Actual Crop Evapotranspiration Research Articles

Optimized ridge-furrow technology with biochar amendment for alfalfa yield enhancement and soil erosion reduction based on a structural equation model on sloping land

Water scarcity and water-related soil erosion are severely exacerbated by inappropriate human activities and global climate change. Hence, to find a suitable technology to mitigate drought and soil erosion, three consecutive field experiments were conducted to explore the impact of ridge-furrow cropping with biochar amendment on soil water storage, runoff, sediment yield, soil nutrient losses, alfalfa (Medicago sativa L) fodder yield, crop water productivity (WPc), and economic benefit from 2019 to 2021. This experiment was conducted in a split-plot design, taking biochar amendment patterns (no biochar amendment and biochar amendment at a rate of 3× 104 kg ha−1) as a main plot and ridge-furrow technologies (traditional planting, open-ridging, and tied-ridging) as a split-plot. The combination of biochar amendment with ridge-furrow technology, especially tied-ridging technology, increased soil water storage, and captured runoff, sediment, and related soil nutrient losses, consequently increasing alfalfa fodder yield, WPc, and income. During this study, compared to traditional planting, open-ridging depicted an increase in soil water storage by a range of 9.8–39.6 mm, an alfalfa fodder yield boost ranging from 9.8% to 38.6%, and a WPc increase ranging from 0.1 to 16.5 kg ha−1 mm−1. On the other hand, tied-ridging showed greater improvements with soil water storage increasing by 29.1–65.1 mm, alfalfa fodder yield growing by 11.6–44.4%, and WPc advancing by 0.9–17.5 kg ha−1 mm−1. The mean decrease in runoff, sediment, and nutrients (total nitrogen, total phosphorus, and organic matter) loss for open-ridging was 17.9%-37.7%, 46.4%-75.5%, and 40.4%-75.3%, respectively, while for tied-ridging, it was 22.3%-55.5%, 62.1%-87.6%, and 49.0%-87.3%, respectively. Compared to no biochar amendment, soil water storage, alfalfa fodder yield, and WPc for biochar amendment increased by 9.1%-20.4%, 5.8%-52.7%, and 4.6–7.8 kg ha−1 mm−1, respectively, while runoff, sediment, and nutrients loss for biochar amendment decreased by 32.2%-40.9%, 25.5%-55.5%, and 35.9%-53.3%, respectively. Structural equation modeling analysis indicated that the significant direct effect of biochar amendment and ridge-furrow technology on WPc was 0.20 and 0.62, respectively, whereas the significant direct effect of runoff and actual crop evapotranspiration on alfalfa fodder yield was −0.40 and 0.94, respectively. Tied-ridge cropping combined with biochar addition was a highly suggested approach for addressing soil erosion and enhancing alfalfa fodder yields in the Loess Plateau in China. This technology could mitigate soil water scarcity and soil erosion, and give farmers the confidence to invest in this technology in dryland regions.

Effects of different irrigation methods and mulching on yield, growth and water use efficiency of strawberry

ABSTRACT A greenhouse experiment was conducted from 2015–2016 to 2017–2018 on an Aeric Haplaquept to evaluate the effect of irrigation (surface irrigation at furrows at irrigation water: cumulative pan evaporation = 1, drip irrigation to meet 100%, 80% and 60% of actual crop evapotranspiration demand), and mulch (nonwoven jute agro textile, biodegradable plastic film, rice straw and no mulch) regimes on strawberry. Average soil water storage in root zone (86 mm) and fraction of potential plant available water (61%) was highest in jute agrotextile mulched and drip irrigated at 80% actual evapotranspiration. This combination of mulch and irrigation regime increased belowground (root length density, 7.15 × 103 mm−3) and above ground (leaf area index, 9.4) crop growth and emerged as the best option with three- and four-times higher yield (31.1 Mg ha −1) and water use efficiency (23.1 kg m−3), respectively than surface irrigated unmulched strawberry. Results suggest that these findings be incorporated into packages and practices of strawberry cultivation in the moist tropical sub-humid region of Bengal basin and other similar agroecological regions of South Asia.

