Handheld Sensor-Based NDVI Measurement as an Alternative to Destructive Sampling for Growth and Yield Assessment in Maize

The Normalized Difference Vegetation Index (NDVI) can be an indicator for plant growth response and ultimately yield to water and nitrogen (N) requirements in semi-arid region. To assess the growth and development of maize through NDVI measurements under various N and irrigation water regimes, a field trial was conducted over two consecutive years at the University of Agriculture, Faisalabad, employing a split-plot arrangement. The study involved three irrigation water regimes (IWR): normal irrigation, water deficit at the vegetative growth stage, and water deficit at the reproductive growth stage. Additionally, five N application rates (NR) were applied: 100, 150, 200, 250, and 300 kg ha⁻¹ during each study year. The canopy reflectance NDVI data was measured using a Handheld GreenSeeker at ten-day intervals. The results showed that deficit irrigation regimes reduced NDVI, with the maximum decrease observed in IWR3 during both growing seasons. The results also revealed that an increase in N fertilizer application rates led to higher values for NDVI, leaf area index (LAI), and total dry matter (TDM). A highly significant and positive correlation of LAI and TDM, was observed with NDVI under different irrigation regimes (ranging R² = 0.67 to 0.97) and N application rates (ranging R² = 0.58 to 0.97) throughout the entire growing season. Additionally, all other growth and yield parameters of maize showed a positive and significant correlation with the NDVI values. The study findings suggest that utilization of NDVI measured with a handheld GreenSeeker sensor can effectively determine the impact of irrigation and N on maize grown in a semi-arid region. Therefore, handheld GreenSeeker sensor has emerged as a promising tool as a more efficient and rapid alternative method for non-destructively measuring maize growth and potentially assessing yield.