Crop Transpiration Research Articles

Assessment of upscaling methodologies for daily crop transpiration using sap flows and two-source energy balance models in almonds under different water statuses and production systems

Abstract. Daily transpiration (Td) is crucial for both irrigation water management and increasing crop water productivity. The use of the remote-sensing-based two-source energy balance model (TSEB) has proven to be robust in estimating plant transpiration and evaporation separately for various crops. However, remote sensing models provide instantaneous estimations, and so daily upscaling approaches are needed to estimate daily fluxes. Daily upscaling methodologies have not yet been examined to upscale solely transpiration in woody crops. In this regard, this study aims to evaluate the proper image acquisition time throughout the day and four methodologies used to retrieve Td in almond trees with different production systems and water statuses. Hourly transpiration (Th) was estimated using the TSEB contextual approach (Th–TSEB) with high-resolution imagery five times during two diurnal courses. The tested methodologies were the following: the simulated evaporative fraction variable (EFsim), irradiance (Rs), reference evapotranspiration (ETo), and potential evapotranspiration (ETp). These approaches were first evaluated with in situ sap flow (T–SF) data and were then applied to the Th–TSEB. Daily T–SF showed significant differences among production systems and levels of water stress. The EFsim and ETp methods correlated better with measured T–SF and reduced the underestimation observed using the Rs and ETo methods, especially at noon in the severely water-stressed trees. However, the daily upscaling approaches applied in the TSEB (Td–TSEB) failed to detect differences between production systems. The lack of sensibility of Th–TSEB among production systems poses a challenge when estimating Td in canopies with discontinuous architectural structures. The use of ETp as a reference variable could address this issue as it incorporates various aerodynamic and radiative properties associated with different canopy architectures that influence the daily Th–SF pattern. However, more accurate ETp estimates or more advanced ETp models are needed.

Spatial Variation of Microclimatic Parameters Inside a Polyhouse with Fog Cooling System

The importance of protected cultivation is increasing day by day due to its capability of producing crop all round the year and increase in the crop productivity. This advantage of protected cultivation can be efficiently achieved by adapting the polyhouse cultivation. To obtain the maximum crop productivity inside a polyhouse, it is necessary to understand the variability of microclimate inside it. The present study aims to understand the spatial variability of microclimate inside a naturally ventilated polyhouse installed with fog cooling system during summer season. The main aim of the study is to understand the effect of fogging system in spatial variability of microclimate. For the study, the data of microclimatic parameters were collected daily from April to June at four different time intervals 8.30 AM, 12.30 PM, 4.30 PM and 8.30 PM. The data recorded was then analyzed in Golden Surfer Software to generate contour plots of weekly averages of microclimate parameters. The analysis revealed that the temperature and relative humidity varied across the polyhouse depending upon the wind velocity and its distribution pattern. The light intensity varied based upon the orientation of polyhouse and the position of sun. Carbon dioxide concentration varied based on temperature, light intensity, crop transpiration and respiration. It can be concluded that, inside a naturally ventilated polyhouse, the microclimate varied both spatially and temporally with fogging system also due to wind effect. Thus, having accurate understanding of the microclimate inside a polyhouse helps to maintain optimal conditions for plant growth and thus improve crop yield and productivity.

Effects of different mulching technologies on rainfed maize field energy exchange and evapotranspiration partitioning in northwest China

Artificial mulching, a prevalent water-saving tool in arid and semiarid agroecosystems, complicated energy exchange and water transport process between land surface and atmosphere. The field energy and evapotranspiration (ET) partitioning within a soil-mulch-plant-atmosphere continuum have not been comprehensively examined, which limited cognition of the underlying mechanisms that control hydrological processes and achieve yield improvement. Here, a four-season experiment in a rainfed summer maize field with four mulching treatments (NM: non-mulching, SM: straw mulching, RPBF: plastic-mulched ridge with bare furrow, and RPSF: plastic mulched ridge with straw-mulched furrow) was conducted to study the dynamics of surface energy and ET components and their regulation mechanisms. Results indicated that the effects of mulching on field energy partitioning were most evident at the maize initial stage, during which net radiation was significantly decreased under PM treatments (RPBF and RPSF), while soil heat flux was significantly reduced in SM treatments (p < 0.05). The average latent heat flux (LE) was 3.55 and 5.65 MJ·d−1 for NM maize at sowing and seedling stages, but decreased by 9.01 %, 27.04 %, 29.58 % at sowing, and 7.08 %, 9.56 % and 16.46 % at seedling stages for SM, RPBF and PRSF, respectively. The energy component differences among different treatments were minimal during the middle and late stages with high leaf coverage, and total LE and sensible heats were not significantly different. Mulch exerted a notable impact on soil evaporation (E) and crop transpiration (T), characterized by the average E of 0.96, 0.82, 0.57 and 0.46 mm·d−1 in NM, SM, RPBF and RPSF, while the value for T was 1.67, 1.88, 2.03 and 2.10 mm·d−1, respectively. PM conserved soil water by reducing E during the initial growing season and in dry periods, but also enhancing T and deepening the depth of soil water consumption under higher leaf cover. Energy exchange and ET partitioning were found to be more sensitive to soil water content (SWC) during periods characterized by lower leaf coverage, while the role of underlying canopy coverage characteristics overwhelmed soil properties in controlling energy and ET partitioning along with the leaf expansion. These findings contributed to a more comprehensive understanding of different mulching management on rainfed maize energy exchange and water use in Northwest China.

