A Visual Method for Calibrating Nitrogen Need, Tied to Seasonal NDVI Values in Corn.

Recent advancements in sensing technologies have assisted in determining plant and soil conditions for improving NUE. An optical active light GreenSeeker^TM sensor developed by NTech Industries, Inc., in collaboration with Oklahoma State University allows determining plant responses stimulated by N fertilization. Normalized Difference Vegetative Index (NDVI) readings were collected to estimate the Response Index (RI) and yield potential. Mid-season N rate applications were based on the predicted yield potential of the crop, and temporal N response. This sensing technology has resulted in increased farmer profit of between $20 and $25/ha^-1.  , but adoption is still limited due to the high cost of the technology.

Alternatively, visual evaluation of cereal crop growth, specifically symptoms of early season chlorosis has been used for centuries as a means of determining the need for additional N fertilizer. Simultaneous use of plant leaf color charts and NDVI values , has a potential for improving NUE world wide. The objective of this study was to establish a visual method of calibrating N need, tied to sensor based NDVI values for maize. Previous year digital pictures from the plant canopy did not show significant differences due to the overlapping of leaves. To overcome this problem, side images will be taken because N deficiency symptoms appear first in the lower leaves.