Suitability of foliar N applied to rainfed maize in permanent beds after 12 crop seasons of granular N application

Abstract

Yield and kernel quality of rainfed maize as affected by N fertilizer has been generally evaluated through the application of granular N sources at high rates. The purpose of this work was to estimate the response of maize yield and quality (kernel hardness—floating index, weight and test weight -, P uptake and protein) to foliar N application and preceding granular N. Data for this report were collected in 2014 and 2015 in a long-term experiment established in 2002 under permanent beds in a split plot arrangement. Main plot treatments were three foliar N rates (0, 4.5 and 9 kg ha⁻¹) laid out on the top of four preceding granular N rates (0, 20, 40 and 60 kg ha⁻¹) applied from 2002 to 2013 as subplots. Weather conditions were relatively wetter in 2014 than 2015. In 2014, test weight and floating index improved over that in 2015. Foliar application of 9 kg N ha⁻¹ enhanced yield and protein. In 2014, yield response to preceding N rates showed an increasing trend whereas in 2015 response was null. Kernel P uptake response to preceding N rates showed a differential reaction among foliar N rates; 9 kg ha⁻¹ showed the greatest uptake. Kernel floating index was associated to kernel P uptake. Apparently, this relationship has not been previously reported. Results suggests that the application of 9 kg N ha⁻¹ to foliage of rainfed maize grown in permanent beds has the potential to substitute the traditional fertilization practice of granular N sources.

Keywords:

• Foliar N
• maize
• yield
• kernel hardness
• floating index