Seasonal Water Use Research Articles

Irrigation Management Effects on Crop Water Productivity for Maize Production in the Texas High Plains

Corn (Zea mays L.) was grown under full and deficit irrigation in two research field locations near Bushland, TX, in 2018 to compare seasonal water use of two irrigation management approaches. Full irrigation was achieved in both fields by allowing no more than 55% depletion of plant available soil water. However, irrigation depth and frequency were different in each field. The USDA-ARS Conservation and Production Research Laboratory (CPRL) weighing lysimeter fields were generally irrigated twice weekly using irrigation depths ranging from 19 to 32 mm. The Texas A&M AgriLife Research Emeny field was irrigated only once per week, having greater application depths ranging from 35 to 42 mm. Deficit irrigation treatments of 75% of full irrigation were also performed in both research fields. Yield and crop water productivity values for the 100 and 75% lysimeter field irrigation treatments were greater than corresponding values for the Emeny field. Emeny field yields may have been slightly reduced by heat stress incurred between irrigations during early grain fill whereas more frequent irrigations on the lysimeter fields may have reduced heat stress during that period. Results from this study suggest that evaporative losses associated with the more frequent, smaller application depth irrigations on the lysimeter fields did not contribute to appreciably lower CWP values, as losses were likely mitigated by the rapid development of the corn canopy. These findings suggest that corn yield is principally dependent upon seasonal water inputs and losses from frequent, smaller depth irrigations are minimal outside of incomplete canopy conditions.

中国西南岩溶区水分利用效率变化及其对气象要素的响应

水分利用效率（WUE，Water use efficiency）是衡量水资源利用率的重要指标，对气候变化有明显响应，中国西南岩溶区生态缺水严重，水资源利用问题亟需解决，但该区域水分利用效率对气象要素的响应仍不明晰。利用MODIS总初级生产力（Gross primary productivity，GPP）和蒸散发（Evapotranspiration，ET）数据集计算中国西南岩溶区的水分利用效率，结合气象数据和归一化植被指数（NDVI，Normalized difference vegetation index）数据，采用Theil-Sen Median趋势分析和Pearson相关分析，揭示了其水分利用效率的时空变化特征及对气象要素的响应。结果表明：2000-2014年中国西南岩溶区年水分利用效率与植被生长期水分利用效率（AGS-WUE）时间序列变化趋势相近，春、秋季水分利用效率呈上升趋势，夏季呈下降趋势；年水分利用效率呈上升趋势，与降水呈负相关，喀斯特地区与气温呈正相关，非喀斯特地区呈负相关，NDVI增长是主要驱动因素；年水分利用效率和AGS-WUE从东南到西北逐渐升高；非喀斯特地区水分利用效率高于大部分喀斯特地区；总体上高海拔地区水分利用效率高于低海拔地区。气温、海拔及喀斯特发育程度综合影响喀斯特地区水分利用效率。本研究结果能为提高喀斯特生态系统水分利用效率提供理论参考。;Water use efficiency(WUE) is an important indicator to measure utilization ratio of water resources, which has obvious response to climate change. Ecological water shortage is serious in karst area of Southwest China, and water resource utilization problem needs to be solved urgently. However, the response of water use efficiency to meteorological factors is still unclear. In this paper, MODIS gross primary productivity (GPP) and evapotranspiration (ET) data sets were used to calculate water use efficiency in karst area of Southwest China. Combined with meteorological and normalized difference vegetation index (NDVI) data, the temporal and spatial variation characteristics of water use efficiency and its response to meteorological factors were revealed by using the Theil-Sen Median trend analysis and Pearson correlation analysis. The results showed that the change trend of the annual water use efficiency was similar with the active growing season water use efficiency (AGS-WUE) in the karst area of Southwest China from 2000 to 2014. In spring and autumn, water use efficiency demonstrated an upward trend and a downward trend in summer. The annual water use efficiency showed an upward trend, which was negatively correlated with precipitation, positively correlated with temperature in karst areas, while negatively correlated with temperature in non-karst areas. The growth of NDVI was the main driving factor. Annual water use efficiency and AGS-WUE increased gradually from southeast to northwest. The water use efficiency in non karst areas was higher than that in most karst areas. In general, water use efficiency in high altitude areas was higher than that in low altitude areas. Temperature, altitude and the degree of karst development affected water use efficiency in karst areas comprehensively. The results of this study can provide theoretical reference for improving the water use efficiency of karst ecosystem.