Enhancing Water and Soil Resources Utilization via Wolfberry-Alfalfa Intercropping.

The impact of the intercropping system on the soil-plant-atmosphere continuum (SPAC), encompassing soil evaporation, soil moisture dynamics, and crop transpiration, remains an area of uncertainty. Field experiments were conducted for two years in conjunction with the SIMDualKc (Simulation Dual Crop Coefficient) model to simulate two planting configurations: sole-cropped wolfberry (Lycium barbarum L.) (D) and wolfberry intercropped with alfalfa (Medicago sativa L.) (J). These configurations were subjected to different irrigation levels: full irrigation (W1, 75-85% θfc), mild deficit irrigation (W2, 65-75% θfc), moderate deficit irrigation (W3, 55-65% θfc), and severe deficit irrigation (W4, 45-55% θfc). The findings revealed that the JW1 treatment reduced the annual average soil evaporation by 32% compared with that of DW1. Additionally, mild, moderate, and severe deficit irrigation reduced soil evaporation by 17, 24, and 36%, respectively, compared with full irrigation. The intercropping system exhibited a more efficient canopy structure, resulting in reduced soil evaporation and alleviation of water stress to a certain extent. In terms of temporal dynamics, monocropping resulted in soil moisture levels from 1% to 15% higher than intercropping, with the most significant differences manifesting in the mid to late stages, whereas differences in the early stages were not statistically significant. Spatially, the intercropping system exhibited 7-19% lower soil water contents (SWCs) than sole cropping, primarily within the root water uptake zone within the 0-60 cm soil layer. The intercropping system showed an enhanced water absorption capacity for plant transpiration, resulting in a 29% increase in transpiration compared with sole cropping, thereby achieving water-saving benefits. These findings contribute to our understanding of the agronomic and environmental implications of intercropping wolfberry and alfalfa in arid regions and provide insights into optimizing water and soil resource management for sustainable agricultural practices.

Agronomic response, transpiration and water productivity of four almond production systems under different irrigation regimes

In recent years, more intensive production systems have been developed, coinciding with a growing scarcity of water resources. This context underscores the imperative of prioritizing water productivity (WP) as a critical factor in choosing the optimal production system to minimize agricultural water use. This study aims to contribute by evaluating WP in almond orchards under four production systems: open vase with severe pruning (open vase), open vase with minimal pruning (open vase (MP)), central axis and hedgerow. Three irrigation treatments were applied over two consecutive growing seasons: fully irrigated, mild stress and severe stress. Crop transpiration was monitored over the two years using both sap flow sensors and the two-source energy balance (TSEB) model with remote sensing. The severe stress treatment exhibited a notable reduction in kernel yield and nut load of 31.6 % and 34.5 %, respectively, in the second year of water deficit. The hedgerow system tended to have similar kernel yield to the open vase (MP) and central axis systems, and higher compared to the open vase system. Additionally, both transpiration measurement methods revealed that hedgerow exhibited lower transpiration rates across all irrigation treatments. Therefore, the highest WP was observed in the hedgerow system throughout both studied years. Similar findings were derived from the analysis of long-term data. Our findings indicate that the hedgerow production system had the highest WP, averaging 0.43 kg m−3 historically, compared to 0.33 kg m−3 for the open vase, 0.34 kg m−3 for the open vase (MP), and 0.36 kg m−3 for the central axis systems.

