Calibration of Nitrogen Fertilizer for Quality Protein Maize (Zea mays L.) Based on In-Season Estimated Yield using a Handheld NDVI Sensor in the Central Rift Valley of Ethiopia

Maize is one of a highly valued crop in the national diet of Ethiopians especially in southern and southeastern regions of the country; it is produces across various agro-ecologies of the country. However, its productivity is constrained by blanket application of mineral nutrients, in particular, nitrogen (N). In this study, we aimed to test site-specific nutrient management supported by precision agriculture tools can provide extension agents and farmers better ways to manage nitrogen, to increase net benefit and reduce environmental pollution. The drastic increase in N fertilizer cost, environmental pollution and increased public scrutiny have encouraged development and implementation of improved N management practices. In this context, on-farm and on-station experiment was conducted during 2014 main cropping season in the central rift valley of Ethiopia. The objective of the study was calibrating N fertilizer rate using the handheld NDVI sensor for efficient management of N to optimize grain productivity. The trials were layout in a randomized complete block design with seven levels of N fertilizer with phosphorus applied uniformly. The study evaluated the relationship between grain yield and NDVI using the handheld Green seeker sensor. The result shows that a strong nonlinear relationship (R2=0.79) were exist between NDVI values and harvest grain yield. In similarly fashion positive exponential relationship (R2=0.71) between INSEY and grain yield during vegetative growth stage six (V6) at both locations. Overall this study shows that the handheld NDVI sensor can be an indicator to better manage N fertilizer application.