Seasonal Water Use Research Articles

Higher phosphorus and water use efficiencies and leaf stoichiometry contribute to legume success in drylands

Abstract Legumes are essential plants in dryland ecosystems worldwide because they increase nitrogen availability, so their understanding is vital for improving knowledge and modelling in the face of climate change. This work studies the differences in resource use efficiency and their relationship with photosynthetic, photochemical, bioelemental, and stoichiometric traits of coexistent legumes and non‐legumes in a Sonoran Desert ecosystem. We found that legumes had higher photosynthetic rates, intrinsic and seasonal water use efficiency (WUE), phosphorus use efficiency (PPUE), and higher light utilisation mediated by chlorophyll content and active reaction centers, which may increase their photoprotection. Legumes can increase their WUE and PPUE with no changes in nitrogen use efficiency (PNUE). Consequently, observed trait relationships between studied traits in these legumes have significant differences with the non‐legume species in the study. Stoichiometry is helpful, in some cases, as an indicator of nutrient use efficiency and enables functional group differentiation. Our results strongly relate legumes' higher resource use efficiency with their success in dryland ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

Assessing the impact of early and terminal droughts on root growth, grain yield and yield stability in old and modern wheat cultivars on the Loess Plateau

Understanding changes in root traits of high-yielding genotypes that consistently perform during different drought periods is crucial for improving wheat production and yield stability. A 2-year field trial and a pot experiment were conducted to determine the response of root growth and grain yield to early and terminal droughts in old and modern cultivars (FC3: 1960s and CH1: 2010s) under rainfed and irrigated conditions in the field. Rainfed wheat faced terminal drought in 2015–2016 and early drought in 2016–2017. Plants in the pot experiment were exposed to terminal drought, early drought, and well-watered. Both field and pot experiments showed higher grain yield in modern cultivar CH1 compared to FC3. Early and terminal droughts reduced grain yield in both cultivars, with a greater reduction in FC3. CH1 exhibited higher yield stability under drought conditions and experienced less reduction in early drought. Compared to FC3, CH1 produced more root biomass in the early growth stage. At anthesis, CH1 had significantly lower root biomass and root length density in the topsoil layer (00.2 m) and higher in the subsoil layer (0.21.0 m) than FC3, respectively. At maturity, the retention rate of subsoil root biomass in CH1 was higher, especially under early drought (80.2 % in field and 93.9 % in pot experiments). Both cultivars consumed similar seasonal water use, but CH1 reduced pre-anthesis water use and consumed more water after anthesis. This study indicates that modern cultivar had vigorous root growth at early stage. A higher proportion of root biomass preserved in deep soil after anthesis enhanced post-anthesis water use and photosynthetic rate, improved post-anthesis dry matter accumulation, and thus resulted in higher thousand kernel weight. These factors ensure higher yield and yield stability under both early and terminal drought stress.

Diurnal and Seasonal Variations of Water Use Efficiency of Rice–Wheat Rotation Cropland in the Jianghuai River Basin of China

ABSTRACTRice–wheat rotation cropland is one of the most important agroecosystems in South China, the escalation of conflict between food demand augment and water supply shortage increased with climate change. Water use efficiency plays a more significant role in optimising water and carbon management. Thus, the diurnal and seasonal variations of water use efficiency were assessed by the 3‐year eddy covariance observations in the Shouxian National Observatory, a typical rice–wheat rotation station. The results revealed a ‘U’‐shaped diurnal pattern of water use efficiency for winter wheat (Triticum aestivum L.) and rice (Oryza sativa L.). Seasonal water use efficiency had two peaks with the highest in the winter wheat‐growing season. The average water use efficiency for the rice–wheat rotation cropland was 2.85 g C kg−1 H2O over the whole year with 2.62 and 3.11 g C kg−1 H2O for winter wheat and rice, respectively. However, gross primary productivity and evapotranspiration of rice were higher than those of winter wheat. Temperature, photosynthetically active radiation were the principal impact factors of water use efficiency in the rice‐growing season. Comparatively, soil water and vapour pressure deficit dominated the water use efficiency changes in the winter wheat‐growing season. Our analyses can help understand the water use requirements for carbon assimilation on rice–wheat rotation cropland on the field scale.

