Location: Water Management Research
2022 Annual Report
Objectives
The San Joaquin Valley of California is one of the richest agricultural regions in the world. Crop production in this region relies on irrigation water, which is increasingly jeopardized by a substantial water crisis. This multidisciplinary project includes three main goals. Our first goal is to develop agricultural management strategies that enhance soil quality and water productivity. Secondly, our work will help optimize the efficiency of irrigation practices. Finally, this work helps maximize the potential for using low-quality water. Specifically, we will evaluate the impacts of soil conservation practices, cover crops, and whole orchard recycling in cropping systems dominant in the San Joaquin Valley. These strategies impact soil’s capacity to store and filter water. Next, through on-farm experimentation and remote-sensing modeling, we will identify ways to enhance irrigation efficiency. To achieve this, we will determine seasonal crop water demands, optimize irrigation timing and amounts, and evaluate if lower irrigation inputs impact nectarine, pomegranate, and citrus yield and quality. Further, salt, selenium (Se), and boron (B) laden drainage and groundwater sources will be considered for irrigation of many cropping systems. Salt and B tolerant crops utilize such poor-quality waters, manage trace elements residing in the soil from the use of these waters, and can serve as Se-enriched products of economic and nutritional value. Altogether, this systems-level approach thoroughly evaluates many tools that California growers and producers can use to manage their farms under increasing water limitations. This research is urgent and addresses the critical needs of growers and commodity boards. Moreover, these data can be used to address the goals of government and non-profit organizations to enhance agricultural sustainability within the decade.
Objective 1: Identify benefits of conservation practices (cover crop, crop diversification, whole orchard recycling, organic soil amendment) for irrigated agriculture.
• Sub-objective 1.A: Evaluate the capacity of conservation practices to enhance irrigation water productivity.
• Sub-objective 1.B: Determine greenhouse gas emissions, understand N dynamics, and develop N management strategies in almonds orchards after WOR.
• Sub-objective 1.C: Investigate interactive effects of organic and inorganic N fertilization and soil building conservation practices for improving soil and water quality in California almond orchards.
Objective 2: Develop deficit irrigation strategies for perennial fruiting crops.
• Sub-objective 2.A: Determine water requirement and deficit irrigation strategies in early-season nectarine.
• Sub-objective 2.B: Develop deficit irrigation strategies for optimized water productivity in pomegranate.
• Sub-objective 2.C: Determine watershed-scale crop water use and water savings using simulated deficit irrigation in commercially grown citrus.
Objective 3: Develop sustainable agricultural water reuse systems with alternative crops to protect soil/environmental health of drainage impacted soils when using poor-quality water.
Approach
Sub-objective 1A: We aim to reveal impacts of cover crops on soil water holding capacity, soil biological diversity, berry yield and quality, and weed pressure in a table grape vineyard. Soil and vines will be analyzed to quantify soil microbial biomass and community compositions, soil carbon (C) and nutrients, and crop yield, quality, and water productivity. If cover crops fail to re-establish, we will re-seed.
Sub-objective 1B: We aim to quantify GHG emissions, woodchip mineralization, and nutrient availability in orchard soils after whole orchard recycling (WOR). Using field plots, soil GHG emissions, nitrate leaching potential, and nitrogen (N) transformation and movement will be quantified. Lab experiments will evaluate impacts of woodchip sizes and soil moisture on similar soil properties. If field operations interfere with sampling, we will sample the field, once accessible.
Sub-objective 1C: We aim to reveal impacts of compost with conservation practices on soil biological properties. Soil microcosms developed from WOR and cover crop almond orchards will be amended with compost or inorganic N fertilizer and evaluated for soil microbial properties, C, N, and nitrate. Grower selection of cover crop species will not impact the project.
Sub-objective 2A: We hypothesize that postharvest deficit irrigation (DI) reduces consumptive water use in early-season nectarine without affecting fruit yield and quality. DI strategies will be applied to nectarine research plots and tree health and fruit yield and quality metrics will be determined. If the pre-selected DI rates are too high or too low, they will be adjusted.
Sub-objective 2B: We hypothesize that regulated DI increases water use efficiency, water productivity, and economic returns in pomegranate. Field and laboratory measurements will evaluate effects of DI on soil water availability, pomegranate tree growth characteristics, fruit yield and quality, and water productivity. If lysimeters, used to guide irrigation scheduling fail, then water content and weather data will be used.
Sub-objective 2C: We aim to determine consumptive water use in evapotranspiration (ET) of citrus crops under grower practice and simulated DI. At two citrus orchards, eddy-covariance towers with sensors will be used to calculate standardized reference ET, which will be compared to corresponding satellite pixel estimates and to local ground-based estimates. If data is not available from growers, we will use the field, remote sensing, and published data.
Objective 3: We aim to develop agronomic systems tolerant to poor-quality water that can manage soil selenium; determine drainage water impacts on salt-tolerant crops in crop rotation; and reveal the effects of long-term saline irrigation in pistachio. Guayule, agretti, and pistachio crop yield, quality, and salt accumulation will be evaluated in field trials with poor-quality irrigation water. If cooperator field plots are no longer available, alternative sites will be used.