Preliminary crop coefficients for late planted short‐season soybean: Texas High Plains

AbstractHaving similar profit potential but roughly half of the water requirements of corn (Zea mays L.), cotton (Gossypium hirsutum L.) has become an attractive crop in the Southern High Plains (SHP) where groundwater levels and well capacities continue to decline. However, unpredictable and erratic precipitation often results in conditions either too wet or too dry for ideal germination. Coupled with a relatively short planting window for adequate heat unit accumulation and the threat of severe weather events, cotton crops can fail, leaving limited options for producers wanting to plant a second summer crop. One option is short‐season soybean [Glycine max (L.) Merr.]. However, limited data on crop water use (evapotranspiration, ET), crop coefficient (Kc), and yield exist for late‐planted soybean in the semiarid SHP. After unseasonably wet conditions in May 2019, a short‐season soybean variety was planted on 13 June in irrigated weighing lysimeter fields at the USDA‐ARS Conservation and Production Research Laboratory at Bushland, TX. Results showed profitable yields (4,786–4,996 kg ha–1), and although maximum daily Kc values were not different than published values, season length was 24–29 d shorter than for soybean planted in mid‐May. Seasonal water use was less than that of archived data using earlier planting dates in 2 of 3 yr, although those studies used different varieties. Crop coefficient functions using both short and tall standardized reference ET values are presented for sprinkler and subsurface drip irrigation systems. Although these data are useful to producers in the SHP, additional data are needed to develop Kc functions that better characterize interannual variations in weather.

Deficit irrigation improves maize yield and water use efficiency in a semi-arid environment

Uncertainty in the availability of water supply pose challenges to traditional irrigation approaches. Regulating the amount and time of irrigation at different crop growth stages could provide a solution to optimize the irrigation water amid drought periods. This study evaluated the effect of different deficit irrigation levels on maize (Zea mays L.) at several growth phases over two growing seasons (2012 and 2013) in Yangling, Shaanxi province of China. Total nine irrigation treatments incorporated three irrigation amount ratios, i.e., control irrigation (CK, 100 % of crop evapotranspiration), and 80 % and 60 % of control irrigation; named as T2–T9. Among the irrigation treatments, grain yield ranged from 6392 to 9362 kg ha–1 and seasonal water use efficiency (WUE) varied from 20.3 to 34.9 kg ha–1 mm–1, whereas the irrigation water use efficiency (IWUE) ranged between 32.0 and 58.1 kg ha–1 mm–1. T2 that received 80 % irrigation between V8 and R6 growth stage had overall higher yield than CK, and this was closely followed by T4 that received 80 % irrigation at growth phase V3-V8 and V11-Tasseling, full irrigation at V8-V11, and 60 % irrigation between Tasseling and Maturity. Due to near optimum growing season temperature in 2013, larger WUE was noted in comparison to 2012, that resulted 16 % larger yield with 10 % lesser ETc, on an average, whereas 2012 growing season had better IWUE because of 37.5 % smaller irrigation consumption. Maize grain yield in response to water stress (Ky, the yield response factor) was 0.66, suggesting that the environmental conditions of the study area favor the application of deficit irrigation. The maize yield response to reduced irrigation supply in this experiment indicated that regulated deficit irrigation might help growers to cope with decline in water availability during growing season.

Determination of Yield and Quality of Different Snap Bean Varieties Under Deficit Irrigation

In the Konya region, snap bean requires frequent irrigation due to high evaporation and low precipitation during the growing season. However the drought in recent years at Turkey, especially in Konya plain has been one of the most important abiotic stress factor affecting the snap bean production. Several ways to reduce yield losses are deficit irrigation practices, to improve and disseminate the varieties that are tolerant to water stress. In this research, the response of two green bean varieties one of which was improved by Prof. Dr. Önder Türkmen, Horticulture Department of Agriculture Faculty of Selcuk University (S3) and a commercial variety existing in Turkey market (Nazende) to different irrigation water levels under drip irrigation has been investigated. The irrigation treatments included five irrigation water level according the amount of water evaporated from Class A Pan within 7 days period and based on 5 different crop pan coefficient. According to the results, it was found that there were significant differences in yield, pod length, pod width, pod thickness and seed per pod among irrigation levels. No significant differences were observed in yield, pod thickness among varieties. The seasonal water use of the snap bean were ranged from 177 mm to 635 mm for Nazende, 181 mm to 655 for S3 . The highest yield was obtained in kcp2 treatment with 3762.2 kg ha-1 for S3 and kcp1 treatment with 3525.0 kg ha-1 for Nazende. It was not observed significant differences in yield between kcp1; kcp2. kcp3 treatment for both genotypes. Linear relations were found between yield and seasonal water use. The yield response factors (ky) were found 1.24 for both varieties. No differences were observed for pod color values (L, a, b) among irrigation levels.

