Water Polishing improved controlled-release characteristics and fertilizer efficiency of castor oil-based polyurethane coated diammonium phosphate

Abstract

The production cost of controlled-release fertilizers is an important factoring limiting their applications. To reduce the coating cost of diammonium phosphate (DAP) and improve its nutrition release characteristics, the fertilizer cores were modified by water polishing with three dosages at 1, 2, and 3%. The effects of modification were evaluated in terms of particle hardness, size distribution, angle of repose and specific surface area. Castor oil-based polyurethane was used as coating material for fertilizer performance evaluation. A pot experiment was conducted to verify the fertilizer efficiency of coated diammonium phosphate (CDAP) with maize. The results showed that polishing with 2% water reduced the angle of repose by 2.48-10.57% and specific surface area by 5.70-48.76%, making it more suitable for coating. The nutrient release period of CDAP was significantly prolonged by 5.36 times. Soil available phosphorous, enzyme activities, maize grain yield, and phosphorous use efficiency were all improved through the blending application of coated and normal phosphate fertilizer. This study demonstrated that water-based surface modification is a low-cost and effective method for improvement and promotion of controlled release P fertilizers. Phosphorus (P) is an essential nutrient for maintaining healthy crop growth, reproduction and yield 1-3 . However, farmers tend to apply excessive amount of P fertilizers in order to obtain high yields 4 , resulting in degradation of microbial community activity and soil tilth 5 , decrease in crop quality 6 , and varying forms of water pollution 7 . Meanwhile, P fertilizers are mainly derived from P rock, a non-renewable resource. With the increasing use of P fertilizer, the global P reserve is facing serious concerns 8 . Innovative technologies for improving the utilization efficiency and reducing the production cost of P fertilizers are urgently needed.Controlled-release fertilizers have been proved to improve the utilization efficiency of both nitrogen (N) and P fertilizer 9,10 . While much research has been conducted on controlled-release N fertilizers 11,12 , relatively much less work has focused on controlled-release P fertilizers. Chemically bound P in soil could become available to plant under certain biogeochemical conditions, serving as a natural reservoir of "slow-release" P 13 . However, the slow release characteristics of soil bound P are affected by many uncontrollable factors, such as temperature, humidity, organic acid secreted by crop roots, soil pH, and soil mineral composition [14][15][16][17] . Thus, P released under these conditions cannot fulfill the crop P demand, especially during the critical growth period. Recent research indicated that the fixed rate of soil P was closely related to the concentration of P in soil solution 18 . Coated P fertilizers have advantages over conventional P fertilizers in that the polymer coating prevents direct contact between soil and fertilizer, thus the controlled release of P promotes uptake by plants and reduces P fix...

Phosphorus Release and Adsorption Properties of Polyurethane–Biochar Crosslinked Material as a Filter Additive in Bioretention Systems

“…The leaching tendency of HB was in agreement with former research on biochar leaching properties [44] and it can be predicted that additional phosphorus would be released with further batching. However, after being crosslinked and interpenetrated by the polyurethane, the release of phosphorus from the internal biochar was prevented, as previously reported [27]. PCB's first round of phosphorus leaching accounted for 44.65-54.85% of the total released quantities and the released quantities were only in the range of 2.67-3.16% for HB.…”

“…Additionally, polyurethane, as a coating material, will prolong the nutrient release period of inner fertilizers in agriculture and reduce their leaching quantities [ 27 ]. Combined with fertilizers, polyurethane composite material has a high potential to preserve moisture and fertility for the amelioration of desertification [ 28 ].…”

Coated Diammonium Phosphate Combined With Humic Acid Improves Soil Phosphorus Availability and Photosynthesis and the Yield of Maize

“…The nutrient release curve of CDAP ( Figure 1A ) is similar to the sigmoidal nutrient uptake curve of maize ( Bender et al, 2013 ). Lu et al (2020) reported similar results pertaining to the nutrient release characteristics of CDAP that match with the nutrient uptake requirement of maize much better than the conventional P fertilizer. Based on soil available P changes during maize growth ( Figure 3A ), it is speculated that CDAP had a longer P-release period in the pot experiment than in the laboratory incubation ( Figure 1A ).…”

Comparative Transcriptome and sRNAome Analyses Reveal the Regulatory Mechanisms of Fruit Ripening in a Spontaneous Early-Ripening Navel Orange Mutant and Its Wild Type

“…We used an enzyme-linked immunosorbent assay (ELISA) [ 29 , 30 , 31 ] to determine the endogenous hormone (IAA, GA, CTK, ABA, ETH, JA, SA) contents in peel samples, and the specific operations were carried out according to the instructions of individual ELISA kit from Shanghai Heng Yuan Biological Technology Company. Each sample was assayed with three replicates.…”