Assessing crop performance in maize field trials using a vegetation index

Abstract

New agronomic systems need scientific proof before being adapted by farmers. To increase the informative value of field trials, expensive samplings throughout the cropping season are required. In a series of trials where different application techniques and rates of liquid manure in maize were tested, a handheld sensor metering the red edge inflection point (REIP) was compared to conventional biomass sampling at different growth stages and in different environments. In a repeatedly measured trial during the 2014, 2015, and 2016 growing seasons, the coefficients of determination between REIP and biomass/nitrogen uptake (Nupt) ascended from 4 leaves stage to 8 leaves stage, followed by a decent towards tasseling. In a series of trials in 2014, and 2015, the mean coefficients of determination at 8 leaves stage were 0.65, and 0.67 for biomass and Nupt, respectively. The predictability of biomass or Nupt by REIP however, is limited to similar conditions (e.g. variety). In this study, REIP values of e.g. ~721, represent Nupt values from ~8 kg ha-1 to ~38 kg ha-1. Consequently, the handheld sensor derived REIP used in this series of experiments can show growth differences between treatments, but referential samples are necessary to assess growth parameters.