Project : USDA ARS

ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Water Management Research » Research » Research Project #432372

Research Project: Develop Water Management Strategies to Sustain Water Productivity and Protect Water Quality in Irrigated Agriculture

Location: Water Management Research

2020 Annual Report

Objectives
The San Joaquin Valley of California is one of the most productive regions in the world with annual agricultural output exceeding $30 billion. Irrigated agriculture faces severe competition for water from municipal, industrial, and environmental interests; therefore, management strategies must be developed to improve water use efficiency, particularly for perennial crops. Development of management alternatives will require characterization of crop water requirements and determination of levels of irrigation and water quality to sustain production. The overall goal of this multidisciplinary project is to develop new management strategies to increase water use efficiency of both good and poor quality waters and reduce impact on soil and water quality from agrochemicals. Objective 1: Develop crop water requirements and water management strategies using good quality water, and reuse strategies using poor quality waters, to maintain or improve water productivity. • Subobjective 1A: Determine effects of deficit irrigation on vegetable crops in biochar-amended soil and evaluate capacity of biochar to stabilize microbial community response to deficit irrigation. • Subobjective 1B: Determine effects of irrigation methods and deficit irrigation on growth and yield of nectarine budded to existing peach rootstock. • Subobjective 1C: Determine effects of deficit irrigation on table grape fruit yield and quality. • Subobjective 1D: Determine water requirements for a mature pomegranate orchard. • Subobjective 1E: Develop sustainable agricultural water reuse systems to protect soil/environmental health of drainage impacted soils when using poor quality water. Objective 2: Reduce the detrimental impacts of irrigated agriculture on water quality by developing practices to increase agrochemical use efficiency.

Approach
Objective 1, Subobjective 1A: The hypothesis for this research is that deficit irrigation in biochar-amended soil can increase crop water use efficiency and mediate changes in soil microbes. Plot experiments with different biochar and irrigation are planned for bulb onion. Crop yield, quality, and soil microbes will be determined and analyzed to assess the interactive effect of deficit irrigation and biochar. If the initial plan with bulb onion is not feasible, other crops will be used. Subobjective 1B: The hypothesis for this research is that grafted nectarine can grow well under different methods of irrigation and deficit irrigation can reduce total water use. This study will be conducted at an existing mature peach orchard that is having nectarine scions grafted to the existing trunks. Furrow, drip, and micro-sprinkler systems will be used under deficit irrigation to determine nectarine yield and quality. If the initial plan for the pre-selected deficit irrigation treatments are too high or too low, adjustments will be made. Subobjective 1C: The hypothesis for this research is that deficit irrigation will yield quantity and quality of grape products similar to a fully irrigated crop. Field experiments will be carried out at growers’ fields where two table grape varieties will be evaluated for performance under deficit irrigation. If the initial plan at the existing sites need to be changed, we will work with the California Table Grape Commission to find alternative cooperators. Subobjective 1D: The research goal for this study is that pomegranate water requirement can be determined using weighing lysimeters. This study will be conducted at an existing mature pomegranate orchard. Differential irrigation will be applied for comparison with the deficit treatments. It is not uncommon that there will be down times for the sophisticated mechanical and electronic components associated with the lysimeters. If that happens, we will use soil water content or nearby weather station data for irrigation scheduling. Subobjective 1E: The research goal for this investigation is that sustainable agronomic systems can be developed for managing soil selenium contributed by use or reuse of poor quality water. We will use drainage waters or poor quality soil and groundwater to grow mustard and canola for biofuel and seed meal production on the west side of the San Joaquin Valley. We will test forage, guayule, and cactus production using micro-plots containing high concentrations of soluble salts, selenium, and boron. If any of the planned research sites is lost, additional research plots can be initiated in areas containing high levels of salt and selenium. Objective 2: The research goal for this study is to develop feasible and sound management practices to use biochar and manure for irrigated crops to significantly increase nitrogen use efficiency and reduce environmental loss. Both laboratory and field experiments will be carried out for developing management strategies to increase agrochemical use efficiency. If selected biochar and manure do not meet the experimental needs, additional materials will be collected and added to the experiment.

