Mechanical Straw Mulching of Irrigation Furrows: Soil Erosion and Nutrient Losses

Abstract

AbstractThere is widespread concern about loss of sediments, NO‐3, and phosphate into surface water from irrigated farmlands. We studied the effects of 900 kg ha−1 wheat (Triticum spp.) straw, mechanically applied to irrigation furrows, on sediments and on N and P losses in the runoff. The field was on a Nyssa silt loam soil (coarse‐silty, mixed, mesic Xerollic Haplodurid) with 3% slope planted to onion (Allium cepa L.), and received 0, 50, or 200 kg P ha−1 incorporated to 0.1 m deep. Furrows were side‐dressed with 200 kg ha−1 N. Averaged across 17 irrigations, straw reduced runoff volume by 43%. Cumulative sediment lost after 17 irrigations was 17 Mg ha−1 for mulched and 333 Mg ha−1 for unmulched furrows. Straw also reduced NO‐3 and NH+4 losses in runoff solution and sediments. Total N losses during the first 6 irrigations were 33 kg ha−1 from mulched and 230 kg ha−1 from unmulched furrows. Straw effect on N loss was only through changes in the runoff volume and sediment loss. In contrast, as fertilizer P increased, PO4 concentrations in runoff solution and sediments also increased. Averaged across the first 6 irrigations, straw mulch reduced PO4 losses in the runoff solution by 59, 61, and 72%, for the 0, 50, and 200 kg P ha−1 treatments, respectively. Straw reduced PO4 losses in the sediment 15‐, 11‐, and 15‐fold for the 0, 50, and 200 kg P ha−1 treatments, respectively. Averaged across P fertilizer rates, total P lost after 6 irrigations was 18 kg ha−1 from mulched and 215 kg ha−1 from unmulched furrows. Mechanically applied straw mulch in irrigation furrows can substantially reduce soil erosion and N and P losses to surface water runoff.