Irrigation Experiment Research Articles

Study on the irrigation uniformity of impact sprinkler under low pressure with and without aeration

The distribution of water deteriorates when the operating pressure of an impact sprinkler (IS) decreases to some level. The aeration jet method is utilized to form an aeration impact sprinkler (AIS), aiming to improve the uniformity of water distribution under low pressure. Based on the structures of a 20PY2 impact sprinkler, an IS and AIS with the same sprinkler discharge were studied under operating pressures range between 150 and 250 kPa. A square test zone was formed by the four sprinklers, and the combined irrigation experiment was conducted under windless conditions. The results showed that the water loss ranged from 3% to 9.5% in all 18 test schemes. The coefficient of uniformity (CU) and distribution uniformity (DU) were used to quantify the degree of uniformity. The AIS had an approximately 3%–7% greater CU than the IS, which resulted in the CU reaching the specified value in the IS standard when the sprinkler functioned under low operating pressure. A linear relationship was found between the CU and DUlq. The uniformity of water distribution clearly changed with the operating pressure (150 kPa, 200 kPa, and 250 kPa) but decreased slightly with the increase in combination spacing (1 R, 1.1 R, and 1.2 R). In addition, the results of field experiment were compared with those of the simulation developed from a single sprinkler indoor experiment based on the water distribution radial curve. The simulated coefficient of uniformity was highly consistent with the experimental data and had an error of <7%. A sprinkler water jet with the aeration method was proven to be a feasible solution to reduce the operating pressure.

The Impact of Pesticide Use on Tree Health in Riparian Buffer Zone

The result of the enormous usage of pesticides in agriculture is the contamination of soil and water bodies surrounding the fields. Therefore, creating buffer zones to prevent water contamination is very useful. Chlorpyrifos (CPS) is the active substance of a number of insecticides widely used all over the world. In our study, we focused on the effect of CPS on plants forming riparian buffer zones: poplar (Populus nigra L., TPE18), hybrid aspen (P.tremula L. × P. tremuloides Michx.), and alder (Alnus glutinosa L.). Foliage spray and root irrigation experiments were conducted under laboratory conditions on in vitro cultivated plants. Spray applications of pure CPS were compared with its commercially available form-Oleoekol®. Although CPS is considered a nonsystemic insecticide, our results indicate that CPS is transferred not only upwards from roots to shoots but also downwards from leaves to roots. The amount of CPS in the roots was higher (4.9 times and 5.7 times, respectively) in aspen or poplar sprayed with Oleoekol than in those sprayed with pure CPS. Although the treated plants were not affected in growth parameters, they showed increased activity of antioxidant enzymes (approximately two times in the case of superoxide dismutase and ascorbate peroxidase) and augmented levels of phenolic substances (control plants -114.67 mg GAE/g dry tissue, plants treated with CPS-194.27 mg GAE/g dry tissue). In summary, chlorpyrifos, especially as a foliar spray pesticide, can create persistent residues and affects not only target plants but also plants surrounding the field.

Optimized border irrigation delays winter wheat flag leaf senescence and promotes grain filling.

Border irrigation is still the main irrigation method in the Huang-Huai-Hai Plain of China (HPC), and the suitable irrigation border length for water saving and high yield under traditional irrigation is still unclear. Therefore, a 2-year traditional border irrigation experiment (2017-2019) was conducted on the HPC. Four border lengths were tested: 20m (L20), 30m (L30), 40m (L40), and 50m (L50). These treatments were given supplementary irrigation at jointing and anthesis. An exclusively rainfed condition formed the control treatment. Compared with other treatments, the activities of superoxide dismutase antioxidant and sucrose phosphate synthetase, and the contents of sucrose and soluble proteins after anthesis were higher in the L40 and L50 treatments, while the content of malondialdehyde content was lower. Therefore, the L40 treatment effectively delayed the decrease in the soil plant analysis development (SPAD) value and chlorophyll fluorescence characteristics, promoted grain filling, and achieved the highest thousand-grain weight. Compared with the L40 treatment, the grain yields of the L20 and L30 treatment were significantly reduced, while the water productivity of the L50 treatment was significantly reduced. These findings suggest that 40m was the optimal border length for both high yield and water saving in this experiment. This study provides a simple and low-cost water-saving irrigation method for winter wheat in the HPC under traditional irrigation, which can help alleviate the pressure of agricultural water use.

