Effects of a Furrow-Bed Seeding System on Stand Establishment, Soil Bacterial Diversity, and the Yield and Quality of Alfalfa Grown in Saline Soils

Purpose: To compare the performance of alfalfa crops and soil properties between a furrow-bed seeding system (FU) and a flat-bed seeding system (FL) in saline soil. Methods: Alfalfa seeds were sown in early fall, 2019, in saline sandy loam soil using FU and FL systems. The soil temperature, moisture, root-zone salinity, bacterial diversity, seedling emergence number in 2019 and soil nutrient contents, alfalfa production characteristics in 2020 were determined for plants in FU and FL treatments.Results: Compared with FL, FU resulted in increased soil moisture content and seedling emergence, and reduced relative abundance of Actinobacteria and Choroflexi in soil at the seedling stage, but it did not affect root-zone salinity. In April 2020, the soil salinity was lower, and the soil available phosphorus, potassium, nitrogen, and soil organic matter contents were higher, in FU than in FL. Compared with FL, FU resulted in increased yield (by 37.5%), protein content (by 3.6%), and potassium concentration (by 33.2%,), and decreased ash content (by 7.7%) and sodium concentration (by 19.0%) in alfalfa plants. The increased yield was positively correlated with seedling emergence, soil available potassium, total nitrogen, and organic matter contents, and shoot potassium content; and negatively correlated with shoot sodium content. The relative abundance of Actinobacteria was negatively correlated with alfalfa ash, calcium, and sodium concentrations, and positively correlated with shoot potassium content. Overall, FU increased alfalfa quality and alleviated salt stress.Conclusions: Furrow-bed seeding in early fall can enhance the yield and quality of alfalfa cultivated in saline soils.

Policy-Driven Sustainable Saline Drainage Disposal and Forage Production in the Western San Joaquin Valley of California

Environmental policies to address water quality impairments in the San Joaquin River of California have focused on the reduction of salinity and selenium-contaminated subsurface agricultural drainage loads from westside sources. On 31 December 2019, all of the agricultural drainage from a 44,000 ha subarea on the western side of the San Joaquin River basin was curtailed. This policy requires the on-site disposal of all of the agricultural drainage water in perpetuity, except during flooding events, when emergency drainage to the River is sanctioned. The reuse of this saline agricultural drainage water to irrigate forage crops, such as ‘Jose’ tall wheatgrass and alfalfa, in a 2428 ha reuse facility provides an economic return on this pollutant disposal option. Irrigation with brackish water requires careful management to prevent salt accumulation in the crop root zone, which can impact forage yields. The objective of this study was to optimize the sustainability of this reuse facility by maximizing the evaporation potential while achieving cost recovery. This was achieved by assessing the spatial and temporal distribution of the root zone salinity in selected fields of ‘Jose’ tall wheatgrass and alfalfa in the drainage reuse facility, some of which have been irrigated with brackish subsurface drainage water for over fifteen years. Electromagnetic soil surveys using an EM-38 instrument were used to measure the spatial variability of the salinity in the soil profile. The tall wheatgrass fields were irrigated with higher salinity water (1.2–9.3 dS m−1) compared to the fields of alfalfa (0.5–6.5 dS m−1). Correspondingly, the soil salinity in the tall wheatgrass fields was higher (12.5 dS m−1–19.3 dS m−1) compared to the alfalfa fields (8.97 dS m−1–14.4 dS m−1) for the years 2016 and 2017. Better leaching of salts was observed in the fields with a subsurface drainage system installed (13–1 and 13–2). The depth-averaged root zone salinity data sets are being used for the calibration of the transient hydro-salinity computer model CSUID-ID (a one-dimensional version of the Colorado State University Irrigation Drainage Model). This user-friendly decision support tool currently provides a useful framework for the data collection needed to make credible, field-scale salinity budgets. In time, it will provide guidance for appropriate leaching requirements and potential blending decisions for sustainable forage production. This paper shows the tie between environmental drainage policy and the role of local governance in the development of sustainable irrigation practices, and how well-directed collaborative field research can guide future resource management.

