Crop Coefficient Research Articles

Winter wheat irrigation parameters in the Brazilian Cerrado

Wheat is the second most produced cereal in the world. The gap between production and consumption in Brazil shows that wheat production must be increased to meet the domestic demand. In this context, the objective of this study was to determine the crop coefficient of wheat and the ideal moment for irrigation, based on the soil water depletion rate (f). The study was carried out in the tropics, on an Oxisoil (Typic Haplustox), in an experimental field of Embrapa Cerrados in Planaltina, Federal District of Brazil. The experimental design consisted of randomized blocks with three replications. The treatments were differentiated by the soil water depletion index (f) of 0.2, 0.4, 0.6, and 0.8. In other words, irrigation was initiated when 20, 40, 60 and 80% of the available soil water capacity (AWC) at a soil depth of 0.4 m was consumed by the crop. Wheat yield and yield components were evaluated. The phenological development was monitored based on Zadok’s scale, in days after emergence, and the management parameters crop coefficient (Kc) and irrigation timing were determined. The results indicated a soil water depletion index of 0.4 as the best indicator for beginning wheat irrigation. Under this condition, Kc can be estimated daily as a function of days after emergence (DAE) by the quadratic polynomial regression or curve fitting method, adjusted as follows: Kc = −0.000298 × DAE² + 0.036695 × DAE + 0.332486. Alternatively, the means of Kc of each phenological crop phase can be used: Kc = 0.45 (establishment); 0.81 (tillering); 1.21 (booting); 1.43 (flowering); 1.27 (grain formation); and 0.89 (maturation). Thus, there is a limit of consumption of soil available water, at which wheat still achieves the full yield potential, with a rational use of water which varies according to the development phase.

Weighing lysimeters for measuring evapotranspiration and developing crop coefficients for trailing blackberry

Weighing lysimeters for measuring evapotranspiration and developing crop coefficients for trailing blackberry

Response of Carrot (Daucus carota L.) to Supplementary Irrigation under Rain-Fed Agriculture at Jimma and Gera, Jimma Zone, South West Ethiopia

Evaluating supplementary irrigation under rain-fed agriculture could help to determine the amount of water depth for water management and increasing productivity. Thus, this study was conducted at the Jimma and Gera to determine the effect of supplementary irrigation (SI) on carrot production. Eight treatments with three replications on a field plot of 9 m2 were used for conducting the experiment. Crop water requirement (ETc) was calculated from reference evapotranspiration (ETo) and crop coefficient (Kc) using CropWat 8.0 software. Yield and yield component data were collected from the field and analyzed using the statistical analysis system (SAS) software 9.0. The result revealed that root shoulder diameter, fresh biomass, and fresh root weight had significant (p <0.05) effects between the treatments, but there was no significant difference (p >0.05) between treatments on plant height and carrot root length at both locations. The highest and lowest plant heights were recorded at 75% SI and at a rain-fed treatment. A root shoulder diameters of 38.37 and 37.86 mm were recorded at Jimma and Gera, respectively, from the application of 75% and two SI at flowering and fruit setting treatment. The application of 75% SI gave the highest root length. A maximum fresh biomass of 3,038.6 kg/ha was obtained at 75% SI, and a minimum fresh biomass of 1,640.00 kg/ha was recorded from the rain-fed treatment at JARC. Application of 75% SI gave the maximum fresh biomass (2,388.9 kg/ha) at Gera, and a minimum fresh biomass of 1,277.8 kg/ha was recorded from rain fed. An application of 75% SI gave the highest fresh root weight of 7,430.6 kg/ha at JARC. In the study, the application of 75% SI gave the highest (6,388.9 kg/ha) fresh root weight, and the lowest was recorded at rain fed (3,883.3 kg/ha). Therefore, for optimum production, 75% SI was recommended for the production of carrots. The total net benefit from the production of carrots was in the range of 36,659–46,950 ETB per hectare at Jimma and from 24,828 up to 39,399 ETB per hectar at Gera. The maximum and minimum marginal return rate (MRR) at Jimma were 300.97%, which is at 75% SI and 43.69%, which is at 25% supplementary irrigation, respectively. At Gera, the maximum and minimum MRR were 490.95%, which were at 25% supplementary irrigation, and the minimum was 23.18%, which was at full supplementary irrigation. Therefore, to get an economic benefit, supplementing carrot crop at 75% irrigation was recommended for both Gera and JARC.