Drip Irrigation at a Soil Water Suction of 30 kPa Helps AMF and GRSP to Enhance Greenhouse Macro-Aggregates

Drip irrigation is fundamental in water-saving agricultural greenhouses, especially in tomato (Solanum lycopersicum L.) greenhouses. However, a long-term drip irrigation has been observed to be associated with soil degradation, concerning both soil aggregate structure and soil microbial community. To evaluate how drip irrigation scheduling influences the soil structure and arbuscular mycorrhizal fungi (AMF), a long-term irrigation experiment was carried out in a tomato greenhouse in 2011, using an irrigation program with dripping water starting when the soil reached a suction of 20 kPa (D20), 30 kPa (D30) and 40 kPa (D40). In 2017, we tested the AMF community and soil aggregate composition by soil wet sieving. Aggregates of 0.25–1 mm represented the main class of aggregates (32.4%–43.1%) in this experiment. At D30, we measured the highest mean weight diameter (MWD) and soil organic carbon (SOC) and glomalin-related soil protein (GRSP) levels. Thus, D30 promoted soil aggregate stability in the greenhouse. According to the high-throughput sequencing results of AMF, Glomus at D30 was the main factor leading to a high soil aggregate stability, because its OTU relative abundance was significantly higher than those of Ambispora and Paraglomus. Through redundancy analysis, the GRSP concentration was positively correlated with the SOC and total N (TN) levels and with the presence of the genera Ambispora, Glomus and Paraglomus. This evidenced that AMF and SOC helped to increase GRSP concentration and aggregate stability. Therefore, initiating irrigation when the soil reaches a water suction of 30 kPa could promote soil aggregate stability by favoring AMF abundance.

Field evaluation of semi-automated moisture estimation from geophysics using machine learning.

Geophysical methods can provide three-dimensional (3D), spatially continuous estimates of soil moisture. However, point-to-point comparisons of geophysical properties to measure soil moisture data are frequently unsatisfactory, resulting in geophysics being used for qualitative purposes only. This is because (1) geophysics requires models that relate geophysical signals to soil moisture, (2) geophysical methods have potential uncertainties resulting from smoothing and artifacts introduced from processing and inversion, and (3) results from multiple geophysical methods are not easily combined within a single soil moisture estimation framework. To investigate these potential limitations, an irrigation experiment was performed wherein soil moisture was monitored through time, and several surface geophysical datasets indirectly sensitive to soil moisture were collected before and after irrigation: ground penetrating radar, electrical resistivity tomography (ERT), and frequency domain electromagnetics (FDEM). Data were exported in both raw and processed form, and then snapped to a common 3D grid to facilitate moisture prediction by standard calibration techniques, multivariate regression, and machine learning. A combination of inverted ERT data, raw FDEM, and inverted FDEM data was most informative for predicting soil moisture using a random regression forest model (one-thousand 60/40 training/test cross-validation folds produced root mean squared errors ranging from 0.025-0.046 cm3/cm3). This cross-validated model was further supported by a separate evaluation using a test set from a physically separate portion of the study area. Machine learning was conducive to a semi-automated model-selection process that could be used for other sites and datasets to locally improve accuracy.

Model based predictive control strategy for water saving drip irrigation

Traditional irrigation control systems is characterized with inefficient management of water and often results in low water productivity index and reduced cultivation yield. In addition, insufficient water supply and high rate of water loss due to evapotranspiration increases plant stress which often affects its growth and development. Therefore, to address this issues, this paper is aimed at developing a model predictive control (MPC) strategy for water saving drip irrigation experiment that will regulate the soil moisture content within the desired field capacity and above the wilting point, while scheduling irrigation to replace the loss of water from soil and plant due to evapotranspiration in the greenhouse environment. The controller design involves a data driven predictive model identified and integrated with the MPC designer in MATLAB and thereafter exported in Simulink for simulation. The generate controller code was modified and deployed on a Raspberry Pi 4 controller to generate a pulse width modulated signal to drive the pump for the control water mixed with fertilizer. To achieve enhancement of controller an Internet of Things (IoT) integration was used for easy soil, weather, and plant monitoring which are used to update the MPC model for the irrigation control. The performance of the proposed MPC controller deployed drip irrigated Greenhouse(GH1) is benchmarked against an existing automatic evapotranspiration (ETo) model based controller in Greenhouse(GH2), with each greenhouse containing 80 poly bags of Cantaloupe plant with similar growth stage. The results obtained shows that, the proposed MPC-based irrigation system has higher water productivity index of 36.8 g/liters, good quality of fruit with average sweetness level of 13.5 Brix compared to automatic ETo-based irrigation system with 25.6 g/liters and 10.5 Brix, respectively. However, the total mass of harvested fruit for ETo-based irrigation system is higher than MPC-based irrigation system by 21.7%. The performance of the proposed MPC controller was achieved through the integration of event based scheduling with IoT monitoring as well as inclusion of evapotranspiration effect in the plant dynamics.

