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Title: A rapid technique for prediction of nutrient release from controlled release fertilizers

item Wang, S
item Alva, Ashok
item Li, Y
item Zhang, M

Submitted to: Open Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2011
Publication Date: 9/1/2011
Citation: Wang, S.S., Alva, A.K., Li, Y.C., Zhang, M. 2011. A rapid technique for prediction of nutrient release from controlled release fertilizers. Open Journal of Soil Science. 1:40-44.

Interpretive Summary: Controlled release fertilizers are in the market with wide range of nutrient release duration to cater the needs of various crops. The label release duration is intended for release at 25 °C. Verification of label nutrient release duration by actual measurement at 25 °C is not practical because of extended released duration of these products. Hence the need to develop a rapid technique for prediction of nutrient release. This technology was based on calibration of nutrient release at 100 °C and 25 °C. Therefore, a rapid test of nutrient release at 100 °C (in 7 to 9 days) can be used to predict the nutrient release pattern and duration of the product in question at 25 °C. This study demonstrates that the nutrient release of controlled release fertilizer in the field conditions can be predicted by a quick test of nutrient release in 100 °C in water and by using the calibration developed in this study.

Technical Abstract: Nutrient release from soluble granular fertilizers can be modified by polymer coating to extend the total duration nutrient release up to 3 to 9 months and rate of release to match the nutrient requirement of the plant during the growing period. Hence these products are termed as “Controlled Release Fertilizers” (CRF). A rapid technique was developed to predict the nutrient release rate and duration at 25° C by measuring the nutrient release in water at 100° C. Polymer-coated urea (43% N) and polymer-coated N, P, K (14-14-14) fertilizer products with designated release of 3 to 6 months were used in this study. At 25° C, only about 63.6 to 70.8 % of total N was released over 220 days period. At 100° C, almost 100 percent N release occurred in about 168 to 216 h. Regression equations were developed for cumulative nutrient release rate as a function of release time separately at 25° C and 100° C. Using the above regressions, the release duration for a given percent nutrient release from each of the CRF products at each temperature were calculated. These values were then used to establish a relationship between the release duration at 25° C as a function of that at 100° C for a given percent release. This relationship is useful to predict the release duration at 25° C by conducting a rapid release test at 100° C. This study demonstrated that the rapid release test at 100°C successfully predicted nutrient release rate and duration at 25° C.