Prediction of nitrogen release from sigmoid-type controlled release fertilizers in greenhouse production of strawberry and cucumber

Dear Editor,The increased demand for economic and environmental benefits with the application of controlled release fertilizers（CRFs）has prompted the need for simple and viable prediction of controlled nitrogen release（CNR）.Sigmoid pattern CRFs（SCRFs）has different release mechanisms and coating processes from parabolic pattern CRFs（PCRFs）.The CNR rate of an SCRF can be very slow at low temperatures;much more time is needed to release the same quantity of nutrients as conventional fertilizers.