METHOD FOR PHOTOCATALYTIC FOLIAR FERTILIZATION

Abstract

The invention discloses a photocatalytic foliar fertilization method, relating to agriculture technology. To be specific, the solution containing photocatalysts and polyols is sprayed on the leaves of crops to provide nitrogen fertilizer under sunlight; the photocatalysts are nanocatalysts responding to the sunlight spectrum, of which the conduction band position is lower than −0.092 V(vs NHE); the mass concentration of photocatalysts in the solution is 100˜2000 mg/L, and the volume fraction of polyols accounts for 1%˜20%. In the invention, with the introduction of hole sacrificial agents to constrain the annihilation of photogenerated carriers, the electrons can be generated over the catalysts under sunlight and then react with dinitrogen to form ammonia as nitrogen fertilizer on the leaves of crops. This method has no demand for extra supplementation of nitrogenous fertilizer. Besides, it improves the utilization rate of nitrogen with a simple, secure and convenient fertilization.

Claims

1. A method for photocatalytic foliar fertilization comprising the step of spraying a solution containing photocatalysts and hole sacrificial agents on leaves of crops to supply nitrogen fertilizer under sunlight; wherein the photocatalysts are nanocatalysts responding to the sunlight spectra, and the potential of conduction band for the photocatalysts should be lower than −0.092 V (vs NHE); wherein the hole sacrificial agents are polyols; wherein the mass concentration of the photocatalysts in the solution is 100-2000 mg/L; wherein the volume fraction of the polyols accounts for 1%˜20% in the solution.

2. The method for photocatalytic foliar fertilization of claim 1, wherein the mass concentration of photocatalysts in the solution is 250˜1000 mg/L, and the volume fraction of the polyols accounts for 2.5%˜10% in the solution.

3. The method for photocatalytic foliar fertilization of claim 1, wherein the nanocatalysts comprise one or more of vacancy-defected catalysts, non-metal doped catalysts, metal ion doped catalysts, and heterojunction catalysts.

4. The method for photocatalytic foliar fertilization of claim 3, wherein the vacancy-defected catalysts include nitrogen-defected g-C.sub.3N.sub.4 and oxygen-defected ZnO; the non-metal doped catalysts include N doped TiO.sub.2 and O doped g-C.sub.3N.sub.4; the metal ion doping catalysts include Fe doped TiO.sub.2 and Cu doped ZnO; the heterojunction catalysts include ZnO-reduced graphene oxide and g-C.sub.3N.sub.4—TiO.sub.2.

5. The method for photocatalytic foliar fertilization of claim 1, wherein the polyols comprised one or more of ethylene glycol, propylene glycol, glycerol, butanediol, butanetriol and pentanediol.

6. The method for photocatalytic foliar fertilization of claim 1, wherein the solution with the polyol volume fraction of 1%˜20% is additionally sprayed periodically, and the interval ranges from 15 to 30 days.

7. The method for photocatalytic foliar fertilization of claim 6, wherein the volume fraction of the polyols in additional solution is 2.5%˜10%.

8. The method for photocatalytic foliar fertilization of claim 1, wherein the edible parts of selected crops exclude leaves and the selected crops includes eggplant, white radish, carrot, sweet potato, potato, yam, tomato, peanut, sunflower, chili and soybean.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0038] In order to further clarify the objects, technical solutions, and advantages of the present invention, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on their understanding of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, and shall be covered by the protection scope of the present invention.

[0039] The raw materials used in the following illustrative embodiments are all purchased from the market, and “part” refers to part by mass.

EXAMPLE 1

Photocatalyst Preparation

[0040] 3 parts of HF solution (≥40 wt %) were added dropwise into 25 parts of tetrabutyl titanate. The mixture was stirred for 1 hour and then sealed. The mixture was put into an oven at 180° C. for 24 hours. After cooling, the sample was filtered and dried at 60° C. to obtain TiO.sub.2.

[0041] 1 part of TiO.sub.2 photocatalyst was ultrasonically dispersed in 100 parts of water, then 0.1 part of urea was added and stirred for 1 hour. The solution was sealed and moved into an oven at 120° C. for 12 hours. After cooling, the sample was filtered and dried at 60° C. to obtain N doped TiO.sub.2.

Preparation of Solution for Supplying Ammonia and Glycerol Solution

[0042] A certain amount of glycerol was dissolved in water and prepared into glycerol solution with a volume proportion of 5%. The solution for supplying ammonia was prepared by dissolving the sample (N doped TiO.sub.2) in glycerol solution with a concentration of 250 mg/L.

