Investigating the Effect of Wheat Straw on Soil Loss by Rill Erosion in Furrows in Different Growth Stages of Rainfed Wheat

Rainfed lands located on slopes are subjected to higher water erosion types, particularly rill erosion. Rill erosion rate can be varied in various growth stages. This study was carried out to find the effect of wheat straw on soil loss resulting from rill erosion in wheat growth stages. A field experiment was done in rainfed wheat land with 10% slope and seven wheat straw levels (0, 25, 50, 75, 100, 125 and 150% of ground cover), using the randomized complete block design with three replications. The land was plowed down slope and various straw amounts were separately incorporated into the soil. A 0.5 kg wheat straw per square meter was used in the 100% straw level. Three rills/furrows with 20-cm width and 10-m length were installed by the the planter machine similare to cultivation furrows for each straw level and rill erosion measurements were done using a discharge flow of 2 L.min-1 at five growth stages (planting, emergence, tillering, stem elongation, grain filling ). Based on the results, soil loss by rill erosion was significantly affected by straw amount (P< 0.05). Soil loss by rill erosion in 100% straw level was the lowest amount at all wheat growth stages and was about 79% [H1] lower than that in the control treatment. There was no significant difference between this treatment and higher straw levels (150% and 125% ground cover) in rill erosion. The emergence stage in each straw level, which was associated with poor vegetation cover and higher soil water content in this period, was the most susceptible stage in the rill erosion among all growing stages. In this stage, application of 100% wheat straw equal to 5 ton per hectare could decrease rill erosion by 71% (0.009 g m-2 equal to 0.34 ton per hectare for each 1-h rainfall event) in the cultivated furrows.