Effects of Water Stress and NPK Levels on Growth and Yield Attributes of Greenhouse-Grown Cucumbers

Judicious use of water and nutrients is a key factor for successful off-season vegetable production in greenhouses. This experiment was conducted under plastic tunnels to evaluate the effect of water stress and NPK levels on the growth and yield attributes of greenhouse-grown cucumbers. Effect of three irrigation levels viz., 100%, 80% and 60% of actual crop evapotranspiration (ETc) and three drip fertigation levels, viz., 100%, 80% and 60% of the recommended dose of NPK (RDF) with control (furrow irrigation with 100% RDF) were studied in a randomized complete block design experiment. The study indicated better plant growth, a greater number of fruits per plant and enhancement in the yield under drip irrigation. Among the various treatments, T5 (W80%ETc.F80% RDF) resulted in the highest mean fresh fruit yield (66.7 ton/ha) while the full irrigation treatments T1 (W100%ETc.F100% RDF) and T2 (W100%ETc.F80%RDF) recorded the lowest mean fresh fruit yield of 12.9 t/ha and 13.9 t/ha, respectively, as against 9.6 t/ha for the control plot. Conversely, the fully stressed T7, T8 and T9 treatments reduced the irrigation requirement by 29%, 26% and 21% but the mean cucumber yield was significantly decreased by 40%, 70% and 59%, respectively. These results suggested that drip irrigation has a great scope for the production of off-season vegetables. A water deficit level of 80% ETc with 80% RDF is the most appropriate treatment and optimal level to obtain better yield, quality and profitability of greenhouse-grown cucumbers under scarce water resources.

Mulching effects on soil evaporation, crop evapotranspiration and crop coefficients: a review aimed at improved irrigation management

AbstractMulching is a widely adopted agronomic practice, often used as a water-saving strategy due to its effectiveness in reducing soil evaporation. However, effects vary depending on the materials used and the extent of mulch soil coverage. Consequently, the impacts of mulching may differ considerably across production systems, preventing the establishment of reliable guidelines for irrigation water management. The objective of this study is to comprehensively review existing literature that compares mulching versus no-mulching management, aiming to gain a deeper understanding of the effects of mulching on soil evaporation (Es), crop coefficients (Kc), and actual crop evapotranspiration (ETc act). 58 studies were selected. The impact of mulching was particularly notable in the early crop stages, when the soil is not fully covered. Data in literature shows that plastic films were more effective in reducing Kc than organic materials. However, this effect, while evident during the early crop stages, diminished throughout the rest of the season. Black plastic films were more effective during the early crop stages compared to other colored plastics, particularly relative to the decrease of Kc, but this effect also diminishes during the rest of the season. Building upon these findings, the study provides guidelines for expected reductions in Kc values based on the type of crop, crop stage, and the mulching material most used in each cropping system.

Assessing multi‐sensor hourly maize evapotranspiration estimation using a one‐source surface energy balance approach

AbstractIn this study, the performance of a one‐source surface energy balance (OSEB) remote sensing (RS) of actual crop evapotranspiration (ETa), incorporating data from different spaceborne, airborne and proximal multispectral data, was evaluated. The RS platforms in this study included Landsat‐8 (30 m pixel size), Sentinel‐2 (10 m), Planet CubeSat (3 m), a handheld (proximal) multispectral radiometer (MSR) (1 m) and an unmanned aerial system (UAS) (0.03 m). A 2‐year data set (2020 and 2021) from two maize research sites in Greeley and Fort Collins, Colorado, USA, provided ground‐based data for estimating and evaluating hourly ETa from the OSEB algorithm. The accuracy of OSEB hourly maize ETa estimates was evaluated using calculated hourly maize ETa using high‐frequency data collected with an eddy covariance energy balance system installed at each research site. The results indicated that the Planet CubeSat multispectral sensor (3 m), combined with on‐site surface temperature data, yielded the least errors when predicting maize ETa. The hourly ETa estimation errors for the Planet CubeSat were MBE ± RMSE of −0.02 (−3%) ± 0.07 (13%) mm h⁻1. These results suggest the urgent need for a specific approach to improve RS multispectral and thermal radiometric data (quality) to better support sustainable irrigation water management practices.