Theoretical Ammonia Production Rate Determination

[0043] 200 mL of the above solution for supplying ammonia was added into the reactor with a 300 W xenon lamp as simulated sunlight. Samples were taken every half hour with filtration and the concentrations of NH.sub.4.sup.+—N in the aqueous ammonia solution were measured by Nessler's reagent Spectrophotometry. The relationship curve of NH.sub.4.sup.+—N concentrations with times was drawn. The slope of the curve was the ammonia production rate and the result was shown in Table 1.

Crop Experiments:

[0044] 10 days after the field planting of tomatoes (Jinguan 58), the solution for supplying ammonia was sprayed on the leaves of tomatoes, and the glycerol solution was sprayed every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature tomatoes were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively, and the result was shown in Table 1 .

EXAMPLE 2

Photocatalyst Preparation

[0045] 3 parts of HF solution (≥40 wt %) were added dropwise into 25 parts of tetrabutyl titanate. The mixture was stirred for 1 hour and then sealed. The mixture was put into an oven at 180° C. for 24 hours. After cooling, the sample was filtered and dried at 60° C. to obtain TiO.sub.2.

[0046] 1 part of TiO.sub.2 photocatalyst was ultrasonically dispersed in 100 parts of water, then 0.4 part of FeCl.sub.2 was added and stirred for 1 hour. The solution was sealed and moved into an oven at 100° C. for 12 hours. After cooling, the sample was filtered and dried at 60° C. to obtain Fe doped TiO.sub.2

Preparation of Solution for Supplying Ammonia and Butanetriol Solution

[0047] A certain amount of butanetriol was dissolved in water and prepared into butanetriol solution with a volume proportion of 5%. The solution for supplying ammonia was prepared by dissolving the sample (Fe doped TiO.sub.2) in butanetriol solution with a concentration of 500 mg/L.

Theoretical Ammonia Production Rate Determination

[0048] The determination of ammonia production rate was the same as that in example 1, and the result was shown in Table 1.

Crop Experiments:

[0049] 10 days after the field planting of pod peppers (Tianyu 3), the solution for supplying ammonia was sprayed on the leaves of pod peppers, and butanetriol solution was sprayed every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature pod peppers were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively.

EXAMPLE 3

Photocatalyst Preparation

[0050] 7 parts of Zn(CH.sub.3COO).sub.2.9H.sub.2O and 11 parts of NaOH were added into 100 parts of water. The mixture was stirred for 1 hour. The solution was sealed and moved into an oven at 100° C. for 12 hours. After cooling, the sample was filtered and dried at 60° C. to obtain ZnO.

[0051] 0.2 part of graphene oxide was ultrasonically dispersed in 100 parts of water, then 1 part of photocatalyst ZnO was added and stirred for 1 hour. The solution was sealed and moved into an oven at 180° C. for 12 hours. After cooling, the sample was filtered and dried at 60° C. to obtain ZnO-reduced graphene oxide.

Preparation of Solution for Supplying Ammonia and Ethylene Glycol Solution

[0052] A certain amount of ethylene glycol was dissolved in water and prepared into ethylene glycol solution with a volume proportion of 6%. The solution for supplying ammonia was prepared by dissolving the sample (ZnO-reduced graphene oxide) in ethylene glycol solution with a concentration of 700 mg/L.

Theoretical Ammonia Production Rate Determination

[0053] The determination of ammonia production rate was the same as that in example 1, and the result was shown in Table 1.

Crop Experiments:

[0054] 10 days after the field planting of eggplants (Xianfeng eggplant), the solution for supplying ammonia was sprayed on the leaves of eggplants, and ethylene glycol solution was sprayed every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature eggplants were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively.

EXAMPLE 4

Photocatalyst Preparation

[0055] Nitrogen-defected g-C.sub.3N.sub.4 was prepared by calcining 0.5 part of (NH.sub.4).sub.2S.sub.2O.sub.8 and 1 part of melamine in muffle furnace at 500° C. for 120 min.

Preparation of Solution for Supplying Ammonia and Pentanediol Solution

[0056] A certain amount of pentanediol was dissolved in water and prepared into pentanediol solution with a volume proportion of 9%. The solution for supplying ammonia was prepared by dissolving the sample (nitrogen-defected g-C.sub.3N.sub.4) in pentanediol solution with a concentration of 1000 mg/L.

Theoretical Ammonia Production Rate Determination

[0057] The determination of ammonia production rate was the same as that in example 1, and the result was shown in Table 1.

Crop Experiments:

[0058] 10 days after the field planting of tomatoes (Jinguan 58), the solution for supplying ammonia was sprayed on the leaves of tomatoes, and pentanediol solution was sprayed every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature tomatoes were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively.

EXAMPLE 5

Photocatalyst Preparation

[0059] G-C.sub.3N.sub.4 was prepared by calcining melamine in muffle furnace at 500° C. for 120 min.