Development of Non-Destructive Testing Device for Plant Leaf Expansion Monitoring

This paper designs a plant leaf expansion pressure non-destructive detection device, aiming to promote plant leaf expansion pressure research and achieve precision irrigation. The design is based on leaf expansion pressure probe technology, which can effectively monitor the plant leaf expansion pressure by detecting the feedback of the leaf under constant pressure. In this paper, the stability of the sensor and the calibration model is tested. The calibration experiments showed that the coefficient of determination R2 of the sensor was over 0.99, the static test results showed that the range of the sensor was 0–300 kPa, and the fluctuation of the sensor was less than 0.2 kPa during the long-term stability test. The indoor comparison tests showed that there was a significant difference in the variation of leaf expansion pressure data between plants under drought conditions and normal conditions. The irrigation experiments showed that the leaf expansion pressure was very sensitive to irrigation. The correlation between the expansion pressure data and the environmental factors was analyzed. The correlation coefficient between expansion pressure and light intensity was found to be 0.817. The results of the outdoor experiments showed that there was a significant difference in the expansion pressure of plants under different weather conditions. The data show that the plant leaf expansion pressure non-destructive detection device designed in this paper can be used both as an effective means of detecting plant leaf expansion pressure and promoting the research of plant physiological feedback mechanisms and precision irrigation.

Evolutionary Model Discovery of Human Behavioral Factors Driving Decision-Making in Irrigation Experiments

Evolutionary Model Discovery of Human Behavioral Factors Driving Decision-Making in Irrigation Experiments

Effect of soil water content threshold on kiwifruit quality at different growth stages with drip irrigation in the humid area of Southern China

• Effects of soil water content threshold (SWCT) on kiwifruit quality depended on SWCT timing and degree. • SWCT of 55% field capacity (FC) increased fruit volume and fruit weight at bud burst to leafing stage. • SWCT of 65% FC elevated total soluble solids, soluble sugar and solid-acid ratio at fruit growth stage. • SWCT of 60% FC improved firmness, total soluble solids, soluble sugar, vitamin C and solid-acid ratio at fruit maturation stage. Fruit quality as affected by soil water content threshold levels (SWCT) at different growth stages remains largely elusive. Therefore, a drip irrigation experiment was conducted to investigate the effect of SWCT on kiwifruit quality at bud burst to leafing stage (stage I), flowering to fruit set stage (stage II), fruit growth stage (stage III) and fruit maturation stage (stage IV) during 2018 and 2019 in the humid area of southern China, respectively. The results showed that SWCT at stage I mainly affected fruit weight (Fw). I-55% treatment significantly elevated Fw by 11.6%-8.0% ( P < 0.05). SWCT at stage II had little effect on fruit quality. SWCT at stage III influenced fruit volume (Fv) and chemical quality. Specifically, Fv was increased by 8.0%-2.2% under III-75% treatment, total soluble solids (TSS), soluble sugar (SS) and solids-acid ratio (SOAR) were increased by 9.4%-10.0% ( P < 0.05), 2.4%-5.8% and 7.9%-10.6% ( P < 0.05) under III-65% treatment, respectively. SWCT at stage IV impacted fruit firmness (Fn) and chemical quality. IV-60% treatment increased Fn, TSS, SS, VC and SOAR by 5.6%-10.5%, 12.0%-12.6% ( P < 0.05), 6.6%-9.1% ( P < 0.05), 2.1%-14.0% ( P < 0.05), and 8.1%-8.3% ( P < 0.05), respectively, which was beneficial to the improvement of nutritional value and taste, and also the storage and transportation of kiwifruit. Collectively, SWCT of 55% FC (field capacity) at stage I or 65% FC at stage III or 60% FC at stage IV was an effective measure to improve the kiwifruit quality.

