Seasonal Water Use Research Articles

Automated cycled sprinkler irrigation for spring frost protection of cranberries

Overhead (sprinkler) irrigation is commonly used for spring frost protection of cranberries in southeastern Massachusetts, United States. Historically, conventional forms of irrigation management have been used, generally consisting of running irrigation pumps continuously throughout the night and into the early morning until ambient air temperature reached 1–2°C above the critical temperature of the plant. However, a general paucity of information exists on the horticultural and hydrological effects of on-off “cycling” of irrigation pumps based on pre-programmed temperature setpoints. To fill this gap, three years of monitoring were conducted to quantify the relative effects of cycled and conventional spring frost irrigation on cranberry bud damage, crop yield, and water use. Results showed that cycled irrigation reduced seasonal water use from 33 to 80% compared to conventional frost irrigation, with water savings under cycled frost irrigation ranging from 113 to 198mm (mean±SD: 176±47mm). Despite some variation in type and amount of observed bud damage, values of cranberry yield were similar between the two methods or higher for cycled irrigation. The conventional frost irrigation method always applied more irrigation water, possibly increasing soil saturation and anaerobic conditions that are known to lower crop yield in cranberry. Together, these results point to cycled irrigation as a water management strategy that can enhance cranberry production and reduce agricultural water use in southeastern Massachusetts.

Reconciling seasonal hydraulic risk and plant water use through probabilistic soil-plant dynamics.

Current models used for predicting vegetation responses to climate change are often guided by the dichotomous needs to resolve either (i) internal plant water status as a proxy for physiological vulnerability or (ii) external water and carbon fluxes and atmospheric feedbacks. Yet, accurate representation of fluxes does not always equate to accurate predictions of vulnerability. We resolve this discrepancy using a hydrodynamic framework that simultaneously tracks plant water status and water uptake. We couple a minimalist plant hydraulics model with a soil moisture model and, for the first time, translate rainfall variability at multiple timescales - with explicit descriptions at daily, seasonal, and interannual timescales - into a physiologically meaningful metric for the risk of hydraulic failure. The model, parameterized with measured traits from chaparral species native to Southern California, shows that apparently similar transpiration patterns throughout the dry season can emerge from disparate plant water potential trajectories, and vice versa. The parsimonious set of parameters that captures the role of many traits across the soil-plant-atmosphere continuum is then used to establish differences in species sensitivities to shifts in seasonal rainfall statistics, showing that co-occurring species may diverge in their risk of hydraulic failure despite minimal changes to their seasonal water use. The results suggest potential shifts in species composition in this region due to species-specific changes in hydraulic risk. Our process-based approach offers a quantitative framework for understanding species sensitivity across multiple timescales of rainfall variability and provides a promising avenue toward incorporating interactions of temporal variability and physiological mechanisms into drought response models.

Daily Landsat-scale evapotranspiration estimation over a forested landscape in North Carolina, USA, using multi-satellite data fusion

Abstract. As a primary flux in the global water cycle, evapotranspiration (ET) connects hydrologic and biological processes and is directly affected by water and land management, land use change and climate variability. Satellite remote sensing provides an effective means for diagnosing ET patterns over heterogeneous landscapes; however, limitations on the spatial and temporal resolution of satellite data, combined with the effects of cloud contamination, constrain the amount of detail that a single satellite can provide. In this study, we describe an application of a multi-sensor ET data fusion system over a mixed forested/agricultural landscape in North Carolina, USA, during the growing season of 2013. The fusion system ingests ET estimates from the Two-Source Energy Balance Model (TSEB) applied to thermal infrared remote sensing retrievals of land surface temperature from multiple satellite platforms: hourly geostationary satellite data at 4 km resolution, daily 1 km imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) and biweekly Landsat thermal data sharpened to 30 m. These multiple ET data streams are combined using the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) to estimate daily ET at 30 m resolution to investigate seasonal water use behavior at the level of individual forest stands and land cover patches. A new method, also exploiting the STARFM algorithm, is used to fill gaps in the Landsat ET retrievals due to cloud cover and/or the scan-line corrector (SLC) failure on Landsat 7. The retrieved daily ET time series agree well with observations at two AmeriFlux eddy covariance flux tower sites in a managed pine plantation within the modeling domain: US-NC2 located in a mid-rotation (20-year-old) loblolly pine stand and US-NC3 located in a recently clear-cut and replanted field site. Root mean square errors (RMSEs) for NC2 and NC3 were 0.99 and 1.02 mm day−1, respectively, with mean absolute errors of approximately 29 % at the daily time step, 12 % at the monthly time step and 0.7 % over the full study period at the two flux tower sites. Analyses of water use patterns over the plantation indicate increasing seasonal ET with stand age for young to mid-rotation stands up to 20 years, but little dependence on age for older stands. An accounting of consumptive water use by major land cover classes representative of the modeling domain is presented, as well as relative partitioning of ET between evaporation (E) and transpiration (T) components obtained with the TSEB. The study provides new insights about the effects of management and land use change on water yield over forested landscapes.