[0060] 1 part of g-C.sub.3N.sub.4 and 60 parts of H.sub.2O.sub.2 (10 wt %) were dispersed and mixed at 70° C. for 2 hours. The solution was sealed and moved into an oven at 140° C. for 1 hour. After cooling, the sample was filtered and dried at 60° C. to obtain O doped g-C.sub.3N.sub.4.

Preparation of Solution for Supplying Ammonia and Butanediol Solution

[0061] A certain amount of butanediol was dissolved in water and prepared into butanediol solution with a volume proportion of 10%. The solution for supplying ammonia was prepared by dissolving the sample (O doped g-C.sub.3N.sub.4) in butanediol solution with a concentration of 500 mg/L.

Theoretical Ammonia Production Rate Determination

[0062] The determination of ammonia production rate was the same as that in example 1, and the result was shown in Table 1.

Crop Experiments:

[0063] 10 days after the field planting of pod peppers (Tianyu 3), the solution for supplying ammonia was sprayed on the leaves of pod peppers, and butanediol solution was sprayed every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature pod peppers were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively.

EXAMPLE 6

Photocatalyst Preparation

[0064] 7 parts of Zn(CH.sub.3COO).sub.2.9H.sub.2O and 11 parts of NaOH were added into 100 parts of water. The mixture was stirred for 1 hour. The solution was sealed and moved into an oven at 100° C. for 12 hours. After cooling, the sample was filtered and dried at 60° C. to obtain ZnO.

[0065] 0.4 part of CuCl.sub.2 was ultrasonically dispersed in 100 parts of water, then 1 part of photocatalyst ZnO was added and stirred for 1 hour. The solution was sealed and moved into an oven at 100° C. for 12 hours. After cooling, the sample was filtered and dried at 60° C. to obtain Cu/ZnO.

Preparation of Solution for Supplying Ammonia and Propylene Glycol Solution

[0066] A certain amount of propylene glycol was dissolved in water and prepared into propylene glycol solution with a volume proportion of 5%. The solution for supplying ammonia was prepared by dissolving the sample (Cu/ZnO) in propylene glycol solution with a concentration of 800 mg/L.

Theoretical Ammonia Production Rate Determination

[0067] The determination of ammonia production rate was the same as that in example 1, and the result was shown in Table 1.

Crop Experiments:

[0068] 10 days after the field planting of eggplants (Xianfeng eggplant), the solution for supplying ammonia was sprayed on the leaves of eggplants, and propylene glycol solution was sprayed every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature eggplants were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively.

Control 1

[0069] 10 days after the field planting of tomatoes (Jinguan 58), water was sprayed on the leaves of tomatoes every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature tomatoes were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively.

Control 2

[0070] 10 days after the field planting of pod peppers (Tianyu 3), water was sprayed on the leaves of pod peppers every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature pod peppers were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively.

Control 3

[0071] 10 days after the field planting of eggplants (Xianfeng eggplant), water was sprayed on the leaves of eggplants every 15 days. The spraying time was 8:00-9:00 in the morning. Other conditions remained the same as normal. These mature eggplants were randomly selected for determinations of vitamin C, soluble sugar and soluble protein through molybdenum blue spectrophotometry, anthrone colorimetry, and coomassie brilliant blue G-250 method, respectively.

[0072] Three experimental areas were selected to conduct these experiments, each with an area of 20 m.sup.2. Each experimental or controlled trail was conducted in quintuplicate, and an averaging value was adopted as the final result, which was shown in Table 1.

[0073] The results in Table 1 showed that the supply system contain photocatalysts, polyols and water had considerable nitrogen fixation efficiency under simulated sunlight. Besides, the method for photocatalytic foliar fertilization was applied to crops, and it could be concluded that the method could generate absorbable ammonia on the leaves of crops. Comparing Examples 1-6 with Controls 1-3, the method could increase crop yield as well as enhance the content of vitamin C, soluble sugar and soluble protein. The results further verified that the method was capable of improving fruit quality of crops.

TABLE-US-00001 TABLE 1 The results of batch trails Theoretical Application on crops ammonia Soluble Soluble production rate Yield Vitamin C sugar protein (mmol/L/hour) Species (g/stock) (mg/kg, FW) (mg/g, FW) (mg/g, FW) Example 1 1.12 tomato 876 3.82 42.1 1.19 Example 2 1.87 pod pepper 443 7.11 25.1 2.31 Example 3 0.748 eggplant 784 4.25 29.5 3.26 Example 4 0.824 tomato 796 4.39 35.6 1.35 Example 5 1.68 pod pepper 517 7.47 19.7 2.74 Example 6 1.27 eggplant 691 4.63 25.9 2.79 Control 1 — tomato 421 2.54 29.4 1.02 Control 2 — pod pepper 264 4.67 15.4 1.94 Control 3 — eggplant 447 3.49 22.4 0.73