Ecosystem level carbon and moisture fluxes from a high biomass fibre producing jute crop (Corchorus olitorius L): An eddy covariance-based analysis

ContextJute (Corchorus olitorius L) is the second-largest natural fibre producing crop in the world and plays a key role in the rural economy of South Asia particularly India and Bangladesh. It has diverse use due to its long length, lusture, biodegradability, high tensile strength, heat resistance and bendability. Jute is also fast-growing high biomass crop and quantification of the carbon / moisture exchanges is need of the hour towards its sustainability. ObjectiveThe study aims at quantitative estimation of the ecosystem level CO2 and H2O exchanges at diurnal, daily, and seasonal scales from jute crop cultivated in the alluvial soil of the Gangetic delta under a tropical hot and moist sub-humid climate during the years 2021–23. MethodsAn eddy covariance flux tower with suite of meteorological sensors were established at the jute growing farm to assess the high frequency ecosystem level exchanges of CO2, H2O and biometeorological parameters. Concurrent crop bio-physical parameters were also measured. The flux data were processed, quality checked, gap-filled and partitioned to construct seamless time-series of half-hourly fluxes for further analysis towards its dynamics, driving parameters, photosynthetic response and derived eco-physiological parameters. ResultsThe half-hourly CO2 fluxes exhibited significant variations across different growth stages of the jute crop, reaching peak values during the fibre development to maturity stages [mean Net Ecosystem CO2 Exchange (NEE) ranging from −20 to −22 µmol m−2 s−1; mean Gross Primary Production (GPP) ranging from 25 to 30 µmol m−2 s−1; and mean Ecosystem Respiration (Reco) ranging from 8 to 10 µmol m−2 s−1]. Seasonal GPP values was found to be high (902–1038 gC m−2) with moderate NEE value of −150 to −223 gC m−2. Seasonal mean Ecosystem Water Use Efficiency (EWUE) was high (2.5–2.7 gC kg−1 H2O) compared to other C3 crop. The daily Crop Coefficient (Kc) peaked at 1–1.2 during 90–110 Days After Sowing (DAS), indicative of high physiological activities. ConclusionDespite relatively short crop duration but high biomass (peak Leaf Area Index, LAI ∼6 m2m−2), the jute crop proved to be a robust gross CO2 sink. Due to the rapid growth, the jute crop allocates a significant portion of GPP as Reco (78–84 %), resulting in a relatively lower seasonal NEE. The high EWUE coupled with a net positive CO2 exchange positioned jute as a potential climate-resilient crop. This study provides valuable insights into the ecosystem exchanges of the jute crop, which in turn contribute to the global carbon and moisture budget.

Water use and water use efficiency of three Brassicaceae oilseeds under high‐ and low‐yielding environments

AbstractBrassicaceae oilseed crops have proven potential as vegetable oil feedstock for biofuels and food uses. However, meeting a growing demand for vegetable oils for food and industrial uses will require identifying oilseed species that are best suited for various growing environments within a particular region. The objective of this study was to compare growth dynamics, seasonal water use (WU), seed yields, and water use efficiency (WUE) of canola (Brassica napus L.), camelina (Camelina sativa L.), and white mustard (Sinapis alba L.) to determine their suitability under three different environments within the northern Great Plains. Comparisons were made among these species over three growing seasons between 2013 and 2016 at Morris, MN; Mandan, ND; and Sidney, MT, situated along a strong precipitation gradient from east to west. Generally, growing season precipitation was similar at Morris and Mandan, but both were considerably greater than at Sidney. Seasonal WU was similar among these oilseed species at Morris and Mandan but was greatest for camelina at the drier Sidney environment. Canola seed yield was the greatest at Morris and had higher WUE than camelina and white mustard. At Mandan and Sidney, canola and camelina had similar seed yields and WUE, which were generally greater than white mustard. Under abundant moisture and low stress (e.g., Morris), seed yield per millimeter of water used could be maximized by growing canola, while in a drier more stressful environment like Sidney, seed yield per millimeter of water used could be maximized by growing camelina.

