Evidence for the Ability of Active‐Optical Sensors to Detect Sulfur Deficiency in Corn

Prediction of S deficiency is difficult due to poor soil test relationship to crop response. The purpose of this article is to provide evidence that the use of an N‐sufficient area established for use as a standard for active‐optical (AO) sensor directed in‐season N application could also serve to detect S deficiency in corn ( Zea mays L.). Nitrogen rate experiments at Oakes and Arthur, ND, exhibited corn upper‐leaf yellowing in high N treatments while control treatments (0 N) were greenest. Two AO sensors were utilized to record red normalized differential vegetation index (NDVI) and red edge NDVI values. The high‐N treatment had the lowest NDVI readings, and the control treatments had the highest NDVI readings. Within 24 h, an application of gypsum containing 22 kg S ha −1 was applied. Seven days following S application, the sites were revisited. The AO sensors were again used to record red NDVI and red edge NDVI. At both sites, the high N treatment had the highest NDVI readings and the control treatment had the lowest NDVI readings. These experiments indicate that high N treatment can increase the severity of S deficiency in corn. If a lower NDVI reading is recorded in a high N application area than in the surrounding area, S deficiency may be present. Core Ideas Sulfur deficiency in corn is difficult to anticipate using soil analysis. When N availability is low, the affect of S deficiency in corn is minimized. When N availability is high, the affect of S deficiency is intensified. Active‐optical sensors can be used along with an N‐sufficient area to reveal S deficiency.