Comparison of Site-Specific and Conventional Uniform Irrigation Management for Potatoes

Site-Specific Irrigation Management (SSIM) can be defined as irrigation management (depth, timing) based on crop need to defined sub-areas of a field referred to as management zones. Implementation of SSIM will require additional irrigation system hardware, labor, and information on soil and/or plant water status in each management zone. Costs associated with these additional requirements will need to be offset by increased receipts from improved crop yield and quality in order for the technology to be adopted by producers. The potential for SSIM to increase crop yield, quality, and economic return has not been evaluated in field studies. Crops such as potatoes, for which yield and quality are highly sensitive to soil water availability, are most likely to show an economic benefit from site-specific irrigation management. A two-year field study was conducted to evaluate the potential for SSIM to increase yield and quality of potatoes relative to Conventional Uniform Irrigation Management (CUIM). Near real-time soil water content was used to schedule irrigations under both irrigation management treatments. Field average water application was nearly the same for the irrigation management treatments, 503 mm (19.8 in.) in 2001 and 445 mm (17.5 in.) in 2002. In both study years, tuber yield distributions trended 4% greater under site-specific irrigation management but were not significantly different (p < 0.05). Total tuber yield per unit of water applied from irrigation and precipitation was 4% greater in 2001 and 6% greater in 2002 under SSIM. Based on a local tuber quality adjusted potato processing contract price structure, the trend in gross income averaged across the field site was $159/ha ($65/acre) greater with SSIM. This increase in gross income is likely about half the actual cost of commercial site-specific irrigation technology. The required 3- to 5-year crop rotation for potato disease management means that the site-specific irrigation system needs to be mobile or an economic benefit must also be realized from other crops in the rotation. The economic benefit of SSIM needs to be increased or realized for other crops in the rotation for it to be an economically viable technology in potato production systems in Idaho.