As one of the fertilizer varieties, water-soluble fertilizers have received increasing attention from the market in recent years, and the production and consumption have been increasing year by year. Due to the relatively simple production process of water-soluble fertilizers and the fact that the products are mostly fully water-soluble, the production and use of the products are more in line with the requirements of agricultural green economy development. By analyzing the issues of concern for the development of agricultural green economy and the advantages and disadvantages of water-soluble fertilizer products, the impact of water-soluble fertilizers on the development of agricultural green economy is discussed. With the continuous innovation and development of agricultural production technology in China, the product market is becoming more standardized and orderly, and the development prospects of water-soluble fertilizers in agricultural production in China will become broader.

To investigate the effects of straw incorporation combined with different water management practices on phosphorus availability in paddy soils, and to elucidate the correlations between transformation of soil available phosphorus forms and soluble organic carbon content and Fe3+/Fe2+ ratio in soil, an indoor simulated cultivation experiment is conducted. Six treatments are designed: flooding (W1), drought (W2), alternate wetting and drying (W3), flooding + straw incorporation (W1+S), drought+straw incorporation (W2+S), and alternate wetting and drying+straw incorporation (W3+S). Changes in soil available phosphorus forms, content, and fractions are analyzed during different stages of straw decomposition. The results show that straw incorporation significantly increases soil available phosphorus content, with W1+S showing the highest levels, while W2 and W3 exhibited lower values. Flooding can fully release soluble organic carbon in soil after adding straw, with W1+S achieving the highest soluble organic carbon content and W2 the lowest. A highly significant positive correlation is observed between soluble organic carbon content and available phosphorus content. Under flooding with straw incorporation, the Fe3+ from Fe-P in soil is reduced to Fe2+, accompanied by H+ release, leading to a 0.48 pH decrease compared to W1, and promotes the transformation of Ca10-P into more Ca2-P and Ca8-P in soil, significantly increasing their proportions while reducing Fe-P. Straw incorporation under flooding conditions effectively enhances phosphorus availability in paddy soils.

To evaluate the effects of three types of humic acid amendments (T, H, F) on salinealkali soils and cotton growth, a field plot experiment is conducted with application rates of 200 and 400 kg/mu (1 mu = 667 m2), using a control treatment without humic acid amendments (CK). Cotton emergence rate, agronomic traits, yield characteristics, and soil physicochemical properties before and after cultivation are measured. The results show that compared with CK, the T-type humic acid amendment at 400 kg/mu increases cotton emergence rate, plant height, main stem leaf number, leaf area, and seed cotton yield by 32.0%, 17.7%, 18.5%, 27.0%, and 43.5%, respectively. All three amendments effectively reduced soil pH and total salt content, while significantly enhancing soil organic matter, alkali-hydrolyzable nitrogen, available potassium, Mg2+, and Ca2+ contents, and decreasing Na+ and Cl- levels. Soil organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium contents increased with higher amendment application rates. All three amendments improved cotton growth and ameliorated saline-alkali soils, with the T-type exhibiting the most pronounced effects.

To determine the optimal top dressing frequency for wheat under integrated water and fertilizer management, a field plot experiment is conducted with consistent fertilizer application rates and types. The treatments include traditional flood irrigation as the control (CK) and five integrated water and fertilizer treatments with top dressing frequencies of 1, 2, 3, 4, and 5 times (T1-T5). The effects on wheat population density, yield components, and economic benefits are evaluated. The results show that the pre-winter population density of wheat under CK is significantly higher than that of T1-T5, while post-winter population density of wheat in T1-T5 is significantly higher than CK. Yield components in T1-T5 outperform CK, though thousand-grain weight shows no significant differences. T3 achieves the highest spike number per mu (9.4% increase over CK), T5 exhibits the maximum grains per spike (10.6% increase over CK), and T4 delivers the highest theoretical yield (16.9% increase over CK) and net profit (12.6% increase over CK). Under experimental conditions, four top dressing applications under integrated water and fertilizer management prove optimal for wheat production.

Soybean-maize strip composite planting is an intensive and efficient planting mode, which has significant advantages in improving land use efficiency, reducing production costs, and increasing the stress resistance of the planting system. The key points of efficient application technology of fertilizer and water in soybean-maize strip composite planting in southwestern Shandong region, as well as the technical advantages and existing problems of composite planting mode, are summarized. The forward follow-up promotion suggestions are proposed as well.

