Relationship of NDVI to Earliness of Maturity as Affected by Irrigation Regime

Cotton producers are interested in monitoring crop condition by remote methods such as the sensing of spectral reflectance from the canopy.  Earlier research showed that changes in Normalized Difference Vegetative Index (NDVI) of the cotton canopy corresponded to differences in crop maturity governed by nitrogen and potassium fertility.  Objectives of this research were to determine if cotton responses to irrigation regime can be detected by remote sensing of NDVI, and to evaluate the suitability of using NDVI to monitor crop maturity as affected by irrigation. We planted ‘DP143B2RF’ in 2007, and “PHY375WRF’ in 2008, in a Memphis silt loam at Jackson TN.  Irrigation treatments were applied to replicated small plots by drip tape that applied three rates of supplemental irrigation (0.5, 1.0, and 1.5 inches/week) starting at first square, and a nonirrigated check.  Irrigation amounts were reduced to the extent that rainfall supplied the required water.  Canopy NDVI data were collected biweekly starting at mid-bloom, using a hand-held GreenSeeker Red/NIR sensor suspended 28 to 32 inches above the canopy and aligned with the rows.  Earliness of maturity was measured as time required for plants to have four nodes above the highest first-position cracked boll to the highest harvestable boll (NACB=4).  Results will determine the relationship, if any, between NDVI and earliness of maturity as affected by irrigation regime.