Progress Report
Under Sub-objective 1A, processing tomato seedlings were transplanted at the same field sites as in previous years where biochars were incorporated in the soil. The experiment was conducted to evaluate the effect of biochar and irrigation rates on yield and growth responses, and soil microbial characteristics. Three irrigation rates were applied to maintain soil moisture conditions at 100%, 75%, and 50% of crop water requirement. Soil moisture content and matric potential were monitored continuously during the growing season. Plant leaf area index and photosynthetic rates were measured during the flowering stage. At harvest, tomato fresh weight in red, green, and rotten fruits; and quality parameters for red fruits in terms of soluble solids, pH, and color were measured. For assessment of soil microbial properties, soil samples were biologically characterized at three points during the growing season: (i) post establishment, pre- deficit irrigation, (ii) six weeks into deficit irrigation treatments during peak tomato growth rates, and (iii) 12 weeks into deficit irrigation treatments, just prior to harvest. Total soil microbial biomass was quantified using phospholipid fatty acid analyses, community taxonomic profiles were developed using 16S rRNA gene sequencing, and microbial functional processes were estimated by assaying extracellular polysaccharides, soil aggregate stability, and nitrification potential. Preliminary results indicate that compost influences soil microbial abundance and polysaccharide production, which in turn enhances aggregate stability and improves soil water retention. Under Sub-objective 1B, research continued on assessing the effect of furrow, drip, and micro-sprinkler irrigation systems on crop responses in grafted nectarines. Like in the previous year, soil moisture content was recorded over the three irrigation regimes to determine moisture distribution patterns, availability of soil moisture for root water uptake, and to make corrections on irrigation scheduling decisions. At harvest, all nectarine fruit was picked from each measurement tree and total yield and fruit per tree were measured. In addition, twelve fruits were selected from each treatment plot and analyzed for fruit color, firmness, pH, and soluble solids. Under Sub-objective 1C, research continued with Scarlet Royal grapes in a grower’s vineyard. The Vineyard-Soil Irrigation Model (VSIM) was applied to provide weekly irrigation recommendations. A surface renewal station was installed in the field surrounding the experimental site, a well-watered treatment (grower practice). Treatments were: (1) grower practice using existing methods based on soil water measurements, and (2) weekly VSIM irrigation recommendation for the entire season based on the irrigation forecast. Scarlet Royal yield data were taken at two harvest picks, two weeks apart, by weighing the total harvested fruit after commercial pack of two grades of fruit (grade one and two) for each replication and measuring the total culls weight. The total yield was based on 10 harvested vines per replication. The fruit quality was measured at each harvest pick, by collecting 50 berries from each replicate/treatment, one day prior to the harvest. These berries were used to measure berry size and weight, pH, titratable acidity, color, firmness, and soluble solids. Under Sub-objective 1E, research activities are evaluating drought-, salt-, and boron-tolerant plant species that are adapted to grow with high saline drainage or ground waters. Multi-year field trials were continued on the west side of the San Joaquin Valley of California by successfully growing prickly-pear cactus, poplar trees, mustard, agretti, different ecotypes of guayule, and pistachio trees in both saline drainage sediment and in saline soils. All crops were drip-irrigated with drainage water containing salt, boron, and selenium, and thrived (especially agretti) under the tested saline growing conditions. Selenium-enriched food products, e.g., cactus fruit, agretti and pistachio nuts, were produced. Researchers at Albany, California, are determining latex and resin contents in guayule. New agronomic practices are being developed for sustaining long-term production of growing these plants under saline soil and saline irrigation conditions. Under Objective 2, effects of biochar on nitrogen (N) transformation and soil microbiology were investigated in laboratory experiments using the following treatments: three biochar products from almond shell, softwood, or green waste feedstocks; different soil moisture levels and soil types; and incorporation with either green manure or dairy manure. Following urea application to the treated soil, incubation continued for five weeks. Soil samples were collected daily during the first week then weekly at later times to determine changes in pH, mineral nitrogen (N) in ammonium, nitrate and nitrite forms, and soil microbial community. All biochar products increased soil pH buffering capacity and nitrification in dry soil when moisture was below water holding capacity. Soil pH changed the fastest in a sandy loam compared to sandy or loam soils, representing varying N transformation rates. Both green or dairy manure resulted in more pH changes, suggesting enhanced N transformation rate. These results will be used to select a subset of soils for molecular analyses of microbial enzymes involved in N transformations, allowing a better understanding of the role of biochar in N dynamics. Biochar effects on plant N uptake, soil N status, and N leaching were investigated in the tomato field experiment described under Sub-objective 1A and in a garlic field experiment. In the tomato experiment, soil samples were taken at the beginning and end of the growing season for nitrate analysis. N collectors were installed in the soil for measuring N leaching loss. At harvest, plant samples were collected, along with tomato fruits, for estimating plant N uptake. Preliminary results showed that irrigation, not biochar, primarily controlled nitrate movement or leaching in soil. Data on plant N uptake are being analyzed. In the garlic field experiment, treatments included two biochar products derived from almond shell or softwood feedstocks, two biochar amendment rates, and incorporation with composted dairy manure or inorganic fertilizer. Higher ammonia volatilization was observed from biochar treatments with inorganic fertilizer compared to manure. There were no apparent differences in N leaching among all treatments. Soil carbon (C) and N dynamics and greenhouse gas emissions were investigated to determine the influence of whole orchard recycling (WOR). WOR is a practice that returns tree biomass as woodchips to soil. Two almond orchards were monitored, where woodchips were incorporated in soils after tree removal. New almond trees were planted following the incorporation. Control plots without woodchips were included for comparisons. Greenhouse gas carbon dioxide (CO2) and nitrous oxide (N2O) emissions were measured year-round. Data from both fields showed that CO2 emissions were the highest during the first year following woodchip incorporation and reduced substantially in the second year. Much higher CO2 emissions were measured from woodchips-incorporated soil than in the control. There were large seasonal and spatial differences, especially in woodchip incorporated soils. In addition to soil organic C, woodchips increased soil water retention, especially in surface soils. Nitrogen fertilizer was the main driver for N2O emissions, but woodchips enhanced N2O emission from fertilization. The N2O emissions decreased with time corresponding to reduced C mineralization rates. This research continues to determine the long-term benefits of orchard recycling as a conservation practice on orchard performance, C and N dynamics, and soil improvement. New research was initiated examining the impacts of cover crops on soil health and water demands in a new table grape vineyard in Parlier, California, with support from the California Department of Food and Agriculture, and in an established pecan orchard in Colusa, California, with support from the Environmental Defense Fund and in collaboration with the National Center for Appropriate Technologies and Pacific Gold Agriculture. The vineyard experiment includes two cover crop treatments (mixtures of either introduced or native plant species) and a bare alley control. Soil moisture sensors were installed to monitor water movement and retention under the cover and vines at three depths (20, 50, and 150 cm). Soil samples were collected to monitor the impacts of the establishing cover crops. Soil phospholipid fatty acids and DNA are being extracted from all collected samples. The pecan experiment includes mixed species cover crops with and without native plants. Soil biological health is being evaluated under the cover crops and in the tree rows. Preliminary data from both experiments indicate the cover is building soil carbon and increasing soil microbial biomass. The enhancement of soil carbon and microbial biomass can improve water infiltration in soils, which reduces evaporative losses, and can enhance soil water holding capacity, which reduces irrigation demands and nitrate leaching.