Calibration and Global Sensitivity Analysis for a Salinity Model Used in Evaluating Fields Irrigated with Treated Wastewater in the Salinas Valley

Treated wastewater irrigation began two decades ago in the Salinas Valley of California and provides a unique opportunity to evaluate the long-term effects of this strategy on soil salinization. We used data from a long-term field experiment that included application of a range of blended water salinity on vegetables, strawberries and artichoke crops using surface and pressurized irrigation systems to calibrate and validate a root zone salinity model. We first applied the method of Morris to screen model parameters that have negligible influence on the output (soil‐water electrical conductivity (ECsw)), and then the variance-based method of Sobol to select parameter values and complete model calibration and validation. While model simulations successfully captured long-term trends in soil salinity, model predictions underestimated ECsw for high ECsw samples. The model prediction error for the validation case ranged from 2.6% to 39%. The degree of soil salinization due to continuous application of water with electrical conductivity (ECw) of 0.57 dS/m to 1.76 dS/m depends on multiple factors; ECw and actual crop evapotranspiration had a positive effect on ECsw, while rainfall amounts and fallow had a negative effect. A 50-year simulation indicated that soil water equilibrium (ECsw ≤ 2dS/m, the initial ECsw) was reached after 8 to 14 years for vegetable crops irrigated with ECw of 0.95 to 1.76. Annual salt output loads for the 50-year simulation with runoff was a magnitude greater (from 305 to 1028 kg/ha/year) than that in deep percolation (up to 64 kg/ha/year). However, for all sites throughout the 50-year simulation, seasonal root zone salinity (saturated paste extract) did not exceed thresholds for salt tolerance for the selected crop rotations for the range of blended applied water salinities.

SaltMod estimation of root-zone salinity Varadarajan and Purandara Application of SaltMod to estimate root-zone salinity in a command area

Waterlogging and salinity are the common features associated with many of the irrigation commands of surface water projects. This study aims to estimate the root zone salinity of the left and right bank canal commands of Ghataprabha irrigation command, Karnataka, India. The hydro-salinity model SaltMod was applied to selected agriculture plots at Gokak, Mudhol, Biligi and Bagalkot taluks for the prediction of root-zone salinity and leaching efficiency. The model simulated the soil-profile salinity for 20 years with and without subsurface drainage. The salinity level shows a decline with an increase of leaching efficiency. The leaching efficiency of 0.2 shows the best match with the actual efficiency under adequate drainage conditions. The model shows a steady increase, reaching the levels up to 8.0 decisiemens/metre (dS/m) to 10.6 dS/m at the end of the 20-year period under no drainage. If suitable drainage system is not provided, the area will further get salinised, thus making the land uncultivable. We conclude from the present study that it is necessary to provide proper drainage facilities to control the salinity levels in the study area.

Bigtooth Maples from Three Geographically Different Origins Endure Root Zone Salinity

The contiguous geographic range of bigtooth maple (Acer grandidentatum Nutt.) covers Utah, Idaho, Wyoming, Arizona, New Mexico, and Texas and suggests that this deciduous tree is a potential landscape plant for many regions. Using bigtooth maples selected from provenances in New Mexico (NM), Utah (UT) and Texas (TX), we evaluated physiological and growth traits of plants subjected to root zone salinity treatments at concentrations 0 (control), 2.5, 5.0 or 10.0 dS·m−1 (0, 1,600, 3,200, or 6,400 ppm). At harvest, foliar Kjeldahl nitrogen, potassium, magnesium, phosphorus, and calcium concentrations of salinity-treated plants were not different from control plants. Plants from the TX provenance had the highest leaf dry weight (DW) (15.7 g [0.55 oz]), larger stem diameter (11.4 mm [0.45 in]), less foliar injury, and less negative midday stem water potentials while accumulating three and two times more foliar sodium than plants from the UT and NM provenance plants, respectively. Total DW (95.9 g [3.4 oz]) of TX plants was triple that of the other two provenances. While bigtooth maples from the three provenances tolerated salinity, those from the TX provenance show enhanced resiliency to root zone salinity.