Seasonal transpiration dynamics and water use strategy of a farmland shelterbelt in Gurbantunggut Desert oasis, northwestern China

Farmland shelterbelts provide an ecological barrier to oases, but their growth is inhibited or even dies under water scarcity. Therefore, it is necessary to understand the response of farmland shelterbelts to environmental changes for their own survival in order to promote the long-term healthy development of agroforestry systems and improve water management in oases in the northwest arid region. In this study, we measured the sap flow and environmental factors to determine the transpiration dynamics and its influencing factors. The seasonal variations in water use strategy of Populus alba var. pyramidalis Bunge were identified by using stable isotopes of δ18O in xylem, soil water and groundwater coupled with the Iso-Source model. The results showed that the transpiration of the populus was significantly higher in the growing season (more than 80% of the total transpiration) than in the non-growing season, and the transpiration was closely related to air temperature, vapor pressure deficit, soil water content, and soil temperature. The water use strategy had seasonal variations. The populus obtained water predominantly from 0–40 cm soil water (approximately 75%) in the wet spring and then switched to deeper water sources (40–150 cm soil water and groundwater) as the season progressed. The contribution of deeper water sources increased to 84–92% in summer and autumn. This suggested that Populus alba var. pyramidalis Bunge has ecological plasticity, as it could explore deeper water sources as the water stress increased. The ability to switch rapidly among different water sources could put a plant at an advantage if competition for water occurs within the ecosystem. Our findings can provide insights into temporal transpiration dynamics as well as the strategy adopted by farmland shelterbelts to counteract the drought stress associated with the shallow soils in desert oasis ecosystems.

Evaluation of Canopy Temperature Based Crop Water Stress Index for Deficit Irrigation Management of Sugar Beet in Semi-Arid Climate

Highlights Sugar beet irrigation scheduling was based on daily average crop water stress index between 13:00 and 16:00 hours. Three crop water stress index thresholds, 0.2, 0.35, and 0.55, were evaluated for irrigation scheduling. Season evapotranspiration decreased and soil water extraction increased as crop water stress threshold increased. There was no significant difference in root or sucrose yield between full irrigation and 0.2 crop water stress index, while seasonal irrigation depths were reduced from133 to 185 mm. Abstract. Sugar beet is an economically important crop in the semi-arid Intermountain Western U.S., with seasonal water use ranging from 500 to 900 mm. Sugar beet is a deep-rooted crop (1.5-2 m) in unrestricted soil profiles that can utilize stored soil water to reduce seasonal irrigation requirements. Effective use of stored soil water below 0.6 m requires precise irrigation scheduling and knowledge of soil water availability below 0.6 m, which is usually unknown due to the labor and expense of soil water monitoring at deeper depths and uncertainty in effective rooting depth and soil water holding capacity. Deficit irrigation (DI) management of sugar beet using a thermal-based crop water stress index (CWSI) has the potential to overcome soil water monitoring limitations and facilitate the utilization of stored soil water to reduce seasonal irrigation requirements. The objective of the research summarized in this paper was to implement and evaluate the effect of automated DI scheduling of sugar beet using three daily average CWSI thresholds (0.2, 0.35, and 0.55) on seasonal irrigation requirement, crop evapotranspiration, seasonal soil water depletion, root yield, estimated recoverable sugar (ERS) yield, and water use efficiency compared to full irrigation. There were no significant differences in root and ERS yield between full irrigation and 0.2 CWSI DI treatment, while seasonal ET was significantly decreased, seasonal soil water extraction was significantly increased, and seasonal irrigation depths were reduced from 133 to 185 mm. Root and ERS yield water production functions were curvilinear with a downward concave. Root and ERS yield water use efficiencies were constant or increased slightly for crop evapotranspiration reductions up to 85% of full irrigation evapotranspiration. The results indicate that irrigating when the average daily CWSI sugar beet exceeds 0.2 is an effective means for mild deficit irrigation scheduling to reduce seasonal irrigation requirements with no significant effect on root and ERS yield. Keywords: Crop water stress index, Evapotranspiration, Irrigation, Irrigation scheduling, Root yield, Sucrose yield, Sugar beet.