Accomplishments
1. Deficit irrigation saves water in peach production under arid conditions. Agriculture irrigation is a major user of fresh water in arid and semi-arid areas of the world. About 23,000-hectare peaches grown in the Central Valley of California depend on irrigation using the scarce water resources. Deficit irrigation is a potential strategy to save water without severely impacting crop production; however, the long-term impact of deficit irrigation on productivity is not well understood. ARS researchers at Parlier, California, demonstrated in a 10-year field study, that deficit irrigation of up to 40% water savings did not lead to significant yield losses for eight to nine years or reduction in fruit quality such as firmness, total soluble solids, pH, malic acid, or total phenolics. Findings from this long-term research provide peach growers an alternative irrigation strategy to save water.

2. Alternative crops grown in saline soils provide value-added products. Extreme drought conditions and stark reductions in precipitation and available high-quality water supplies have increased the importance of identifying drought-, salt-, and boron-tolerant plant species that are adapted to grow with high saline drainage or ground waters in poor-quality soils. Researchers in Parlier, California, are conducting multi-year field trials in both saline drainage sediment and in saline/boron soils on the westside of the San Joaquin Valley of California, by irrigating salt- and boron-tolerant poplar-tree clones, Opuntia cactus, guayule, mustard, agretti, and pistachio, with drainage waters containing high levels of salt, boron, and selenium. Among the tested species, pistachio fresh weight and nut yields were 15-20% lower when soil salinity exceeded 10 decisiemens per meter (dS/m) and soil boron exceeded 10 parts per million (ppm). All tested plants and trees produced selenium-enriched plant products, and guayule produced increased amounts of latex and resin under saline conditions. The successful use of alternative drought-, salt-, and boron-tolerant crops and the production of new bio-based products, provides growers new agronomic strategies with alternative crops for continuing farming in drainage-impacted regions of western Central Valley of California.

3. Biochar soil application increases soil carbon and water retention. Biochar has the potential to improve soil properties, retain nitrogen (N), and reduce N losses to the environment; however, the benefits have not been demonstrated in field incorporation, thus limiting adoption as an agronomic practice. This research investigated the effects of biochar and its interactions with irrigation levels on N movement in soil, N volatilization and leaching losses, as well as soil beneficial microbes and plant yield in an irrigated field for processing onion production. Three irrigation levels and three biochar amendment rates were studied. Biochar increased soil organic carbon, improved soil water holding capacity, and increased some beneficial microbes’ population, but there were no apparent benefits to reduce ammonia and nitrous oxide emissions as well as leaching loss and yield. Irrigation showed greater impact on crop yield, N accumulation in soil, and N leaching than biochar incorporation. Thus, irrigation management must be considered in developing practices with biochar amendment for soil and N improvement in irrigated agriculture.

4. Perennial roots promote soil carbon and water storage. Perennial grasses are known for their ecological benefits in reducing erosion and providing a habitat for beneficial insects and other animals. However, the benefits on soils are less understood. Researchers in Parlier, California, revealed that root systems from perennial grasses stimulated soil microbial biomass and production of microbial products that enhance soil structure and water holding capacity. These soil health benefits promote soil carbon content and enhance soil’s capacity to retain water, reduce irrigation demands, and filter nitrate and pesticides, preventing groundwater contamination.

U.S. DEPARTMENT OF AGRICULTURE

Water Management Research: Parlier, CA