Irrigated hectares for crop production in Georgia increased from 70,875 ha in 1970 to 587,250 in 2000. The majority of the increase was planted in peanut, corn, and cotton. In 1970, these crops accounted for 40,500 of Georgia's irrigated hectares, and in 2000, these crops totaled 465,750 irrigated hectares. Simultaneously, demand for water resources due to urban expansion and interstate litigation coupled with repeated drought are collectively threatening irrigation water supplies in the southeast U.S. peanut producing regions. A study was conducted during the 2001 to 2003 crop years to quantify the impacts of reduced irrigation amounts and different crop rotation sequences including peanut, corn, and cotton. On average, irrigated peanut pod yield was significantly increased by 906 kg/ha as compared to nonirrigated peanut yield. The affect of crop rotation on peanut yield was also significant. One year out of peanuts, in either corn or cotton, increased irrigated peanut yield an average of 1072 kg/ha over continuous peanut. Two years out of peanuts, in either corn or cotton, increased irrigated peanut yield an average of 2333 kg/ha over continuous peanut. In nonirrigated peanuts, crop rotation sequence had less affect on pod yield than did precipitation during the growing season.

Conservation tillage is a commonly adopted best management practice for improving soil quality and reducing erosion. However, there are currently no methods in place to monitor conservation tillage adoption at the watershed scale. The primary objective of this study was to evaluate the usefulness of Landsat TM data as a tool to depict conservation tillage in a small Coastal Plain watershed. Satellite imagery was used to calculate four commonly used indices: Normalized Difference Vegetation Index, Crop Residue Cover Index, Normalized Difference Tillage Index, and the Simple Tillage Index. Ground truth data consisted of a windshield survey, assigning each site a tillage regime (conventional or conservation tillage) at 138 locations throughout the watershed and surrounding areas. A logistical regression approach was used on two subsets of the data set (n = 20 or n = 44) to determine the influence of the number of ground control points on the success of modeling the occurrence of conservation tillage. The most accurate model was re-applied to the satellite image and evaluated using an independent sample of 94 survey sites. Results indicate that the normalized difference tillage and simple tillage indices performed best, with an overall accuracy of 71% and 78% for models developed using n = 20 and n = 44 sample locations, respectively. Errors were typically in the form of commission. Results are encouraging and suggest that currently available satellite imagery can be used for rapid assessment of conservation tillage adoption using minimal a priori information.

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