Effect of vegetation treatment and water stress on evapotranspiration in bioretention systems

Evapotranspiration is a key hydrological process for reducing stormwater runoff in bioretention systems, regardless of their physical configuration. Understanding the volumes of stormwater that can be returned to the atmosphere via evapotranspiration is, therefore, a key consideration in the design of any bioretention system. This study establishes the evapotranspiration dynamics of three common, structurally different, bioretention vegetation treatments (an Amenity Grass mix, and mono-cultures of Deschampsia cespitosa and Iris sibirica) compared with an un-vegetated control using lab-scale column experiments. Via continuous mass and moisture loss data, observed evapotranspiration rates were compared with those predicted by the FAO-56 Penman–Monteith model for five 14-day dry periods during Spring 2021, Summer 2021, and Spring 2022. Soil moisture reductions over the 14-day trials led to reduced rates of evapotranspiration. This necessitated the use of a soil moisture extraction function alongside a crop coefficient to represent actual evapotranspiration from FAO-56 Penman–Monteith reference evapotranspiration estimates. Crop coefficients (Kc) varied between 0.65 and 2.91, with a value of 1.0 identified as a recommended default value in the absence of treatment-specific empirical data. A continuous hydrological model with Kc=1.0 and a loading ratio of 10:1 showed that evapotranspiration could account for between 1 and 12% of the annual water budget for a bioretention system located in the UK and Ireland, increasing to a maximum of 35% when using the highest Kc observed (2.91).

Evapotranspiration and potential water saving effect evaluation of mulched maize fields in China

To alleviate the contradiction between crop evapotranspiration (ET) and available water resources, and to develop agricultural production, mulched irrigation, as a water saving technology, is popularized in arid areas of China. However, the observations of ET in long-term mulched farmlands are scarce, so the inter-annual variation and controlling factors of ET after mulching remain uncertain, and the overall water saving effect of mulching in arid areas has not been quantified. Therefore, we conducted the observation experiments (2007–2021) on a mulched maize field, applied the modified Shuttleworth-Wallace model and obtained multi-source data statistics to fill in the gaps in the previous research. The results showed that the mean ET in the past 15 years was 521.68 mm, and the arid areas faced more severe water demand pressure. The inter-annual ET trend of the mulched maize field increased significantly, mainly caused by the reference evapotranspiration (ET0), while the inter-annual fluctuation was mainly attributed to the crop coefficient (Kc). The contribution of plant transpiration (Tr) to ET was always greater than that of soil evaporation (Es), and the contribution of solar radiation (Rs) to ET was the largest among environmental factors. In addition, based on observation data and model simulation, it was revealed that the water saving amount and ratio of the long-term mulched maize field were estimated to be 83.8 mm and 13.3 %, respectively. Furthermore, the statistical results from 49 sites in five provinces (regions) in Northwest China showed that compared with the agricultural water use in the recent 10 years, the mean annual total potential water saving amount and ratio of the mulched maize field were 2.2 billion m3 and 2.5 %, respectively. Our study will provide important guidance for understanding the variation of crop ET and water resources allocation.

Variation and Transformation of Evapotranspiration at Different Scales in a Desert Steppe

Water resources are severely scarce in desert steppes, and precipitation rarely collects in rivers or is transformed into groundwater. Evapotranspiration (ET) is the primary “export” of precipitation conversion and is the main mechanism for water vapor exchange between the underlying surface and atmosphere. ET changes have certain scale effects. This study focused on the natural grasslands in the Xilamuren Desert Steppe and analyzed and estimated the ET patterns at different scales, including micro-, point-, and surface scales, using observational data from instruments such as a photosynthetic meter, Eddy-covariance system (EC), and large-aperture scintillometer (LAS) from the Ecological Hydrology National Field Science Observation Station in the northern foothills of the Yin Mountains, Inner Mongolia. The spatial scale was extended based on this analysis. The results showed that at the microscale, the diurnal variation in the photosynthetic and transpiration rates of Leymus chinensis followed a bimodal curve. In July and August (high-temperature months), photosynthetic and transpiration rates were almost synchronous. In May and October, when the temperature was moderate, the transpiration rate was delayed compared to the photosynthetic rate at the first peak, and the second peak was significantly smaller than the first peak. At the point-scale, the daily average ET during the growing season was 1.37 mm·d−1 and the total cumulative ET was 251 mm. Transpiration levels exhibited significant seasonal variation in the following order: July > August > June > September > May > October. At the surface-scale, the daily average ET during the growing season was 1.60 mm·d−1 and the total cumulative ET was 294 mm, which was 17% higher than that of the point-scale. The surface-scale ET was estimated using the observed values of the EC and the scale relationship formula and was optimized using different spatial scales of crop coefficients. This well reflected the ET patterns at the surface-scale. Therefore, this study proposes a spatial scale expansion method for a homogeneous underlying surface, verifies its value, and provides methodological support for estimating ET in cases of data scarcity.