Progress Report
This is a new project that started in January 2022 and continues research from expired project 2034-13000-012-000D. For additional information, see the report for the expired project.
Under Sub-objective 1A, a table grape vineyard with two alleyway cover crop treatments and a bare alley control was established in 2019 at the USDA-ARS San Joaquin Valley Agricultural Sciences Center (SJVASC) in Parlier, California. To address California growers’ concerns that cover crop uptake of soil water and nutrients will negatively impact vineyards, soil water infiltration, soil properties, and grape quality and yield were determined. There was not a significant impact of cover crops in alleys or vine rows on water infiltration. During most seasons the weed percent cover was also not impacted by cover crops, with the exception of Spring 2022 when weeds were significantly lower in alleys of both cover crop treatments compared to the bare alley control, and in Summer 2021 when the introduced cover treatment plots had higher weed coverage in vine rows. The Lacy Phacelia cover crop treatment had higher soil microbial biomass in vine rows and in alleyways as well as higher soil total carbon than the Merced Ryegrass cover. Vine vigor estimates also demonstrated positive benefits of the Phacelia cover with potential negative benefits of the Merced Rye cover on trunk diameter and dry pruning weight. October 2022 will be the first grape harvest conducted for this vineyard.
In support of Sub-objective 1B, two almond orchards were monitored for greenhouse gas (GHG) emissions after whole orchard recycling (WOR) and orchard establishment. WOR is an emerging conservation practice that returns tree biomass to soil in woodchips and can significantly sequester carbon, improve soil properties, and reduce GHG emission compared to burning or hauling biomass to cogeneration plants. One orchard is a commercial field established in late 2017 and the other is in University of California Kearney Agricultural Research and Extension Center (UC KARE) at Parlier established in early spring 2019. Both fields included woodchip soil incorporation at a rate of 60-80 tons per acre (t/ac) after old orchard trees were pulled out and before new trees were planted. Control plots without woodchips are included for comparisons. In the UC KARE field, different nitrogen fertilizer application rates were also included. Three major GHGs, including carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions are being measured year-round in two different locations: tree rows and alleyways between tree rows. Methane emissions were extremely low in both orchards, but significant differences in CO2 and N2O emissions between woodchips and no woodchip treatments as well as temporal and spatial variations were observed. Data showed that the CO2 emissions were the highest following woodchip incorporation and reduced significantly with time. Much higher CO2 emissions were measured from woodchip-incorporated soil than the control. There were larger seasonal and spatial differences in woodchip incorporated soils that were highly associated with soil moisture conditions. CO2 emissions were generally low in alleyways in dry summer but increased during winter season due to increased soil water content from precipitation. These variations contributed to the complexity to accurately estimate cumulative GHG emissions in the orchards. Nitrogen fertilization is shown as the main driver for N2O emissions and woodchips enhanced the N2O emission, but the effect was reduced with time corresponding to reduced C mineralization rates. The interaction between C and N that impacted N2O emission needs further understanding. A laboratory experiment was conducted to investigate the effects of woodchip size on GHG emissions. This research continues to better understand C and N dynamics after WOR to develop effective management practices that maximize the benefits of WOR for soil improvement and orchard production.
In support of Sub-objective 1C, ARS researchers visited a grower cooperator’s field site in Kern County, California, to detail plans to establish cover crops. All plans are on track to seed the cover.
In support of Sub-objective 2A, uniform irrigation was applied to a nectarine orchard at the San Joaquin Valley Agricultural Sciences Center (SJVASC) using furrow, micro-sprinkler, and drip irrigation systems. Irrigation scheduling was based on soil moisture sensor readings by maintaining 18 to 25% volumetric water content in the tree root zone. New radiation and humidity sensors were installed and calibrated for the Bowen ratio system located in the orchard for real-time evapotranspiration measurement. Nectarine bloom count and fruit set were measured by irrigation treatment. Average number of blooms per meter were 26.6, 27.2, and 26.4 for furrow, micro-sprinkler, and drip, respectively. Average number of fruits per meter were 9, 7.1, and 7.7 for furrow, micro-sprinkler, and drip, respectively. Periodic leaf stomatal conductance readings were also taken with values ranging from 210 to 458 millimoles per square meter per second (mmol/m2/s).
In support of Sub-objective 2B, uniform irrigation was applied to the pomegranate orchard at SJVACS using surface drip irrigation systems. Soil Vue TDR systems were installed at multiple locations in the orchard to measure soil water content in the plant root zone. Although weighing lysimeters are in the orchard, irrigation scheduling was based on soil moisture sensor readings due to software and hardware challenges. The orchard was pruned minimally this year following recommendations by our stakeholders from Wonderful Orchard Farming Company. The goal was to maximize canopy size and tree volume for potential higher yield in the following seasons. The same amount of water was applied to the entire orchard to mitigate residual treatment effects from the previous years’ experiment. Periodic leaf stomatal conductance readings were also taken with values ranging from 450 to 500 mmol/m2/s.