Seawater irrigation on nests can increase male marine turtle production

Global warming is increasing marine turtle nesting beach sand temperatures throughout the world. All marine turtles have temperature-dependent sex determination, with female hatchlings produced at warmer incubation temperatures. These warmer sand temperatures are causing a scarcity of male hatchlings at many nesting beaches. A range of mitigation strategies including shading and freshwater irrigation are being trialled at marine turtle nesting beaches around the world to address this issue. Because seawater is always abundant at marine turtle nesting beaches, we trialled a number of intense, one-off seawater irrigation experiments (equivalent to 100 and 200 mm rainfall) to test if male green turtle Chelonia mydas hatchling production could be increased without decreasing overall hatching success at Heron Island, southern Great Barrier Reef, Australia. We found that different combinations of seawater volume and temperature could produce a short-term drop in nest temperature by 2°C. When applied during the middle of embryonic development, these irrigation treatments could increase the proportion of male hatchlings compared to non-irrigated control nests, with less than a 10% decrease in hatching success. Hence, seawater irrigation has the potential to be a viable management strategy to increase the proportion of male marine turtle hatchlings at beaches that produce all, or nearly all, female hatchlings.

Impact of Reclaimed Water Irrigation on Rice Yields and Quality

Poultry and livestock farming wastewater is one of the main sources of agricultural non-point source pollution. Using reclaimed poultry and livestock farming wastewater for rice irrigation can not only provide nutrition for rice, but also reduce agricultural water consumption, and also further control non-point source pollution through the self-purification of rice ecosystem. It has been considered to be environmentally friendly and reliable for poultry and livestock farming wastewater treatment. However, the effect of reclaimed water irrigation on rice yield and quality is still unclear. In order to explore the effects of reclaimed water irrigation on rice yield and quality, we conducted a rice reclaimed irrigation experiment in the Erhai lake basin in 2017. The rice yield and quality were compared among different irrigation modes, different irrigation water quality and different fertilization schemes of reclaimed water. The results showed that the yield of W1F2, under intermittent irrigation with reclaimed water, was the highest, reaching 11.7t/hm2. The differences of rice yield and its components between different irrigation and fertilization methods were not significant. The yield and its components of rice under different irrigation and fertilization treatments were not significant. In terms of yield, the intermittent irrigation was 7.6% higher than that of flood irrigation. The amount of fertilizer applied by intermittent irrigation of reclaimed water was 7.0% less than that of clear water, and the yield increased by 3.5%. Correspondingly, the amount of fertilization of flood irrigation of reclaimed water is equivalent to that of clear water, which increases yield by 1.9%. In summary, the effect of reclaimed water irrigation on yield increase is obvious. There were significant differences in brown rice rate and chalky grain rate between different irrigation modes, which showed that the brown rice rate of intermittently irrigated rice was 0.7% smaller than that of flooded rice, and the white grain of intermittently irrigated rice was 45% larger than that of flooded irrigation. Intermittent irrigation has an adverse effect on the processing quality and appearance quality of rice. There were significant differences in brown rice rate, whole milled rice rate, gel consistency and depletion value under different irrigation water quality. The results showed that the brown rice rate and the depletion value of reclaimed water irrigation were smaller than those of clear water, and the whole milled rice rate and gel consistency were larger than that of clear water. Regularity, reclaimed water irrigated rice processing quality and cooking taste quality is better. In terms of nutritional quality of rice, the crude protein content in flooding treatment was 4.2% higher than that in intermittent irrigation, and the irrigation treatment of reclaimed water was 13.8% higher than that in clear water irrigation.

Effect of surface water and underground water drip irrigation on cotton growth and yield under two different irrigation schemes.