Estimating crop water requirement in Madhya Pradesh's agro-climatic regions: A CROPWAT and CLIMWAT software case study

Estimating actual crop evapotranspiration is vital in water-scarce environment affected by climate change, particularly for optimizing irrigation and enhancing crop yield. This research focuses on assessing crop water and irrigation requirement for major crops across six districts of Madhya Pradesh, India, spanning diverse agro-climatic regions. Employing CLIMWAT 2.0 and CROPWAT 8.0 software, calculated crop evapotranspiration and devised irrigation strategies tailored to local climatic conditions. The FAO-Penman-Montieth (FAO-PM) equation for reference evapotranspiration (ET0), aiding in crop water requirement computation and irrigation planning. Our findings reveal substantial variations in crop water requirements across crops and districts. For instance, soybean in Indore requires the highest water input at 380 mm, while in Guna, was least at 303 mm. Wheat, on the other hand, register the highest water needs in Khandwa at 510.6 mm and the lowest in the Neemuch district at 370.8 mm, particularly during the rabi season. Besides that, this study underscores the need for district-specific considerations, taking into account climate and soil characteristics when formulating water management strategies. Employing efficient irrigation practices and techniques to manage water stress becomes imperative for optimizing crop yield and achieving economic returns. Implementing customized approaches to enhance water use efficiency and promote sustainability in agricultural production is crucial. These research outcomes provide valuable insights for policymakers, agricultural practitioners, and water resource managers to develop context-specific water management strategies.

Impact of ET and biomass model choices on economic irrigation water productivity in water-scarce basins

Using Economic Irrigation Water Productivity (EIWP) as an indicator for on-farm irrigation decision-making is of utmost importance in addressing the challenges posed by poor policies in managing agricultural water use, particularly in water-scarce basins. Various modeling systems are available for quantifying crop actual evapotranspiration (ETa) and biomass needed for measuring the economic output obtained from each unit of irrigation water utilized. The difference in ETa and biomass estimates between the modeling systems could translate into a difference in EIWP outcomes, which influences the basin-wide irrigation water management. In this paper we examine the influence of selecting different ETa and biomass models, particularly the hybrid single-source energy balance HSEB, the Global Field-Scale Crop Yield and ET Mapper in Google Earth Engine GYMEE, and FAO’s WaPOR V2, on evaluating EIWP on a basin-wide level. The method includes combining remote sensing and economic data to compare variability in ETa, biomass, and EIWP values derived from HSEB, GYMEE, and WaPOR. The approach is demonstrated with field survey data from the upper hydrologic unit of Lebanon’s largest catchment, the Litani River Basin, in its three productive districts Baalbak, Zahleh, and West Bekaa for the year 2021. Field-scale mean monthly ETa and biomass estimates for all crops, obtained from both models, are very comparable. On a district level, the results reveal a reasonable model agreement for the four crops in the estimation of ETa with moderate to strong correlation (0.75 < r < 0.95). WaPOR consistently produces slightly higher mean ETa values for potato, wheat, and table grapes when compared to HSEB. Both models reasonably agree when estimating biomass for the four crops with high correlation (r > 0.9). Contrary to the ETa results, the GYMEE model consistently estimates slightly higher mean biomass values for all crops compared to WaPOR. The EIWP values produced by both models consistently indicate that potato holds the highest EIWP across all districts, followed by onion, table grapes, and wheat. The mean district HSEB-GYMEE model derived EIWPs are slightly higher than those derived from the WaPOR model for most crops. For EIWP obtained from HSEB-GYMEE, mean EIWP for potato is 12 times higher than that of wheat. As for that obtained from WaPOR, mean EIWP for potato is 10 times higher than that of wheat. The paper establishes a basis for future research on the application of remote sensing models in addressing water-stressed and socioeconomically challenged basins, with the potential to inform strategic irrigation management decisions based on model selection.