In support of Sub-objective 2C, protocols were developed for utilizing OpenET database and other remote sensing data products to determine water productivity of commercial citrus under various management strategies. A new post-doctoral scientist is training in the OpenET API and geospatial statistics required to utilize remote sensing data products. Field experiments in commercial citrus continued, and new field experiments were initiated, using eddy-covariance and other methods to estimate actual crop utilization of applied irrigation. Several analyses were completed to reconcile ground-based and remote sensing estimates of field scale evapotranspiration (ET), and to utilize soil moisture sensing to inform improved irrigation scheduling. Several ongoing analyses will improve error estimation of the ground-based methods. A related paper was published in Boundary-Layer Meteorology documenting one of these methods.
In support of Objective 3, research continues on successfully growing and evaluating salt and boron (B) tolerant varieties of cactus, agretti, guayule, perennial grass species, hybrid poplars, and young and mature pistachios for physiological and yield responses to irrigation with high saline water ranging from 6 to 14 decisiemens per meter (dS/m), and soluble B ranging from 6 to 14 milligrams boron per liter (mg B/L). In all studies, uptake, and speciation of selenium (Se), B, sodium (Na) and chloride (Cl) were respectively analyzed, as well as their effects on nutritional quality, nut yield, and arsenic uptake. In collaboration with ARS researchers in Albany, California, we are currently evaluating effects of saline water on latex and rubber production and quality in guayule. The tested plant species have accumulated Se ranging from 2 to 8 milligram of selenium per kilogram plant dry weight (mg Se/kg DW) and produced bio-based products, e.g., edible selenium enriched vegetables and soups. Additionally, measurements were made to determine the amount of Se removed from soil by plant uptake. Among the plant species studied, agretti accumulated Na concentration as high as 5%, while mature pistachio leaves contained B and Na as high as 3000 and 5000 mg kg-1 DW, respectively. The excessive accumulation of B and Na in the soil significantly contributed to slight decreases in yields in most crops, except in agretti. Approximately 15% net losses of soluble soil Se were accounted for in harvested plant material and less than 5% was estimated lost by leaching with minimal precipitation.
Accomplishments
1. Cover crops promote beneficial soil biota in a California orchard. Although numerous benefits of cover crops have been described in temperate, annual cropping systems, it is less clear how cover cropped alleyways between trees impact nutrients and resources in orchard soils. ARS researchers in Parlier, California, revealed the soils in a cover cropped orchard had divergent patterns in alleys and tree rows, wherein the cover crops promoted beneficial fungi and conditions with available nutrients and resources for soil microorganisms. This suggests an important advantage of cover crops in irrigated orchards with semi-arid climate. These findings directly benefit growers by documenting how the incorporation of cover crops, which are incentivized through many federal and state agencies, impact California orchards and vineyards. Further, citizens also benefit from ecological improvements of cover crops in neighboring agricultural landscapes, such as expanded insect habitat, reduced airborne soil and dust, and improved water quality.
Review Publications
Banuelos, G.S., Freeman, J., Arroyo, I.S. 2021. Selenium content and speciation differences in selenium enriched soups made from selenium biofortified plants. Journal of Food Composition and Analysis. 105. Article 104255. https://doi.org/10.1016/j.jfca.2021.104255.
Mangan, M., Oldroyd, H.J., Paw U, K., Clay, J.M., Drake, S.A., Kelley, J.R., Suvocarev, K. 2022. Integrated quadrant analysis: A new method for analyzing turbulent coherent structures. Boundary Layer Meteorology. 184:45-69. https://doi.org/10.1007/s10546-022-00694-w.
Duan, Y., Gao, S., Hanson, B.D. 2022. Effects of biochar and fertilizer sources on nitrogen uptake by chilli pepper plants under Mediterranean climate. Soil Use and Management. 38(1):714-728. https://doi.org/10.1111/sum.12759.
Gao, S., Duan, Y., Wang, D., Turini, T. 2022. No significant influence of biochar and manure application on nitrogen fate and sequestration by tomato and garlic crops: A field experiment in California, USA. Soil Use and Management. 38(1):676-690. https://doi.org/10.1111/sum.12749.
Rodriguez-Ramos, J.C., Scott, N.M., Marty, J., Kaiser, D., Hale, L.E. 2022. Cover crops enhance resource availability for soil microorganisms in a pecan orchard. Agriculture Ecosystems and the Environment. 337. Article 108049. https://doi.org/10.1016/j.agee.2022.108049.
Hao, S., Banuelos, G.S., Zhou, X. 2022. Can As concentration in crop be controlled by Se fertilization? A meta-analysis and outline of As sequestration mechanisms. Plant and Soil. 838. Article 155967. https://doi.org/10.1016/j.scitotenv.2022.155967.
