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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Water Management Research » Research » Research Project #440524

Research Project: Improved Management, Quality and Utilization of Alfalfa for Dairies in the Western U.S.

Location: Water Management Research

2021 Annual Report

U.S. dairy industry’s economic value is estimated at $51.4 billion. About 30% of the total U.S. milk production comes from the Western states with 20% of it from California. Alfalfa production in California is heavily dependent on irrigation. Competition for declining water resources for domestic, industrial, and agricultural uses, combined with frequent droughts, have resulted in reduced alfalfa acreage. With high milk producing dairy cows requiring high-quality forage, sustainable management strategies are needed for alfalfa production in the West with maximized water productivity and forage quality. The overall goal of this multidisciplinary project is to develop new tools and strategies for alfalfa production in the Western U.S. that conserve scarce water resources and lead to high yield and quality dairy forage. Objective 1: Develop new tools and strategies for management of alfalfa production in the Western U.S. that conserves scarce water resources, maintains water quality, and leads to high-quality dairy forage and the delivery of environmental services. Sub-objective 1A: Determine the effects of irrigation and cutting schedules management on forage yield, quality, water use efficiency and water extraction patterns of non-dormant reduced-lignin and conventional alfalfa varieties under semi-arid growing conditions. Sub-objective 1B: Utilize remotely sensed data products to quantify differences in consumptive water use and water productivity for commercial alfalfa produced with different irrigation techniques, on different soil types, and considering inter-annual variability of growing conditions. Objective 2: Develop agronomic management strategies for production of alfalfa forage with improved yield, quality, nutritional and economic value. Sub-objective 2A: Optimize yield and quality of reduced-lignin alfalfa varieties by altering cutting schedules. Sub-objective 2B: Determine effects of specific traits on growth, yield, quality and plant stand persistence of new and conventional varieties.

Objective 1, Sub-objective 1A: The research goal for this study is to develop a sustainable irrigation strategy for alfalfa that can ensure optimum forage yield, stand persistence, and nutritional and economic values. Field experiments with frequent and infrequent irrigation are planned for alfalfa varieties with reduced- and non-reduced lignin traits. Yield, quality, and plant biophysical parameters of alfalfa will be determined and analyzed to evaluate the interactive effect of irrigation frequency and varietal traits. If the pre-selected irrigation level is too low in the first year, adjustments will be made to avoid the loss of alfalfa stands and the experimental treatments. Sub-objective 1B: The research goal for this study is to utilize remote sensing data to evaluate sub-surface drip irrigation for increasing alfalfa water use efficiency and water productivity compared to flood irrigation on dairy farms in the San Joaquin Valley of California. We will assess methodological accuracy and uncertainty of model estimation of crop evapotranspiration using satellite imagery and evaluate the hypothesis that sub-surface drip irrigation increases water use efficiency in actual production settings. Remote-sensing data products will be combined with USDA crop statistics to evaluate soil type, irrigation water source, and irrigation technology associated with optimal water use for alfalfa production. If the daily evapotranspiration estimates provided by commercial systems are not adequate for evaluating time-dependent variability, short-term targeted field experiments will be conducted using eddy-covariance and supporting sensor systems. Objective 2, Sub-objective 2A: The research goal of this study is to develop a sustainable cutting schedule management strategy for reduced-lignin alfalfa varieties that can ensure optimum yield, dairy quality forage, stand persistence, and nutritional and economic values. The field experiment treatments include 3 cutting schedules (28-day, 35-day, and staggered/alternating between 21- and 35-day) and 8 varieties. Treatment effects on alfalfa yield, quality, stand persistence, and nutritional and economic values will be determined annually. This study will be located at a University of California field facility, and we rely on farm labor support from the university. If the farm support becomes unavailable, we will provide labor support from ARS project employees and work with the university collaborator to continue the project as planned. Sub-objective 2B: The research goal of this study is to evaluate 20 diverse alfalfa varieties for growth, biomass, and quality dynamics, yield forming traits, and plant biophysical characteristics to improve variety development and to develop a growth model using a regression analysis approach for predicting growth dynamics, forage yield and quality. Plant samples will be collected at each harvest for forage quality analysis. For model development, plant height, biomass, leaf area index, photosynthetic rate, and stomatal conductance will be measured. Planting is in the spring and if some varieties do not establish well, they will be classified as poor performers.

Progress Report
This report documents progress for project 2034-13210-002-00D, Improved Management, Quality and Utilization of Alfalfa for Dairies in the Western United States, which started in June 2021 and continues research from project 2034-13210-001-00D with the same title. For additional information, see the expired project report. In support of Sub-objective 1A, irrigation systems have been installed and are being tested for uniformity. After the first harvest, differential irrigation treatments were started in the experimental plots and will continue through the growing season. In support of Sub-objective 1B, progress was made on acquiring sensors needed for field deployment and on recruitment of a research associate or postdoc with specialized training in remote sensing and computer modeling. The equipment will be installed in grower fields for onsite collection of alfalfa water use or evapotranspiration (ET) measurement. Data collected will be used for calibration and validation of the estimated ET using satellite images. In support of Sub-objective 2A, cutting schedule treatments were initiated on the alfalfa experimental plots. Soil moisture sensors were installed at multiple depths and locations before the field season. Hand plant sampling was taken from each plot for analysis of alfalfa nutritional quality. Plant biophysical parameters were measured before mechanical harvest for yield determinations. In support of Sub-objective 2B, uniform irrigation was applied to the experimental field to meet crop water demands. One week before each harvest, alfalfa leaf photosynthetic rate, stomatal conductance, and leaf area index were measured from selected treatment plots.