To investigate the effect of surface water and underground water drip irrigation on cotton yield, dry matter accumulation and nutrients uptake, two consecutive field experiments were conducted. The first experiment (different mixing ratio irrigation) comprised of five ratios of underground water to surface water including; 1:0 (U), 0:1 (S), 1:1 (U:S = 1:1), 1:2 (U:S = 1:2) and 1:3 (U:S = 1:3). Whereas, the second experiment (round irrigation) comprised of eight treatments including: 1:3 (T1), 2:2 (T2), 3:1 (T3), {S:U 3:1 (T4)}, 2:2 {S:U (T5)}, 1:3 {S:U (T6)}, 4:0 (T7) and 0:4 (T8). The average concentration of leaves dry matter after 8th irrigation in different mixing ratio experiment was significantly increased by 131.2% (S), 34.4% (U: S = 1:1), 59.3% (U: S = 1:2), and 93.7% (U: S = 1:3), respectively, relative to U treatment. Likewise, the stem dry matter increased from 48.5 g (U), to 122.2 g (S) and 101.6 g (U:S = 1:3). The soil available N at 0-20 cm after 8th irrigation recorded an average increase rate of 40.1%, 6.6%, 13.5%, and 29.5%, respectively. However, at 20-40cm an average increase rate of 37.4% (S), 7.1% (U: S = 1:1), 20.0% (U: S = 1:2), and 21.9% (U: S = 1:3) were noted (p < 0.05). The highest cotton yield of 6571 kg h-1 was recorded in S treatment compared with the U treatment (5492 kg h-1), U: S = 1:1 (5502 kg h-1), U: S = 1:2 (5873 kg h-1) and U: S = 1:3 (6111 kg h-1). Contrastingly, in round irrigation experiment the highest leaves dry matter at various growth stages were recorded in T8 treatment. For instance, compared with T7 treatment an average increase rate of 50.6% (growth), 100.9% (boll) and 93.3% (boll opening), in stem dry matter were recorded in T8 treatment. Moreover, the concentration of N in round irrigation at 0-20 cm at different growth stages were 83.3±2.8 (growth stage), 79.01±1.84 (boll stage), and 96.16±3.83 (boll opening stage) in T8. Whereas, in T7 the concentration of N was 36.1±5.9 (growth), 54.51±2.81 (boll), and 53.9±3.83 (boll opening) (p < 0.05). Similarly, cotton yield were substantially higher in T8 applied treatment and follows the sequence of T8 > T1 > T4 > T2 > T5 > T3 > T6 > T7. Overall, our findings provide meaningful information to current irrigation practices in water scarce regions. Improving water use efficiency is a viable solution to the water scarcity. Therefore, surface water irrigation is recommended as an effective irrigation strategies to improve cotton yield and growth.

Effect of irrigation during the dry season on leaf yield of Trichanthera gigantea

The experiment was conducted at Thai Nguyen University of Agriculture and Forestry from 2019 to 2020 to determine the effect of irrigation on the leaf yield of Trichanthera gigantea green fodder in the dry season. The experiment consisted of 4 independent variables (NT1, NT2, NT3, NT4), corresponding to 4 different irrigation levels (0, 40, 80,and 120 m3/ha/harvest) and designed in a completely randomised block with 5 replicates. Plantation density, fertilizer application, and other factors were similar among the four variables. The results showed that the dry matter and crude protein yields of leaves of the irrigated experiments were higher than that of the control (without watering). The dry matter yields of leaves in NT1 to NT4 were 2.410, 2.934, 3.292, and 3.594 tons/ha/dry season, respectively. If the yield of NT1 was considered as 100% then that of NT2, NT3, and NT4 was 121.7, 136.6, and 149.1%, respectively. The protein yields of NT1 to NT4 grew up from 0.618 tons (100%) to 0.922 tons/ha/dry season (149.2%). Dry matter and crude protein yields of NT2, NT3, and NT4 were significantly different from NT1; that of NT4 was significantly different compared to that of NT2 and NT3. Research results have shown that irrigation in the dry season has a significant effect on leaf yield of Trichanthera gigantea green fodder and should be irrigated at 120 m3/ha/harvest.

Water Requirement of Naked Oats under Subsurface Drip Irrigation in the North Foot of Yinshan Mountain Based on Single Crop Coefficient Approach

In order to accurately and rapidly calculate the water requirement of naked oats under drip irrigation in the north foot of Yinshan Mountain, the study adopted the K c and calculation method for potential evapotranspiration recommended in document FAO56 and applied SCCA to calculate the water requirement of crops based on the deficient irrigation experiments. The results indicated that the water requirements of naked oats without drought influence was 383.8 mm, and the maximum daily average water requirement intensity was heading flowering, which was the critical period of crop water requirement, and the mean value of E T 0 in the whole growth period was 3.89 mm/d. After correction, K C of naked oats in the initial growth stage, crop development growth stage, mid-season growth stage, and late season growth stage was 0.34, 0.94, 1.05, and 0.36. The average K C of naked oats in the whole growth stage was 0.71. SCCA does not consider the influence of wetting depth in the initial growth period of crops and the correction of local irrigation in the mid-season and late season stage of crops. Therefore, when the irrigation quota of naked oats is 315 mm, the crop water requirement calculated by SCCA is 363.84 mm, which is about 10% different from the measured value. The results show that SCCA can be used to calculate the water requirement of naked oats under drip irrigation at the northern foot of Yinshan Mountain in Inner Mongolia, and the calculation error is within the allowable range. However, it is also necessary to consider the influence of different irrigation forms and plant height of crops on calculation value.

