Cropping systems for sustainable nutrient management and dairy production

Cropping systems for sustainable nutrient management and dairy production

Summary

The establishment year for Tifway and Tifton-85 bermudagrass produced one sod harvest and three forage harvests. Following planting, laboratory incubations of soil cores indicated immobilization of soil N was occurring in CM amended soils, warranting application of fertilizer N to stimulate forage and turfgrass sod production. After the final turfgrass sod and forage harvest, field scale nutrient imports and exports were calculated. Results indicate that one sod harvest had greater nutrient export compared to three forage harvests. Field plots are currently being managed for harvesting of sod and forage during a second year of production. Manure managements practices for turfgrass and forage production systems are currently being evaluated in box lysimeters to compare runoff losses of carbon and nutrients.

Objectives/Performance Targets

1. 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

Accomplishments/Milestones

• Composted manure (CM) with and without Alum was incorporated in soil April 22. Field plots of Tifway and Tifton-85 Bermudagrass were established April 25. Surface application of CM with and without Alum was applied April 26. Soil was sampled and analyzed for extractable and total nutrients after planting (April 25) and after forage harvest (July 1, August 4, September 24). Fertilizer N was applied June 18, July 4, August 7, and October 9. Composite samples of harvested forage was sampled and analyzed for total N and P. Sod was harvested and sampled. Sod samples were separated into turf and soil fractions and analyzed for nutrient concentration October 6. Soil was sampled and analyzed following final forage and sod harvest October 8. Soil cores (6-cm d x 5-cm depth) taken from field plots May 14 for carbon mineralization study. Soil core were incubated for 28 days under laboratory conditions for measurement of carbon and nitrogen mineralization. Four CM management practices plus one control were installed in box lysimeters and planted to Tifway Bermudagrass on December 17 for comparison of nutrients in runoff in January 2009.

Impacts and Contributions/Outcomes

• Comparison of field scale nutrient export revealed that harvesting one turfgrass sod crop removed 3.7 fold greater total N and 3.8 fold greater total P than three forage harvest during 2008. Topdressing or incorporating CM with and without alum in soil to grow sod resulted in greater export of total N and P compared to sod grown without CM. One sod harvest removed 56-57% of total N in surface applied CM compared to incorporating CM which removed 21-24% of CM applied total N. A single sod harvest removed 52-59% of CM applied total P for sod grown with a surface application of CM compared to incorporating CM that removed only 20-24% of CM applied total P. Topdressing or incorporation CM with and without alum in soil to produce forage decreased export of total N and P compared to forage produced without CM. Three forage harvests removed 12-19% of total applied N and 10-17% of total applied P. Laboratory incubations of soil cores indicated that carbon evolution rates were greatest for treatments where CM was incorporated in soil, followed by surface applied CM, and soil without CM having the lowest carbon evolution rates. Application of alum to CM had no affect on carbon evolution rates. Although incorporation or surface applications of CM increased carbon mineralization rates compared to soil without CM, application of CM did not result in a net mineralization of inorganic N.

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