Monday, November 5, 2007 - 9:30 AM
48-1

Coupling Cover Crops and Manure Injection: Cover Crop N and P Uptake.

Jeremy W. Singer, Tom B. Moorman, and Cynthia A. Cambardella. USDA-ARS, National Soil Tilth Laboratory, 2150 Pammel Drive, Ames, IA 50011

Injecting manure into established cover crops may reduce N and P losses by increasing nutrient cycling. The objectives of this research were to quantify fall and spring cover crop shoot dry matter (DM) production and N and P uptake following manure injection at increasing target N rates. Liquid swine manure was injected at 112, 224, or 336 kg N ha-1 approximately six to eight weeks after a 70% rye (Secale cereale L.)/30% oat (Avena sativa L.) cover crop mixture was drop-seeded in soybean [Glycine max (L.) Merr.] prior to leaf abscission in the fall of 2005 and 2006 near Ames, IA . A cover crop only control treatment was also included. No difference in fall DM, N, or P uptake occurred either fall for any treatment comparison. Fall DM, N, and P uptake ranged from 149 to 526 kg ha-1, 5.3 to 13.1 kg ha-1, and 0.2 to 1.5 kg ha-1, respectively. In the spring, no difference in DM occurred for any treatment and ranged from 767 to 2111 kg ha-1. Both springs, N uptake was greater than the control (38.9 and 32.5 kg N ha-1) when 224 kg ha-1 manure N was injected (86.6 and 43.1 kg N ha-1). In the spring of 2006, P uptake was greater than the control (7.7 kg ha-1) when at least 224 kg ha-1 manure N was applied (14.1 kg ha-1). These results quantify the potential for enhanced plant nutrient uptake in farming systems utilizing manure.

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