Using sap flow data to assess variations in water use and water status of apple orchards of varying age groups in the Western Cape Province of South Africa

No accurate quantitative information currently exists on how water use of apple (Malus domestica) orchards varies from planting to full-bearing age, leading to poor irrigation and water allocation decision making. This study sought to address this knowledge gap by investigating how the water use and tree water status vary with canopy cover, cultivar, and climatic conditions in 12 orchards growing in prime apple-producing regions in South Africa. The orchards were planted to the Golden Delicious/Golden Delicious Reinders cultivars which are widely planted in South Africa and the Cripps’ Pink/Cripps’ Red/Rosy Glow which are high-value late-season cultivars. The performance of two transpiration reduction coefficients, one based on sap flow (Ksf) and the other based on soil water depletion (Ks) (FAO approach) were evaluated against the midday stem water potential (MSWP) in all the orchards. While canopy cover had a clear effect on the whole-tree sap flow rates, there were no significant differences in the transpiration per unit leaf area among the cultivars. The daily average sap flux density under unstressed conditions was highest (~284 cm3∙cm-2) in the medium canopy cover orchards (30–44% fractional cover), followed by the mature orchards (~226 cm3∙cm-2), and was lowest in the young orchards (~137 cm3∙cm-2). Canopy cover rather than growing season length had a greater effect on seasonal total water use. Peak daily orchard transpiration ranged from 1.7 mm for young Golden Delicious Reinders trees to 5.0 mm in mature Golden Delicious trees that were maintained with large canopies to reduce sunburn damage to the fruit. For the red cultivars, the peak daily transpiration ranged from 2.0 to 3.9 mm, and the mature trees were maintained with less dense canopies to facilitate the development of the red fruit colour. The less dense canopies on the red cultivars had water-saving benefits since the seasonal total transpiration was lower relative to the Golden Delicious cultivar. The sap flow derived stress coefficient was strongly correlated to the MSWP (R2 ~ 0.60–0.97) in all the orchards while Ks was not able to detect plant stress due to over-irrigation.

Using sap flow data to assess variations in water use and water status of apple orchards of varying age groups in the Western Cape Province of South Africa

No accurate quantitative information currently exists on how water use of apple (Malus domestica) orchards varies from planting to full-bearing age, leading to poor irrigation and water allocation decision making. This study sought to address this knowledge gap by investigating how the water use and tree water status vary with canopy cover, cultivar, and climatic conditions in 12 orchards growing in prime apple-producing regions in South Africa. The orchards were planted to the Golden Delicious/Golden Delicious Reinders cultivars which are widely planted in South Africa and the Cripps’ Pink/Cripps’ Red/Rosy Glow which are high-value late-season cultivars. The performance of two transpiration reduction coefficients, one based on sap flow (Ksf) and the other based on soil water depletion (Ks) (FAO approach) were evaluated against the midday stem water potential (MSWP) in all the orchards. While canopy cover had a clear effect on the whole-tree sap flow rates, there were no significant differences in the transpiration per unit leaf area among the cultivars. The daily average sap flux density under unstressed conditions was highest (~284 cm3∙cm-2) in the medium canopy cover orchards (30–44% fractional cover), followed by the mature orchards (~226 cm3∙cm-2), and was lowest in the young orchards (~137 cm3∙cm-2). Canopy cover rather than growing season length had a greater effect on seasonal total water use. Peak daily orchard transpiration ranged from 1.7 mm for young Golden Delicious Reinders trees to 5.0 mm in mature Golden Delicious trees that were maintained with large canopies to reduce sunburn damage to the fruit. For the red cultivars, the peak daily transpiration ranged from 2.0 to 3.9 mm, and the mature trees were maintained with less dense canopies to facilitate the development of the red fruit colour. The less dense canopies on the red cultivars had water-saving benefits since the seasonal total transpiration was lower relative to the Golden Delicious cultivar. The sap flow derived stress coefficient was strongly correlated to the MSWP (R2 ~ 0.60–0.97) in all the orchards while Ks was not able to detect plant stress due to over-irrigation.