Evaluation of Spatial-Temporal Variations of Water Quality and Plankton Assemblages and Its Relationship to Water Use in Kulekhani Multipurpose Reservoir, Nepal

Spatial and temporal variation in planktons and water quality parameters were investigated in order to determine the effects of seasonal water use on reservoir water quality and planktons’ diversity in Kulekhani Multipurpose Reservoir, Nepal. This study also focuses on interactions among various water quality parameters with planktons and how such interactions can affect the second major utility, the fish farming in the reservoir. The analyses of seasonal water samples collected from three different sampling locations in the reservoir showed that select water quality parameters varied significantly (P < 0.05) with sampling seasons (transparency: 30 - 250 cm, pH: 7 - 7.5, alkalinity: 30 - 120 mg/L, DO: 6 - 11.5 mg/L, CO2: 0.1 - 1.1 mg/L) and sampling locations (phosphate: 0.1 - 0.25 mg/L, nitrate 0.01 - 0.19 mg/L) in the reservoir. Three groups of zooplankton and four classes of phytoplankton, respectively with eleven and twelve genera, were identified and quantified in the reservoir. Among them, Cyclops, Asplanchana, and Keratella were most dominant zooplanktons while Synedra, Melosira and Peridinum were the most dominant phytoplankton in the reservoir water. The abundance of select zooplanktons (Cyclops, Keratella, Polyanthra), and phytoplankton (Navicula, Melosira, Amphora, Chroococcus, Staurastrum, Scendesmus) showed significant interaction between sampling sites and sampling seasons, while the other varied only with sampling seasons and/or sites. These results showed that seasonal water level fluctuations, along with the variation of water quality parameters, change the abundance and diversity of planktons’ in the reservoir. Such changes can negatively impact the fish in cage culture, affecting the livelihood of people extensively relying on these fish farming.

Effect of climate change on seasonal water use efficiency in subalpine Abies fabri

Abies fabri is a typical subalpine dark coniferous forest in southwestern China. Air temperature increases more at high elevation areas than that at low elevation areas in mountainous regions, and climate change ratio is also uneven in different seasons. Carbon gain and the response of water use efficiency (WUE) to annual and seasonal increases in temperature with or without CO2 fertilization were simulated in Abies fabri using the atmospheric-vegetation interaction model (AVIM2). Four future climate scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) were selectively investigated. The results showed that warmer temperatures have negative effects on gross primary production (GPP) and net primary production (NPP) in growing seasons and positive effects in dormant seasons due to the variation in the leaf area index. Warmer temperatures tend to generate lower canopy WUE and higher ecosystem WUE in Abies fabri. However, warmer temperature together with rising CO2 concentrations significantly increase the GPP and NPP in both growing and dormant seasons and enhance WUE in annual and dormant seasons because of the higher leaf area index (LAI) and soil temperature. The comparison of the simulated results with and without CO2 fertilization shows that CO2 has the potential to partially alleviate the adverse effects of climate warming on carbon gain and WUE in subalpine coniferous forests.

A Model to Assess the Economic Viability of Alfalfa Production Under Subsurface Drip Irrigation in California

This study was carried out to develop a model to explore the economic viability of subsurface drip irrigation (SDI) for alfalfa production in the major alfalfa production regions of California. Data from previously published studies on alfalfa under drip irrigation were applied to establish the relationship between hay yield and seasonal water use. A correction factor was defined to adjust the potential impacts of SDI due to regional differences in yield potential. A partial economic analysis was developed to assess economic benefits of SDI in alfalfa. The model predicted an additional 7.9 Mg ha−1 yield as a result of switching from surface flood irrigation to SDI, averaged across the principal alfalfa-growing counties and regions in California. The hay yield improvements predicted by the model are in good agreement with the preliminary reports of improved hay yields from the 12 commercial farmers who have implemented SDI in Sacramento Valley, Low Desert, and Southern San Joaquin Valley regions. While the proposed model illustrated the potential profitability of SDI in alfalfa in several regions, further on-farm experience and analysis would be required to confirm these results in practice. Copyright © 2016 John Wiley & Sons, Ltd.