Benchmarking Water-Limited Yield Potential and Yield Gaps of Shiraz in the Barossa and Eden Valleys

Background and Aims. Vineyard performance is impacted by water availability including the amount and seasonality of rainfall, evapotranspiration, and irrigation volume. We benchmarked water-limited yield potential (Yw), calculated yield gaps as the difference between Yw and actual yield, and explored the underlying environmental and management causes of these gaps. Methods and Results. The yield and its components in two sections of 24 Shiraz vineyards were monitored during three vintages in the Barossa zone (GI). The frequency distribution of yield was L-shaped, with half the vineyards below 5.2 t·ha−1, and an extended tail of the distribution that reached 24.9 t·ha−1. The seasonal ratio of actual crop evapotranspiration and reference evapotranspiration was below 0.48 in 85% of cases, with a maximum of 0.65, highlighting a substantial water deficit in these vineyards. A boundary function relating actual yield and seasonal rainfall was fitted to quantify Yw. Yield gaps increased with an increasing vine water deficit, as quantified by the carbon isotope composition of the fruit. The yield gap was smaller with higher rainfall before budburst, putatively favouring early-season vegetative growth and allocation to reproduction, and with higher rainfall between flowering and veraison, putatively favouring fruit set and berry growth. The gap was larger with higher rainfall and lower radiation between budburst and flowering. The yield gap increased linearly with vine age between 6 and 33 yr at a rate of 0.3 t·ha−1·yr−1. The correlation between yield gap and yield components ranked bunch weight ≈ berries per bunch &gt; bunch number &gt; berry weight; the minimum to close the yield gap was 185,000 bunches ha−1, 105 g bunch−1, 108 berries bunch−1, and 1.1 g berry−1. Conclusions. Water deficit and vine age were major causes of yield gaps. Irrigation during winter and spring provides an opportunity to improve productivity. The cost of dealing with older, less productive vines needs to be weighed against the rate of increase in yield gap with vine age. Significance of the Study. A boundary function to estimate water-limited yield potential returned viticulturally meaningful yield gaps and highlighted potential targets to improve vineyard productivity.

Estimation of Crop-coefficients and Evapotranspiration of Field Pea (Pisum sativum L.) Using Lysimeter and Empirical Models under Temperate Climate

During Rabi 2020-21, a field experiment was conducted at SKUAST-K, Shalimar, India, focusing on field Pea (Pisum sativum L.). The aim of this study was to determine the water requirement and single crop coefficient (Kc) of pea using a lysimeter setup. Four empirical models were employed to calculate the reference evapotranspiration and were then compared with the actual crop evapotranspiration at different growth stages. The Kc values for field pea were 0.50, 0.80, 1.15, and 1.10 during the initial, development, mid-season and late season stages, respectively. The water requirement was found as 239.9 mm for the whole cropping period of the pea. Among the models, the Penman Montieth crop evapotranspiration model exhibited the closest agreement with the corresponding values obtained in the field through water balance study, yielding RMSE, RSR, and NSE values of 0.97, 9.5, and 11.6, respectively. These findings highlight the significance of using Penman Monteith crop evapotranspiration model for estimating crop evapotranspiration in temperate regions.

Evaluation of transpiration in different almond production systems with two-source energy balance models from UAV thermal and multispectral imagery

AbstractA growing number of intensive irrigated production systems of the almond crop have been established in recent years. However, there is little information regarding the crop water requirements. Remote sensing-based models such as the two-source energy balance (TSEB) have proven to be reliable ways to accurately estimate actual crop evapotranspiration. However, few efforts have been made to validate the transpiration with sap flow measurements in woody row crops with different production systems and water status. In this study, the TSEB Priestley-Taylor (TSEB-PT) and contextual approach (TSEB-2T) models were assessed to estimate canopy transpiration. In addition, the effect of applying a basic clumping index for heterogeneous randomly placed clumped canopies and a rectangular hedgerow clumping index on the TSEB transpiration estimation was assessed. The TSEB inputs were obtained from high resolution multispectral and thermal imagery using an unmanned aerial vehicle. The leaf area index (LAI), stem water potential (Ψstem) and fractional intercepted photosynthetically active radiation (fIPAR) were also measured. Significant differences were observed in transpiration between production systems and irrigation treatments. The combined use of the TSEB-2T with the C&amp;N-R transmittance model gave the best transpiration estimations for all production systems and irrigation treatments. The use of in situ PAR transmittance in the TSEB-2T model significantly improved the root mean squared error. Thus, the better agreement observed with the TSEB when using the C&amp;N-R model and in situ PAR transmittance highlights the importance of improving radiative transfer models for shortwave canopy transmittance, especially in woody row crops.