Effect of irrigation commutative flow technology on reducing deposition and improving anticlogging performance of a flat labyrinth drip pipe

Abstract This paper proposes a commutative flow technology of drip irrigation in a looped pipe network. Switching the flow direction of the drip irrigation pipe can improve the flow velocity in the lateral, consequently washing up the sediment deposited in the lateral and flow channel of the emitter. Thus, this technology can reduce sediment deposition and prevent blockage of the drip irrigation pipe. To verify the effectiveness of the commutative flow technology, the drip irrigation experiment was conducted, and the unidirectional flow technology experiment was the control. At the end of the tests, the emitter average relative discharge (Dra) of the commutative and unidirectional flow drip irrigation pipes decreased to 92.8 and 62.9%, the emitter blocking rate was 7.7 and 35.9%, respectively; the total amount of sediment deposited in the commutative flow lateral was 37.5% of that in the unidirectional flow lateral. Compared with the unidirectional flow technology, the commutative flow technology could significantly mitigate the decline rate of flow discharge, and effectively reduce the emitter blockage rate and the lateral sediment amount. Thus, the application of the commutative flow technology in the drip irrigation field pipe network can improve irrigation quality and promote the development of muddy water drip irrigation.

What Indicative Information of a Subsurface Wetted Body Can Be Detected by a Ground-Penetrating Radar (GPR)? A Laboratory Study and Numerical Simulation

Nondestructive and noninvasive visualization and quantification of soil wetted bodies (SWBs) is of great significance to the development of water-saving agriculture. Unfortunately, measuring the parameters of SWBs is difficult due to the invisibility of SWBs buried underneath the ground and the non-variability of the soil moisture under partial irrigation conditions. Therefore, we performed a laboratory experiment to investigate what SWB attributes can be detected by a GPR. In the laboratory, three typical partial irrigation experiments were conducted to collect the GPR data of SWBs of different sizes, shapes, and burial depths. Additionally, numerical simulation scenarios were designed according to the laboratory experiment. Then, the simulated and measured GPR data were processed by the FK migration method. Based on the simulation, a calibration model for the width of SWBs was constructed. We found that SWB attributes, such as type and location can be obtained from raw radargrams owing to the obvious reflection of the top and bottom interfaces. The results showed that estimating the depth and thickness of SWBs from FK migration radargrams is more reliable than from raw radargrams. Moreover, estimation of the width of SWBs relies on the FK migration radargrams. Our findings indicate that the size and depth of SWBs dominate the width detection accuracy, and the estimated width gained via the width calibration model is improved. Our results highlight the potential for using GPR data to detect SWBs, as well as the potential of using numerical simulation, FK migration, and calibration modeling in combination to extract the size information of SWBs from GPR radargrams.

Evaluation of irrigation experiments with GGE biplot method and economic analysis of drip irrigation system: a case study of peanut production

Besides irrigation water quantity and quality, there is a decrease also in soil quality and fertility. Agricultural production lands are decreasing both in quantity and quality. There is a search for different operational alternatives in sandy soils with low production potentials. Drip irrigation is largely practised to get greater yields per unit area. This study was conducted under sand soil conditions, commonly preferred for peanut farming, in the 2017- 2018 growing seasons. A drip irrigation system was used in production. Two different irrigation intervals (2 and 4 days) and four different irrigation levels (I50, I75, I100 and I125, calculated based on cumulative evaporation from the class-A pan) were applied. Evapotranspiration values varied between 402-832 mm, applied irrigation water quantities between 313-783 mm, yields between 5269-8269 kg ha-1, water use efficiency (WUE) values between 0.63-1.55 kg ha-1 m-3, economic water productivity (EWP) over gross revenues between 1.29-3.81 $ m-3 and benefit and cost ratios (B/C) varied between 4.73-10.95. The GGE biplot statistical method is a useful tool in the evaluation of irrigation research where the number of applications and materials is high.