Deconstructing Demand: The Anthropogenic and Climatic Drivers of Urban Water Consumption.

Cities in drought prone regions of the world such as South East Australia are faced with escalating water scarcity and security challenges. Here we use 72 years of urban water consumption data from Melbourne, Australia, a city that recently overcame a 12 year "Millennium Drought", to evaluate (1) the relative importance of climatic and anthropogenic drivers of urban water demand (using wavelet-based approaches) and (2) the relative contribution of various water saving strategies to demand reduction during the Millennium Drought. Our analysis points to conservation as a dominant driver of urban water savings (69%), followed by nonrevenue water reduction (e.g., reduced meter error and leaks in the potable distribution system; 29%), and potable substitution with alternative sources like rain or recycled water (3%). Per-capita consumption exhibited both climatic and anthropogenic signatures, with rainfall and temperature explaining approximately 55% of the variance. Anthropogenic controls were also strong (up to 45% variance explained). These controls were nonstationary and frequency-specific, with conservation measures like outdoor water restrictions impacting seasonal water use and technological innovation/changing social norms impacting lower frequency (baseline) use. The above-noted nonstationarity implies that wavelets, which do not assume stationarity, show promise for use in future predictive models of demand.

Crop kites: Determining crop-water production functions using crop coefficients and sensitivity indices

The crop-water production function quantitatively evaluates the relationship between seasonal water use and crop yield and is used to evaluate optimal irrigation depth and assess the potential of deficit and supplemental irrigation. A simple and easily applicable methodology to develop crop- and region-specific crop-water production functions using crop coefficients and sensitivity-indices is presented. Previous efforts to describe the crop-water production function have not accounted for the effects of the temporal distribution of water use and trivialize the associated variability in yields by assuming an optimized or arbitrary temporal distribution. The temporal distribution of water use throughout the growing season can significantly influence crop yield, and the ability of farmers to manage both the timing and amount of irrigation water may result in higher yields. We propose crop kites, a tool that explicitly acknowledges crop yield as a function of the temporal distribution of water use to both evaluate the complete space of water use and crop yield relationships, and extract from this space specific crop-water production functions. An example for winter wheat is presented using previously validated crop-specific sensitivity indices. Crop-water production functions are extracted from the crop kite related to specific irrigation schedules and temporal distributions of water use. Crop-water production functions associated with maximizing agricultural production agree with previous efforts characterizing the shape as a diminishing curvilinear function. Crop kites provide the tools for water managers and policy makers to evaluate crop- and region-specific agricultural production as it relates to water management and the associated economics, and to determine appropriate policies for developing and supporting the infrastructure to increase water productivity.

Comparison of multi-level water use efficiency between plastic film partially mulched and non-mulched croplands at eastern Loess Plateau of China

Multi-level crop water use efficiency, i.e. ratio of productivity to water use at canopy, ecosystem, biomass, grain yield and net biome production (NBP) levels, is essential for evaluating water productivity and footprints of agronomy technologies and may vary with different methods of dryland tillage. This study investigated their changes under two tillage methods: conventional flat tillage without mulching (CK) and plastic film partially mulched furrow-ridge (MFR) for three years through synchronous measurements of two eddy covariance systems with multi micro-lysimeters on the eastern Loess Plateau of China. Water flux linearly correlated to canopy assimilated CO2 and net ecosystem CO2 exchange at half-hourly and daily scales, and also to biomass increments at seasonal scale with significant levels for both treatments for all three years. At canopy level, the slopes for these correlations in MFR were very close to those of CK for three years. However, the absolute slopes for these correlations in MFR were always higher than those of CK at ecosystem and biomass levels. Seasonal water use efficiency significantly changed with green leaf area index (GLAI) at ecosystem but not canopy and biomass levels. During three whole growing seasons, average water use efficiency in MFR were higher by 24.4%, 36.7%, 29.3% and 25.7% than those of CK at ecosystem, biomass, grain and net biome production levels, respectively. These results demonstrated that MFR can significantly enhance water use efficiency at ecosystem, biomass, grain and NBP levels except for canopy level, which should help sustainable crop production with minimum water footprints in water-limited environment.