Integrated application of fertilization and reduced irrigation improved maize (Zea mays L.) yield, crop water productivity and nitrogen use efficiency in a semi-arid region

Water scarcity as well as soil degradation and environmental problems potentially caused by excessive application of chemical fertilizers are major challenges to agricultural production in semi-arid areas. It is crucial to explore a suitable and eco-friendly strategy to achieve sustainable production of maize with high crop water productivity and nitrogen use efficiency. Here, a two-year field experiment with three irrigation levels of W1 (220 mm), W2 (140 mm) and W3 (60 mm), and five fertilization types of no fertilizer (CK), chemical fertilizer (CF), bio-fertilizer combined with CF (CFB), organic fertilizer combined with 70% CF (CFO) and bio-fertilizer combined with CFO (CFOB) was conducted to investigate the effect on dry matter, N uptake and remobilization, grain yield, crop water productivity, nitrogen use efficiency and economic benefits of maize in 2021 and 2022. The results showed that the W2 and W3 decreased in the leaf area index, photosynthetic rate, dry matter accumulation, the maximum dry matter accumulation rate and actual crop evapotranspiration. Under W1 condition, the CFB improved the growth of maize, increased the dry matter and nitrogen accumulation and yield, with 8.1% and 7.4% higher than CF in 2021 and 2022, respectively. Under deficit irrigation (W2 and W3), CFOB significantly increased the leaf area index, photosynthetic rate, dry matter accumulation at later growth stage, in addition, CFOB increased the post-silking N uptake and the percentage in total N content, finally improved the grain yield with 23.8% and 22.8% under W2, 22.5% and 25.7% under W3 higher than that of the CF in 2021 and 2022, respectively. Irrigation and fertilizer showed a coupling effect on grain yield, crop water productivity, agronomy efficiency and nitrogen use efficiency. Overall, the CFOB under moderate deficit (W2) exhibited the highest water productivity, nitrogen use efficiency and economic benefits, as well as maintained the high yield, could be a promising approach to sustainable development of local maize.

Predicting Crop Evapotranspiration under Non-Standard Conditions Using Machine Learning Algorithms, a Case Study for Vitis vinifera L. cv Tempranillo

This study focuses on assessing the accuracy of supervised machine learning regression algorithms (MLAs) in predicting actual crop evapotranspiration (ETc act) for a deficit irrigated vineyard of Vitis vinifera cv. Tempranillo, influenced by a typical Mediterranean climate. The standard approach of using the Food and Agriculture Organization (FAO) crop evapotranspiration under standard conditions (FAO-56 Kc-ET0) to estimate ETc act for irrigation purposes faces limitations in row-based, sparse, and drip irrigated crops with large, exposed soil areas, due to data requirements and potential shortcomings. One significant challenge is the accurate estimation of the basal crop coefficient (Kcb), which can be influenced by incorrect estimations of the effective transpiring leaf area and surface resistance. The research results demonstrate that the tested MLAs can accurately estimate ETc act for the vineyard with minimal errors. The Root-Mean-Square Error (RMSE) values were found to be in the range of 0.019 to 0.030 mm·h⁻¹. Additionally, the obtained MLAs reduced data requirements, which suggests their feasibility to be used to optimize sustainable irrigation management in vineyards and other row crops. The positive outcomes of the study highlight the potential advantages of employing MLAs for precise and efficient estimation of crop evapotranspiration, leading to improved water management practices in vineyards. This could promote the adoption of more sustainable and resource-efficient irrigation strategies, particularly in regions with Mediterranean climates.

