Chlorophyll meter as a tool to determine the time of application of N in rice (Oryza sativa L.) – A review

Chlorophyll meter is a promising tool for adjusting the rate and time of nitrogen application for different rice fields. Chlorophyll meter measures the leaf chlorophyll content, which is closely related to the leaf N content as well as photosynthetic rate. The SPAD (Soil Plant Analysis Division) technique ensures supply of N to the crop as and when there is demand for N and has been reported to result in higher N use efficiency. Fixing the critical SPAD value for N top dressing in the rice has been discussed.