Effect of No‐Till and Extended Rotation on Nutrient Losses in Surface Runoff

No‐till crop production can reduce soil erosion compared to conventional tillage, but there is concern that lack of fertilizer incorporation will increase loss of dissolved nutrients in surface runoff. Therefore, we compared nutrient and sediment loss from two no‐till and two chisel‐till small (0.45–0.79 ha) watersheds managed in a 2‐yr corn ( Zea mays L.)/soybean [ Glycine max (L.) Merr]–rye ( Secale cereale L.) cover crop rotation for 16 crop years. We also investigated the effect of replacing some of the mineral N with manure and red clover by monitoring runoff from three watersheds in a 3‐yr corn/soybean/wheat–red clover ( Triticum aestivum L.– Trifolium pratense L.) extended rotation. The reduced‐input watersheds were disked in corn and soybean years. For all tillage treatments, NO 3 –N losses were greatest with corn and averaged from 3.7 (no‐till) to 5.5 kg ha −1 yr −1 (chisel) for all crop years. Average dissolved P losses were 0.21 kg ha −1 yr −1 (chisel), 0.32 kg ha −1 yr −1 (no‐till), and 0.84 kg ha −1 yr −1 (reduced‐input). Total P losses were least from no‐till (0.79 kg ha −1 yr −1 ), intermediate for chisel (0.84 kg ha −1 yr −1 ), and greatest for reduced‐input watersheds (1.68 kg ha −1 yr −1 ). Soil loss was least from no‐till (807 kg ha −1 yr −1 ), intermediate from chisel (1073 kg ha −1 yr −1 ), and greatest from reduced‐input watersheds (1177 kg ha −1 yr −1 ). Thus, no‐till had only slightly greater dissolved P losses compared to chisel, but had smaller soil, NO 3 –N, and total P losses. The greater dissolved and total P losses, as well as greater soil loss, compared to chisel and no‐till watersheds, indicated that there was no surface water quality benefit to the reduced‐input extended rotation.