Maize nitrogen uptake and use efficiency, partial factor productivity of nitrogen, and yield response to different nitrogen and water applications under three irrigation methods

AbstractThe effects of irrigation and nitrogen (N) on grain yield, actual crop evapotranspiration (ETa), N uptake efficiency (NUE), partial factor productivity of N (PFPN), and N utilization efficiency (NUtE) of maize (Zea mays L.) under centre pivot (CP), subsurface drip (SDI) and gravity (furrow) irrigation (FI) were quantified. Field experiments were conducted in two growing seasons under the full irrigation treatment (FIT), limited irrigation treatments of 80% FIT and 60% FIT and rainfed treatment (RFT). The highest NUE was observed under limited irrigation in the order of 80% FIT &gt; FIT ≥ 60% FIT in non‐traditional treatment‐1 (NT‐1) in both the CP and SDI methods. NUtE increased with irrigation amount. There were strong correlations between NUtE and grain yield regardless of irrigation method. ETa increased with N amount, and the slopes of these relationships varied substantially between irrigation and N levels and irrigation methods. PFPN increased with irrigation amount across the irrigation methods and N treatments. A higher PFPN was observed in the lowest total applied N plots and in‐season split N application treatments. The pooled data for the CP and SDI methods showed significantly higher PFPN (20.3%) than the FI method, whereas the PFPN values in the CP and SDI methods were equal.

Accuracy of Estimated Crop Evapotranspiration Using Locally Developed Crop Coefficients against Satellite-Derived Crop Evapotranspiration in a Semiarid Climate

Actual crop evapotranspiration (ETa) is measured or estimated using different methods, and its accuracy is critical for water management under precision agriculture. The objective of this study was to compare maize ETa estimated by the two-step approach using a locally developed crop coefficient curve with satellite-retrieved evapotranspiration by six models incorporated in the OpenET to identify the best evapotranspiration estimation alternatives to the two-step approach for water management in northern New Mexico. Maize (Zea mays L.) was planted at the NMSU Agricultural Science Center at Farmington from 2017 to 2022 and uniformly managed across years. Water management in plants was based on maize’s actual evapotranspiration estimated as the product of the reference evapotranspiration and the local crop coefficient, which is described as a third-order polynomial function of the accumulated heat units by maize plants. For the same growing seasons, maize ETa was retrieved from satellite, and was estimated by six models listed within the OpenET from 2017 to 2022. The results show that maize daily ETa was consistently smaller when measured by SIMS and PT-JPL during maize initial and actively growing stages, while ETc(kc), SIMS and eeMETRIC showed similar maize daily ETa during maize full canopy development and mid-season, and which overcome the evapotranspiration estimated by DisALEXI, PT-JPL, geeSEBAL, and SSBop. ETc(kc) drastically dropped and became the lowest value among all ETa estimation models after the first fall snow or the first killing frost. Regarding the seasonal average, all six models included in OpenET showed smaller maize evapotranspiration. Maize seasonal evapotranspiration varied from 589.7 to 683.2 mm. eeMETRIC compares most similarly to the ETc(kc) model, followed by SIMS, with percent errors of 2.58 and 7.74% on a daily basis and 2.43 and 7.88% on a seasonal basis, with the lowest MBE and RMSE values, respectively, and could be used as an alternative for maize actual daily evapotranspiration for water management in northern New Mexico. The results of this study could be used by water managers and crop growers to improve water management in the Four Corners region, using eeMETRIC for crop water use to improve water management and conservation under sustainable agriculture.

Calibration and assessment of evapotranspiration methods for cucumber plants in a Venlo‐type greenhouse