Quinoa growth and yield, soil water dynamics, root growth, and water use indicators in response to deficit irrigation and planting methods

To address the growing issue of scarce water in the arid and semi-arid areas, it is essential to investigate the potential of drought tolerant crops and implement promising farm management strategies to improve water productivity and yield production. Therefore, a split plot experiment to investigate how different irrigation levels (I-1:100% water requirement (WR), I-2:75%WR, and I-3: 50%WR) and planting methods (P-1: basin, P-2: on-ridge, and, P-3: in-furrow) interact and affect quinoa water use, yield, root growth, and water productivity in southern Iran over two growing seasons. The results showed high seasonal crop evapotranspiration (993–1030 mm) in I-1 as a result of the high advection ratio (α), which ranged from 1.02 to 1.46 from the early vegetative to the seed filling stages. The P-3 increased transpiration rate by 4.5% and 7.7%, and decreased soil evaporation by 17% and 29% compared to P-1 and P-2, respectively. Single (Kc) and dual (Kcb + Ke) crop coefficients varied between 0.41 and 1.38 over the two growing seasons. Grain yield in P-3 were 25%, 34%, and 44% higher compared to P-1 and P-2 under I-1, I-2 and I-3, respectively. The study revealed that nearly 67% and 80% of the total root dry matter was in the 0–30 cm and 0–60 cm of the soil profile in all experimental treatments, respectively. Regardless of irrigation treatment, root length density (RLD) and root mass density (RMD) were found to be 18.9% and 15.7% lower in P-1’s top 0–20 cm of the soil profile than those obtained in P-2 and P-3, respectively. Analyses showed that the increased root length in deeper soil layers contributed to higher soil water uptake, and consequently higher crop water productivity. In addition, root-to-shoot ratio increased as the amount of the applied irrigation water was decreased. Quinoa exhibited the highest acclimation to water stress in P-3 based on water stress sensitivity coefficients (λi) and yield response factor (Ky) values. Crop water productivity (WPC) and irrigation water productivity (WPI) for grain yield varied between 0.17 and 0.28 kg m−3. In conclusion, in terms of grain yield, shoot and root dry matter and water productivity, I-2 and P-3 (75% WR irrigation level and in-furrow planting method treatment) is recommended as the optimum water and planting management strategy for quinoa cultivation in the study area as a measure to address water scarcity and food sustainability. Still, to improve yield and irrigation water efficiency, the effect of soil management practices such as mulching and organic amendments on soil water retention and nutrient availability for quinoa should be investigated.

Crop Coefficient of Sunflowers under Drip Irrigation with Plastic Film in Different Hydrological Years in the Hetao Irrigation District

An accurate assessment of crop water requirements during the crop growth period can help organize irrigation schedules and investigate the hydrological environments in irrigation districts, especially in shallow groundwater districts. In irrigation scheduling, crop coefficients, representing three development stages, play a critical role in modeling evapotranspiration. Therefore, in this study, the crop coefficient (Kc) of sunflowers under drip irrigation in different hydrological years in the Hetao irrigation district with shallow groundwater is determined. Based on the analysis of rainfall frequency, the experimental situations of 2012, 2013, and 2014 are adopted as high, normal, and low flow years. Using the water balance method, groundwater recharge and crop evapotranspiration in different hydrological years were investigated. The results showed that the groundwater recharge in a high-flow year was larger than that in normal and low-flow years with values of 67.47, 66.75, and 42.61 mm, respectively. Crop evapotranspiration is directly related to the irrigation amount at the same growth stage. The Kc of sunflowers in a high-flow year is higher by 0.1 and 0.15 than that in normal and low-flow years. The Kc of sunflowers under drip irrigation is lower than that under surface irrigation by 8.9% in the initial and late stages of sunflower growth, but higher than that by 10.6% in the mid-stage, which is due to differences in small water potential differences and less evapotranspiration in the initial and late stages under drip irrigation. The study is of great significance for formulating a reasonable schedule of drip irrigation with shallow groundwater and improving the field environment.

