Impacts of Cereal Rye Cover Crop and Tillage Systems on Phosphorus Loss with Runoff from Fields Managed with Corn-Soybean Rotations

GÓMEZ BOTERO MARIANA; MALLARINO ANTONIO P. ; BARBIERI PABLO ANDRÉS; HAQ MAZHER; HELMERS MATTHEW; THOMPSON LOUIS B; PEDERSON CARL; SAWYER JOHN; CRUSE RICHARD

Congreso; 2020 ASA-CSSA-SSSA International Annual Meeting; 2020

ASA CSSA SSSA

Excessive P application to fields results in P losses that impair water resources. No-till minimizes soil and particulate P loss with surface runoff. However, scarce research has assessed impacts of both no-till and cover crops on P loss. This study assessed these practices effects on soil and P loss with runoff in corn-soybean rotations. A 5-year field study was conducted beginning with corn in an Iowa field with Clarion loam soil (Typic Hapludolls) with (15-cm depth) 44 mg kg-1 Bray-1 P, pH 6.3, and 25 g kg-1 organic matter. Management systems replicated three times were established on 12 watersheds 0.61 to 1.22 ha in size each with 1.5 to 3.1% slope delimited in the same field using H-flumes and ISCO 6712 equipment for runoff monitoring and sampling. The systems evaluated were chisel-plow/disk tillage without (TILL) or with cover crop (TILLCC) and no-tillage without (NT) or with (NTCC) cover crop. The cover crop was cereal rye (Secale cereale L.) over-seeded at crops physiological maturity. Measurements were crop grain yield, cover crop biomass yield and P recycled at its termination in the spring, and loss with runoff of soil, total P, and dissolved reactive P (DRP). Cover crop biomass yield and P recycled were not affected by tillage and were 2563 kg ha-1 and 9.5 kg ha-1. Compared with TILL, NT, NTCC, and TILLCC decreased corn yield 6, 16, and 12% and soybean yield 9, 15, and 12%. Compared with TILL, NT, NTCC, and TILLCC decreased runoff, soils, DRP, and total P losses 30, 39, and 43%; 77, 84, and 69%; 12, 21, and 26%; and 38, 51, and 51%; respectively. Therefore, no-till and the cover crop reduced crop yield and greatly reduced runoff, soil, DRP, and total P although the cover crop was much more useful with tillage than with no-till