Contrasting response of growing season water use efficiency to precipitation changes between alpine meadows and alpine steppes over the Tibetan Plateau

Alpine grasslands are the dominant vegetation of the Tibetan Plateau (TP) and are essential to understanding the mechanism of change in water use efficiency (WUE) in high-cold ecosystems in a changing environment. However, it is still unclear how the WUE of different alpine grasslands respond to changes in precipitation. Therefore, we investigated the variations in growing season WUE and its drivers among different grassland types, including alpine meadow of permafrost (PAM), alpine meadow of seasonal frost (SAM), alpine steppe of permafrost (PAS), and alpine steppe of seasonal frost (SAS), in different precipitation years. The mean growing season WUE was significantly higher for alpine meadow and seasonal frost regions and lower for alpine steppe and permafrost regions. WUE increased significantly in the alpine meadow (PAM and SAM) but decreased (PAS) or varied little (SAS) in the alpine steppe during the period of 1982–2014. Compared to normal years, WUE in the PAS region increased by 22% and 10% in severe and mild dry years, respectively, and decreased by approximately 10% in wet years. For the alpine meadow, WUE decreased more in severe dry years than in mild dry years and increased slightly in wet years. In different precipitation years, WUE for all grassland types was mainly controlled by the vegetation factor. Results suggest that the WUE in alpine grasslands, especially in the PAS region, may decline if the “dry gets wet, wet gets dry” happen over the TP in the future.

Balancing water and radiation productivity suggests a clue for improving yields in wheat under combined water deficit and terminal heat stress.

Sustaining crop yield under abiotic stresses with optimized resource use is a prerequisite for sustainable agriculture, especially in arid and semi-arid areas. Water and heat stress are major abiotic stresses impacting crop growth and yield by influencing complex physiological and biochemical processes during the life cycle of crops. In a 2-year (2015-2017) research, spring wheat cv. HD-2967 was grown under deficit irrigation and delayed sowing conditions to impose water and terminal heat stresses, respectively. The data were analyzed for seasonal crop water use, radiation interception, water productivity (WP), and radiation productivity (RP) under combined water deficit and terminal heat stresses. Seasonal crop water use was significantly affected by stresses in the order of water + terminal heat > water > terminal heat. Water stress showed minimal effect on the light extinction coefficient and consequently on seasonal intercepted photosynthetically active radiation (IPAR). However, seasonal IPAR was primarily affected by combined water + terminal heat and terminal heat stress alone. The slope of crop water use and IPAR, i.e., canopy conductance, an indicator of canopy stomatal conductance, was more influenced by water stress than by terminal heat stress. Results showed that linear proportionality between WP and RP is no longer valid under stress conditions, as it follows a curvilinear relation. This is further supported by the fact that independent productivity (either water or radiation) lacked the ability to explain variability in the final economic yield or biomass of wheat. However, the ratio of RP to WP explained the variability in wheat yield/biomass under individual or combined stresses. This suggests a clue for improving higher wheat yield under stress by managing WP and RP. The highest biomass or yield is realized when the ratio of RP to WP approaches unity. Screening of genotypes for traits leading to a higher ratio of RP to WP provides an opportunity for improving wheat productivity under stressed environments.

Radon prevalence in domestic water in the Ría de Vigo coastal basin (NW Iberian Peninsula)

The Ría de Vigo catchment is situated in the largest radon-prone area of the Iberian Peninsula. High local indoor radon (222Rn) levels are the preeminent source of radiation exposure, with negative effects on health. Nevertheless, information on radon levels of natural waters and the potential human exposure risks associated with their domestic use is very sparse. To elucidate the environmental factors increasing human exposure risk to radon during domestic water use, we undertook a survey of local water sources, including springs, rivers, wells, and boreholes, over different temporal scales. Continental waters were highly enriched in 222Rn: activities ranged from 1.2 to 20.2 Bq L−1 in rivers and levels one to two orders of magnitude higher were found in groundwaters (from 8.0 to 2737 Bq L−1; median 121.1 Bq L−1). The geology and hydrogeology of local crystalline aquifers support one order of magnitude higher 222Rn activities in groundwater stored in deeper fractured rock compared to that contained within the highly weathered regolith at the surface. During the mean dry season, 222Rn activities nearly doubled in most sampled waters in comparison to the wet period (from 94.9 during the dry season to 187.3 Bq L−1 during wet period; n = 37). Seasonal water use and recharge cycles and thermal convection are postulated to explain this variation in radon activities. The high 222Rn activities cause the total effective dose of radiation received from domestic use of untreated groundwaters to exceed the recommended 0.1 mSv y−1. Since more than 70% of this dose comes from indoor water degassing and subsequent 222Rn inhalation, preventative health policy in the form of 222Rn remediation and mitigation measures should be implemented prior to pumping untreated groundwater into dwellings, particularly during the dry period.