Evaluating the precise grapevine water stress detection using unmanned aerial vehicles and evapotranspiration-based metrics

AbstractPrecise irrigation management requires accurate knowledge of crop water demand to adequately optimize water use efficiency, especially relevant in arid and semi-arid regions. While unoccupied aerial vehicles (UAV) have shown great promise to improve the water management for crops such as vineyards, there still remains large uncertainties to accurately quantify vegetation water requirements, especially through physically-based methods. Notably, thermal remote sensing has been shown to be a promising tool to evaluate water stress at different scales, most commonly through the Crop Water Stress Index (CWSI). This work aimed to evaluate the potential of a UAV payload to estimate evapotranspiration (ET) and alternative ET-based crop water stress indices to better monitor and detect irrigation requirements in vineyards. As a case study, three irrigation treatments within a vineyard were implemented to impose weekly crop coefficient (Kc) of 0.2 (extreme deficit irrigation), 0.4 (typical deficit irrigation) and 0.8 (over-irrigated) of reference ET. Both the original Priestley-Taylor initialized two-source energy balance model (TSEB-PT) and the dual temperature TSEB (TSEB-2T), which takes advantage of high-resolution imagery to discriminate canopy and soil temperatures, were implemented to estimate ET. In a first step, both ET models were evaluated at the footprint level using an eddy covariance (EC) tower, with modelled fluxes comparing well against the EC measurements. Secondly, in-situ physiological measurements at vine level, such as stomatal conductance (gst), leaf (Ψleaf) and stem (Ψstem) water potential, were collected simultaneously to UAV overpasses as plant proxies of water stress. Different variants of the CWSI and alternative metrics that take advantage of the partitioned ET from TSEB, such as Crop Transpiration Stress Index (CTSI) and the Crop Stomatal Stress Index (CSSI), were also evaluated to test their statistical relationship against these in-situ physiological indicators using the Spearman correlation coefficient (ρ). Both TSEB-PT and TSEB-2T CWSI related similarly to in-situ measurements (Ψleaf: ρ ~ 0.4; Ψstem: ρ ~ 0.55). On the other hand, stress indicators using canopy fluxes (i.e. CTSI and CSSI) were much more effective when using TSEB-2 T (Ψleaf: ρ = 0.45; Ψstem: ρ = 0.62) compared to TSEB-PT (Ψleaf: ρ = 0.18; Ψstem: ρ = 0.49), revealing important differences in the ET partitioning between model variants. These results demonstrate the utility of physically-based models to estimate ET and partitioned canopy fluxes, which can enhance the detection of vine water stress and quantitatively assess vine water demand to better manage irrigation practices.

Adapting service crop termination strategy in viticulture to increase soil ecosystem functions and limit competition with grapevine

Soil management and particularly service crops are a promising solution for addressing current challenges in viticulture as they limit the use of herbicides while increasing potential ecosystem services. Scientific literature barely considers the importance of service crop management to reach trade-offs between ecosystem services and disservices. This study evaluates during a three-year experiment, 6 service crop termination strategies for winter service crops, combining two service crops termination periods (early termination in February vs. termination at grapevine budburst) and three termination methods (mower (M), mower + tillage (T), roller-crimper (R)). Service crop (biomass, C:N ratio, weeds, and mulch following termination), soil ( soil organic matter, microbial biomass, and water and nitrogen stocks), and grapevines (predawn leaf water potential, yield components, δ13C, yeast assimilable nitrogen in juice, and pruning weight) were monitored from 2019 to 2022. Allowing service crops to develop until the budburst of the vine resulted in a two to three-fold increase in biomass compared to early destruction. Termination involving soil tillage was the most effective method, as treatments destroyed early with soil tillage exhibited almost no regrowth. Soil tillage termination led to the lowest biomass of weeds at the grapevine flowering two years out of three, and prevented the regrowth of certain sown plants, especially Poaceae. The roller was less effective in destroying service crop species but was the best method for maintaining plant residues on the soil surface. A higher soil microbial biomass was observed with termination at budburst, combined with no-till termination methods. Termination involving soil tillage was notably more effective in stopping service crop transpiration, increasing soil water stocks and improving grapevine water status. In 2020 and 2022, soil inorganic nitrogen stocks were almost 4 times higher in the T treatments compared to the other two termination methods, achieving a level of approximately 61 kg ha−1 that closely corresponds to the annual nitrogen requirements of grapevines. The yeast-assimilable nitrogen (YAN) content in grape juice mirrored this trend. Pruning weight varied significantly between different termination methods, with T treatments exhibiting a higher pruning weight per vine in comparison to R and M treatments. In general terms, the T treatment had a significantly higher number of bunches, the M treatment had the lowest, and the R treatment exhibited intermediate values. Overall, the average grapevine yield ranged from 7.25 to 13.7 t ha−1, corresponding to 52–98 hL ha−1 (with 4000 vines ha−1, 140 kg hL−1). This level of production may be accepted for Protected Designations of Origin that limit grapevine yield to 40 or 60 hL ha−1, but it could be a limitation for Protected Geographical Indications, which permit 90 hL ha−1, or unlabeled productions without yield limitations. Given the Mediterranean climate context, with rising frequencies of dry winters due to climate change, termination involving soil tillage appears to be the least risky strategy to preserve grapevine vigor and production while improving soil-based ecosystem functions. However, this might be contingent on the targeted yield and wine valuation.

