Coastal agriculture frequently relies on surface water for irrigation. However, in Florida, surface water availability can become limited during the dry season, leading growers to switch to groundwater. Groundwater in coastal areas often contains high salt concentrations which can negatively affect crop production. Citrus species, one of the most cultivated crops in Florida, are sensitive to salt stress. Among other strategies, irrigation management is used to mitigate salinity buildup in soil by leaching salts away from the root zone. Increased irrigation rates with water sources in the ‘slight’ to ‘moderate’ range of salinity (0.7 to 3 dS/m) have been shown to reduce salt accumulation in the soil without affecting production. However, when the water has high salinity concentrations (>3 dS/m), increasing the irrigation rate beyond 125%-130% of the crop evapotranspiration (ETc) is not sustainable due to the high-water usage. Conversely, a limited volume of water applied for leaching the salts can exacerbate the accumulation. In coastal Florida, where often only high salinity water is available during the dry season, evaluating short-term strategies to maintain crop production is crucial. The objective is to understand how irrigation water with high salinity concentrations and different irrigation rates impact plant performance and soil salinity accumulation. In this study, one-year-old ‘Ruby Red’ grapefruit trees grafted on ‘US-942’ rootstock were planted in a weighing lysimeter phenotyping platform (“Plant Array”) under greenhouse-controlled conditions. Irrigation water with high salinity concentration (5 dS/m) was precisely applied at three different irrigation rates: 75% (deficit), 100% (regular), and 125% (excessive) of the ETc. A control treatment with water at a low salinity concentration (0.3 dS/m) was applied at 100% ETc for comparison. Transpiration, plant net weight, soil moisture and soil electrical conductivity (EC) were recorded daily. Bulk leaf water potential, osmotic potential, and dark-adapted chlorophyll fluorescence were measured at the beginning and at the end of the experiment. Results showed that ETc and net weight decreased for those plants irrigated with high salinity concentration compared to the control. Salt EC was higher for those trees irrigated with 75% ETc under high salinity concentration resulting in the lowest ETc rates. Plants irrigated with 100% and 125% ETc rates showed similar results, likely due to decreasing transpiration of trees upon high salinity treatment application. Different plant performance under different irrigation rates emphasized the need of evaluating irrigation strategies in mitigating salt stress in citrus, particularly in region with limited water resources.
Replicated irrigation trials were performed on cauliflower (Brassica oleracea var. botrytis cv. Symphony) in California’s Salinas Valley during 2018 and 2019. The CropManage online decision-support system was used to guide evapotranspiration-based irrigation scheduling. Overhead sprinklers were used to establish the crop with 60-70 mm of water, followed by surface drip for the remaining crop cycle. A randomized complete block design, with six replications, was used to administer four treatments near 50%, 75%, 100% and 150% of estimated full crop water requirement (T50, T75, T100, T150) during the drip phase. An additional drip treatment at 125% (T125) was added in 2019. Applied water totals across treatments ranged from 199-410 mm in 2018 and 179-369 mm in 2019 (plus 35 mm of precipitation). No significant differences were observed between total curd (head) yields from T100 and T150 in year 1 (> 30 Mg ha-1), although marketable yield from T150 was greater. Total yield of T100 and T125 were significantly greater than T150 during year 2, but marketable yield was similar among T100-T150. No significant difference was observed in fresh or aboveground dry biomass production from T100 and T150. Significant reductions in yields and biomass production were observed in T50 and T75 for both years. T100 and T150 had the highest irrigation water productivity with respect to marketable yield. Nitrogen uptake and fertilizer N recovery were highest in T100 and T150 during 2018, but no significant treatment differences were observed in 2019. These field trials demonstrated that estimating crop evapotranspiration and irrigation requirements of cauliflower through a decision support service such as CropManage can be a reliable tool for irrigation scheduling.