Trakya Bölgesi Koşullarında Kısıntılı Sulama Programlarının Darıda (Panicum miliaceum L.) Verim Üzerine Etkileri

Millets are indigenous to many parts of the world and are more widely grown, especially in areas where water is limited. The most widely grown millet type is sorghum (Sorghum bicolor L.). A field study was carried out to determine the effect of deficit irrigation regimes on grain yield and seasonal evapotranspiration of proso millet (Panicum miliaceum L.) in the Thrace Region of Turkey. The field trials were conducted on a loam Entisol soil, on Öğretmenoğlu and Beydarı, the most popular varieties in the research area. In the study, the split plots experimental design with three replications was used. Eight different irrigation issues are considered, including combinations of the vegetative (V), flowering (F) and grain formation (Y) phases of the plant (including dry conditions, NoI). Results showed that proso millet was significantly affected by water stress during the sensitive flowering stage. The highest grain yield was obtained with 4.09 t ha-1 from Öğretmenoğlu and 4.03 t ha-1 from Beydarı, which was rinsed (VFY) in all development periods. Seasonal irrigation water use and evapotranspiration of the irrigated (VFY) in all development periods were 318 and 579 mm, respectively, for the non-stressed treatment. The seasonal water yield function was calculated as Y = 0.4087 ET + 144.03, and the seasonal yield-water response factor value was calculated as 0.57'.

Water sources used by artificial Salix psammophila in stands of different ages based on stable isotope analysis in northeastern Mu Us Sandy Land

Understanding the water use pattern of artificially restored vegetation is important to provide reasonable water management strategies. However, the characteristics, controls and differences of water sources of planted Salix psammophila at different developmental stages remain poorly understood. In this study, the hydrogen and oxygen isotope compositions of xylem water, soil water, and rainwater were measured and coupled with the MixSIAR model to investigate the variations and controls of water use patterns of different aged S. psammophila in a semi-arid region in northeastern Mu Us Sandy Land. Results showed that >60% of water used by 6-yr S. psammophila derived from 0 to 120 cm soil layer throughout the growing season due to the relatively shallow roots (0–100 cm). In contrast, water sources used by 12- and 18-yr S. psammophila differed markedly between the dry and rainy seasons, which were attributed to the developed dimorphic root systems and seasonal changes in soil water profile. In the dry season, 12- and 18-yr S. psammophila extracted 71.93% and 68.91% of water from 120 to 300 cm and 40–200 cm soil layer, respectively; in the rainy season, however, they both shifted main water sources to 0–120 cm soil layer (65.09% and 56.14%). The severe soil desiccation and dead roots observed in the 18-yr stand decreased the ability of old S. psammophila to extract water from the deep soil layer (200–300 cm) in the dry season. Thus, changes in the vertical distribution of roots and soil water contents controlled the seasonal water use pattern of different aged S. psammophila. Our study demonstrates that the age-dependent water use pattern of S. psammophila should be considered to implement the corresponding management measures in future afforestation plans to avoid overuse of water and maintain sustainable vegetation restoration in the water-limited desert regions.

Modeling seasonal vegetation phenology from hydroclimatic drivers for contrasting plant functional groups within drylands of the Southwestern USA

In dryland ecosystems, vegetation within different plant functional groups exhibits distinct seasonal phenologies that are affected by the prevailing hydroclimatic forcing. The seasonal variability of precipitation, atmospheric evaporative demand, and streamflow influences root-zone water availability to plants in water-limited environments. Increasing interannual variations in climate forcing of the local water balance and uncertainty regarding climate change projections have raised the potential for phenological shifts and changes to vegetation dynamics. This poses significant risks to plant functional types across large areas, especially in drylands and within riparian ecosystems. Due to the complex interactions between climate, water availability, and seasonal plant water use, the timing and amplitude of phenological responses to specific hydroclimate forcing cannot be determined a priori, thus limiting efforts to dynamically predict vegetation greenness under future climate change. Here, we analyze two decades (1994–2021) of remote sensing data (soil adjusted vegetation index (SAVI)) as well as contemporaneous hydroclimate data (precipitation, potential evapotranspiration, depth to groundwater, and air temperature), to identify and quantify the key hydroclimatic controls on the timing and amplitude of seasonal greenness. We focus on key phenological events across four different plant functional groups occupying distinct locations and rooting depths in dryland SE Arizona: semi-arid grasses and shrubs, xeric riparian terrace and hydric riparian floodplain trees. We find that key phenological events such as spring and summer greenness peaks in grass and shrubs are strongly driven by contributions from antecedent spring and monsoonal precipitation, respectively. Meanwhile seasonal canopy greenness in floodplain and terrace vegetation showed strong response to groundwater depth as well as antecedent available precipitation (aaP = P − PET) throughout reaches of perennial and intermediate streamflow permanence. The timings of spring green-up and autumn senescence were driven by seasonal changes in air temperature for all plant functional groups. Based on these findings, we develop and test a simple, empirical phenology model, that predicts the timing and amplitude of greenness based on hydroclimate forcing. We demonstrate the feasibility of the model by exploring simple, plausible climate change scenarios, which may inform our understanding of phenological shifts in dryland plant communities and may ultimately improve our predictive capability of investigating and predicting climate-phenology interactions in the future.