Simulation Model Construction of Plant Height and Leaf Area Index Based on the Overground Weight of Greenhouse Tomato: Device Development and Application

Plant height and leaf area index (LAI) are crucial growth indicators that reflect the growth status of tomatoes in greenhouses, enabling accurate determinations to effectively estimate crop transpiration and formulate irrigation strategies for reducing agricultural water waste. There is a need for the increased application of related models to simulate tomato growth indices in the traditional greenhouse production in China. This study proposes a nondestructive, real-time monitoring and simulation device for measuring tomato plant height and leaf area index. The weight of aboveground tomatoes was obtained by suspending tomato plants on dynamometers, while the total weight of stem and leaf organs was determined using a distribution coefficient simulation model. The R2 value between the measurements from the electronic scale and those from the aboveground fresh weight device for tomatoes was 0.937, with an RMSE value of 0.05 kg. The monitoring device did not affect the average tomato growth during operation. The device will not affect the growth of tomatoes during monitoring. A multiple linear regression was used to compare the measured and simulated values of the plant height and leaf area index of various types of greenhouse tomatoes cultivated in different greenhouse types. The average R2 value for simulating plant height was 0.817 with an RMSE of 10.81 cm. The average R2 value for the leaf area index was 0.854, with an RMSE of 0.55 m2·m−2. The simulated values for plant height and leaf area index closely matched the measured values, indicating that the model has high accuracy and applicability in traditional Chinese greenhouses (solar greenhouses and insulated plastic greenhouses). However, further optimization is required for commercially produced, continuous plastic greenhouses equipped with greenhouse environmental control equipment.

Soil Salt and Water Regulation in Saline Agriculture Based on Physical Measures with Model Analysis

Enhancing crop production in the saline regions of the Yellow River Delta (YRD), where shallow saline groundwater is prevalent, hinges on optimizing water and salt conditions in the root zone. This study explored the effects of various physical methods on soil water and salt dynamics during the cotton growing season in these saline areas. Three approaches were tested: plastic film mulching (FM), plastic film mulching with an added compacted soil layer (FM+CL), and ridge-furrow planting (RF). The HYDRUS-2D model (Version 3.02) was used to analyze changes in soil water and salt content in the root zone over time. The results showed that subsoil compaction significantly lowered salt build-up in the root zone, especially in the top 20 cm. Film mulching was crucial for reducing water loss in the Yellow River Delta. Crop transpiration increased by 7.0% under FM and 10.5% under FM+CL compared to RF planting. Additionally, FM+CL reduced soil salinity in the top 10 cm by 11.5% at cotton harvest time compared to FM alone. The study concludes that combining film mulching with a soil compaction layer is a promising strategy for local farmers, addressing soil water retention, salt management, and boosting cotton yields.

Assessing the feasibility of sprinkler irrigation schemes and their adaptation to future climate change in groundwater over-exploitation regions

Promoting appropriate water-saving irrigation is an important pathway to alleviate groundwater overexploitation in irrigated agriculture. Whether an alternative irrigation method is feasible relies on quantitative assessments of its impacts on crop yield and hydrological cycle, especially in the groundwater overdraft area that faces a dilemma between water scarcity and food security. Using a groundwater-module-improved SWAT (Soil & Water Assessment Tool) model, five GCMs (General Circulation Models) projections of CMIP6 (Coupled Model Intercomparison Project 6), and a linear programming algorithm, sprinkler irrigation was simulated, evaluated, and optimized in a representative global groundwater mining location, the piedmont plain of the North China Plain. During the historical period (1993–2012), the results showed that, in general, sprinkler irrigation had advantages in benefiting crop transpiration of winter wheat and reducing percolation, hence improving water use efficiency with reference to traditional surface irrigation. Specifically, compared to traditional surface irrigation schemes, winter wheat yields increased by 12%− 14% with a 225 mm irrigation quota; they were stable with a 150 mm irrigation quota; but they decreased by 4% with a 75 mm irrigation quota. The shallow groundwater tables would decline at an average rate of 1.29 m/yr, 0.83 m/yr, and 0.35 m/yr, respectively, under sprinkler irrigation with 225 mm, 150 mm, and 75 mm irrigation quotas. Future climate changes (increased precipitation, air temperatures, and CO2 concentration) would bring effects of improving wheat yield by 6%− 7% and increasing groundwater vertical recharge by 58%− 122% in 2030–2049. The variations of predicted future shallow groundwater tables were − 0.37 m/yr, 0.01 m/yr, and 0.40 m/yr with the 225 mm, 150 mm, and 75 mm irrigation quotas, respectively, in the SSP2–4.5 scenario; and the corresponding results were − 0.45 m/yr, − 0.05 m/yr, and 0.34 m/yr in the SSP5–8.5 scenario. The optimization results showed that sprinkler irrigation could be implemented in approximately 50% of the study area to achieve shallow groundwater equilibrium and stable wheat production simultaneously in the near future. And the dominant sprinkler irrigation schedule after optimization was found to be scheme S3 (irrigation frequency for wheat was 5 times) with a limited irrigation quota of 150 mm. This study provides detailed data for planning sprinkler water-saving irrigation regimes and groundwater pumping strategies in China’s breadbasket, as well as a reference for global irrigated agriculture with over-drafted aquifers to balance groundwater conservation and grain production.