Cotton Water Productivity and Growth Parameters in the Humid Southeast: Experimentation and Modeling

Abstract. A global challenge for the coming decades will be increasing food and fiber production with less water. This can be partially achieved by increasing water productivity (WP) or crop water use efficiency (WUE), i.e., yield or biomass produced per unit water used. Cotton ( L.) is a major rainfed and irrigated crop in the U.S. and worldwide. While there is abundant information on cotton water use and yield relationships in drier regions, relevant field data and modeling in humid regions is not well developed. Robust crop models help complement field experimentation and predict the impact of irrigation management on production. The Food and Agriculture Organization (FAO) of the United Nations has developed a crop model (AquaCrop) that has been parameterized for a number of crops including cotton, but not in a humid region. The objective of this study was twofold: (1) to quantify cotton water use and in-season biomass and growth parameters, and (2) to parameterize and validate AquaCrop to simulate cotton water use and productivity in the humid Southeast U.S., where water conservation and sustainability are emerging issues. Irrigation experiments were conducted from 2009 to 2011 under field conditions as well as under a newly installed automated rainout shelter at a Clemson University research site near Blackville, South Carolina. Extensive season-long soil, crop, and climate data were collected under irrigation regimes ranging from rainfed (i.e., no irrigation) to fully irrigated (i.e., meeting 100% of crop water needs). Season-long data collected in 2009 and 2011 under different irrigation regimes were used to parameterize the model. Cotton seasonal water use ranged from 320 mm at 33% irrigation to 718 mm at full irrigation, corresponding to average seed cotton yields of 2134 to 3682 kg ha -1 . Water use efficiency in the three years ranged from 0.48 to 0.71 kg of seed cotton per m 3 of water applied (irrigation and rainfall). Normalized water productivity for the local climate was nearly the same during the three years, averaging 12.5 g m -2 . Model parameterization was less demanding than expected, requiring adjustments of a few model parameters. Using the parameterized model with independent field data from 2010, the model simulated canopy cover, soil water content, aboveground dry biomass, and yield values that were highly correlated with measured values, with coefficients of determination (R 2 ) greater than 0.66. Seasonal crop water use was predicted within 5% for most treatments but underpredicted by as much as 18% for the 100% treatment at the shelter and for all irrigation treatments in 2010. The underprediction of crop water use corresponded to values of deep percolation simulated by AquaCrop. Field measurements were inadequate to verify deep percolation, but such measurements are suggested for future model investigations. Results of this study suggest that a properly parameterized AquaCrop model provides a useful tool to study yield response to water stress and evaluate the effects of drought and alternate management practices on productivity.

Effect of mulching on plant water status, soil salinity and yield of squash under summer-fall deficit irrigation in salt affected soil

Field studies were conducted for two consecutive seasons (summer and fall) under sub-temperate climatic conditions at southwest of Cairo, Egypt (29° 35′ N 30° 23′ E) in saline soil (ECe 12.6dSm−1) to investigate the effect of different mulches (without mulch, WM as a control, farmyard manure: FYM, rice straw: RSM and white polyethylene: PM) on soil salinity, plant water status, water-use efficiency (WUE), and yield of squash under three levels of irrigation (I100=100%, I85=85% and I70=70% of crop evapotranspiration). Under full irrigation, seasonal water use by squash was 479 over 86days in summer and 306mm over 91days in fall season, respectively. Plant water status (as evaluated by relative water content, canopy temperature), fruit quality yield and water use efficiency (WUE) were significantly (P≤0.05) affected by season and both irrigation quantity and mulching materials. Photosynthesis efficiency, total soluble sugars (TSS), leaf area index, harvest index (HI), yield and WUE were not significantly affected by interaction between growth season and both irrigation and mulching treatments. All mulching materials effectively reduced salt accumulation in the root zone. Mulching treatments markedly increased WUE and yield in the order of FYM>RSM>PM>WM. Results showed that, under different mulches, the I85% strategy studied here could be successfully applied during summer and fall seasons in commercial squash production allowing water savings of 15% without any detrimental effect on plant growth or yield.

