Sediment and Nutrient Losses in Reduced Tillage Systems on Dairy Farms
Open Access
- Author:
- Verbree, David
- Graduate Program:
- Agronomy
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 17, 2008
- Committee Members:
- Sjoerd Willem Duiker, Thesis Advisor/Co-Advisor
Sjoerd Willem Duiker, Thesis Advisor/Co-Advisor - Keywords:
- nitrogen
tillage
no-till
runoff
nutrient
sediment
rain simulation
phosphorus - Abstract:
- No-tillage (NT) cropping systems have been promoted as a way to reduce sediment and nutrient losses in runoff from agricultural fields. However, on dairy farms where manure is surface applied, NT may have lower nitrogen (N) use efficiency along with higher nutrient losses in runoff than when manure is incorporated. The N efficiency of applied manure and the amount of sediment and nutrient loss in runoff may be influenced by soil drainage properties. This study was conducted in 2007 and 2008 to compare the effects of NT and chisel/disking (CD) on the N-fertilizer equivalence of manure and sediment and nutrient loss on a well-drained (WD) and somewhat poorly drained (SPD) soil. The first experiment compared the N-fertilizer equivalence of incorporated dairy manure in a CD corn silage (Zea mays, L.) system without cover crop with that of surface-applied manure in a NT system with a cereal rye (Secale cereale, L.) cover crop. The study was done on a well-drained (WD) site (Hagerstown silt loam; fine, mixed, semiactive, mesic Typic Hapludalf) and a somewhat poorly-drained (SPD) site (Buchanan gravelly loam; fine-loamy, mixed, semiactive, mesic Aquic Fragiudult), both of which had been in NT for more than 10 years. The trial was laid out in a randomized complete block split-plot design with four replications, with the tillage systems as main-plots and four nitrogen fertilizer rates as sub-plot treatments. The same amount of manure, calculated to supply approximately 50% of N-needs of corn with incorporation within 24 hours, was applied in both NT and CD. In the first year, manure was incorporated in CD in 24 hours, but in the second year manure could not be incorporated in CD until after 7 days due to rainfall shortly after manure application. The N-fertilizer equivalence of surface applied manure and the optimum nitrogen application rates in NT were not significantly different than in CD on both soil types. In the second year of the study, NT yields were significantly greater than CD yields at higher N-rates on the WD soil, most likely due to greater moisture stress in the CD system as well as reduced soil quality. Pre-sidedress soil nitrate test levels on both soil types and crude protein content of silage on the WD soil was lower in NT in both years, which suggest nitrogen uptake was reduced in NT, although this did not negatively affect crop yield. The study suggests that the nitrogen fertilizer equivalence of surface applied manure in a long-term NT system with cover crop is not significantly different from that of incorporated manure in a CD system without a cover crop. A rainfall simulation experiment was done in the same study on plots that received 56 kg N ha-1. Rainfall simulations (6 cm hr-1) were performed shortly after planting, at mid-season, and after harvest on runoff plots (2x2 m). In both years and on both soils, NT had significantly lower runoff volumes and lower total sediment loads than CD. Runoff and sediment loss generally did not differ between tillage systems immediately after planting on both soil types. In NT, runoff volume declined throughout the season resulting in NT having significantly lower runoff volumes than CD by mid-season on the WD soil but not until after harvest on the SPD soil. On average, NT had lower total phosphorus loads than CD on the WD soil, but had higher loads on the SPD soil. Total dissolved phosphorus constituted 73% of total phosphorus in NT, whereas it constituted only 15% in CD with little difference between soils. Highest dissolved phosphorus losses occurred in NT immediately after manure application, whereas particulate phosphorus losses (in CD) occurred throughout the season. Total dissolved nitrogen losses appeared to be primarily affected by runoff volume, and were therefore reduced in NT on the WD site. NT may reduce runoff and erosion on WD and SPD soils, may reduce total phosphorus loss on WD soils, but may increase it on SPD soils. Most phosphorus loss in NT occurred shortly after manure application and was in dissolved form. Runoff and sediment control are significant benefits of NT on WD and SPD soils, however, dissolved phosphorus losses shortly after surface application of manure can be a concern.