Saltwater intrusion into coastal areas is a major problem that reduces acreage under vegetable production. Cultivating salt-tolerant varieties is one of the approaches to overcome this problem. The long-term goal of this project is to screen and identify salt-tolerant watermelon germplasm. We assessed the impact of salinity stress from natural brackish water collected in Charleston, South Carolina (32o47’38” N and 80o3’25” W), on the growth morphology of four watermelon cultivars to identify one discriminatory concentration to be used for evaluating hundreds of watermelon accessions available in USDA-ARS Germplasm Resources Information Network. Watermelon plants were hydroponically grown in a Nutrient Film Technique (NFT) system at various EC levels (natural brackish water diluted with de-ionized water to generate 5.5, 10, 12, 14, and 19 dS/m and control, 0 dS/m) and plant growth and shoot morphology were monitored. All cultivars failed to withstand salinity stress at 19 dS/m. Surprisingly watermelon cultivars tolerated fairly high levels of salinity (5.5-14 dS/m ⁓3,530 - 8,960 ppm salt concentration) with inhibited growth. Increasing EC levels correlated with decreased growth parameters such as plant height, leaf number, and shoot fresh and dry weight. Chlorophyll content and electrolyte leakage values increased with higher brackish water concentrations, peaking at 14 dS/m. These values were notably elevated, with chlorophyll content and electrolyte leakage being 5 and 2 times higher than the control, respectively. Cultivar Sugar Baby had significantly greater shoot length, chlorophyll content, and electrolyte leakage compared to other cultivars (Crimson Sweet, Charleston Grey, and Black Diamond). The other growth parameters were similar across all cultivars. Further research to identify an optimal EC between 14 and 19 dS/m for use in large-scale evaluation of germplasm accessions will be needed.
Increasing salinity levels pose significant challenges to coastal vegetable cultivation, particularly impacting salt-sensitive crops like cucumber, leading to reduced growth, development, yield, and quality. This study assessed the responses of six commercial cucumber cultivars to different salinity levels. Cucumber plants were grown in a hoop house hydroponically using various dilutions of brackish water in a Nutrient Film Technique (NFT) system at EC levels 3, 6, and 12 dS/m, along with adequate controls (0 dS/m). Increasing salinity levels caused a significant decline in plant growth parameters (shoot length, biomass, leaf number). Overall a 59% reduction in shoot length and 52% decrease in dry biomass was observed at 12 dS/m compared to control. The cultivar, Stripped Armenian had significantly greater shoot length (163 cm) and dry biomass (59 g), compared to the others (Diva, Katrina, Lemon, H-19 Little Leaf, and Suyolong) by 52-207% and 126-409%, respectively. Additionally, Stripped Armenians dry weight exceeded the control by 120%, 115%, and 25% in 3, 6, and 12 dS/m treatments, respectively. Gaseous exchange parameters measured with Licor 6850 (photosynthetic rate, stomatal conductance, transpiration rate, and intercellular CO2 concentration) declined significantly with increasing salinity at vegetative and reproductive stages. The photosynthetic rate and stomatal conductance showed reductions of 15-17% and 13-50%, at salinity levels of 3 dS/m, 6 dS/m, and 12 dS/m, compared to the control treatment respectively. Similar reductions were also observed at the reproductive stage. Stripped Armenian consistently exhibited higher photosynthetic rate (4-27%), stomatal conductance (7-75%), and transpiration rate (6-56%) compared to other cultivars at vegetative and reproductive stages. In conclusion, Stripped Armenian demonstrated substantial tolerance to 12 dS/m salinity compared to other cultivars and may prove useful in saline environments, however further research is needed.
A rapid decline in water table of the Ogallala aquifer necessitates water conservation farming practices in Texas High Plains (THP). Deficit irrigation (DI) and biochar amendment strategies are widely adopted to sustain agriculture in semi-arid regions like THP. Although these practices are studied individually, research involving the combined effect of these factors is lacking, especially in THP. The goal of this study was to investigate the effect of DI and biochar application on soil water depletion, root distribution, and water use efficiency of cucumber in West Texas. A two-year field study was conducted in a split-plot design with irrigation levels as the main plots: I1[100% crop evapotranspiration (ETc) replacement before mid-season (EBM))-100% ETc replacement after mid-season (EAM), I2 (80% ETc EBM- 60% ETc EAM), I3 (60% ETc EBM - 80% ETc EAM), I4 (40% ETc EBM-40% ETc EAM)] and biochar rates [ 0 t/ha,15 t/ha, and 20 t/ha] as sub-plots with four replications. Results showed that I4 had the largest and I1 had the least soil water depletion, and the differences in water depletion among irrigation levels were significant up to 1-m soil depth. Root length density (RLD) and root surface area density (RSAD) were significantly higher in I1 followed by I2 and I3, and these parameters were the least in I4. Water Use Efficiency (WUE) showed I2 being the most water productive DI treatment with an average increase of 5% compared to I1. Biochar didn't influence water depletion, RLD, and WUE but significantly increased RSAD compared to non-amended plots. Thus, deficit irrigation level I2 can be a potential alternative irrigation to full irrigation for enhancing water productivity of cucumber in the THP. More pronounced biochar effects could be expected in long term studies.
