Alfalfa water use under deficit irrigation for farm savings

Includes bibliographical references.2022 Fall.Colorado water law allows for water rights to be leased between agriculture and municipality users. Decreasing the consumptive use (CU) of agricultural land while maintaining profits and yields will allow farmers to lease their water rights for revenue. Deficit irrigation is a water-saving approach to avoid the complete dry up of irrigated farmland while providing profitable yields and monetary gains from water transfers. To maximize water savings, efficient irrigation systems such as subsurface drip irrigation (SDI) are used to prevent water losses from soil evaporation. This study evaluated the feasibility of using SDI with deficit irrigation practices to grow alfalfa (Medicago Sativa L.) at production scale in northeast Colorado (2018 – 2022). Alfalfa was found to have good potential for decreasing CU due to its drought tolerance, multiple harvests per season, and improved quality of hay with less irrigation water. The Water Irrigation Scheduler for Efficient Application (WISE) model was also found to be a useful tool for estimating CU of deficit irrigated alfalfa and the regrowth phases after multiple harvests in a growing season. Mid-season corrections of the soil water deficit in WISE improved the accuracy of modeled CU. Overall the water savings from deficit irrigation at low, medium, and high irrigation levels with an SDI system can be profitable when prices for leasing water exceed hay prices per unit area of production

Developing a Crop Water Production Function for Alfalfa under Deficit Irrigation: A Case Study in Eastern Colorado

Recent Colorado, USA water law provisions allow a portion of irrigation water to be leased between agricultural and other users. Reducing consumptive use (CU) through deficit irrigation while maintaining some crop production could allow farmers to earn revenue from leasing water rights. This observational study aimed to determine if deficit irrigation of alfalfa (Medicago sativa L.) can be used to reduce CU, provide parameters for an alfalfa crop water production function (WPF), and evaluate the potential for improved farm income by leasing water. Soil water balance, evapotranspiration (ET), and dry matter yield from eight commercial fields (1.70 to 2.14 ha zones), growing subsurface drip-irrigated alfalfa, were monitored for five seasons (2018–2022) at Kersey, Colorado. Four irrigation treatments [Standard Irrigation (SI) = irrigate when soil water deficit (D) exceeds management allowed depletion (MAD); Moderate Deficit Irrigation (MDI) = 70% of SI; Severe Deficit Irrigation (SDI) = 50% of SI; and Over Irrigation (OI) = 120% of SI] were applied, with two zones per treatment. Reductions in CU ranged from 205 to 260 mm per season. The shape of the alfalfa WPF (dry biomass yield vs. ET) was concave, indicating that water use efficiency (WUE) could be optimized through deficit irrigation. The average WUE was 0.17 Mg ha−1 cm−1 and tended to increase with greater deficits. Deficit irrigation also increased the relative feed value. If conserved CU from deficit irrigation can be leased into a transfer water market, farmers could profit when the water lease revenue exceeds the forgone profit from alfalfa production. We found incremental profit from deficit irrigation and water leasing to be positive, assuming 2020 prices for hay ($230 bale−1) and water prices above$0.50 m−3

Divergent impacts of crop diversity on caloric and economic yield stability

Food security and the agricultural economy are both dependent on the temporal stability of crop yields. To this end, increasing crop diversity has been suggested as a means to stabilize agricultural yields amidst an ongoing decrease in cropping system diversity across the world. Although diversity confers stability in many natural ecosystems, in agricultural systems the relationship between crop diversity and yield stability is not yet well resolved across spatial scales. Here, we leveraged crop area, production, and price data from 1981 to 2020 to assess the relationship between crop diversity and the stability of both economic and caloric yields at the state level within the USA. We found that, after controlling for climatic instability and differences in irrigated area, crop diversity was positively associated with economic yield stability but negatively associated with caloric yield stability. Further, we found that crops with a propensity for increasing economic yield stability but reducing caloric yield stability were often found in the most diverse states. We propose that price responses to changes in production for high-value crops underly the positive relationship between diversity and economic yield stability. In contrast, spatial concentration of calorie-dense crops in low-diversity states contributes to the negative relationship between diversity and caloric yield stability. Our results suggest that the relationship between crop diversity and yield stability is not universal, but instead dependent on the spatial scale in question and the stability metric of interest