Comparison of Lysimeter-Derived Crop Coefficients for Legacy and Modern Drought-Tolerant Maize Hybrids in the Texas High Plains

HighlightsDaily maximum crop coefficient (Kc) values were similar for legacy hybrids and a modern drought-tolerant (DT) hybrid.Later planting dates for a DT hybrid resulted in average season lengths ~25 days shorter than those of legacy hybrids.Results illustrated the effects of environment, planting date, interannual variation in temperature, and the importance of climate-specific Kc functions.DT hybrids may be more effective at reproductive growth during periods of heat stress in semi-arid environments, although additional data are needed to support this conclusion.Abstract. Corn (Zea mays L.) is a major irrigated crop grown in the Southern High Plains including the Texas Panhandle. Irrigation from the Ogallala Aquifer is required to sustain profitable corn production in the region by supplementing inadequate and erratic rainfall. Effective irrigation scheduling works to extend limited groundwater resources by avoiding water losses associated with runoff and/or percolation below the root zone. The use of crop coefficient (Kc) and reference evapotranspiration (ETo) values to estimate daily crop water use (ETc) remains an effective scheduling tool that can complement other irrigation scheduling approaches. Both Food and Agriculture Organization (FAO-56) piecewise and curvilinear Kc values for corn are found in the literature. However, advances in corn genetics have led to questions about the applicability of Kc values developed using legacy corn hybrids to irrigation of modern drought-tolerant (DT) hybrids. Lysimeter-derived Kc values for legacy corn hybrids grown in large weighing lysimeter fields at the USDA-ARS Conservation and Production Research Laboratory at Bushland, Texas, were compared with those derived from a modern DT corn hybrid recently grown in the same fields. Results indicated that although midseason daily Kc values were similar for all hybrids, average season length was ~25 days shorter for the modern DT hybrid, characterized by a shortened initial growth period followed by more rapid increase of Kc during the development period. However, plots of Kc over thermal time illustrated that the differences in season length were likely attributable to later planting dates associated with the DT corn hybrids. Average seasonal water use was 730 and 811 mm for the legacy and modern DT hybrids, respectively (three years each), with corresponding average yields of 1.2 and 1.4 kg ha-1. Results suggest that published Kc and Kcb values developed with legacy corn hybrids remain largely applicable to modern DT corn hybrids when used with accurate estimates of effective canopy-based growth stages and climate-specific Kc functions. Keywords: Crop coefficients, Drought-tolerant, Evapotranspiration, Maize, Weighing lysimeters.

Assessing planting date effects on seasonal water use of full- and short-season maize using SWAT in the southern Ogallala Aquifer region

A SWAT model equipped with an alternative auto-irrigation algorithm was used to evaluate the effects of planting date on hybrid corn yield and seasonal water use in the Texas High Plains. Research field data from the USDA-ARS Conservation and Production Research Laboratory at Bushland, TX and the Texas A&M AgriLife North Plains Research Field near Etter, TX were used for model calibration. A long-term weather data set was used to simulate continuous corn using five planting dates (15-April, 1-May, 15-May, 1-June, and 15-June) for both long- and short-season corn hybrids. Results suggested that delayed planting resulted in a reduction of seasonal water use for both hybrids. Reductions in seasonal irrigation between the 15-April and 15-June were 28 % and 31 % for long- and short-season hybrids, respectively, using an application depth of 25.4 mm. Corresponding reductions in yield were considerably less at 8.9 and 8.8 % for long- and short-season hybrids. Reduced irrigation was attributed to decreased temperature stress and lower evapotranspiration of the later growing season. However, simulation of long season corn for the 15-June planting resulted in late season cold temperature stress. Further analysis of 19.1 mm and 31.8 mm irrigation depths revealed the latter resulted in an average of 4.4 and 4.7 % reductions in seasonal irrigation for long- and short-season hybrids, respectively. Results from this assessment study suggest the delayed planting of corn may result in decreased irrigation while maintaining profitable yields, potentially reducing withdrawals from the Ogallala Aquifer in the Texas High Plains region.

