots of the banana plants were separated. The plants were blanched at 105℃ for 30 minutes, then dried at 60℃ to constant weight. The dry weight was measured, and the plant biomass was determined. The dried plants were pulverized, and the total potassium content was determined using flame photometry, the total nitrogen content using the Kjeldahl method, and the total phosphorus content using the molybdenum-antimony colorimetric method, as shown in Table 8. The total calcium and magnesium content were determined using atomic absorption spectrophotometry, as shown in Table 9.

[0063] Table 6. Effects of different nitrogen concentrations on apparent growth indicators of banana seedlings.

[0064]

[0065] Note: Data in the table are mean ± standard deviation, n = 3. Different lowercase letters in the same column indicate significant differences between different treatments, p < 0.05.

[0066] Table 7 Effects of different nitrogen concentrations on banana seedling biomass.

[0067]

[0068] Note: Data in the table are mean ± standard deviation, n = 3. Different lowercase letters in the same column indicate significant differences between different treatments, p < 0.05.

[0069] Table 8. Effects of different nitrogen concentrations on nitrogen, phosphorus, and potassium absorption in different parts of banana plants.

[0070]

[0071]

[0072] Note: Data in the table are mean ± standard deviation, n = 3. Different lowercase letters in the same column indicate significant differences between different treatments, p < 0.05.

[0073] Table 9. Effects of different nitrogen concentrations on calcium and magnesium absorption in different parts of bananas.

[0074]

[0075] Note: Data in the table are mean ± standard deviation, n = 3. Different lowercase letters in the same column indicate significant differences between different treatments, p < 0.05.

[0076] Table 6-9 shows the effects of different nitrate nitrogen concentrations on potted bananas in Comparative Example 1. As can be seen from Table 6-9, the optimal nitrogen concentration range for banana growth obtained through sand culture is 70–280 mg·L⁻¹. -1 The range of nitrate nitrogen concentration in the soil solution most suitable for banana growth is the same as that in Example 1, confirming the reliability of using soil solution to guide fertilization.

Claims

1. A method for precise fertilization of bananas based on the concentration of nitrate nitrogen in soil solution, characterized in that, The specific steps are as follows: (1) Collect soil solution and determine the concentration of nitrate nitrogen in the soil solution; (2) The measured concentration of nitrate nitrogen was compared with the concentration range of nitrate nitrogen in the soil solution suitable for banana growth, which is 70–280 mg•L. -1 ; (3) Determine the fertilizer application rate based on the comparison results. When the measured nitrate nitrogen concentration is below 70 mg·L⁻¹ -1 At that time, apply 60-70 kg / hm² of nitrogen fertilizer. 2 When the concentration of nitrate nitrogen obtained by measurement is between 70 and 100 mg / L -1 At that time, apply a small amount of nitrogen fertilizer, 30-35 kg / hm². 2 When the measured concentration of nitrate nitrogen is higher than 100 mg·L⁻¹ -1 At this time, no fertilizer is needed; The specific steps for collecting the soil solution in step (1) are as follows: Before planting, based on the depth of the main root system of the crop, a soil solution collector is buried in the soil and the soil solution is collected under negative pressure conditions of -60 to -80 kPa. When the soil solution was collected, the matric potential of the soil was -5 kPa.

2. The method for precise fertilization of bananas based on the concentration of nitrate nitrogen in soil solution according to claim 1, characterized in that, The soil solution is soil pore water containing dissolved solutes.

3. The method for precise fertilization of bananas based on the concentration of nitrate nitrogen in soil solution according to claim 1, characterized in that, The depth is 15-20cm.

4. The method for precise fertilization of bananas based on the concentration of nitrate nitrogen in soil solution according to claim 1, characterized in that, The specific steps for determining the concentration of nitrate nitrogen in the soil solution as described in step (1) are as follows: The concentration of nitrate nitrogen in the soil solution was measured in the field using an ion meter or by collecting the soil solution and refrigerating it, and then measured in the laboratory after refrigeration.

5. The method for precise fertilization of bananas based on the concentration of nitrate nitrogen in soil solution according to claim 4, characterized in that, The laboratory determination method is either the phenol disulfonic acid colorimetric method or the ultraviolet spectrophotometric method.

6. The method for precise fertilization of bananas based on the concentration of nitrate nitrogen in soil solution according to claim 4, characterized in that, The refrigeration treatment temperature is 0–4°C.

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