Effect of highly processed calcined kaolin residues on apple water use efficiency

Processed calcined kaolin particle films (PKPF) have been shown to repel some insects and reduce various environmental stresses often resulting in improved yield and quality of horticultural crops. PKPF studies in the literature have various water use efficiency (WUE) responses. The purpose of this study was to evaluate 2 application rates of PKPF (3% and 12%) on the whole tree water use efficiency and compare gas exchange values with carbon isotopic discrimination and seasonal water use efficiency in order to determine if there are consistent effects on WUE in apple and infer the mechanisms of action. Fruit yield and total biomass influence WUE whether WUE is measured directly in whole plant chambers, estimated by biomass/unit evapotranspiration, or Δ13C. Δ13C analysis of WUE generally found that the untreated control had lower values and therefore higher WUE than PKPF treatments. Whole plant gas exchange analysis of WUE generally lacked the sensitivity to identify the treatment differences observed using Δ13C analysis and those treatment differences identified were contrary to Δ13C analysis. A lysimeter study supported the reduced WUE of PKPF treated plants by demonstrating increased E with a range of PKPF residue amounts. The lysimeter results suggest that for well-watered and presumably non-stressed conditions, gas exchange is limited by leaf temperature and the concomitant leaf-air vapor pressure deficit that influence stomatal conductance. When leaf temperature is reduced by PKPF, the response results in increased stomatal conductance and gas exchange, as measured by increased E. The reduction in WUE by PKPF treatment is balanced by an increase in overall gas exchange and increased yield and quality.

WATER USE EFFICIENCY, YIELD AND YIELD COMPONENTS OF SECOND CROP SUNFLOWER UNDER DEFICIT IRRIGATION

This study was conducted to observe the effects of different irrigation treatments on yield and yield components of second crop sunflower (Helianthus annuus L.) grown in western Turkey in 2012 and 2013. Trials comprised of two irrigation intervals (4-day and 8-day) and six different water levels (125, 100, 75, 50, 25 and 00% of cumulative Class-A pan evaporation on a 4-day and 8-day interval basis) were investigated. Seasonal water use values varied between 191.1-662.6 mm in 2012 and 194.0-675.8 mm in 2013. Interactions between irrigation interval and irrigation levels were found to be significant for seed yield in both years. Maximum and minimum seed yield were obtained from the 8-day IL-100 and 8-day IL-00 treatments as averaging 5072.6 kg ha-1 and 2327.9 kg ha-1 , respectively. Significant curvilinear relationships between seed yield and crop water use were obtained for 2012 and 2013. Water use efficiency and irrigation water use efficiency values were influenced by the irrigation intervals and levels. Water use efficiency varied from 1.21 kg m-3 to 0.70 kg m-3 among treatments in both years. The yield response factor (ky) was determined to be 0.70 for 4-day irrigation interval and 0.69 for 8-day irrigation interval. Deficit and frequent irrigation caused a remarkable decline in all yield components (head diameter, stem diameter, plant height, 1000 seed weight and oil yield) investigated in both experimental years. The yield components decreased as irrigation levels decreased for each irrigation interval. The IL-100 treatment in 8-day irrigation interval could be proper for sunflower irrigated in semi-arid regions under no water shortage and the 8-day IL-75 treatment could be used as a good basis for reduced drip irrigation strategy development under water shortage.

Evaluation of seasonal water use and crop coefficients for ‘Cabernet Sauvignon’ grapevines as the base for skilled regulated deficit irrigation

Evaluation of seasonal water use and crop coefficients for ‘Cabernet Sauvignon’ grapevines as the base for skilled regulated deficit irrigation

Evapotranspiration of rubber (Hevea brasiliensis) cultivated at two plantation sites in Southeast Asia

AbstractTo investigate the effects of expanding rubber (Hevea brasiliensis) cultivation on water cycling in Mainland Southeast Asia (MSEA), evapotranspiration (ET) was measured within rubber plantations at Bueng Kan, Thailand, and Kampong Cham, Cambodia. After energy closure adjustment, mean annual rubber ET was 1211 and 1459 mm yr−1 at the Thailand and Cambodia sites, respectively, higher than that of other tree‐dominated land covers in the region, including tropical seasonal forest (812–1140 mm yr−1), and savanna (538–1060 mm yr−1). The mean proportion of net radiation used for ET by rubber (0.725) is similar to that of tropical rainforest (0.729) and much higher than that of tropical seasonal forest (0.595) and savanna (0.548). Plant area index (varies with leaf area changes), explains 88.2% and 73.1% of the variance in the ratio of latent energy flux (energy equivalent of ET) to potential latent energy flux (LE/LEpot) for midday rain‐free periods at the Thailand and Cambodia sites, respectively. High annual rubber ET results from high late dry season water use, associated with rapid refoliation by this brevideciduous species, facilitated by tapping of deep soil water, and by very high wet season ET, a characteristic of deciduous trees. Spatially, mean annual rubber ET increases strongly with increasing net radiation (Rn) across the three available rubber plantation observation sites, unlike nonrubber tropical ecosystems, which reduce canopy conductance at high Rn sites. High water use by rubber raises concerns about potential effects of continued expansion of tree plantations on water and food security in MSEA.