Forecast of urban water consumption under the impact of climate change

The proper planning of future urban water supply is essential to sustainable development. This paper answers two questions: What quantity of water will be needed in the long term? To what extent will water consumption be affected by climate change? We forecast water consumption using Bayesian statistics methods. A clustering analysis of observed daily water consumption and climate variables splits observations into base water use and seasonal water use, on the basis of the correlation between water consumption and air temperature. We show that the base water use is independent of climate change, but is subject to weekend effects. The seasonal water use depends on daily air temperature and total precipitation. Our forecast allows for uncertainties in climate variables and model parameters. The results from Bayesian linear regression give a probability distribution of daily water use. We obtained climate projections from multiple general circulation models and downscaled them for Greater Montreal. Bias corrections were made to the downscaled daily minimum temperature, maximum temperature and total precipitation. Using these corrected data as input to the Bayesian linear regression model, we forecast water consumption for the next three decades. The forecast results show a trend of increasing seasonal water use over time.

An experimentally-calibrated model of photosynthesis, assimilate partitioning and tuber yield in cassava in response to water supply to assist crop management and improvement

A model (DYNCAS 1.0) is presented of photosynthesis and partitioning of carbon-based (C) assimilate to respiration and growth of leaves, stems, tubers and roots in cassava in response to environmental atmospheric conditions and water supply. It comprises 9 state variables and 40 parameters (including 7 functional relationships), all of direct physiological significance. The important characteristic of the model is the simultaneous consideration of assimilate supply and crop water status by hourly calculations that integrate diurnal physiological responses of photosynthesis, respiration and transpiration to seasonal crop growth and water use under existing environmental conditions.Crop photosynthesis is the integral of a single leaf-response through the canopy according to intercepted radiation determined by an extinction coefficient and by temperature together with canopy conductance determined from crop water potential and vapour pressure deficit. Respiration of organs is calculated individually according to chemical composition and growth processes, including mobilization of reserves. Transpiration proceeds with photosynthesis according to canopy conductance, but in response to evaporative demand, extracting water from the root zone depending upon crop and soil water potentials and the root length that explores it. Partitioning of carbon assimilate from a single crop pool to leaves, stems, tubers and roots depends upon diurnal oscillations in supply according to organ-specific Michaelis-Menten kinetics. Phenological development, here the branching of stems, rate of node and leaf production, and maturity and senescence of leaves and of roots, is determined by temperature and crop water status.The model is shown to capture the response reported in a published study of the growth and yield of two cultivars of cassava of distinct branching habit to water supply. The principles of assimilate partition and the simulation of diurnal responses of growth processes employed here are presented as a guide for further research in cassava productivity and response to environment and management.

Seasonal water use strategy of canopy tree species and possible implication for their coexistence in a subtropical secondary forest

AbstractWe investigated the seasonal water use patterns of five canopy tree species, Schima superba, Liquidambar formosana Hance, Quercus griffithii Hook, Quercus acutissima Carruth, and Pinus massoniana, in a subtropical secondary forest in Guangxi province, which were pervasively planted in South China. The hypothesis is that the trees can make different temporal use of environmental resources that change seasonally and consequently contribute to their coexistence. Sap flow technique was used to measure the daily and seasonal transpiration during the period from June 2016 to May 2017. The sap flow—derived daily transpiration (EL), leaf water potential (ΔΨ), hydraulic conductance (K), as well as the responses of EL to driving factor—water vapour pressure deficit (VPD) was determined in dry and wet seasons. Measured data of stem sap flow showed that L. formosana, Q. griffithii, and P. massoniana transpired more water than S. superba and Q. acutissima during the whole monitoring period, whereas daily EL of P. massoniana rapidly decreased under dry season. We attributed the different water use patterns to the significant difference in ΔΨ, K, and wood density among the five species. Moreover, linear relationships between the daily transpiration and VPD might suggest diverse water use strategies. For the species of S. superba, Q. acutissima, and P. massoniana, less water consumption and relatively flat change of transpiration with VPD were observed, suggesting a relatively tighter stomatal control. The slope values for L. formosana and Q. griffithii, which were much higher even under dry season, might own a weak stomatal control. These different functional and hydraulic traits, together with the associated water use strategies, might facilitate the coexistence of these five canopy tree species, which would assist in predicting the impact of future environmental changes on plant biodiversity and ecosystem services in the investigated region.

