Irrigated Small-Grain Residue Management Effects on Soil Chemical and Physical Properties and Nutrient Cycling

Abstract

The effects of straw removal from irrigated wheat and barley fields cropped to wheat and barley on soil properties and nutrient cycling is a concern due to its potential impact on the sustainability of agricultural production. Increasing demand of straw for animal bedding and the potential development of cellulosic ethanol production will likely increase the demand in the future. Previous reviews addressing changes in soil properties when crop residues are removed focused primarily on rain-fed systems. This paper reviews published research assessing the effects of wheat and barley straw removal on soil organic carbon (SOC), and analyzes changes in nutrient cycling within irrigated wheat and barley production systems. The effects of straw removal on bulk density (BD), saturated hydraulic conductivity, and other properties are reported from selected studies. Six studies compared SOC changes with time in irrigated systems in which wheat straw was removed or retained. These studies indicated that SOC either increased with time or remained constant when residues were removed. It is possible that belowground biomass is supplying C to soils at a rate sufficient to maintain or in some cases, slowly increase SOC with time. A separate research review calculated the minimum aboveground residue required to maintain SOC levels (MCS) from nine wheat system studies. Calculations of the MCS values were from rain-fed systems and are some of the best information available presently for use in evaluating residue removal effects in irrigated systems. However, long-term studies are needed to obtain reliable data for diverse irrigated systems. Nutrients removed from the soil/plant system with straw can be worth $7 to $20 per Mg of straw removed. Producers will need to determine the cost of the nutrient removal from their systems to determine the value of the straw.