Compacted crops of medicinal and essential oil crops

The characteristics of the growth and development of medicinal and essential oil plants in mono and compacted crops in open ground were studied. Compacted cropping involves the joint cultivation of two (binary) or more crops in one field. Compared to monospecies crops, this method effectively solves the problems of increasing productivity and plant resistance to stress. Purpose of the work: to establish the allelopathic effect of medicinal and essential oil plants in dense sowing. The experimental methodology included the joint cultivation in open ground of medicinal main crops - spearmint (Menthaspicata L.), lemon balm (Melissaofficinalis L.), garden strawberry (Fragariachiloensis L.), and calendula officinalis (Calendulaofficinalis L.) were chosen as complementary crops.), dill (Anethumgraveolens L.). Compacted crops significantly reduce the intensity of transpiration and stomatal conductivity of the main crops. The intensity of photosynthesis largely depends on the species characteristics of the plants, so strawberry plants in binary crops increased photosynthetic activity, while mint and lemon balm on the contrary, they increased the intensity of photosynthesis during monospecies cultivation. According to the results of the studies, the inhibitory effect of calendula officinalis plants in binary crops with lemon balm, spearmint, and garden strawberries was established. At the same time, the use of dill in binary crops increases the yield of spearmint and lemon balm.

Diurnal Trends of Maize Canopy Cover Under Water Stress

Highlights RGB trail cams above maize crop collected images every 15 minutes, day and night, to monitor leaf curl. Fractional canopy cover (fc,%) was constant for full irrigation but reduced during the day for limited irrigation. Techniques were developed to estimate reductions in water use (i.e., evapotranspiration) using images of fc. Measurements of fc prior to wilting represent transpiration demand (Kcb ), and reductions of fc represent stress (Ks ). Abstract. By differentiating green and non-green pixels of RGB images of crop canopy, the fractional canopy cover (fc,%) can be estimated and subsequently used to estimate crop transpiration demand (e.g., Kcb, basal crop coefficient, following FAO-56 methodology). While unstressed maize crops maintain consistent fc through the day, leaves of heat or water stressed crops will curl, thereby reducing the instantaneous fc and the associated transpiration. This paper reports the effects of diurnal leaf curl and subsequent fc reduction on full and limited water treatments of irrigated maize through nadir images obtained every 15 minutes. Results suggest that fc images obtained in the early morning (fcNS) are typically representative of a non-stressed condition and can be used to estimate Kcb. Reduction of fc throughout the day (i.e., fc/fcNS) was compared to water stress coefficient Ks obtained from neutron probe and TDR measurement and showed that fc/fcNS from hours 11 a.m. to 2 p.m. had a high correlation (R2 = 0.773), indicating that mid-day fractional canopy cover reduction could be used as a proxy for Ks. This method creates new opportunities for estimating crop water stress during vegetative growth but also highlights potentially unknown challenges regarding lower resolution remote sensing during the same growth stages. Keywords: Basal crop coefficient, Canopy cover, Crop coefficient, Evapotranspiration, Stomatal conductance, Stress crop coefficient, Transpiration, Water stress.

Comparison of Infrared Thermometry and Soil Water Derived Stress Indices and Crop ET in Cotton