A comparative study of fifteen cover crop species for orchard soil management: water uptake, root density traits and soil aggregate stability

Increasing the use of cover crops (CCs) is a necessity in sustainable viticulture, although it might clash with possible excessive competition towards vines. Especially in a climate-change scenario, the latter feature should be minimized while maintaining ecosystem services. Aimed at identifying CCs for vineyard floor management, the trial characterized several species according to their evapotranspiration (ET) rates, root growth patterns, and soil aggregate stability potential. The study was performed in 2020 in Piacenza (Northern Italy) on 15 CC species grown in pots kept outdoor and classified as grasses (GR), legumes (LE) and creeping (CR). Together with bare soil (control), they were arranged in a complete randomized block design. CCs ET was assessed through a gravimetric method, starting before mowing and then repeated 2, 8, 17 and 25 days thereafter. Above-ground dry biomass (ADW), root length density (RLD), root dry weight (RDW) and root diameter class length (DCL) were measured, and mean weight diameter (MWD) was calculated within 0–20 cm depth. Before mowing, ET was the highest in LE (18.6 mm day−1) and the lowest in CR (8.1 mm day−1) the latter being even lower than the control (8.5 mm day−1). The high ET rates shown by LE were mainly related to very fast development after sowing, rather than to a higher transpiration per unit of leaf area. After mowing, the 15 species’ ET reduction (%) plotted vs leaf area index (LAI, m2 m−2) yielded a very close fit (R2 = 0.94), suggesting that (i) a linear decrease in water use is expected anytime starting with an initial LAI of 5–6, (ii) a saturation effect seems to be reached beyond this limit. Selection of cover crop species to be used in the vineyard was mainly based on diurnal and seasonal water use rates as well as dynamic and extent of root growth patterns. Among GR, Festuca ovina stood out as the one with the lowest ET due to its “dwarfing” characteristics, making it suitable for a permanent inter-row covering. CR species confirmed their potential for under-vine grassing, assuring rapid soil coverage, lowest ET rates, and shallow root colonization.

Comparing water use patterns of sand‐binding species in an alpine semi‐arid desert

AbstractThe processes of species obtaining water resources are crucial to evaluate the adaptability of plantations, which can affect the establishment and survival of restored ecosystems and functions of water‐limited ecosystems. However, there are still limitations in understanding water use patterns of different four plantations (Populus sylvestris, Salix cheliophe, Hippophae rhamnoides and Artemisia ordosica) in the Qinghai Lake basin. Stable isotopes of xylem water of four individual species were analysed at different dunes located at the eastern shore of Qinghai Lake in 2018 and 2019. The purpose of this study was to explore potential water sources used by different life form plants, to identify whether the soil moisture content and root distribution determined the plants water use patterns. Results from the Bayesian mixing model MixSIAR showed that all species mainly uses three levels of soil water, but they extracted soil water from different layers in different growing seasons among species. All species primarily depended on water from upper soil layers at the early growing stage, but P. sylvestris and S. cheliophe also absorbed much proportion middle and deep soil layers' water in dry year of 2019. All four species shift to use middle or deep soil layer water rather than shallow water in July with the most rainfall and soil water content (SWC). However, it was only used by P. sylvestris and H. rhamnoides in 2018. In all, seasonal water use pattern of different species was affected by SWC, soil texture and root distribution. Compared with moratorium plantations such as S. cheliophe, mixed afforestation of P. sylvestris and H. rhamnoides maximized of soil water sources absorbed by the plants. The study can shed light on plant–water relationships to facilitate the woody species for afforestation and desertification restoration management in the semi‐arid desert ecosystem.