Assessing the water use efficiency of irrigated fruit crops in semi‐arid regions of Brazil using remote sensing and meteorological data

AbstractThe irrigated perimeter of Jaíba‐MG is located in a semi‐arid region of Brazil, which makes irrigation practices necessary in order to guarantee agricultural production. This need occurs in the context of limited water resources and, therefore, it is necessary to study ways to optimize water use efficiency (WUE). For this, it is necessary to obtain local and precise estimates of the crop coefficient (Kc) and the reference evapotranspiration (ET0). The objective of this study was to evaluate the water requirements and WUE of banana, lemon and mango crops in the irrigated perimeter region of Jaíba using satellite images and meteorological data. Landsat 8 satellite images from 2020 and 2021 were used to estimate the local Kc of these crops. Three methodologies for estimating local Kc were adopted: METRIC, NDVI and NDVI 2. The Kc NDVI method stood out when compared with the standard method (FAO Bulletin 56), with RMSEs of 0.11, 0.16 and 0.20 for banana, lemon and mango, respectively, showing the potential of this methodology. The overall average WUE values for banana, lemon and mango crops were 2.19, 1.58 and 1.58 kg m−3, respectively. The results could allow important advances in water management for fruit crops under semi‐arid conditions.

Determination of Evapotranspiration and Crop Coefficient for Tomato by Using Non-Weighing Lysimeter in Semiarid Region

Providing an accurate amount of water to crops based on their requirements is the primary objective of irrigated agriculture. The crop evapotranspiration and coefficient of tomato were measured using non-weighing lysimeters. The trial was conducted at the Melkassa Agricultural Research Center’s experimental farmland in Ethiopia. The soil water balance approach was applied to compute tomato crop evapotranspiration, whereas the reference evapotranspiration was computed using the Penman-Monteith method. The crop coefficient was calculated using the ratio between the measured crop evapotranspiration and the reference evapotranspiration. A total of 590.4 and 413.3 mm of tomato seasonal evapotranspiration was recorded in the experimental years 2022 and 2023, respectively. The mean crop evapotranspiration for tomatoes over the two experimental years was 501.83 mm. The mean locally produced crop coefficient values were 0.63 for the initial, 1.18 during the mid, and 0.94 at the end of the season. The FAO-adjusted Kc values were 1.12 during the mid and 0.86 at the end of the season. The FAO-adjusted crop coefficient values differed from the crop coefficient values developed. Hence, to ensure efficient irrigation scheduling and planning, measuring the crop evapotranspiration and coefficient for optimal crop production under specific climatic conditions is vital.

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 Locally Determined Crop Coefficients to FAO 56 (The Case of Ethiopia)

Comparison of Locally Determined Crop Coefficients to FAO 56 (The Case of Ethiopia)

Net radiation partitioning, evapotranspiration, and crop coefficients of the green dwarf coconut in Santa Izabel do Pará, Brazilian Amazon

Net radiation partitioning, evapotranspiration, and crop coefficients of the green dwarf coconut in Santa Izabel do Pará, Brazilian Amazon

Irrigation Response, Water Use, and Lint Yield of Upland Cotton Cultivars

Highlights In-season crop water use and canopy temperatures after first square did not differ among cultivars. Lint yield was significantly affected by cultivar in all study years. Cultivar effects on lint yield were significant only at higher irrigation levels. Crop water productivity increased with increasing irrigation in two of the three study years. Abstract. Upland cotton (Gossypium hirsutum L.) production requires less irrigation compared with other crops and thus provides an opportunity to reduce risk and maintain profitability in areas where water is limited. Water use, canopy temperature, lint yield, and crop water productivity were evaluated for four early to medium maturity upland cotton cultivars under three levels (100%, 66%, and 33%) of alternate furrow subsurface drip irrigation (SDI) in a thermally limited environment. Crop evapotranspiration (ET) across cultivars and years averaged 627, 547, and 467 mm for the 100%, 66%, and 33% irrigation levels, respectively, and did not differ among cultivars (P > 0.05). Changes in stored soil water within each irrigation level were similar among cultivars, with significant differences occurring infrequently. Measured canopy temperatures from first white flower to two weeks after cutout did not significantly differ among cultivars (P > 0.10) within each irrigation level. Crop water use during boll maturation, as inferred from the developed crop coefficient curve, was considerably less than reported by other studies, signifying that irrigation could be terminated earlier without reducing lint yield. The cultivar effect on lint yield was significant in all study years (P < 0.001), but only at the 66% and 100% irrigation levels, with one cultivar exceeding the average yields of all evaluated cultivars by 13% across the three study years. Medium maturity cultivars usually yielded less than early maturity cultivars, especially for a year with less accumulation of thermal energy. Crop selection and late season irrigation water management were both key to improving cotton water productivity. Keywords: Upland cotton, Subsurface drip irrigation, Water productivity, Root water uptake, Canopy temperature.