AbstractAccurate estimation of actual crop evapotranspiration (ETc) is a necessary step in water resource management. Several ETc models have been developed and applied to estimate ETc in open fields. To date, there is no standard equation to estimate ETc under greenhouse conditions due to the structural and environmental differences between greenhouses and open fields. Therefore, an experiment was conducted in a Venlo‐type greenhouse in south‐east China during four planting seasons of cucumber plants in 2018 and 2019. Four methods, the pan evaporation method (Kp‐method), crop coefficient model (Kc‐method), Penman–Monteith model (rc‐method) and Priestley–Taylor model (αPT‐method), were employed and parameterized to estimate the ETc of cucumber in the Venlo‐type greenhouse. The performances of the four models were evaluated using ETc measured by lysimeters. The Kp‐method and αPT‐method underestimated and overestimated ETc values with root mean square errors (RMSEs) equal to 0.79 and 0.49 mm day−1 for the spring‐summer planting season (SSPS) and 0.35 and 0.51 mm day−1 for the autumn‐winter planting season (AWPS), respectively. The Kc‐method and rc‐method showed comparatively good performances in estimating cucumber ETc, with RMSEs equal to 0.53 and 0.34 mm day−1 for SSPS and 0.35 and 0.47 mm day−1 for AWPS, respectively.

Cactus–sorghum intercropping combined with management interventions of planting density, row orientation and nitrogen fertilisation can optimise water use in dry regions

Some strategies can optimise the use of water in crops under deficit, either by increasing yield or by reducing actual crop evapotranspiration (ET), to promote the sustainable intensification of production systems. The objective was to evaluate how the spacing, planting orientation, nitrogen fertilisation and intercropping strategies impact the dynamics of water in the soil, ET partitioning, and water use indicators for forage cactus and cactus–sorghum intercropping. Four experiments were conducted between 2018 and 2020 in the Brazilian semi-arid region. In the first two sites (I and II), the cladodes of the intercropped forage cactus and sorghum were spaced at 0.10, 0.20, 0.30, 0.40 and 0.50 m with rows-oriented east–west and north–south. In site III, the intercropped rows were spaced at 1.00, 1.25, 1.50 and 1.75 m. Site IV, which contained the forage cactus crop exclusively, was treated with four nitrogen levels (50, 150, 300 and 450 kg N ha−1). The management interventions improved water use more by increasing dry matter than by reducing ET in the cropping system. Intercropping promoted the greatest increase in water productivity (130 %). Increasing N doses in the forage cactus-only crop reduced ET by up to 39 % but increased deep drainage losses by up to 365 %. The most promising management practices for optimising water resources were as follows: spacing of 0.10 m between cactus plants in the intercropping trial under east–west row orientation, as it promoted greater water use efficiency (76 %); spacing of 0.30 m in the north–south orientation; and row spacing of 1.50 m, as it improved water productivity (6.89 kg m−3). Thus, interventions in management should be adopted to optimise water use in intercropping systems with forage cactus, aiming at sustainable intensification in dry environments.

Nitrogen reduction combined with ETc irrigation maintained summer maize yield and increased water and nitrogen use efficiency.

High rainfall and excessive urea application are counterproductive to summer maize growth requirements and lower grain yield and water/nitrogen (N) use efficiency. The objective of this study was to determine whether ETc irrigation based on summer maize demand and reduced nitrogen rate in the Huang Huai Hai Plain increased water and nitrogen use efficiency without sacrificing yield. To achieve this, we conducted an experiment with four irrigation levels [ambient rainfall (I0) and 50% (I1), 75% (I2), and 100% (I3) of actual crop evapotranspiration (ETc)] and four nitrogen rates [no nitrogen fertilizer (N0), recommended nitrogen rate of urea (NU), recommended nitrogen rate of blending controlled-release urea with conventional urea fertilizer (BCRF) (NC), and reduced nitrogen rate of BCRF (NR)] in 2016-2018. The results show that reduced irrigation and nitrogen rate reduced Fv/Fm, 13C-photosynthate, and nitrogen accumulation both in the kernel and plant. I3NC and I3NU accumulated higher 13C-photosynthate, nitrogen, and dry matter. However, 13C-photosynthate and nitrogen distribution to the kernel was decreased from I2 to I3 and was higher in BCRF than in urea. I2NC and I2NR promoted their distribution to the kernel, resulting in a higher harvest index. Compared with I3NU, I2NR increased root length density by 32.8% on average, maintaining considerable leaf Fv/Fm and obtaining similar kernel number and kernel weight. The higher root length density of I2NR of 40-60 cm promoted 13C-photosynthate and nitrogen distribution to the kernel and increased the harvest index. As a result, the water use efficiency (WUE) and nitrogen agronomic use efficiency (NAUE) in I2NR increased by 20.5%-31.9% and 11.0%-38.0% than that in I3NU, respectively. Therefore, 75%ETc deficit irrigation and BCRF fertilizer with 80% nitrogen rate improved root length density, maintained leaf Fv/Fm in the milking stage, promoted 13C-photosynthate, and distributed nitrogen to the kernel, ultimately providing a higher WUE and NAUE without significantly reducing grain yield.