In order to investigate the effects of blending common urea with nano magnesium hydroxide on winter wheat yield and soil nitrate nitrogen content, a field plot experiment is conducted. The experiment included five treatments: conventional fertilization control (CK), common urea (T1), common urea+0.3% (mass fraction, the same below) nano magnesium hydroxide (T2), common urea+0.4% nano magnesium hydroxide (T3), and common urea reduced application of 20%+0.3% nano magnesium hydroxide (T4). The results show that the yield of winter wheat treated with the mixture of common urea and nano magnesium hydroxide is higher than that treated with CK. When the amount of nano magnesium hydroxide added is the same, the yield of winter wheat increases with the increase of common urea application. At the same application rate of common urea, the yield of winter wheat does not increase with the increase of nano magnesium hydroxide addition, indicating that adding 0.3% nano magnesium hydroxide is suitable in this region. There is no significant difference in wheat yield between T4 treatment and T1 treatment, indicating that the mixture of common urea and nano magnesium hydroxide can reduce the amount of nitrogen fertilizer applied. Compared with CK and T1 treatments, the blending of common urea and nano magnesium hydroxide reduced the nitrate nitrogen content in the 0-100 cm soil to varying degrees.

A pot experiment is conducted to investigate the effects of compound fertilizers with different sulfur chlorine ratios on the growth and development of potatoes. The experiment used pure sulfur based compound fertilizer treatment as the control (CK). The sulfur to chlorine ratios of the compound fertilizers in T1-T6 treatments are 1.5∶1, 2.5∶1, 3.5∶1, 4.5∶1, 5.5∶1, and 6.5∶1, respectively. The plant height, stem diameter, chlorophyll relative content (SPAD value), aboveground fresh weight, single potato weight, and quality of potatoes are measured. The results show that compared with CK treatment, when the sulfur chlorine ratio is greater than 2.5∶1, it has a promoting effect on potato plant height, stem thickness, SPAD value, aboveground fresh weight, single potato weight, and quality indicators. Under experimental conditions, T2 treatment has an ideal effect on promoting the growth and development of potatoes.

Polyaspartic acid (PASP), a biodegradable and environmentally friendly material, enhances fertilizer use efficiency through chelating with nutrient ions, improving nutrient retention capacity in soil, and reducing nutrient loss. Modified PASP features lengthened molecular side chains and an increased number of chelating groups, leading to superior performance in agricultural production. Field experiments show that application of fertilizer containing modified PASP significantly increases both yield and economic benefits of the three major staple crops: rice, maize, and wheat. Among them, rice has a yield increase exceeding 12.15% and a net benefit increase of over 255.09 yuan/mu (1 mu = 667 m2); Maize has a 10.40% yield increase under a 20% reduction in fertilizer input; Wheat shows a 16.65% yield increase and a net benefit increase of 222.83 yuan/mu. Future research should focus on applying fertilizers containing modified PASP to diverse crops and at various growth stages to facilitate industrial-scale adoption.

In order to investigate the effects of the combined application of water-soluble fertilizer containing humic acid and pesticide on the control effect of flue-cured tobacco bacterial wilt and agronomic traits, a field plot experiment is carried out. Seven treatments are set in the experiment. The treatment without the application of water-soluble fertilizer containing humic acid and pesticide is used as the control (CK). Treatments T1, T3 and T5 are applied with 15.0, 22.5 and 30.0 L/hm2 of water-soluble fertilizer containing humic acid, respectively, and combined application of 63 g/hm2 of the active ingredient of 12% prothioconazole-kasugamycin suspension. And treatments T2, T4 and T6 are applied with 15.0, 22.5 and 30.0 L/hm2 of water-soluble fertilizer containing humic acid, respectively, and combined application of 281 g/hm2 of the active ingredient of 37.5% copper hydroxide suspension. The results show that treatments T1 to T6 all can improve the agronomic traits of flue-cured tobacco such as plant height, stem circumference, fresh leaf weight, and leaf expansion degree. The combined application of humic acid and pesticide has a synergistic effect on the control of bacterial wilt. Among them, the control effect of treatment T5 on bacterial wilt is significantly higher than that of other treatments. The control effect of 12% prothioconazole-kasugamycin suspension on bacterial wilt is better than that of 37.5% copper hydroxide suspension. The combined application of humic acid and pesticide has a significant effect on improving the agronomic traits of flue-cured tobacco and controlling bacterial wilt, providing a new way for the comprehensive control of flue-cured tobacco bacterial wilt.

In order to guide the scientific fertilization of facility celery and verify its effect on increasing yield and income, a plot experiment is conducted on foliar spraying of water-soluble fertilizer containing humic acid on facility celery. The experiments use conventional fertilization as the control (CK) treatment, and set up two foliar spraying treatments: spraying water (T1) and spraying water-soluble fertilizer containing humic acid (T2). The growth indicators, quality indicators, and yield of celery are measured respectively. The results show that the plant height, number of leaves per plant, number of tillers per plant, and weight per plant of T2 treatment are superior to those of CK and T1 treatments. Compared with CK and T1 treatments, the nitrate content in celery treated with T2 decreased by 14.50% and 6.85%, while the vitamin C content increased by 21.88% and 18.18%, respectively. The celery yield of T2 treatment is significantly higher than that of CK and T1 treatments, and better economic benefits can be obtained.