Maize Evapotranspiration Estimates Using Planet Dove Mini-Satellites and Field-Level InfraRed Thermometers

Highlights Multispectral images from mini-satellites can be used in a reflectance-based crop coefficient model to estimate crop water use. Surface reflectance from mini-satellites and temperature from in-situ infrared thermometers can be used in a land surface energy balance model to more accurately estimate maize actual evapotranspiration. It is feasible to monitor daily maize actual evapotranspiration using Planet Dove mini-satellites on cloud-free days. Abstract. Water scarcity, climate change, and the need to sustain irrigated agriculture demand improved methods to manage irrigation water. Irrigation scheduling can be improved when remote sensing (RS) images are used because RS captures the actual crop field conditions. Mini-satellites (mS) are small spaceborne RS platforms that can provide high spatial and temporal resolution multispectral (MS) images. These multispectral images can be used to estimate maize actual evapotranspiration (ETa) on a daily basis. Thus, the main objective of this study was to assess the accuracy of maize ETa estimates when mS MS images were used in two different ETa algorithms. This study was conducted at two research sites in northern Colorado, USA. A reflectance-based crop coefficient and a one-source surface energy balance (OSSEB) models were applied, using MS Planet Dove images, to map maize ETa. An Eddy Covariance energy balance system was used to assess the accuracy of distributed ETa estimates. Results indicate that the reflectance-based crop coefficient method can be used with mS MS images yielding acceptable estimates. Both ETa models performed better in the case of the sub-surface irrigated maize. Further, OSSEB-based estimates of ETa model were more accurate over the surface irrigated maize and homogeneous soils; when surface reflectance images were paired with radiometric surface temperature data from ground-based infrared thermometers. These results imply that potentially maize ETa could be mapped, on a daily basis with good accuracy, using Planet Dove mS-based MS reflectance images and ground-based radiometric surface temperatures. Keywords: Agricultural water management, Crop water use, Irrigation, Land surface energy balance, Reflectance-based crop coefficients, Remote sensing.

旱作条件下大豆玉米复合种植系统水分利用特征和生产力的比较研究

Quantitative investigation of the utilization characteristics of precipitation resources and the production capacity of the intercropping production system under the soybean maize intercropping mode in northern China is of great significance for improving the resource utilization rate of dryland agriculture and regional sustainable development. This study adopted a completely randomized block design, and six planting modes were set up: soybean monoculture, maize monoculture, and four soybean maize intercropping modes. Plant height and grain yield data were observed, and precipitation resource utilization efficiency was calculated. Based on the FAO-56 recommended crop coefficients, the crop coefficients were corrected according to the actual growth of crops in the experimental area; combined with meteorological data, the crop water demand under different planting modes was estimated based on the Penman-Monteith principle. The results showed that crops' daily growth water demand under different planting modes was generally deficient in water in the early and middle stages of growth, and surplus in the later stages. Compared with the monoculture mode, there were significant differences in precipitation resource utilization efficiency under different intercropping modes (P < 0.05), with soybeans reduced by 67.50% ~ 89.56%, and corn reduced by 43.99% ~ 61.05%. Based on the semi-humid and semi-arid area of the eastern Loess Plateau, an appropriate irrigation system needs to be designated for soybean and corn intercropping systems in the early and middle stages of crop growth. Under a certain proportion of water resource supply, different modes have different water resource utilization efficiency and final production capacity for the intercropping system.