Estimation of actual crop evapotranspiration using artificial neural networks in tomato grown in closed soilless culture system

Estimation of actual crop evapotranspiration using artificial neural networks in tomato grown in closed soilless culture system

Modelling effects of water stress on the productivity of irrigated wheat (Triticum Aestivum L.) in a semiarid condition of Northeastern Nigeria

Lake Chad region is currently experiencing trending issues. Climate change is among the major influencers of these issues that require inevitable consideration for a sustainable ecosystem. Various crop models have been developed and employed in various environmental conditions and management practices, which are cheaper and easier than field experiments. Therefore, crop models could be used to simulate various water management strategies and suggest suitable options. In this work, the FAO AquaCrop model has been evaluated to simulate deficit irrigation (DI) scenarios for wheat crops using data generated from a field experiment. The model simulated grain yield (GY), biomass yield (BMY), biomass production (BMP) and canopy cover (CC) adequately during its calibration and validation. However, its performance in simulating water productivity (WP) and actual crop evapotranspiration (ETa) was low with average r2, NRMSE, model efficiency (EF) and Willmot Index of agreement (d) of 0.58, 11.0 %, -1.40 and 0.69 respectively. The study of DI scenarios using the model revealed that the application of DI throughout the growth stages of the crop could significantly affect GY and WP. The highest GY and WP of 5.3 t/ha and 1.50 kg/m3 were respectively obtained at the application of full irrigation (T100). Increasing DI beyond 20 % depressed both GY and WP significantly. However, increasing the irrigation interval from seven to ten days did not affect GY, thereby improving WP from 1.28 kg/m3 to 1.38 kg/m3. Therefore, applying an 80 % irrigation requirement throughout the wheat growing season at 10-day intervals could save 25 % of irrigation water, a valuable strategy to improve irrigation water use without significant yield reduction. Furthermore, irrigation-related scientists and managers can use the validated model to decide the current and future irrigation water management for similar wheat varieties in similar environmental conditions.

Remote Sensing and Aerodynamic Temperature-Based Energy Balance Models to Estimate Crop Evapotranspiration Rates

Different methods exist to measure or estimate actual crop evapotranspiration (ETa). However, some methods require a large number of data input or strict field conditions. Remote sensing based ETa algorithms based on extreme thermal pixels (hot and cold) have limitations when required extreme pixels are not present in the acquired thermal infra-red imagery. In addition, satellite overpass frequency and spatial pixel resolution may be a limitation for some agricultural fields and micro-climates. Surface energy balance methods that use surface radiometric temperatures often fail to perform well under drought, limited irrigation, salt affected soils, or under sparse vegetation conditions. One option is to measure or estimate the crop/surface sensible heat flux through the aerodynamic temperature approach, then calculate the available energy and solve the energy balance for latent heat flux. Thus, this study presents different published algorithms that characterize the crop or field surface aerodynamic temperature and then applies them to different conditions for evaluation. Determining spatial ETa continuously has the potential to improve the irrigation water management decision making. The aerodynamic temperature approach was initially developed with good results as a function of surface radiometric temperature, air temperature, crop leaf area index, and wind speed or surface aerodynamic resistance. However, the inclusion of the crop fractional percent cover and of a new resistance term (turbulent-mixing row resistance) greatly improved the estimation of the sensible heat and latent heat fluxes, when evaluated with heat flux data derived from eddy covariance energy balance towers. Results also indicate that the aerodynamic method has transferability potential to different regions, crops, and irrigation methods than the conditions encountered in the method development.