Thursday, November 16, 2006 - 9:15 AM

Tillage and Irrigation Interactions in a typical Southeastern US Cropping System.

Wilson Faircloth1, Diane Rowland1, and Kipling Balkcom2. (1) USDA-ARS-NPRL, PO Box 509, Dawson, GA 39842, (2) USDA-ARS, 411 S Donahue Drive, Auburn, AL 36832, United States of America

The possibility of water conservation using reduced tillage is of vital interest to growers.  Three tillage systems were established in 2002 each in one of four irrigation levels (100% of a recommended amount, 66%, 33%, and 0% or dryland) on a Greenville clay loam soil.  Tillage systems were conventional tillage, wide-strip tillage, and narrow-strip tillage, with three replications.  The test area was planted in triplicate, in a peanut-cotton-corn rotation, with each crop being present each year.  Yield of all three crops was highly dependent on seasonal rainfall and degree day accumulation.  Peanut yield was equivalent at the 100% and 66% levels in three of four years, regardless of tillage.  Peanut yield under conservation systems (both wide and narrow-strip tillage) was equal to or greater than conventional tillage systems in all years, regardless of irrigation amount.  These results alone have mitigated grower apprehension in conversion to conservation systems such as difficulty in digging, peg penetration into a dense cover crop, and cover crop contamination of harvested pods. Corn yield was equal to the 100% level with one-third less water in one season, and two-thirds less in 2004.  Much like peanut, corn yielded 36 bu acre-1 increase for either type of conservation system versus conventional.  Cotton has demonstrated few differences to either tillage or irrigation.  All crops yielded significantly greater under conservation systems on dryland, suggesting that non-irrigated farms may see the most benefit from conservation tillage practices.  Profitability analysis of the four-year average net return for each tillage/irrigation treatment demonstrated that profitability is directly linked to peanut yield and grade within the three-year rotation.  Furthermore, overall profitability decreased with increased amounts of irrigation.  However, only conservation systems gave positive net returns at all irrigation levels, whereas conventional systems were minimally profitable in dryland systems only.