Soil moisture forecasting for precision irrigation management using real-time electricity consumption records

The installation of the smart electricity meters (SEMs) to the high-density pumping wells in the North China Plain (NCP) provided a method to control the groundwater withdraw. The record in real-time electricity consumption from SEMs also provided an alternative method to forecast soil moisture to make irrigation decisions to improve irrigation efficiency. The irrigation timing and the irrigation amount could be obtained on-line from the SEMs based on the coefficients obtained for electricity-to-water conversion (E-Wc). The real-time recordings in the irrigation timing and amounts were further used to forecast the next irrigation timing and amount based on the water rights per area of land, the lower limit of soil water contents for different crops at their different growing stages and online meteorological data. A smartphone app was developed based on this framework. The running of the app to simulate soil water contents based on the soil water balance equation was supported by databases on soil texture, crop coefficients, water rights, E-Wc and threshold soil water content values as well as the real-time collection of electricity consumption and meteorological data. The simulated real-time soil water contents were shown on the mobile phone screen and could be compared with the threshold values for making irrigation decisions for users. The accuracy in forecasting the soil water contents using the methods developed in this framework was tested under different irrigation schedules for winter wheat and summer maize during 2018–2019 and 2021–2022, and the app was tested for three locations starting from sowing winter wheat in October 2022 to April in 2023. The results showed that the app could be easily run, and precise real-time soil water contents were simulated. With the application of the pumping well renovation project in the NCP, most of the pumping wells were installed with the SEMs, and using SEMs for groundwater pumping control and irrigation decisions should be possible.

Distribusi Kadar Air Tanah Dengan Irigasi Curah Pada Budidaya Tanaman Stevia (Stevia rebaudiana B.)

Sprinkler irrigation emulates rainfall patterns to supply plant water, improving soil conditions and ensuring sustained field performance. This study investigated the impact of sprinkler irrigation on Stevia's Coefficient of Uniformity (CU), soil moisture level, and crop coefficient (Kc). The experiment was conducted in Karangploso Village, Malang Regency, 700 m above sea level. Stevia plants were cultivated using sprinkler irrigation, and their water requirements were assessed by analyzing changes in soil moisture after irrigation. The results showed that sprinkler irrigation significantly increased soil moisture content. At a depth of 0-20 cm, soil moisture increased by an average of 0.135 cm3/cm3 (water depth of 27 mm), while at depths of 20-40 cm and 40-60 cm, the increase was 0.121 cm3/cm3 (24 mm) and 0.065 cm3/cm3 (13 mm), respectively, with a total water depth of 64 mm for 0-60 cm soil depth of 70 mm irrigation event. The crop coefficient (Kc) of Stevia varied during its growth stage, starting from 0.55 in the first week and gradually increasing to 0.57 in the 6th week. The total water requirement for Stevia until harvest at 60 days reached 279.8 mm. This finding emphasize the importance of monitoring and adjusting irrigation practices to ensure optimal growth of Stevia. Sprinkler irrigation effectively increased soil moisture content and determined the appropriate water requirement and Kc value for Stevia cultivation.

Productivity of olive oil (Coratina variety) in response to irrigation treatments in sandy soil

AbstractA 2‐year field experiment was conducted on drip‐irrigated olive oil orchards (Coratina var.) on a private farm in the newly reclaimed sandy soil of the West Nile Delta region, Egypt, during the 2020 and 2021 seasons to evaluate the effect of five irrigation treatments (120%, 100%, 80% and 60% reference crop evapotranspiration [ETo] and farmer practice) on applied irrigation water (AIW), water consumptive use, olive fruit and oil yields and some fruit quality parameters, water use efficiency, water productivity, electric energy consumed, farm income and benefit–cost ratio and to develop local crop coefficients (Kc) and yield response factors (Ky). The results indicated that the 2‐year average AIW values were 9953 (17.9 m3/tree/year), 8484 (15.3 m3/tree/year), 6971 (12.5 m3/tree/year), 5480 (9.9 m3/tree/year) and 17,488 m3/ha (31.5 m3/tree/year) for the tested irrigation treatments. Olive fruit and oil yields and quality parameters were significantly affected by the tested treatments. The highest fruit and oil yields were recorded for the 120% ETo treatment. A seasonal Kc of 0.75 and a seasonal Ky of 0.83 were obtained. It can be concluded that producing oil from olive trees (Coratina var.) in sandy soils can be achieved by applying amounts of water equal to 80% or 60% ETo.

Investigation of a simple method to estimate daily crop water requirement and crop coefficient of sugarcane

Investigation of a simple method to estimate daily crop water requirement and crop coefficient of sugarcane