A preliminary investigation of the water use efficiency of sweet sorghum for biofuel in South Africa

Sweet sorghum ( Sorghum bicolor (L.) Moench) has been recognized globally as a potential biofuel crop for ethanol production. Sweet sorghum is a drought-tolerant crop that is widely adapted to different environmental growing conditions. The aim of this study was to determine the water use efficiency (utilisable yield per unit amount of water used) of drip-irrigated sweet sorghum (variety Sugargraze) under two different climatic conditions in South Africa. The sweet sorghum trials were conducted at Ukulinga research farm (University of KwaZulu-Natal, Pietermaritzburg) and Hatfield experimental farm (University of Pretoria, Pretoria), South Africa. Field trials were conducted in two successive seasons, viz., 2010/11 and 2011/12. Seasonal water use was estimated using eddy covariance and surface renewal methods. Fresh and dry aboveground biomass yield, stalk yield and stalk Brix % were measured at final harvest. Theoretical ethanol yield was calculated from fresh stalk yield and Brix %. Water use for the two growing seasons was 415 mm at Ukulinga and 398 mm at Hatfield. The ethanol water use efficiency (WUE) values for the sweet sorghum at Ukulinga were 0.27 and 0.60 L∙m -3 for 2010/11 and 2011/12 growing seasons, respectively. The ethanol WUE estimate of the sweet sorghum at Hatfield was 0.53 L∙m -3 for the 2010/11 season and 0.70 L∙m -3 for the 2011/12 growing season. WUE estimates of the sweet sorghum crop were higher for Hatfield compared to Ukulinga research farm. The results from this study showed that the WUE of sweet sorghum was sensitive to plant density. The WUE values confirm that sweet sorghum has high WUE under different climatic conditions. Keywords: water use efficiency; ethanol yield; biofuel crop; plant density, sweet sorghum, South Africa

Effect of Irrigation Method and Non-Uniformity of Irrigation on Potato Performance and Quality

Potato growth, yield, and quality under improved irrigation methods and non-uniformity of their irrigation applications are important to enhance water management in arid regions. A field experiment was conducted in 2014 spring and fall growing seasons using potato (Solanum tuberosum) grown in northern Egypt at Shibin El Kom, Menofia, Egypt to evaluate potato response to furrow or trickle irrigation. A Randomized Split-Plot Design with irrigation method randomly distributed and non-uniformity of irrigation applications evaluated along either irrigation furrow or trickle lateral as dependent variables measured at the 3rd, 13th, 23rd, 33rd, 43rd and 53rd m along the 55 m irrigation line. Traditional (TF) and partial (PF) furrows as well as trickle point (TP) and line (TL) sources were used as irrigation methods. Each treatment was repeated three times. For a 33rd m treatment, seasonal optimum water use by potato was 328, 234, 269 and 292 mm over 118 days in spring and 200, 164, 178 and 186 mm over 122 days in fall under TF, PF, TP and TL irrigation methods, respectively. Potato tuber yield and quality were significantly affected by growing season (S), irrigation method (I) and non-uniformity of irrigation application (U). Tuber yield, total soluble solid (TSS) and leaf area index (LAI) were significantly affected by I and U, and their interaction I * U; harvest index (HI) was not affected by I but U. Except for TSS by S * I and HI by U * I and S * I, results showed no significant differences. Moreover, tuber weight, number and marketable yield were significantly affected by S, I, U and I * U interaction, except medium tuber size and culls by S. A given 33rd treatment under partial furrow and trickle irrigation, relative to that of traditional furrow, enhanced tuber yield and improved quality in both growing seasons. In non-un- iform irrigation application over two growing seasons, potato crop response was developed under varied irrigation methods. Tuber yields were significantly affected in a linear relationship (r2 ≥ 0.75) by either water deficit or excessive water under irrigation methods.