Does fluctuation of meteorological conditions across years influence stand transpiration of Tectona grandis plantation?

AbstractTectona grandis (teak) is widely planted as high‐quality timber in the seasonal tropics, yet detailed data on its seasonal water use and the effect of climatic fluctuations on its transpiration behaviour are limited. We measured sap flux density (SFD) using Granier's sap flow sensors for three wet and two dry seasons in the years 2012, 2014, and 2015 (wet season only) in 7 to 14 trees and made a calibration of Granier's equation for teak to calculate SFD for estimating whole‐tree water consumption and stand‐level transpiration. We also characterized the effects of daily rainfall, vapour pressure deficit, and photosynthetically active radiation on the daily SFD of individual trees. We found a large fluctuation in rainfall in the wet seasons of 2012 to 2015 (1,159 mm in 2012, 778 mm in 2014, and 727 mm in 2015). Total wet and dry season stand‐level transpiration were 824 and 501 mm in 2012 and 446 and 214 mm in 2014, respectively, whereas the wet season transpiration of 2015 was 358 mm. Namely, reduced wet season rainfall reduced the total stand‐level transpiration of teak at the study site. Most variations in daily SFD were due to differences in meteorological conditions, that is, day‐time mean vapour pressure deficit, photosynthetically active radiation, and daily rainfall associated with the seasons of particular year. We also established models to estimate the stand‐level transpiration of a teak plantation. The findings of the present study could be useful for forestation program and hydrological management in tropical regions with seasonal drought.

New Miscanthus hybrids cultivated at a Polish metal-contaminated site demonstrate high stomatal regulation and reduced shoot Pb and Cd concentrations

The increased bioeconomy targets for the biomass share of renewable energy production across Europe should be met using land unsuitable for food production. Miscanthus breeding programs targeted the production of plants with a diverse range of traits allowing a wider utilization of land resources for biofuel production without competing with arable crops. These traits include increasing tolerances to drought, chilling, and to metal(loid)s excess. Two novel Miscanthus hybrids, GNT41 and GNT34, were compared against Miscanthus x giganteus (Mxg) on metal-contaminated arable land in Poland. This study aimed at evaluating their yield, biomass quality and quantifying seasonal differences in photosynthetic and transpiration parameters. A secondary objective was to identify key physiological mechanisms underlying differences in metal accumulation between the investigated plants. The new hybrids produced a similar yield to Mxg (13–15 t ha−1 yr−1), had shorter shoots, higher Leaf Area Index and stem number. Based on gas exchange measurements, GNT34 exhibited isohydric (water-conserving) behavior. The stomatal response to light of the new hybrids was at least twice as fast as that of Mxg, a trait that is often associated with increased seasonal water use efficiency. This contributed to the almost 40% reduction in shoot Pb and Cd concentrations for the new hybrids as compared to Mxg. This suggested that promoting stomatal regulation in conjunction with improved water conservation may be a target for improving plants for wider use on metals contaminated land.

The Importance of Interflow to Groundwater Recharge in a Snowmelt‐Dominated Headwater Basin

AbstractUnderstanding the sensitivity of groundwater generation to climate in a mountain system is complicated by the tight coupling of snow dynamics to vegetation and topography. To address these feedbacks, we combine light detection and ranging (LiDAR)‐derived snow observations with an integrated hydrologic model to quantify spatially and temporally distributed water fluxes across varying climate conditions in a Colorado River headwater basin. Results indicate that annual groundwater flow is an important and stable source of stream water. However, interflow decreases during drought as a function increased plant water use and the relative fraction of groundwater to streams increases. Seasonal snowmelt and vegetation water use regulate small recharge rates in the lower portions of the basin, but snowmelt transported via interflow from high mountain ridges toward convergent topographic zones defines preferential recharge in the upper subalpine. Recharge in this zone appears decoupled from annual climate variability and resilient to drought.

