Urease inhibitors technologies as strategy to mitigate agricultural ammonia emissions and enhance the use efficiency of urea-based fertilizers

Experiments were conducted to evaluate the stability and degradation of NBPT under storage conditions and to quantify urease activity, ammonia losses by volatilization, and agronomic efficiency of urea treated with different urease inhibitors, measured in the field. Experiments included urea treated with 530 mg NBPT kg-1 (UNBPT) in contact with six P-sources (monoammonium phosphate-MAP; single superphosphate; triple superphosphate; P-Agrocote; P-Phusion; P-Policote), with two P-concentrations (30; 70%); the monitoring four N-technologies (SoILC; Limus; Nitrain; Anvol); and the application of conventional urea (UGRAN) or urea treated with urease inhibitors as topdressing in three maize fields, at three N rates. It is concluded that: the mixture of UNBPT and P-fertilizers is incompatible. When MAP granules were coated to control P-release (P-Agrocote), the degradation of NBPT was moderate (approximately 400 mg kg-1 at the end of the storage test). SoILC and Limus solvent technologies extended the NBPT half-life by up to 3.7 and 4.7 months, respectively. Under field, each inhibition technology reduced urease activity, and lowered the intensity of ammonia emission compared to UGRAN by 50-62%. Our results show that the concentration of NBPT is reduced by up to 53.7% for mixing with phosphates. In addition, even with coatings, the storage of mixtures of urea with NBPT and phosphates should be for a time that does not reduce the efficiency of the inhibitor after application, and this time under laboratory conditions was 168 h. The reduction of NBPT concentration in urea is reduced even in isolated storage, our results showed that the half-life time is variable according to the formulation used, being 4.7, 3.7, 2.8 and 2.7 days for Limus, SoILC, Nitrain and Anvol, respectively. The results of these NBPT formulations in the field showed that the average losses by volatilization in the three areas were: 15%, 16%, 17%, 19% and 39% of the N applied, for SoILC, Anvol, Nitrain, Limus and urea, respectively. The rate of nitrogen application affected all agronomic variables, with varied effects in Ingaí. Even without N, yields were higher than 9200 kg ha-1 of grains. The increase in nitrogen rates resulted in linear increases in production and N removal in Luminárias and Ingaí, but in Lavras, production decreased above 95.6 kg ha-1 of N. The highest production in Lavras (13,772 kg ha-1 of grains) occurred with 100 kg ha-1 of N. The application of Anvol reduced the removal of N in Ingaí.

Sulfate supply decreases barium availability, uptake, and toxicity in lettuce plants grown in a tropical Ba-contaminated soil

Barium (Ba) is a non-essential element that can cause toxicity in living organisms and environmental contamination. Plants absorb barium predominantly in its divalent cationic form Ba2+. Sulfur (S) can decrease the availability of Ba2+ in the soil by causing its precipitation as barium sulfate, a compound known for its very low solubility. The objective of this study was to evaluate the effect of soil sulfate supply in soil Ba fractions, as well as on plant growth, and Ba and S uptake by lettuce plants grown in artificially Ba-contaminated soil under greenhouse conditions. The treatments consisted of five Ba doses (0, 150, 300, 450, and 600 mg kg-1 Ba, as barium chloride) combined with three S doses (0, 40, and 80 mg kg-1 S, as potassium sulfate). The treatments were applied to soil samples (2.5 kg) and placed in plastic pots for plant cultivation. The Ba fractions analyzed were extractable-Ba, organic matter-Ba, oxides associated-Ba, and residual-Ba. The results indicate that the extractable-Ba fraction was the main one responsible for Ba bioavailability and phytotoxicity, probably corresponding to the exchangeable Ba in the soil. The dose of 80 mg kg-1 of S reduced extractable-Ba by 30% at higher Ba doses while it increased the other fractions. Furthermore, S supply attenuated the growth inhibition in plants under Ba exposure. Thus, S supply protected the lettuce plants from Ba toxicity by reduction of Ba availability in soil and plant growth enhancement. The results suggest that sulfate supply is a suitable strategy for managing Ba-contaminated areas.

Interfaces between biodegradable organic matrices coating and MAP fertilizer for improve use efficiency

Improving phosphorus (P) use efficiency is a challenge to promote a circular economy and greening the phosphorus cycle towards planetary sustainability. The disruptive innovation for phosphate fertilizers may help to reduce some unwelcome reactions that occur to P in soils. Monoammonium phosphate (MAP) coating with biodegradable organic polymers and the addition of magnesium (Mg) - a nutrient with a synergistic effect on the uptake of P, zinc (Zn), and boron (B) - emerge as a smart strategy to applying these micronutrients uniformly in soils. The objectives of this study were: to characterize the coated-MAP with biodegradable organic polymers, quantify the diffusion and availability of P in the soil, and evaluate the corn crop nutrition and yield during two crop seasons. The treatments were: MAP, MAP coated with biodegradable organic polymer (BOP), MAP + BOP + 1.3% of Zn + 0.33% of B, and MAP + BOP + 1.76% of Mg. The laboratory tests showed that the diffusion of MAP-based fertilizers was: MOMg (7.86 mm) = MO (8.82 mm) = MAP (8.84 mm) = MOM (8.51 mm) after 432 h. Coatings did not cause delays in the P-release in water at 25 °C since more than 95% of P was released within 24 h. In the field trials, the application of Mg, Zn, and B in the MAP coating did not increase nutrient leaf concentration. In the summer crop season, grain yield increased up to the P-rates of 85 kg of P₂O₅ ha^-1, reaching the value of 6731 kg ha^-1. Physical and chemical characteristics of MAP-fertilizers tend to improve with the coatings. The addition of biodegradable organic polymers, Mg, B, and Zn, as MAP-coatings did not enhance P diffusion, release, and availability in the soil and the crop nutrition. Coated-MAP improved corn yield only in the 2^nd crop season.