Impact of commercial organic ameliorants on nitrogen and phosphorus concentrations of maize biomass at ninth leaf and silking growth stages.

Abstract

The response of grain yield, biomass yield and harvest index of maize to the application of commercial organic ameliorants was inconsistent and poor. Hence it was hypothesized that the supply of N and P to maize plants was inadequate during vegetative growth, resulting in low concentrations of the two nutrients in maize biomass. The effects of nine ameliorants on the N and P concentrations of maize plants at ninth leaf (V9) and silking (R1) stages of maize were studied over three years at Bothaville (8% clay), Ottosdal (12% clay) and Potchefstroom (34% clay). All ameliorants were applied as prescribed by manufacturers. The N and P concentrations in maize biomass of the ameliorants at V9 and R1 were lower, comparable or higher, showing that the inconsistent and poor response of yield parameters can not be ascribed to inadequate uptake of N and P. A matter of concern that justifies thorough investigation, is the prescribed use of Crop care and Growmor with partial and of Montys and Promis with no NPK fertilization, an unsustainable practice over the long term. Characterization of the active ingredient(s) of the ameliorants is deemed also of importance for better insight.