Optimizing Irrigation for Mechanized Concord Juice Grape Production

<h3>Background and goals</h3> Economic considerations and water shortages associated with climate change are driving the conversion of many hand-pruned and furrow- or sprinkler-irrigated juice grape vineyards in arid eastern Washington to mechanical pruning and drip irrigation. However, juice grape producers have traditionally avoided plant water deficits, fearing a decline in vineyard productivity. <h3>Methods and key findings</h3> We conducted a six-year field trial to test the impact of eight drip-irrigation treatments on large, mechanically-pruned Concord grapevines. We found an estimated crop coefficient of 1.05 between fruit set and harvest. Replacing 75% of crop evapotranspiration (ET_c) from fruit set through harvest reduced annual irrigation water supply by 20% below that of the 100% ET_c control without altering canopy size, yield, or juice composition. Decreasing the water supply from 100% to 50% ET_c at veraison saved only 8% irrigation water, while irrigating at 50% ET_c from fruit set through veraison, and 100% ET_c thereafter, reduced irrigation water use by 30% but decreased canopy size and reduced yield by 14%. Replacing 150% of ET_c between fruit set and veraison increased seasonal water use by 20% but did not alter yield or juice composition. <h3>Conclusions and significance</h3> Deficit irrigation does not impact crop yield and juice composition, so long as vines experience only mild water stress (midday stem water potential &gt; −1 MPa) before veraison. Irrigating at 75% ET_c to impose mild preveraison water stress and mild to moderate postveraison stress optimally balances the goals of water conservation and yield and quality sustainability in juice grape production.

Rainfed cotton crop in central India is a strong net CO2 sink: An eddy covariance-based analysis of ecosystem fluxes

The present study reports ecosystem CO2, H2O exchanges (at diurnal, daily, and seasonal-scale) from a rainfed (dryland) cotton crop (Gossypium sp) grown in deep black soil of tropical central India during 2019–20 and 2020–21, using an Eddy Covariance (EC) system. The half-hourly CO2 fluxes were found to vary significantly across the growth stages of cotton crop with peak values during first boll opening to first picking stage [mean Net Ecosystem CO2 Exchange (NEE), −16 to −18 µmol m-2 s-1; mean Gross Primary production (GPP), 20–22 µmol m-2 s-1; and mean Ecosystem Respiration (Reco), 5–6 µmol m-2 s-1]. The response of daytime GPP to Photosynthetic Photon Flux Density (PPFD) was found to be poor during 1–30 days after sowing (DAS) with R2∼0.4. It improved during 30–150 DAS (R2∼0.6), while deteriorating further as the crop started senescing. The rainfed cotton crop was found to be a strong net CO2 sink, with seasonal NEE, GPP, Reco, and evapotranspiration (ET) of − 333.66 gC m-2, 990.16 gC m-2, 656.50 gC m-2 and 468.32 mm during 2019–20, respectively. The cotton season of 2020–21 had seasonal NEE, GPP, Reco, and ET of − 391.85 gC m-2, 1063.89 gC m-2, 672.04 gC m-2, and 545.25 mm respectively. The seasonal Ecosystem Water Use Efficiency (EWUE) was estimated to be 1.9 and 2.1 gC kg-1 H2O during 2019–20 and 2020–21, respectively. Maximum values of crop coefficient (Kc) were observed to be 1–1.2 during 30–75 DAS, signifying favourable conditions for crop growth. The inter-seasonal differences in the CO2 and H2O exchanges were mainly driven by the differences in incoming PPFD due to cloudiness. Results of the present study will help in understanding the ecosystem processes and exchanges from a rainfed cotton-based cropping system, which in turn can significantly contribute to the global carbon and moisture budget.