This study aimed at conducting an impact evaluation of irrigation management practices in processing onion production. A three-year experiment was carried out in 15 commercial processing onion fields under different irrigation methods of furrow, solid-set sprinkler, and subsurface drip. The experimental sites were located in the Imperial Valley, California’s low desert region. All fields were on a 40-inch bed, six plant rows per bed with a spacing of 2.5-in between planting lines. The fields had a variable soil type with predominate soil texture from fine sandy to silty clay loam. Water, nitrogen, and energy used, bulb weights, soil moisture, soil nitrate and salinity, and actual evapotranspiration were measured in each site. A wide range of seasonal irrigation water applied was observed across the experimental sites. Irrigation water applied varied from 3.3 ac-ft/ac in a drip irrigated field to 6.9 ac-ft/ac in a furrow irrigated field. The results demonstrated that utilizing subsurface drip irrigation in processing onions could conserve 0.8 and 2.4 ac-ft/ac water in compared with solid-set sprinkler and furrow irrigation systems, respectively. The water productivity, the ratio of onion bulb weight to water applied, was determined 4.9, 4.3, and 2.7 t/ac-ft for the drip, sprinkler, and furrow irrigated fields, respectively. A greater nitrogen use efficiency was found in the drip irrigated fields compared to the sprinkler (15.2% points) and furrow (62.1% points) irrigated fields. The findings illustrated a higher salt accumulation on the topsoil (0-6 in. depth) in the drip irrigated fields. In other words, drip irrigation could cause salinity impacts in desert processing onions, and therefore, more frequent light irrigation events may be an effective tool to manage salinity. More nitrate leaching was also observed from the topsoil in the sites irrigated by sprinklers. Energy productivity, the ratio of onion bulb weight to fuel consumption, was 48.3% points higher in the drip fields than the sprinkler fields. The results revealed that irrigation practice has a significant impact on resource-use efficiency and environmental issues.
Glyphosate is the most widely used herbicide in the world due to its relevance in agricultural practices and urban lawncare. While this herbicide is prominent in various countries, it has been continuously surrounded by controversy for the past decade. With reports of potential dangers to human health, contradicting reports from government agencies, and lawsuits against the company Monsanto, the creator of Roundup whose key active ingredient is glyphosate, there is opinion-based literature and confusion among the public. There is a plethora of published literature discussing what glyphosate is and the potential dangers to the environment; however, there is minimal research on the effects glyphosate has on water quality through runoff in urban areas. This research is aimed to assess the presence of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in the waterways of Stillwater, OK. This is done by collecting water samples where runoff was present in urban areas. It is important to understand the presence of glyphosate in runoff to view the persistence of this chemical within waterways and different environments. Keywords: glyphosate, AMPA, water quality, runoff, controversy, samples
The escalating regulatory pressure to achieve sustainable groundwater use in California will demand improved irrigation efficiency. Even though approximately 80 to 90% of the sprinkler-applied water to a strawberry crop is lost through runoff, deep percolation and evaporation, all the strawberry fields in Ventura County are still irrigated with overhead sprinklers during crop establishment. This study quantified differences in water use, yield, canopy coverage and root depth between drip tape and micro-sprinkler irrigation during crop establishment at a commercial field located in Oxnard, CA during the 2023-2024 growing season. Treatments consisted of three irrigation methods used during the first five weeks: 1) primarily drip tape (DT), 2) micro-sprinklers only (MS), and 3) a combination of drip tape and micro-sprinklers (C). The irrigation scheduling of the MS treatment was defined by the irrigator (grower standard), while the DT and C treatments were guided by tensiometers and field observations. All other production practices remained the same. Each treatment was replicated four times in a randomized complete block design, with an area of approximately 1.7 acre per plot (40 beds of 350ft long). Treatments were carried out for 35 days from planting (Oct 5), after which drip irrigation became the only irrigation method. Total water use during establishment was very similar among treatments: 3.9, 3.6 and 4.0 acre-in for DT, C and MS, respectively. With four plant rows and three drip lines per bed, the DT treatment was irrigated for longer than anticipated to assure uniform soil moisture around the plant roots. Marketable yield until Mar 14 was 4,583, 4,229 and 4,297 lb/acre for DT, MS and C, respectively. Although not statistically significant, DT yield was 8.4% greater than MS (p-value = 0.802), and 6.7% greater than C (p-value = 0.865). Canopy cover trends were very similar between DT and C, while MS was between 13 and 29% lower than DT from 48 to 61 days after planting. Canopy coverage equalized at 90 days after planting after significant precipitation during Dec and Jan. Average root depth of DT was 38 and 19% greater than MS for 15 and 28 days after planting, respectively. In summary, this study found equal or superior crop performance of DT compared to MS during strawberry establishment. We expect that increasing the number of drip tape per bed from three to four would significantly decrease the irrigation time needed to provide ideal soil moisture, consequently decreasing water use.