HighlightsA crop water stress index (CWSI) was calculated using a theoretical approach.Averaged daily rather than one to two hour daily maximum CWSI correlated better with soil-based crop water stress.Crop ET scaled with the CWSI accurately predicted ET for a dissimilar canopy and irrigation level.Sub-hourly canopy resistance and transpiration were inferred from canopy temperature measurements.Abstract. Upland cotton (Gossypium hirsutum L.) is increasingly being managed under subsurface drip irrigation (SDI) in the semiarid Texas High Plains (THP). Scheduling irrigation using a thermally based crop water stress index (CWSI) has the potential to overcome limitations of soil water-based methods and facilitate efficient use of water. The objectives of this study were to develop a CWSI calculation procedure using stability correction, determine an appropriate window for averaging CWSI during daytime hours, compare CWSI with soil water-based indicators of crop water stress, and evaluate methods for estimating crop evapotranspiration (ET) using measured canopy temperatures. Infrared thermometer measurements of canopy temperature and corresponding cotton water use derived from soil water measurements were acquired under two irrigation levels (100% and 33%) under SDI during three growing seasons. A theoretical approach was used to calculate the CWSI using the Businger-Dyer stability correction. Basing daily CWSI on short 1- or 2-h periods in the afternoon overestimated crop water stress. In contrast, CWSI averaged during daytime periods with 0.25-h solar radiation and air temperature exceeding 0.3 MJ m-2 and 24°C, respectively, was strongly correlated (R2=0.76) with the soil water depletion-based stress coefficient Ks with a plausible lower canopy resistance of 25 s m-1. The CWSI was weakly correlated (R2=0.48) to the fraction of plant available water, with the CWSI exhibiting the greater increase of these two indices in response to irrigation events. Using the proposed CWSI scaling at different locations for canopies with dissimilar cover fractions yielded satisfactory estimates of crop ET (RMSE=0.74 mm d-1) compared with soil water balance-calculated ET (ETswb). When summed over weekly intervals, energy balance predictions of 0.25-h crop transpiration inferred from canopy temperature measurements had an acceptable agreement with ETswb (RMSE=0.92 mm d-1). Employing the CWSI to trigger irrigation will require targeted field studies to evaluate thresholds and strategies to optimize water management. Keywords: Canopy temperature, Crop water stress index, Evapotranspiration, Subsurface drip irrigation, Upland Cotton.

Use of intercropping and mulch to improve the water and natural resources use efficiencies of forage cactus and millet production in a semiarid region

1. CONTEXT - Improving the use of natural resources (e.g., water, nutrients, and radiation) within production systems under different technologies (mulch and intercropping) is fundamental to intensifying sustainable agriculture. 2. OBJECTIVE - The objective was to quantify the parameters of water consumption and the efficiency of using natural resources of forage cactus and millet under different technologies of crops in a semiarid environment. 3. METHODS - The forage cactus (clone Orelha de Elefante Mexicana) and millet (cv. IPA Bulk-1-BF) were evaluated to six cropping arrangements: single cactus with mulch (CWM), single cactus with no mulch (CNM), single millet with mulch (MWM), single millet with no mulch (MNM), a cactus-millet intercropping system with mulch (CMWM), and cactus-millet intercropping system with no mulch (CMNM). Data on crop growth, crop production, and soil moisture were collected, and the following were determined: crop evapotranspiration (ETc), crop transpiration (T), soil water evaporation (E), single crop coefficient (Kc), dual crop coefficient (Kcb and Ke), water use efficiency (WUE), nutrient use efficiency (NUE) and radiation use efficiency (RUE). Biological efficiency and competitive ability indicators were calculated for the intercropped systems. 4. RESULTS AND CONCLUSIONS - The ETc (mm day −1) was higher under MWM (4.69), MNM (3.60), and CMWM (3.81). There was little variation in the values of ETc, T, or E between CNM and CWM, unlike between MNM and MWM. Intercropping reduced E compared to the single crops of cactus (8%) and millet (58%). On average, Kc was higher under MWM (0.98), CWM (0.69), and CMWM, (0.88), compared to MNM (0.75), CNM (0.63), and CMNM (0.48). The intercrops were more efficient for WUE (44%) and RUE (2.28 g MJ −1), with no difference for NUE. It can be concluded that the cactus-millet intercropping system is a good alternative for more-resilient agriculture in semi-arid environments, especially when the use of mulch. 5. SIGNIFICANCE - The results of this study are significant for the management of water resources in the semi-arid region, as they favour knowledge of the water needs of these crops in different production systems, and how the adoption of technologies such as intercropping and mulching can improve efficiency in the use of available natural resources, compared to exclusive planting.

Management practices regulate the response of canopy and ecosystem water use efficiency in cropland ecosystems

ContextWith rising global temperature and frequent drought events, water resource supply is facing to great challenge. Understanding the effects of different management practices on cropland water use efficiency (WUE) is crucial to promote effective allocation of water resources and food security. ObjectiveThe objective of this study was to reveal the contrasting effects of different farm management practices including continuous and rotational, tillage and no-till, irrigated and rainfed on cropland water use efficiency from canopy (WUET) to ecosystem (WUEET) scales, respectively. MethodsOn the basis of 26 site-years eddy covariance-based carbon and water flux observations, this study used the underlying WUE (uWUE) model to partition evapotranspiration (ET) across maize and soybean ecosystems. Three control groups were used to compare the effects of different management practices on the coupling relationships between terrestrial carbon and water cycles, respectively. ResultsCompared with the rotational maize-soybean site, both WUET and WUEET at the continuous maize site were larger, which was mainly ascribed to stronger gross primary productivity (GPP) for the C4 crop. But over the maize-planting years, both WUET and WUEET at the rotational site were higher than the continuous site owing to the nitrogen fixation by rhizobia for preceding year, especially for WUET. Under conventional tillage and no-till management, multi-year mean WUEET and WUET were contrasting. WUEET under no-till was apparently larger than WUEET under till, because of similar GPP but relatively lower ET. Meanwhile, more water was consumed by crop transpiration (T) under no-till, which led to lower WUET in comparison with WUET under till. In comparison with the rainfed farming, GPP, ET and T all increased apparently after irrigation. However, both WUET and WUEET at the irrigated site were not improved owing to more water lost with relatively fewer GPP increase. ConclusionsThe study suggested that the crop rotation system can improve both WUEET and WUET apparently. Meanwhile, fewer water resource was consumed by cropland under no-till management. Finally, irrigation farming improved the cropland GPP but reduced WUEET and WUET. ImplicationsOur results provide valuable management implications for understanding the mechanisms that can enhance water use efficiency and result in significant water savings and high yield.