To solve the problem of the continuous increase in the stockpile of phosphogypsum produced as a byproduct in wet process phosphoric acid production, phosphogypsum is purified and used as a raw material to produce secondary-element soil conditioner. The process flow of producing secondary-element soil conditioner and product quality indicators are introduced. A field plot experiment is conducted using potatoes as the research object, with single application of chemical fertilizer as the control (CK) treatment, and the combination of chemical fertilizer and secondaryelement soil conditioner (T treatment). The results show that compared with CK treatment, T treatment increases potato yield by 11.51% and economic benefits by 28.65%. The use of purified phosphogypsum as a source for the production of secondary-element soil conditioner not only helps alleviate the problem of increasing phosphogypsum storage, but also turns waste into treasure and broadens the utilization of phosphogypsum.

Wet process purification of phosphoric acid and industrial grade urea are used as raw materials. Through orthogonal experiments, the effects of urea to phosphoric acid molar ratio, wet process purification of phosphoric acid impurity coefficient, pre-polymerization temperature, prepolymerization time, curing temperature, curing time and other factors on the average polymerization degree, P2O5 and N content of ammonium polyphosphate are studied. The results show that the optimal process conditions are when the molar ratio of urea to phosphoric acid of 1.8∶1, wet purification phosphoric acid impurity coefficient of 0.003 84, pre-polymerization temperature of 145 ℃, prepolymerization time of 17 min, curing temperature of 235 ℃, and curing time of 2 h. Under optimal process conditions, the obtained ammonium polyphosphate product is a white solid, meeting the requirements of Class Ⅱ first-class products in the industry standard " Ammonium Polyphosphate for Industrial Use" (HG/T 2770—2020).

Due to the high content of organic matter in weathered coal and differences in physical properties depending on the place of origin, the repeatability of the measurement results is not ideal when using the potassium dichromate oxidation method in the industry standard " Organic Fertilizer" (NY/T 525—2021) to determine the organic matter content in weathered coal. An experimental study is conducted on the influence of sample particle size, moisture content, sample weight, and measurement conditions on the determination of organic matter content in weathered coal from Xinjiang and Inner Mongolia. The results show that after crushing weathered coal through a 0.200 mm sieve and drying to an air dry state, controlling the sample weight to 0.1-0.2 g (organic carbon mass ≤ 80 mg) and shaking the triangular flask every 5 minutes during the oxidation process can accurately determine the organic matter content in weathered coal. The maximum absolute difference of parallel measurement results is ≤ 0.7%, which meets the requirements of NY/T 525—2021, and the organic matter mass fraction measured by the improved method is 7.9% to 9.1% higher than that measured by the method in NY/T 525—2021, indicating that the improved method has a more complete oxidation of organic matter in weathered coal.

The sample is dissolved in hydrochloric acid-nitric acid (3+1) mixed acid, and the content of cadmium and chromium in fertilizer is simultaneously determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that the mass concentration of cadmium has a linear relationship (r>0.999) with the corresponding emission spectral intensity in the range of 0.05-0.80 g/mL, with detection limit and quantification limit of 0.203 and 0.678 g/L, respectively. The mass concentration of chromium is linearly related to the corresponding emission spectral intensity in the range of 0.50-4.00 g/mL (r>0.999), with detection limit and quantification limit of 0.250 and 0.833 g/L, respectively. The spiked recovery rate of the two elements are 96.0% and 99.2% and the relative standard deviations of 1.7% and 2.0%, respectively. Compared to atomic absorption spectrometry, ICP-AES method has advantages in accuracy, detection efficiency, and safety, which can provide reliable technical support for the rapid detection of heavy metal content in fertilizer.

Atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) are employed to determine the chromium content in fertilizer. Method ological evaluations are conducted in terms of limit of detection, precision, and the spiked recovery rates. The results show that the limit of detection for AAS is 20 g/L, with a relative standard deviation (RSD) of 0.92%-1.38% and the spiked recovery rate of 95.35%-95.80%. For ICP-AES, the limit of detection is 10 g/L, with an RSD of 0.35%-0.86% and the spiked recovery rate of 96.60%-97.60%. Both methods can accurately determine the content of heavy metal chromium in fertilizers.

A method for determining the content of polyglutamic acid in water-soluble fertilizer using an ultra-high speed fully automatic amino acid analyzer is proposed. Water-soluble fertilizer containing polyglutamic acid is respectively subjected to hydrolysis treatment and extraction with ultrapure water. Under the selected instrument operating conditions, a single point external standard method is used to measure the content of hydrolyzed glutamic acid and free glutamic acid using a ultrahigh speed fully automatic amino acid analyzer. The difference between the two is the content of polyglutamic acid. The detection limit of the method is 0.004 8 nmol/mL, the relative standard deviation (n=10) of the measurement results is 0.68% to 3.73%, and the ratio of the measured value to the actual value is 96.2% to 106.0%.