Evaluation of determination methods for nutrient release characteristics of coated controlled-release fertilizer under soil and water incubation conditions

The basic property of controlled-release fertilizer(CRF) is its release-delay of nutrients from fertilizer.A series of soil and water incubation trials were conducted to compare three methods of determining nutrient release rate and characteristics of coated fertilizer,including chemical analysis method,coated fertilizer weighting method,and total soil mineral nitrogen method.In addition,the relationship between nutrient release rates of CRF in soil and water was discussed.The results showed that each method could represent nutrient release rate of CRF in soil.Chemical method is very complicated and more suitable for study and development of coated fertilizer.On the other hand,the fertilizer nutrient weighting method is suitable for rapid online monitoring under coated fertilizer production and it is simple,rapid,reliable and inexpensive.Total soil mineral nitrogen method is applicable to evaluation of fertilizer efficiency and crop response.The nutrient release rates of CRF under soil and water conditions were comparable.There was a significant positive linear correlation between accumulative nutrient release rate of CRF in soil and that in water,and its correlation coefficient(r) was greater than 0.920.