Land–Atmosphere Interactions during GRAINEX: Planetary Boundary Layer Evolution in the Presence of Irrigation

Abstract This paper analyzed observations from the Great Plains Irrigation Experiment (GRAINEX) to better understand land–atmosphere (L–A) interactions and PBL evolution. This study is focused on a day when the largest forcing on the boundary layer originated from the land surface/land use. To examine these impacts, we also applied the Weather Research and Forecasting (WRF) Model. Results from the observations show that compared to nonirrigated areas, air temperature, wind speed, and PBL height (PBLH) were lower while dewpoint temperature and latent heat flux were higher over irrigated areas. Findings suggest that entrainment layer drying and differences in energy partitioning over irrigated and nonirrigated areas played an important role in PBL evolution. In the final hours of the day, the PBL collapsed faster over nonirrigated areas compared to irrigated. The WRF Model simulations agree with these observations. They also show that the extent of irrigation [expressed as irrigation fraction (IF)] in an area impacts L–A response. Under ∼60% IF, the latent heat flux and mixing ratio reach their highest value while temperature and PBLH are at their lowest, and sensible heat flux is near its lowest value. Results are reversed for ∼2% IF. It is concluded that irrigation notably impacts L–A interactions and PBL evolution.

Using Visible and Thermal Images by an Unmanned Aerial Vehicle to Monitor the Plant Water Status, Canopy Growth and Yield of Olive Trees (cvs. Frantoio and Leccino) under Different Irrigation Regimes

An efficient management of water relies on the correct estimation of tree water requirements and the accurate monitoring of tree water status and canopy growth. This study aims to test the suitability of visible and thermal images acquired by an unmanned aerial vehicle (UAV) for monitoring tree water status and canopy growth in an irrigation experiment. We used mature olive trees of two cultivars subjected to full irrigation, deficit irrigation (41–44% of full irrigation), or rainfed conditions. Deficit irrigation had limited or no effect on fruit and oil yield. There was a significant relationship between the remotely sensed crop water stress index derived from thermal images and the stem water potential (R2 = 0.83). The RGB images by UAV allowed to estimate tree canopy volume and were able to detect differences in canopy growth across irrigation regimes. A significant relationship between canopy volume and LAI was found for both cultivars (R2 of 0.84 and 0.88 for Frantoio and Leccino, respectively). Our results confirm the positive effects of deficit irrigation strategies to save relevant volumes of water and show that aerial images from UAV can be used to monitor both tree water stress and its effects on canopy growth and yield.

Crop yield estimation and irrigation scheduling optimization using a root-weighted soil water availability based water production function

The crop-water production function (CWPF) is widely used to quantitatively describe relationships between crop water deficit and yield, and evaluate the effects of different irrigation strategies in agro-hydrological models. In order to reasonably and reliably estimate crop yield and optimize irrigation scheduling , a novel CWPF was proposed by combining the plant water deficit index (PWDI), estimated based on root-weighted soil water availability, with a daily water sensitivity index derived from a sigmoidal cumulative function. Parameterized using data from a two-year winter wheat field lysimetric experiment conducted in the North China Plain and from a previously published two-year spring maize field drip irrigation experiment in Inner Mongolia, China, the CWPFs provided reasonable estimation of different crop yields with different water stress response characteristics under different field environments. Through coupling the genetic algorithm with the integrated simulations of soil water dynamics, PWDI and CWPF in the soil-wheat system, an optimization procedure was developed to determine PWDI threshold combinations to timely trigger irrigation according to pre-designed crop water deficit status. Crop yield and water use efficiency (WUE) of winter wheat were estimated and compared under different optimized constant and variable PWDI threshold combinations. In addition, the effects of climate change on the optimized variable PWDI threshold combinations were investigated using 38 years of historic meteorological data . The results showed that regulated deficit irrigation (RDI) with a variable threshold combination, in which the sensitivity characteristics to water deficit were considered for the crop at different growth stages, was superior to a constant threshold in enhancing crop yield and WUE. Irrespective of the number of irrigation events (1, 2, 3 or 4) during the growing season, the coefficients of variation (CV) of optimized PWDI thresholds for different combinations of irrigation sequence and events were not very large under the same kind of hydrological year (wet, normal or dry), with CV < 0.39 and a median of 0.21. When the mean (MN) of the optimized PWDI threshold combinations for different irrigation sequence and events was used to schedule RDI of winter wheat in terms of various hydrological years, up to 91% of the estimated relative yield was found to be higher than 90% of the corresponding maximum values. Therefore, the MN can be valuable in formulating rational irrigation management strategies of winter wheat to achieve relatively high yields with limited water under changing climatic conditions.