Location: Water Management Research2020 Annual Report
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. (C1: 1A; C3: 3A, 3B) 2. Develop and evaluate tools, technologies and strategies for improved harvesting, storage and handling of alfalfa forage that ensures the delivery of dairy forage of high quality and nutritional value. (C1: 1A; C3: 3B; C4: 4B, 4C)
Objective 1: The hypothesis for this research is that water use efficiency and water quality can be improved in alfalfa production in the arid and semi-arid western U.S. while maintaining high nutritional value as dairy forage. Plot- and farm- scale experiments will be carried out to quantify water productivity of existing production systems of alfalfa and other forage crops (corn silage, grain forages, etc.) and to test production potential using more efficient irrigation methods such as drip irrigation and reuse of low quality water. Crop yield and quality will be determined and analyzed to assess the effect of new water management strategies on water savings and water quality. If the initial plan with drip irrigation or low quality water is not feasible, current irrigation methods with improved irrigation scheduling strategies such as deployment of cloud-based soil and plant water status sensors or aerial evapotranspiration surveillance with drones will be used as the alternate approach. Objective 2: The research goal for this study is to develop new tools and technologies to improve the current process involved with the harvesting, storage, and handling of alfalfa as high quality dairy forage. Both laboratory and field experiments will be carried out to evaluate the current practices of harvesting, storage, and handling of alfalfa forage, their effects on forage quality, and determine the potential processes that can be improved for maximizing operation efficiency and preserving forage quality. New tools, technologies, or management strategies will be tested for the improvement of the harvesting, storage, and handling of alfalfa forage for sustainable dairy production. If selected tools and techniques do not meet the industrial needs for dairy production, additional technologies will be added to the study.
Major progress has been made establishing the new project. Extensive interviews were carried out and a research agronomist, an engineering technician, and a biological science technician have been hired and reported to duty. With the new staff on board, new alfalfa field trials were initiated during the current fiscal year. Interviews have also been carried out to hire a research civil engineer, a selection has been made, and we are in the process of finalizing the recruitment package. We are also closely engaging with ARS Office of National Programs and other ARS locations in an agency-wide effort to develop a blueprint for alfalfa research in the United States and prepare for an Alfalfa Summit meeting with the National Alfalfa and Forage Alliance and other stakeholders. In support of Objective 1, new research was initiated in grower’s fields to investigate responses of alfalfa forage yield, quality, water use, and yield variability to sub-surface drip and flood irrigation systems. The field site is located at Buttonwillow, California, in the southern portion of the Central Valley where there is a high concentration of dairy farms and alfalfa production. The research is in collaboration with an alfalfa grower/dairy producer and researchers from the University of California, Davis, and Kearney Agricultural Research and Extension Center. The alfalfa grower/dairy producer has several alfalfa fields totaling about 4,000 acres, under sub-surface drip and flood irrigation systems. In this study, one sub-surface drip and one flood irrigated field are being examined. Each field is about 73 acres in size. Irrigation for these fields had manure water mixed in, applied twice a year, then irrigated with fresh water. Sensors were installed in both fields for soil moisture and evapotranspiration monitoring. Alfalfa yield is being determined using both the grower’s commercial harvest (number and weight of bales per acre) and a specialized plot harvester in a gradient fashion following the grower’s cutting schedule one day before each commercial harvesting. Hand plant samples are also taken for moisture and forage quality analysis. Results so far indicate alfalfa yield under sub-surface drip is 20% higher than under flood irrigation, which also means higher water use efficient and sustainable alfalfa production under sub-surface drip than under flood irrigation. In addition, within-field yield variability is lower under sub-surface drip than under flood irrigation. Hand plant samples will be processed and analyzed for forage quality determination. Progress was also made on a subordinate project with the University of California Kearney Agricultural Research and Extension Center. Alfalfa irrigation trials are being conducted at Parlier and Holtville, California. The trials at Parlier include comparing flood irrigation systems with sub-surface drip irrigation system as well as utilizing alfalfa fields for groundwater recharge to increase the availability of irrigation water to growers during drought years. Sub-surface drip irrigation is compared to flood irrigation while meeting full crop evapotranspiration or under deficit irrigation at 75% and 50% water application rates. In addition, wireless automated flood irrigation control mechanisms are compared to the conventional flood irrigation system. Using existing irrigation systems on alfalfa when flood water is available could help farmers increase the availability of groundwater for irrigation during the growing season. The trials at Holtville, California, include comparing alfalfa production under various sub-surface drip irrigation scenarios, comparing three drip tape placement depths to determine effect on alfalfa productivity and water use efficiency. In support of Objective 2, a new plot experiment was initiated at the field station at Parlier, California, to determine effects of alfalfa varietal differences on crop growth, yield, quality and persistence. Both reduced lignin (developed through genetic engineering and conventional breeding) and conventional (without reduced lignin traits) varieties are used in the study. The experimental design is a randomized complete block with 20 varieties replicated four times. Plots are irrigated using an overhead sprinkler system. Plant growth, maturity, leaf/stem proportion, yield and forage quality are being determined based on hand-clipped plant samples and harvest data. In addition to the plot experiment at the ARS field station at Parlier, a new plot experiment was also initiated, in collaboration with the University of California Kearney Agricultural Research and Extension Center, to determine effects of alfalfa cutting schedule on yield and quality and persistence of reduced-lignin and conventional alfalfa varieties. The trial involves three cutting schedules (standard- 28 days, late- 35 days, and staggered- 21 and 35 days in alternate pattern) as main-plot and varieties (eight) as sub-plot treatments and replicated four times. Alfalfa varieties used in this trial are from HarvXtra with reduced-lignin trait (genetically engineered) and conventionally bred reduced-lignin and non-reduced lignin alfalfa. Alfalfa yield is being determined using a forage plot harvester. Hand-sampling is taken for moisture and forage quality analysis. Optimizing cutting schedule is a practical consideration for growers to balance yield and forage quality. Reduced-lignin varieties can be harvested on a late cutting schedule with comparable forage yield as conventional varieties while providing higher forage quality for dairy cows. They can potentially reduce harvesting-related cost (fewer cuts), increase crop stand (persistence), and reduce soil compaction, leading to more sustainable alfalfa production. Progress was also made on a new subordinate project with the University of California Davis on laboratory analysis of reduced lignin alfalfa and a bioassay feeding study using sheep. The overall purpose is to assess the fiber content, in vitro digestibility, and in vivo digestibility of the two varieties of alfalfa at two cutting schedules. Low-lignin and control alfalfa were harvested at 28 and 42 days for each variety and baled for a sheep digestibility study. During harvest, multiple core samples were taken from each bale and a representative sample was obtained. These samples were then ground and used for in vitro analysis to determine dry matter, organic matter, and neutral detergent fiber digestibility. The digestibility (determined from gas production) of the highly fermentable cell components will be compared with the more slowly fermentable cell wall components (fiber). In addition, an in vivo sheep digestibility study is being conducted using the two varieties of alfalfa at two different cuttings. Each sheep is fed with the alfalfa sample for a two-week period with total output collection taking place during the second week. This allowed for total digestibility to be calculated since total intake and outtake are recorded. These results are being analyzed and will be used in conjunction with the in vitro work to determine quality and digestibility of each sample of alfalfa.