Water deficit and potassium affect carbon isotope composition in cassava bulk leaf material and extracted carbohydrates.

Cassava (Manihot esculenta Crantz) is an important root crop, which despite its drought tolerance suffers considerable yield losses under water deficit. One strategy to increase crop yields under water deficit is improving the crop's transpiration efficiency, which could be achieved by variety selection and potassium application. We assessed carbon isotope composition in bulk leaf material and extracted carbohydrates (soluble sugar, starch, and cellulose) of selected leaves one month after inducing water deficit to estimate transpiration efficiency and storage root biomass under varying conditions in a greenhouse experiment. A local and improved variety were grown in sand, supplied with nutrient solution with two potassium levels (1.44 vs. 0.04 mM K+) and were subjected to water deficit five months after planting. Potassium application and selection of the improved variety both increased transpiration efficiency of the roots with 58% and 85% respectively. Only in the improved variety were 13C ratios affected by potassium application (up to - 1.8‰ in δ13C of soluble sugar) and water deficit (up to + 0.6‰ in δ13C of starch and soluble sugar). These data revealed a shift in substrate away from transitory starch for cellulose synthesis in young leaves of the improved variety under potassium deficit. Bulk δ13C of leaves that had fully developed prior to water deficit were the best proxies for storage root biomass (r = - 0.62, r = - 0.70) and transpiration efficiency (r = - 0.68, r = - 0.58) for the local and improved variety respectively, making laborious extractions redundant. Results obtained from the youngest fully developed leaf, commonly used as a diagnostic leaf, were complicated by remobilized assimilates in the improved variety, making them less suitable for carbon isotope analysis. This study highlights the potential of carbon isotope composition to assess transpiration efficiency and yield, depending on the chosen sampling strategy as well as to unravel carbon allocation processes.

A Review of Plastic Film Mulching on Water, Heat, Nitrogen Balance, and Crop Growth in Farmland in China

Plastic film mulching has been widely used to improve crop yield and water use efficiency, although the effects of plastic film mulching on water, heat, nitrogen dynamics, and crop growth are rarely presented comprehensively. This study investigated a large number of studies in film mulching fields from the past 10 years (mostly from 2019 to 2023) and summarized the impact of plastic film mulching, progress in modeling with film mulching, and future research directions. The effects of plastic film mulching were intricate and were influenced by film mulching methods, irrigation systems, crop types, crop growth stages, etc. Overall, plastic film mulching showed a positive effect on improving soil water, temperature, and nitrogen status, enhancing crop transpiration and photosynthetic rates, and promoting crop growth and yield, although film mulching may have negative effects, such as increasing rainfall interception, blocking water entering the soil, and reducing net radiation income. The crop yield and water use efficiency could increase by 39.9–84.7% and 45.3–106.4% under various film mulching methods. Coupled models of soil water and heat transport and crop growth under plastic film mulching conditions have been established by considering the effects of plastic film mulching on the upper boundary conditions of soil water and heat, energy budget and distribution processes, and the exchange of latent and sensible heat between soil and atmosphere. The models have good applicability in film mulched farmland of maize, rice, and potato for different regions of China. Further development is needed for soil water, heat, nitrogen migration, and crop growth models under different plastic film mulching methods, and the acquisition of soil and crop indicators under plastic film mulching conditions based on big data support. The study will provide reference for the subsequent development and innovation of plastic film mulching technology.

