Manure and Cover Crops Effect on Nitrogen Dynamics in No-till Soil.

Organic amendments improve soil nutrient availability, and dairy manure, as a soil organic amendment supplies N and other nutrients to plants. A randomized complete experiment was conducted to determine the effects of dairy manuring with or without cover crops on soil available N dynamics. Dairy manure was applied in fall of 2006 at 0, 3000 and 6000 gallons per acre to standing annual ryegrass and cereal rye with a bare field as control. Soil samples were randomly collected in September of 2006 prior to application of dairy manure, and in March, April, May, June, July and August of 2007, respectively after manure application. The 2-mm sieved field-moist soil samples were analyzed for ammonium and nitrate concentration. A portion of the soil was air-dried and analyzed for antecedent moisture content and bulk density. Dairy manure significantly influenced the ammonium, nitrate, and plant available N concentration in soil. Significantly greater ammonium, nitrate and plant available N content was reportedly found in soil when applied at 6000 gallons of dairy manure application per acre. Among the cover crops, both annual ryegrass and cereal rye initially reduced available N content; however over time, increased the nitrogen content compared to control (bare field). As expected, the ammonium, nitrate and plant available N content in soil significantly changed over time. Soil nitrate content was highest (17 to 76 kg ha-1) during May to August 2007 and lowest (14 kg ha-1) in September 2006. Ammonium content was highest (8 to 12 kg ha-1) during May to July 2007 and lowest (0.22 kg ha-1) in August 2007. Likewise, plant available N content was highest (48 to 77 kg h-1) during May to August 2007 and lowest (18 to 23 kg ha-1) during September 2006 to March 2007. Results suggest that annual ryegrass and cereal rye as cover crops significantly reduced available N in soil during fall and spring, and may have released biomass N upon decomposition in late spring and summer.