Evaluation of irrigation scheduling approaches within sand‐capped turfgrass systems

AbstractIn an effort to improve performance of turfgrass irrigated with poor‐quality water, the practice of sand capping is increasing. Given current strains on water supplies, evaluation of various methods of irrigation scheduling approaches for these systems is needed. The objectives of this 2‐yr field study were to evaluate turfgrass performance, temporal and spatial soil moisture and salinity dynamics, and comparative water use among four irrigation scheduling approaches including (a) wireless soil moisture sensor (SMS), (b) on‐site reference evapotranspiration (ETo), (c) National Oceanic and Atmospheric Administration forecasted reference evapotranspiration, and (d) visual‐wilt‐based treatment. The turfgrass used was ‘Latitude 36’ hybrid bermudagrass [Cynodon dactylon (L.) Pers. ×C. transvaalensis Burtt‐Davy] planted atop a 17.8‐cm medium‐coarse textured sand cap. Results demonstrated that all approaches produced similar levels of acceptable turfgrass quality and percentage green cover with no apparent differences in root development. Forecasted reference evapotranspiration was found to be a good predictor of on‐site ETo (R2 = .97) when comparing daily values across two growing seasons. Under wilt‐based irrigation, the volumetric water content (7.6 cm sand‐cap depth) at which wilt occurred was highest mid‐summer (4.1–4.7%) but declined during early and late summer months (1.8–2.2%), suggesting different thresholds may be needed throughout the season when using SMS‐based scheduling. Finally, seasonal water use was 23% lower for the on‐site ETo–based approach compared with SMS‐based scheduling, although this did not result in elevated electrical conductivity within the sand cap. The results provide important information to guide adoption of data‐driven approaches to irrigation scheduling.

Inter-annual variability of land surface fluxes across vineyards: the role of climate, phenology, and irrigation management

Irrigation and other agricultural management practices play a key role in land surface fluxes and their interactions with atmospheric processes. California’s Central Valley agricultural productivity is strongly linked to water availability associated with conveyance infrastructure and groundwater, but greater scrutiny over agricultural water use requires better practices particularly during extended and severe drought conditions. The future of irrigated agriculture in California is expected to be characterized neither by perpetual scarcity nor by widespread abundance. Thus, further advancing irrigation technologies and improving management practices will be key for California’s agriculture sustainability. In this study, we present micrometeorological observations from the Grape Remote Sensing Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX) project. Daily, seasonal, and inter-seasonal surface flux patterns and relationships across five vineyards over three distinct California wine production regions were investigated. Vineyard actual evapotranspiration showed significant differences at the sub-daily and daily scale when comparisons across wine production regions and varieties were performed. Water use in vineyards in the Central Valley was about 70% greater in comparison to the vineyards at the North Coast area due to canopy size, atmospheric demand, and irrigation inputs. Inter-annual variability of surface fluxes was also significant, even though, overall weather conditions (i.e., air temperature, vapor pressure deficit, wind speed, and solar radiation) were not significantly different. Thus, not only irrigation but also other management practices played a key role in seasonal water use, and given these differences, we conclude that further advancing ground-based techniques to quantify crop water use at an operational scale will be key to facing California’s agriculture present and future water challenges.

Effect of Planting Cotton in Solid and Single-skip Row Configurations on Yield and Soil Water Use

Australian growers plant crops using different skip row configurations to minimize production risk in water-limiting environments. Previous studies have focused on comparing the effect of row configuration on crop yield, and information on soil water is still lacking. The objective of this study was to compare the water use, soil water extraction, and yield of dryland cotton (Gossypium hirsutum L.) planted using solid and single-skip row configurations. An experiment comparing two row configuration treatments (solid and single-skip) was conducted in a cotton field with heavy-clay soil in the sub-tropical climatic environment of Queensland, Australia, during 2007-2008. Water content in the soil profile was measured about weekly using the neutron probe method. Measurements were taken from three positions from the crop row: within a row (P1), between two rows (P2), and skip or planted row (P3). The soil water measurements indicated that, in general, the solid treatment tended to extract more water from shallower depths earlier in the growing season. The single-skip treatment resulted in taller plants, which extracted more water from deeper in the soil profile later in the season. For the entire season, however, both treatments used around the same amount of soil water (128 mm), suggesting that both treatments were water-limited and used all the water available to the crop. The 128 mm added to the seasonal rainfall of 271 mm allowed us to estimate the seasonal crop water use at about 399 mm, which was around half of the seasonal grass-reference evapotranspiration (ETo = 804 mm) for the site. The lint yield was statistically the same for both treatments, although the taller plants from the single-skip treatment tended to have a greater yield per plant (but not significantly different). The estimated water use efficiency (WUE) for the solid and single-skip configuration were 3.5 and 3.3 kg lint/ha/mm water use, respectively.