Cotton Irrigation Timing with Variable Seasonal Irrigation Capacities in the Texas South Plains

Abstract. Within the Ogallala Aquifer Region of Texas, the irrigation capacity (IC) for a given field often changes within a growing season due to seasonal depletion of the aquifer, in-season changes in crop irrigation needs in dry years, or consequences of irrigation volume limits imposed by irrigation district rules. Irrigation planning is further complicated by erratic seasonal rainfall. A field experiment was conducted from 2010 to 2013 to determine cotton ( L.) irrigation productivity using a range of ICs common to the Texas South Plains during three irrigation periods. The treatments included in-season ICs (maximums of 0, 3.2, and 6.4 mm d-1) in combination with irrigation periods determined by accumulated growing degree days (GDD15.6) and were designated as period 1 (P1= emergence to 525 GDD15.6), period 2 (P2= 525 to 750 GDD15.6), and period 3 (P3>750 GDD15.6). Combinations of these factor levels resulted in 27 irrigation treatments with applications made by the low energy precision application (LEPA) method. Annual rainfall totals ranged from 137 to 557 mm over the four years. In all years, results indicated that attempting to store water in the soil profile, or irrigating in excess of the cotton evapotranspiration rate, early in the growing season reduced seasonal irrigation water use efficiency (SIWUE), and sometimes yield, compared to treatments with limited or no early irrigations. Treatments with 0 and 3.2 mm d-1 ICs during P1 used up to 20% less seasonal irrigation with minor yield loss (

Increased water use in dry season in eight dipterocarp species in a common plantation in the northern boundary of Asian tropics

AbstractThe seasonal water use and stand‐level transpiration of the important tropical timber tree family, Dipterocarpaceae, have not been well investigated. Here, we characterized the seasonal water use and stand‐level transpiration of eight, evergreen, dipterocarps in tropical Southwest China in the 2013 wet and dry seasons: six species grown in monoculture and two species in mixture. We estimated stand‐level transpiration using a power model, combining data from 22 trees of all species measured in the two seasons. Despite significant decreases in soil volumetric water content within 1‐m depth, predawn leaf water potentials (&gt; −0.5 MPa) of all trees indicated access of roots to water. Daily sap flux density (SFDd) of all species closely responded to vapour pressure deficit (VPD). Dry season VPD increased by 29%, compared to in wet season, resulting 27–52% increased SFDd in six of the eight species. Whole tree daily water use was scaled with diameter at 1.3 m height for the 22 trees (r2 = 0.91 and 0.93 in the wet and dry seasons, respectively). Daily mean stand‐level transpiration ranged from 0.63 to 2.23 mm d−1 (mean = 1.05) and from 1.18 to 2.29 mm d−1 (mean = 1.63) in the wet and dry seasons, respectively. Our results reveal conservative water use of dipterocarps and increased transpiration in dry season when a stable soil water source is available. In comparison with introduced fast‐growing timber species, such as Eucalyptus and Acacia mangium, dipterocarp trees and forests consume much less water, making them more suitable as plantation timber crops for the region. Copyright © 2015 John Wiley &amp; Sons, Ltd. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Soil water capture trends over 50 years of single-cross maize (Zea mays L.) breeding in the US corn-belt.

Breeders have successfully improved maize (Zea mays L.) grain yield for the conditions of the US corn-belt over the past 80 years, with the past 50 years utilizing single-cross hybrids. Long-term improvement for grain yield under water-limited conditions has also been reported. Grain yield under water-limited conditions depends on water use, water use efficiency, and harvest index. It has been hypothesized that long-term genetic gain for yield could be due, in part, to increased water capture from the soil. This hypothesis was tested using a set of elite single-cross hybrids that were released by DuPont Pioneer between 1963 and 2009. Eighteen hybrids were grown in the field during 2010 and 2011 growing seasons at Woodland, CA, USA. Crops grew predominantly on stored soil water and drought stress increased as the season progressed. Soil water content was measured to 300cm depth throughout the growing season. Significant water extraction occurred to a depth of 240-300cm and seasonal water use was calculated from the change in soil water over this rooting zone. Grain yield increased significantly with year of commercialization, but no such trend was observed for total water extraction. Therefore, the measured genetic gain for yield for the period represented by this set of hybrids must be related to either increased efficiency of water use or increased carbon partitioning to the grain, rather than increased soil water uptake.