Tillage Practices Affected Yield and Water Use Efficiency of Maize (Zea mays L., Longdan No.8) by Regulating Soil Moisture and Temperature in Semi-Arid Environment

Tillage practices can regulate soil environmental factors and, thus, affect crop yield. Farmers’ acceptance of this is not high because of a lack of awareness, and, in the dryland farming region of the Longdong Loess Plateau in China, the lack of acceptance is due to the established use of the no-till operation. It is urgent to explore suitable tillage practices for maize (Zea mays L., Longdan No.8) planting in this area. The impact of tillage practices on the soil water content, soil temperature, field water consumption structure, yield, and water use efficiency (WUE) of maize was determined. Six tillage practices were implemented in 2021 and their effects were determined in 2021 and 2022, including conventional tillage with no straw (T), conventional tillage with straw incorporated (TS), subsoiling tillage with no straw (SST), subsoiling tillage with straw incorporated (SSTS), no-tillage with no straw (NT) and no-tillage with straw mulching (NTS). Over two years, compared to T, the soil volumetric water content (SWv) with SSTS was significantly increased in the 5–10 cm soil layer at the V12 (big flare stage of maize) stage in 2022. SSTS significantly reduced soil temperature (ST) in the 20 and 25 cm soil depths at the V12 stage, and in every soil layer of the R2 (grain-filling stage of maize) stage. SSTS significantly reduced soil evaporation during the growing season (Ec), and significantly increased crop transpiration (Tc) when compared to T. Compared with T, SST and SSTS significantly increased biomass yield (BY), by 29.7–32.1 and 41.2–53.5%, respectively, increased grain number per ear by 6.3–16.5 and 10.4–38.8%, respectively, improved grain yield (GY) by 4.9–6.9 and 6.2–13.7%, respectively; SSTS significantly increased WUE by 5.5–15.4%. The correlation between soil volumetric water content at the V12 stage and grain yield was highly significant; the ST at the R2 stage had a significant positive correlation with grain number per ear, GY, and BY. Therefore, subsoiling tillage with straw incorporated increased the soil moisture content and reduced the soil temperature, optimized the water consumption structure, and improved the effective utilization of soil water, resulting in the accumulation of a higher biomass yield, and increased the number of ears, obtaining a higher yield, and improved water use efficiency. Therefore, subsoiling tillage with straw incorporated is a suitable tillage practice in the dry farming area of Longdong Loess Plateau, China.

The Response Characteristics of Sugarcane Yield, ET and WUE to Meteorological Drought Based on DSSAT-Canegro Model in Lai-bin, China

Crop water use efficiency is an important indicator of the scientific and rational nature of agricultural water use. Studying the response characteristics of sugarcane yield accumulation and water use efficiency to meteorological drought scenarios is a key scientific issue to promote smart management and sustainable development of China's sugarcane industry. In this paper, based on SPEI index, different meteorological drought scenarios were set and the DSSAT-Canegro model was used to simulate the response mechanisms of sugarcane yield accumulation and canopy evapotranspiration to irrigation regime scenarios under different meteorological drought scenarios. Furtherly, in this study, the total on-farm water use efficiency (WUEg), field water use efficiency (WP), true irrigation water use efficiency (WUEti), and irrigation water use efficiency (WUEi) of sugarcane in the study area were evaluated quantitatively to screen the optimal irrigation regime. Specific studies have shown that the stem extension stage is the most sensitive growth stage for sugarcane response to irrigation. Soil evapotranspiration and crop transpiration in sugarcane fields in Laibin varied with irrigation quotas, and that reducing soil evapotranspiration could improve sugarcane water use efficiency. In meteorological drought scenarios with longer and more intense droughts, irrigation has a stronger stimulating effect on sugarcane growth and is more favourable to its yield accumulation.The correlations between WUEg index and WP, WUEi) and WUEti indicators of sugarcane in the study area were all significant, which can be used as key analytical indicators for the optimization of sugarcane irrigation regimes in Laibin. The results of this study can provide important scientific support for the accurate quantification of water demand and consumption of sugarcane in southern China and their coupled and coordinated intelligent management.

Empirical insights on the use of sun-induced chlorophyll fluorescence to estimate short-term changes in crop transpiration under controlled water limitation

Knowledge of actual crop transpiration (T) is important for advanced crop management but challenging to obtain due to the large spatial and temporal variation of T. Remote sensing offers various possibilities to assess T dynamics, while particularly sun-induced chlorophyll fluorescence (SIF) has been demonstrated as a sensitive empirical proxy for T. Despite this success, the advancement of the mechanistic understanding of how SIF relates to T dynamics is key for the future development and implementation of robust and reliable SIF-based T products. This study aims to contribute insights by experimentally assessing the sensitivity of several SIF-based T estimation strategies for evolving soil water limitation. We investigated extensive in situ and airborne data acquired during a water limitation experiment in a maize canopy in northern Italy. We evaluated five empirical strategies to integrate SIF in a T modelling framework based on the Penman-Monteith (PM) and the Ball-Berry-Leuning (BBL) concepts. Our results indicate that replacing model parameters sensitive to canopy conductance with SIF results in the best agreement between modelled and measured T under evolving water limitation. Our study contributes expanding existing knowledge with empirical insights on the sensitivity of SIF based T approaches under increasing soil water limitation at short time scales.