Ammonium and nitrate in soil and upland rice yield as affected by cover crops and their desiccation time

Adriano Stephan Nascente,Tarcísio Cobucci,Carlos Alexandre Costa Crusciol

doi:10.1590/s0100-204x2012001200004

Abstract

The objective of this work was to evaluate the effect of cover crops and their desiccation times on upland rice yield and on the levels of nitrate and ammonium in a no-tillage soil. The experiment was carried out in a randomized blocks, with split plots and three replicates. Cover crops (plots) were sowed in the off-season (March 2009). In November 2009, at 30, 20, 10 and 0 days before rice sowing (split plots), herbicide was applied on the cover crops (fallow, Panicum maximum, Urochloa ruziziensis, U. brizantha and millet). Straw and soil were sampled (0 - 10 cm) at the sowing day, and after 7, 14, 21, 28 and 35 days. Straws from millet and fallow were degraded more rapidly and provided the lowest level of nitrate in the soil. Urochloa ruziziensis, U. brizantha and P. maximum produced higher amounts of dry matter, and provided the highest levels of nitrate in the soil. Millet provides the lowest nitrate/ammonium ratio and the highest upland rice yield. Desiccations carried out at 30 and 20 days before sowing had the largest levels of nitrate in the soil at the sowing date. Nitrogen content and forms in the soil are affected by cover crops and their desiccation times.

Highlights

Rice is grown mostly on irrigated lands (Prasad, 2011)
An essential factor to be considered in no‐tillage system (NTS) is the decomposition of cover crops
The objective of this work was to evaluate the effect of cover crops and their desiccation times on the levels of nitrate and ammonium in a no‐tillage soil and on upland rice yield

Summary

Introduction

Rice is grown mostly on irrigated lands (Prasad, 2011). Water availability is decreasing due to the competing demands of industry and population. Alternatives are sought to allow a greater water use efficiency (Qu et al, 2008). Some alternatives include growing rice under aerobic conditions, in no‐tillage system (Tao et al, 2006). An essential factor to be considered in no‐tillage system (NTS) is the decomposition of cover crops. The time interval between cover crop desiccation and sowing of cash crops is important (Nascente & Crusciol, 2012; Nascente et al, 2012). The ideal timing should be set according to cover crop traits, cultivation density, developmental stage, and the nature and level of herbicide used (Dabney et al, 2001).

Objectives

Methods

Results