Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 26, 2006
Publication Date: November 9, 2006
Citation: Parkin, T.B., Kaspar, T.C., Singer, J.W. 2006. Cover crop effects on the fate of swine manure-N applied to soil. Plant and Soil Journal. 289:141-152. Interpretive Summary: The nitrogen in manure is a valuable plant nutrient. However, because manure nitrogen only becomes available slowly over time, it is difficult to manage after it is applied to the soil. Manure nitrogen added as a crop fertilizer to soil may be converted to gaseous forms (such as nitrous oxide and ammonia), and lost from the soil to the atmosphere. Also, manure nitrogen can be converted to nitrate and lost to the groundwater. Losses of manure N, both to the atmosphere and to the groundwater represent a loss nutrients to the crop, and also contribute to air and water pollution. The use of a grass cover crop, such as rye, may be a way to keep manure nitrogen in the soil and reduce losses. This study was conducted to test the use of a rye cover crop in reducing manure nitrogen losses from soil. Experiments were conducted in a controlled environment chamber using soil in plastic buckets as the experimental units. We found that nitrate losses in water draining from the soil with the rye cover crop were 10 to 20 times lower than manure treated soil without the rye. Gaseous nitrogen losses were 20% to 50% less with the cover crop. This information will help farmers design cropping systems to better utilize manure as a nitrogen fertilizer, while reducing adverse environmental effects.
Technical Abstract: Cereal grain cover crops increase surface cover, anchor corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] residues, increase infiltration, reduce both rill and interrill erosion, scavenge excess nutrients from the soil, and are easily obtained and inexpensive compared to other cover crop options. The use of cereal grain cover crops in fields where manure application occurs should increase nitrogen (N) recovery and cycling for use in subsequent crops. The objectives of this study were to determine if a rye (Secale cereale L.) cover crop increases N retention after soil application of swine lagoon slurry and reduces gaseous N losses. Experiments were conducted in a controlled environment chamber using plastic buckets as the experimental units. Three manure-N loading rates were used (0, low, high) and nitrate leaching and N2O and NH3 emissions were measured. Cumulative nitrate load in the drainage water was less than 3.1 kg ha-1 NO3-N for rye treatments regardless of the manure treatment. Conversely, the no rye high manure rate treatment lost the most N, 62.8 and 37.7 kg ha-1 NO3-N, for experiments 1 and 2, respectively. Manure treatments increased rye shoot dry matter, shoot N concentration, and total shoot N content. Nitrogen uptake by rye accounted for more than 70% of the N lost by the treatments without rye. Rye had lower cumulative N2O emission than the no rye treatment for the high manure treatment. Rye, however, did not have a significant influence on cumulative N2O flux for the low manure or the no manure treatments compared to the no rye treatments. Ammonia emissions were low for all treatments during both experiments, which was probably related to the rapid manure incorporation after application. Rye can increase N retention and reduce cumulative N2O emissions and cumulative N load in drainage water when manure is applied to soils.