On-the-go Sensor System for Cotton Management for Application of Growth Regulators

Abstract

Sensors can be used to measure reflectance indices for different crops which in turn can be used to estimate crop parameters. Normalized Difference Vegetative Index (NDVI) is one of the common indices. A sensor system was developed to record NDVI data for cotton along with crop height using ultrasonic sensors, to estimate cotton physiological parameters and canopy coverage. The experiments were conducted at Altus, OK. Average values of NDVI and plant height for each plot measured by on-the-go sensors were compared with the manually measured cotton structural parameters. A good correlation for accumulative data of different growth stages was observed between manually measured height (Hm) and height measured by the sensors (R2 = 0.80), showing that ultrasonic sensors can be used to measure height of cotton . For mid July data when there is need of growth regulators, NDVI over the row (NDVIOR) and weighted average of NDVI were significantly correlated with Hm and height to node ratio (HNR). Also it was found that HNR and Hm can be represented as a function of NDVI and plant height, which could be used to construct a real time plant growth regulator (PGR) applicator in future. Strong correlation (R2=0.71) was obtained between Sensor height and NDVIOR which implies that the NDVI sensors can solve the purpose of height sensor in future studies on cotton management. On the other hand HNR was found to be correlated with Hs for one of the studies, which infers that HNR can directly be calculated from crop height for application of PGR for upland cotton.