Location: Water Management Research2017 Annual Report
1a. Objectives (from AD-416):
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. • 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.
1b. Approach (from AD-416):
Objective 1, Subobjective 1A: The hypothesis for this research is that deficit irrigation can increase crop water use efficiency in biochar-amended soil. Plot experiments with different biochar and irrigation treatments are planned for vegetable crops such as bulb onion. Crop yield and quality 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 as the bioassay crop. 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.
3. Progress Report:
This report documents progress for the project 2034-13000-012-00D, "Develop Water Management Strategies to Sustain Water Productivity and Protect Water Quality in Irrigated Agriculture," which started in January 2017 and continues research from expired Project 2034-13000-011-00D, "Developing Sustainable Cropping Systems to Improve Water Productivity and Protect Water and Soil Quality in Irrigated Agriculture." Under Objective 1A, a plot experiment was established using a softwood biochar product as either pure biochar or in combinations with biochar mixed with compost or biochar mixed with compost and mineral sulfur. A dehydrator bulb onion was planted as a bioassay crop to test the effect of biochar amendment and irrigation at three rates. Soil moisture and matric potential were monitored on real-time bases and used as a guide for irrigation scheduling. Onion yield and quality will be determined and analyzed to assess the interactive effect of deficit irrigation and biochar. Under Objective 1B, grafting new stone fruit varieties to existing trees is a common practice in central California but there is no information on effect of methods of irrigation and sensitivity to water stress of the practice. Nectarine scions were grafted to the existing trunks of a mature peach orchard. Furrow, drip, and micro-sprinkler systems were used to re-establish the orchard at full irrigation rate. The early grafted growth was pruned to two to three major branches per tree that will be maintained as the production branches for the study. Effect of irrigation method on tree growth and fruit yield and quality will be determined in following seasons. Under Objective 1C, research on Sugraone grapes in the Coachella Valley of California continues from the previous project. The irrigation treatments have been revised to provide nearly full irrigation to determine whether grapevines will recover after extended periods of deficit irrigation. Harvest was completed in early June, and the data are being analyzed. A second experiment is being conducted on a Scarlet Royal table grape in the Central Valley of California. This is a newer variety with little information available on water requirements and response to deficit irrigation. Under Objective 1D, research to determine water requirements for mature pomegranate orchard continues from the previous project. Four irrigation treatments are being maintained, and the irrigation is controlled by the weighing lysimeter. A greater than average rainfall in 2016-2017 winter months has resulted in vigorous tree growth in all treatments. Under Objective 1E, extreme drought conditions and stark reductions in precipitation and available water supplies increased the importance of identifying drought-, salt-, and boron (B)-tolerant plant species that are adapted to grow with high saline drainage or ground waters. Research in the previous project has been extended and includes new salt- and boron- tolerant plant species in the current project. Multi-year field trials are being conducted in drainage sediment and in the west-side of the San Joaquin Valley of California on Opuntia (prickly-pear cactus), poplar clones, agretti, and different ecotypes of guayule. Initial evaluation for salt and B tolerance and selenium accumulation is in progress for agretti and guayule plants irrigated with poor quality water. Under field conditions, both agretti and guayule appear to thrive under saline conditions. Selenium-enriched agretti was produced and utilized as a food crop, while latex produced from guayule plants under saline conditions will be analyzed in conjunction with the Plant Gene Expression Center in Albany, California. Longer term evaluation of new plant species will continue. Under Objective 2, research is being conducted to develop feasible and sound management practices to use biochar and organic nitrogen (N) sources for irrigated crops to significantly increase nitrogen use efficiency (NUE) and reduce environmental losses that include greenhouse gas nitrogen oxide (N2O) emissions and nitrate (NO3-) leaching. Both laboratory and field experiments are being conducted. Seven biochar products have been made, selected, and are being characterized. Two products were made from almond shells. The biochar products will be evaluated for ammonium (NH4+) adsorption isotherm and adsorption capacity onto biochar and biochar-amended soils to estimate their ability to retain N in soil, increase availability to crops, and reduce losses to the environment. Two field experiments have been established. One is to determine the effects of irrigation and biochar on N availability, plant uptake, and environmental loss in onion production. The treatments include irrigation level (main treatments) and biochar amendment (subplots). Drip irrigation and fertigation are used. Biochar treatments include softwood feedstock biochar and combination with manure. Three irrigation levels are 100%, 75%, and 50% of current practice. Ammonia (NH3) and nitrous oxide (N2O) emissions, N2O production in soil, and soil pore water N concentration below the rooting zone are being determined during the growing season. Preliminary data showed that fertilizer application event and irrigation level impacted NH3 and N2O emissions more than biochar amendments. Nitrogen leaching risk appears high based on increased N concentration in soil pore water N at 50 cm depth compared to those at the 25 cm, but all continuously decreased with time. The second field experiment is being conducted to determine the effectiveness of biochar amendment and nitrogen fertilizer sources on NUE improvement in Serrano pepper production. A micro-plot experiment was set up with biochar at different rates and various combinations of inorganic and organic N fertilizers. Preliminary data did not show significant differences in pepper yield, however biochar amendment and incorporation of organic N at lower ratio appeared to increase total plant N uptake. During the growing season, NH3 volatilization increased after fertilization events, but with lower or delayed peaks from organic N. Nitrous oxide production in soil profile increased after each fertilizer application, but was reduced from both biochar amendment and organic N source. Yield, N use efficiency, and soil N will be determined upon harvest in both field experiments.
1. Thermal infrared for scheduling irrigation in peach trees. Remotely-sensed canopy temperature from infrared thermometer sensors can be an effective method for detecting plant water stress in some field crops. To help alleviate water shortage, researchers in Parlier, California, conducted a multi-year field study. New algorithms were developed and validated for determining levels of water stress and scheduling postharvest deficit irrigation for peach trees using canopy temperature. The experimental site consisted of six irrigation treatments including furrow, micro-spray, and surface drip irrigation systems with and without postharvest deficit irrigation in a four-acre early maturing peach orchard. Results showed that the number of fruits and fruit weight from trees under postharvest deficit irrigation treatment were less than those from well-watered trees; however, no statistically significant reduction in fruit size or quality was found for trees irrigated by surface drip and micro-spray irrigation systems. This research demonstrated that deficit irrigation controlled by infrared sensors could be a practical alternative method for peach growers to manage limited water supply.
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Ayars, J.E., Phene, C.J., Phene, R.C., Gao, S., Wang, D., Day, K.R., Makus, D.J. 2017. Determining pomegranate water and nitrogen requirements with drip irrigation. Agricultural Water Management. 187:11-23. doi: 10.1016/j.agwat.2017.03.007.
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