Evaluation of Evapotranspiration over a Semiarid Region Using Multiresolution Data Sources

AbstractEvapotranspiration (ET) estimation is important for water management decision tools. In this study, different ET data with varying resolution, accuracy, and functionality were reviewed over a semiarid, data-sparse region in southern Iran. Study results showed that the widely used reanalysis and Moderate Resolution Imaging Spectroradiometer (MODIS) datasets have relatively high uncertainty and underestimated ET over the sparse heterogeneous landscape. On the other hand, fine-resolution ET datasets using Landsat imagery with Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC) and Surface Energy Balance System (SEBS) algorithms, yielded high accuracy. Evaluation of METRIC and SEBS models in estimating seasonal crop water use showed a mean absolute error of 5% and 13%, respectively. The Satellite Application Facility on Climate Monitoring (CMSAF) data were used as radiation input to the models and were found to be a representative data source with daily average RMSE of 70 W m−2. An average crop coefficient Kc was estimated for the region and was obtained as 0.77. The study proposes and applies a hybrid framework that uses reference ET from simple diagnostic models (such as the REF-ET tool) and calculates actual ET by using the satellite-derived regionally and locally representative Kc values. The ET estimates generated with the framework were regionally representative and required low computational resources. The study findings have the potential to provide practical guidance to local farmers and water managers to generate useful and usable decision-making tools, especially for ET assessments in the study region and other data-sparse areas.

Diurnal water use patterns for low-cost houses with indigent water allocation: a South African case study

Abstract The diurnal water use patterns are of interest to hydraulic modellers, as these patterns are required for the design of water distribution systems. An extensive body of literature is available with regard to daily, weekly and seasonal diurnal water use patterns of typical suburban houses. However, the characteristics of South African low-cost houses, the socio-economic status of the consumers and the level of water service to such houses differs from typical western suburban houses reported on elsewhere. Notable differences include the limited access to heated water and negligible garden irrigation at the low-cost houses. Knowledge of water use in low-cost houses, which are prevalent in South Africa, is limited. To reduce this lack of knowledge, approximately 2.5 million flow records were collected over a period of 3 years from a sample of 14 low-cost houses as part of this empirical case study. Subsequently, a diurnal water use pattern was constructed for the selected low-cost houses at 15-minute and 1-hour resolution. The diurnal pattern is useful for hydraulic modellers when data that represent extended period time simulation of water networks in low-cost housing developments is required.

Impacts of different soil fertility improvement practices with film mulched ridge-furrow til-lage on soil nutrient content, maize yield, and water use efficiency in Northwest China.

Improvement of soil quality is one of the most important ways to enhance fertility for efficient dryland crop production. However, the effects of different fertilization measurements with film mulched ridge-furrow tillage on soil fertility, crop yield, and water use efficiency (WUE) of maize largely remain unknown. A three-year field experiment was conducted at the Zhuanglang Experimental Station, Gansu Academy of Agricultural Sciences, located in the semiarid region of the Loess Plateau, Northwest China during 2014-2016. Maize breed Funong No.1 was used during the study. There were four treatments, including: 1) conventional planting (CP, served as control), 2) film mulched ridge-furrow with straw incorporation (FS), 3) film mulched ridge-furrow with optimizing fertilization (FF), and 4) film mulched ridge-furrow with controlled fertilization (FC). Seasonal and yearly changes of soil water content, topsoil organic matter (SOM), soil available nitrogen (AN), phosphorus (AP) and potassium (AK) concentration and crop yield were measured. Nitrogen and phosphorus fertilizer partial factor productivity (PFPN and PFPP), soil profile water storage (WC), crop seasonal water consumption (ET) and water use efficiency (WUE) were calculated. The results showed that FS, FF and FC effectively improved soil fertility via synergistic regulation of soil hydrothermal and nutritional condition. Water-fertilizer interaction effect greatly enhanced incorporated straw decomposition and crop growth, resulting in more returning of straw nutrients and crop biomass to soil, thus significantly increased soil water and fertilizer supply capacity. Compared to CP, the three treatments of FS, FF and FC efficiently increased the concentrations of SOM, AN, AP, and AK by 0.27 g·kg-1, 4.44 mg·kg-1, 0.20 mg·kg-1 and 4.53 mg·kg-1 with an order of FC＞FF＞FS, but had no significant difference among them. Meanwhile, in contrast to pre-sowing WC200, the three year's sum of FS,FF and FC increased WC200 at the end of growing season by 107.41, 38.99 and 28.35 mm, respectively. On average, FS, FC and FF significantly reduced maize ET by 60.50, 37.7 and 34.15 mm to CP, with a relative decrease of 12.6%, 7.9% and 7.1% respectively. By the synergistic effect of modified water and fertilizer environment, the three soil fertility improvement strategies greatly enhanced maize growth from tasseling to maturity stages in the relatively dry year. They affected maize growth in relatively more rain and warmer year, resulting in significantly increased maize yield by improving the yield traits (double ear rate, grain number per ear and 100-grain mass), PFPN, PFPP and WUE. Compared to CP, the PFPN,PFPP of FS, FF and FC increased by 1.82, 1.65, 1.62 and 2.41, 1.69, 1.63 times respectively. Yield and WUE were increased by 5986.1, 4972.31, 4585.63 kg·hm-2 and 13.27, 12.65, 14.01 kg·mm-1·hm-2 correspondingly raised by 81.5%, 67.7%, 62.5% and 86.5%, 82.5%, 91.3%. In conclusion, FS was more effective in water harvesting and drought resistance, while FC and FF were effective for high yield.

