SOIL ORGANIC MATTER AND NUTRIENT CYCLING TO SUSTAIN AGRICULTURE IN THE SOUTHEASTERN USA
Location: Athens, Georgia
Title: Soil quality in integrated crop-livestock systems with conservation and conventional tillage
Submitted to: International Soil Tillage Research Organization Abstracts
Publication Type: Proceedings
Publication Acceptance Date: June 15, 2009
Publication Date: June 19, 2009
Citation: Franzluebbers, A.J. 2009. Soil quality in integrated crop-livestock systems with conservation and conventional tillage. Triennial Meeting of the International Soil Tillage Research Organization, June 15-19, 2009, Izmir, Turkey. Paper T8-003, CDROM.
Interpretive Summary: Soil quality needs to be evaluated in diverse cropping systems to understand the potential impacts of management on the sustainability of soil resources. A scientist with the USDA Agricultural Research Service in Watkinsville GA evaluated various chemical, physical, and biological properties of soil subjected to different tillage systems [(a) traditional clean tillage and (b) contemporary no tillage] and manners of managing a cover crop [(a) unutilized only to improve surface soil conditions and (b) grazed by cattle as an annual pasture]. Soil properties were determined at various times from 2002 (initiation of experiment) to 2007 (5 years of continuous management) to evaluate the magnitude and direction of change. Almost all soil quality indicators suggested a better condition under no-tillage management compared with conventional-tillage management, primarily because of the preservation of surface soil organic matter that (a) protected soil from compaction, (b) maintained high organic nutrient contents, and (c) created a favorable environment for soil microbial biomass. Mixed soil quality results were obtained when comparing grazed versus ungrazed cover crop management. Further research is therefore needed to better understand the long-term impacts of integrated crop-livestock systems on soil quality. This research will be valuable to the nearly ½ million farmers and agricultural advisors in the southeastern USA who might consider adopting conservation tillage and integrated crop-livestock systems to increase the productivity, resource efficiency, and environmental quality of their land.
Integration of crops and livestock could be either detrimental or beneficial to soil quality, depending upon timing and intensity of animal traffic and residue cover of the soil surface. Key soil properties (reflective of soil quality) of a Typic Kanhapludult in Georgia USA were analyzed in a 12-ha field experiment testing the effect of tillage [conventional tillage (CT), no tillage (NT)] and cover crop utilization (no utilization, grazed by cattle) variables. Soil organic C and N fractions (total, particulate, microbial biomass, and readily mineralizable), water-stable aggregate distribution, bulk density, penetration resistance, and single-ring infiltration measurements were determined at various times from initiation of the experiment in 2002 until present. With initially high soil organic C due to previous pasture management, depth distribution of soil organic C and N fractions became widely divergent between CT and NT, but changed little in response to whether cover crops were grazed or not. Some evidence of soil compaction with grazing of cover crops eventually became apparent in bulk density, penetration resistance, and water infiltration measurements. However, the compactive effects were relatively small when viewed in terms of the system-level effects on grain, forage, and animal production. Although CT management could initially alleviate compaction with periodic tillage, NT management may also have an advantage in pasture-crop rotation systems by preserving the organic matter-enriched surface soil to buffer against compactive forces.