No abstract

Coating fertilizer is an effective approach to increase the fertilizer use efficiency and reduce fertilizer application rate. However, only a few studies have focused on coating phosphorus (P) fertilizer, especially diammonium phosphate (DAP) due to its irregular shape and high specific surface area. A novel and low-cost strategy centered on wax-based surface modification and bio-based polymer coating was applied to improve the nutrient characteristics of coated DAP (CDAP). Regular DAP was modified with polyolefin wax and then coated with polyurethanes prepared from castor oil. Experimental results indicated that wax modification significantly decreased the specific surface area, angle of repose of DAP particles, increased the particle hardness, and then facilitated the formation of biopolymer-based coating. The CDAP from wax-modified DAP had better controlled-release performance compared with that from normal DAP. Findings from this study indicate that wax modification can be used as an effective technology to prepare highly efficient controlled-release P fertilizers.

Zinc oxide nanoparticles (ZnO NPs) have been applied widely in agriculture, and many studies were conducted to evaluate the effect of ZnO NPs on plant growth. So far, few studies have been investigated with regard to the potential effect of ZnO NPs on cereal yield formation or Zn content in grains. Herein, we used a pot experiment, which was conducted involving five dosages of Zn (0.3, 0.6, 1.2, 2.4, and 4.8 g Zn pot−1), to evaluate the impacts which ZnO NPs made in rice yield, dry matter accumulation, rice quality and grain Zn contents. The results demonstrated that ZnO NPs increased the production of grain, dry matter accumulation and particulate Zn content. Compared with control treatment, ZnO NPs application presented higher rice yield with more panicle number (4.83–13.14%), spikelets per panicle (4.81–10.69%), 1000-grain weight (3.82–6.62%) and filled grain rate (0.28–2.36%). Additionally, the dry jointing, heading and mature periods, LAI, SPAD values, and photosynthetic potentials of ZnO NPs were all significantly higher relative to treatment without ZnO NPs. The more photosynthetic substances and higher dry matter accumulated in the whole rice growing stage resulted in higher rice grain yield. Furthermore, ZnO NPs increased brown rice rate, milled rice rate, head rice rate, chalkiness size, chalkiness grain rate, chalkiness degree, amylose content and protein content, improving rice processing and appearance qualities. For the Zn nutrition in rice grain, ZnO NPs application significantly increased the Zn content of edible polished rice and promoted the relocation of Zn from the aleurone layer. This study effectively demonstrated that ZnO NPs could be a potential high-performed fertiliser for enhancing rice yield and quality.

Previous research into the synthesis of urea-formaldehyde fertilizers was mostly based on orthogonal experimental designs or single factor tests; this led to low precision for synthesis and relatively large ranges of parameters for these processes. To obtain mathematical response models for the synthesis of urea-formaldehyde fertilizers with different nitrogen release properties, a central composite design (CCD) of response surface methodology was used in our research to examine the effects of different reaction times, temperatures, and molar ratios on nitrogen insoluble in either hot or cold water. Our results showed that nitrogen insoluble in cold or hot water from urea-formaldehyde fertilizers were mainly affected by urea: formaldehyde molar ratios. Also, quadratic polynomial mathematical models were established for urea-formaldehyde. According to the models, the optimal process parameters which maximize cold-water-insoluble nitrogen and minimize hot-water-insoluble nitrogen for the synthesis of urea formaldehyde were as follows urea: formaldehyde molar ratio was 1.33, reaction temperature was 43.5 °C, and reaction time was 1.64 h. Under these conditions, the content of cold-water-insoluble nitrogen was 22.14%, and hot-water-insoluble nitrogen was 9.87%. The model could be an effective tool for predicting properties of urea-formaldehyde slow release fertilizers if the experimental conditions were held within the design limits.

A novel, eco-friendly, water-soluble, slow-release nitrogen fertilizer was developed to enhance water solubility and nitrogen use efficiency. A test was performed to determine the interactive effects of process parameters using a central composite design and response surface methodology. The quadratic polynomial mode for slow-release nitrogen was determined and yielded differences (p < 0.01). The soluble, slow-release nitrogen fertilizers were analyzed using nuclear magnetic resonance, and the release characteristics of soil nitrogen from the fertilizer at 25 °C were also determined. The effects of the fertilizer on plant growth were determined using rape (Brassica campestris L.) outdoors. Conversion rates from the fertilizer to inorganic nitrogen were 30.0, 52.2, and 60.0% at 7, 24, and 40 days, respectively. This soluble, slow-release nitrogen fertilizer resulted in increased yields and nitrogen use efficiencies in rape plants compared with a standard urea fertilizer. The yields of rape plants treated with a mixture of the fertilizer and urea (BBW100%) were significantly higher than all of the other treatments. When the nitrogen application rate was reduced by 20%, the resulting "SSNF80%" and "BBW80%" treatments produced nearly the same yields as "UREA100%". Nitrogen use efficiencies for treatments with the study fertilizer ("SSNF") and the mixture bulk blend fertilizer ("BBW") were significantly higher than that with urea ("UREA") treatment by 37−52 and 42−43%, respectively. Hence, the fertilizer showed great potential for improving the production of rape and possibly other crops.