Daily and Seasonal Pistachio Evapotranspiration in Saline Condition: Comparison of Satellite-Based and Ground-Based Results

This study was conducted in 2015 to estimate pistachio (Pistacia vera L.) water use in Marvast region, central Iran. Daily and seasonal pistachio actual evapotranspiration (ETa) was first estimated by running the surface energy balance algorithm for land (SEBAL) model, using 12 Landsat 8 satellite images and other ancillary data. Finally, SEBAL estimates of daily and seasonal water use over three experimental sites of pistachio orchards were compared against ones based on performing water balance analysis for the top 150 cm of the soil layer. For this purpose, a simple funnel-shaped device was made and used to collect the beneath rootzone drainage water and determine the leaching fraction (LF) as well as deep percolation at three scattered points across the sub-sections of each experimental site. The results reveal that the LF varies from 0.16 to 0.34, leading to deep percolation from 95.0 to 334.0 mm of the irrigation water. Eventually, the differences between ground-based and SEBAL-based pistachio ETa were 11% (ranged from 5.7 to 14.0%) and 10% (ranged from 7.1 to 16.4%) for daily and seasonal time scales, respectively. Based on the obtained results, more than 60% of Marvast pistachio orchards have seasonal water use of 410.0 to 680.0 mm (with the average of 594.3 mm), while the cumulative ETo and cumulative pistachio ETc of the same period were 1558.0 mm and 920.0 mm, respectively. In other words, Marvast pistachio trees extract less water from the soil compared with their potential water demands. This is due to the effect of salinity on reducing evapotranspiration rate as well as deficit irrigation of pistachio trees in the water scarce area of Marvast region. In any case, the difference between pistachio ETc and ETa is reflected in declination of the pistachio yield.

Contrasting water use patterns of two important agroforestry tree species in the Mt Elgon region of Uganda

ABSTRACTLack of information on water use of key agroforestry species is an obstacle to understanding their influence on crop productivity. Cordia africana and Albizia coriaria are the dominant tree species of smallholder farming systems in the Mt Elgon region of Uganda and have multiple uses in agroforestry systems. This study deployed six sap flow meters on stems of three selected trees each of C. africana and A. coriaria on-farm. The objective of the study was to assess the daily water use patterns of these agroforestry tree species at different times of the year. We measured the daily sap flow of these two species using the heat ratio method over a period of 18 months. There was a significant main effect of the interaction between tree species and season on daily water use. The two species show contrasting patterns of seasonal water use across leaf shedding stages characterised by episodes of reverse flow in A. coriaria at specific periods of the year. We propose that reverse flows in A. coriaria were triggered by leaf shading while the zero flows in C. africana, which occurred during rainfall events, could have resulted from a lag phase, an indication that the two species may have different water-use strategies. Although C. africana uses 12–15 l day−1 and A. coriaria uses 20–32 l day−1 based on the study trees, C. africana generally uses 12% more water than A. coriaria on a standardised daily basis. Albizia coriaria exhibited radial variation of sap velocities between the inner and outer thermocouples at different periods of measurement, a phenomenon worth investigating further. The leaf shedding patterns of the two trees provide an opportunity for maximising the temporal complementarities of agroforestry systems where these trees exist. This knowledge of C. africana and A. coriaria tree water use provides critical insight for developing successful long-term tree monitoring and management programs in agroforestry systems.