CORN YIELDS AND PROFITABILITY FOR LOW–CAPACITY IRRIGATION SYSTEMS

Abstract

In many areas of the central U.S. Great Plains irrigation well capacities are decreasing due to declines in the Ogallala aquifer. Many producers using furrow surface irrigation are faced with a decision on whether they should convert to a higher efficiency center pivot sprinkler irrigation system. An irrigation scheduling model using 27 years of climatic data for western Kansas was combined with a corn yield production function and economic model to simulate crop yields and economics under four combinations of irrigation system and application efficiency for six different irrigation capacities. Center pivot sprinkler irrigation systems were found to give higher corn yields and greater profitability than furrow surface irrigation, particularly when system flow rates were less than 40 L/s. Sprinkler irrigation systems with application efficiencies of 100, 95, and 85% and a furrow surface irrigation system with 70% application efficiency produced simulated crop yields of 12.3, 12.2, 12.1, and 11.3 Mg/ha, respectively, when irrigation capacity was 6.35 mm/day. Reducing the irrigation capacity to 2.54 mm/day reduced yields to 9.4, 9.2, 8.9, and 8.3 Mg/ha for the respective irrigation systems. Net annual returns for a 65 ha field were increased by US$1000 to $4000 with center pivot sprinkler irrigation compared to furrow surface irrigation for system flow rates between approximately 20 and 40 L/s. Labor savings with sprinkler irrigation are a significant factor in profitability, but increased crop yields are also very important, particularly at lower system flow rates of approximately 20-30 L/s.

Using a Crop Simulation Model to Understand the Impact of Risk Aversion on Optimal Irrigation Management

“…We assumed that farmers set their irrigation schedules prior to planting, when weather is unknown, but the actual water applied depends on the actual weather in the growing season. This is an important distinction from previous studies that assumed the choice of seasonal irrigation depth was fixed, so farmers were restricted to applying the same amount of water in dry and wet years (Llewelyn and Featherstone, 1997;O'Brien et al, 2001;Peterson and Ding, 2005).…”

“…The impact on crop production is more severe in dry years because irrigation may not be able to meet crop water demands. For example, a drought in 2011 in southwest Kansas decreased average corn yields to only 9,800 kg ha -1 compared to an average of 12,200 kg ha -1 in 2010 (NASS, 2016). This weather uncertainty creates risk for irrigation management under limited water availability.…”

“…Many studies have compared irrigation strategies based on profit maximization (e.g., Boggess et al, 1983;O'Brien et al, 2001;Nair et al, 2013a). Adjustments to limited irrigation can occur either along the intensive margin (i.e., reducing seasonal irrigation depth) or along the extensive margin (i.e., reducing irrigated area) (English,equals the marginal benefit of increasing the seasonal irrigation depth.…”

The Heterogeneous Impacts of Groundwater Management Policies in the Republican River Basin of Colorado

“…Well capacity, i.e., the allowable yield of a well (''well yield''), represents a physical constraint imposed by local hydrologic conditions. Declines in well capacity limit an irrigator's ability to meet daily crop water requirements and have been shown empirically to diminish the productivity of groundwater (Colaizzi et al, 2009;Foster et al, 2014;Lamm et al, 2007;O'Brien et al, 2001;Peterson & Ding, 2005), leading to nonlinear changes in irrigated land and producer profits (Foster et al, 2015).…”