- Agronomic: oats, rye, grass (misc. perennial), hay
- Additional Plants: ornamentals
- Animal Products: dairy
- Animal Production: feed/forage, manure management, pasture fertility
- Crop Production: multiple cropping, nutrient cycling, organic fertilizers, tissue analysis
- Soil Management: composting, nutrient mineralization, organic matter, soil analysis, soil microbiology, soil quality/health
Intensification of dairy production increases cow numbers and increases nutrient loading on associated land resulting in non-point source pollution in surrounding watersheds. Diversifying cropping systems and employing alternative manure management strategies could improve environmental quality and contribute to sustainable dairy production. The objectives were to evaluate cropping systems that enable sustainable nutrient management and improved environmental quality for dairy production systems in the southeastern US. Nutrient imports, exports, and forms in soil were compared between Tifton 85 bermudagrass grown for forage and Tifway bermudagrass grown for turfgrass sod under field conditions and varied composted manure (CM) management practices. In addition, a mineralization study was conducted under laboratory conditions to evaluate responses of soil biological and chemical processes to CM nutrients and to relate those processes to nutrient export and environmental quality. Furthermore, relationships of CM management to runoff losses of nutrients and carbon were evaluated under simulated rainfall for each the forage and turfgrass production systems. One harvest of Tifway sod removed 4-fold greater amounts of CM sources of total N and total P than three harvest of Tifton 85 forage biomass. Treating CM with Alum did not affect the amount of total N or P exported in Tifway sod or Tifton 85 forage. Amending soil with CM did result in immobilization of N and reduced biomass production for Tifway and Tifton 85 compared to control soils. Yet, treating CM with Alum before incorporating or topdressing soil reduced the concentration of water extractable P (WEP) in CM 95.1%. Similar to CM, Alum reduced the WEP concentration of amended soil 89 to 91%. The affect of Alum on reducing WEP in CM and CM amended soil was also observed in runoff water. Treating CM with Alum reduced runoff concentration of TDP to levels comparable to control soil over both rain events. The diversification of crop production systems to include turfgrass sod and use of alternative CM management practices will enable producers to optimize and improve net export of nutrients from dairies while protecting water quality.
Similar to other regions in the US, the intensification of dairy production within Texas and other southeastern states has contributed to localized increases in cow numbers, nutrient loading on associated land, and concerns about off-farm environmental impact. Manure and wastewater supply nitrogen (N) for cropping systems on dairies and surrounding watersheds, but 20% or less of land applied phosphorus (P) is typically removed in forage harvests (Sanderson and Jones, 1997). Excess P remaining in soil is a potential nonpoint source of pollution and Texas regulations now mandate export of manure nutrients from dairies and specified watersheds to protect rivers and lakes. Similar situations exist across the USA (Beegle and Lanyon, 1994).
In an effort to prevent pollution from land-applied manure and wastewater, uptake of N and P in forage harvests has been evaluated for year-round cropping systems in the Southern Region. Adapted forage crops are grown and harvested to remove P and prevent nonpoint-source losses of N and P. Woodward et al. (2007) reported annual harvests from a bermudagrass/rye cropping system removed 67 kg P ha-1 cycle-1. Ketterings et al. (2006) reported a two-cut system applied to brown midrib sorghum removed up to 510 kg N ha-1 yr-1 and 101 kg P ha-1 yr-1. Brink et al. (2004) observed average uptake and export of 300 kg N ha-1 yr-1 and 46.5 kg P ha-1 yr-1 for Tifton 85 bermudagrass.
A previous report identified an option for export of two to three times more total P than the year-round forage harvests. A single harvest of Tifway bermudagrass sod exported up to 561 kg ha-1 of total N and 219 kg ha-1 of total P applied as raw or composted dairy manure (Vietor et al. 2002). In addition, an economic analysis indicated turfgrass sod sales were sufficient to purchase forage to replace that grown on the land area allocated to sod production (Vietor et al. 2003).
The introduction of turfgrass sod will diversify forage systems designed to achieve the dual purposes of cow nutrition and nutrient management. Yet, crop and soil responses and export of applied nutrients remain to be compared between forage and sod crops within the same space and time. The fate of manure applied nutrients in soil, which includes sorption reactions, mineralization of N, P and C, and uptake of nutrients by plants, will impact export and nonpoint-source losses (Jiao et al. 2007, Oehl et al. 2001). A side-by-side comparison between sod and forage production is needed to evaluate soil and crop responses and nutrient imports and exports for waste application fields and dairies. In addition, suitable waste management practices are needed for each crop to ensure the sustainability of dairy production in impaired watersheds.
The comparison between forage and turfgrass sod production systems will reveal advantages and disadvantages of diversifying crop enterprises used to manage nutrients in dairy production systems. In addition, measurements of soil, plant, and water quality responses will reveal the comparative effects of forage and turfgrass production practices on components of sustainability for dairy production systems. For example, amending composted manure (CM) with Alum can significantly reduce water extractable P in CM and soluble reactive P in runoff water, which could enhance the feasibility of topdressing CM after sod or forage harvests (DeLaune et al. 2006). Conversely, incorporation of CM may be necessary to protect environmental quality. Incorporation of CM will increase P adsorption to soil particles and limit nonpoint source losses in runoff. In addition, incorporation of large CM rates could improve soil water retention and biomass production compared to surface application (Kleinman et al. 2002). Knowledge of the integrated effects of forage or turfgrass production systems and associated practices on soil processes and plants will enable dairy producers to optimize nutrient management and land allocation to forage and turf crops.
Project objectives:div style="margin-left:1em;">
- Compare forage and turfgrass sod production systems with respect to 1.) field-scale nutrient imports and exports and 2.) responses of plant and soil biological and chemical processes to manure management practices.
Compare runoff losses of N, P, and organic C among manure management practices for forage and turfgrass sod production systems.
Compare mass balance of N and P on field and dairy scale between manure management practices and forage and turfgrass sod production systems.