Comparison of optical sensors in assessing the nitrogen (N) status in corn

Abstract

Nitrogen (N) plays a key role for optimal plant growth and, in particular, for profitable crop production. Optimal N management using optical sensors can provide a rapid assessment of a crop N status. Therefore, this study aimed at comparing the efficiency of two chlorophyll meters in assessing the N status in corn plants when using an economical optimum dose of nitrogen under variable rate application. To do so, a field experiment using a randomized block design with 5 treatments and 5 replicates was carried out in Januária-Brazil (15º 28’ 55’’ S, 44º 22’ 41’’ W; 474 m) in 2018. Treatments consisted of comparing the pre-fixed N fertilization system with three strategies of variable rate N application using different thresholds of the nitrogen sufficiency index (NSI) in the V4, V8, V10, and V14 vegetative stages. As a result, both chlorophyll meters were capable of detecting the need for N application and differentiating between the plants that received or did not receive N application. In addition, readings from both sensors were highly correlated (> 0.92) from the V6 to the V18 stage. Lastly, both chlorophyll meters were able to identify the crop development variability and could be a suitable tool to monitor the nutritional status and for guiding N fertilization in corn crops.