Levels Of Irrigation Treatments Research Articles

Efekti različitih tretmana zemljišta na prinos useva u Jugoistočnoj Nigeriji

In this study, a PVC drip irrigation system was designed to investigate the effect of different soil treatments on crop yield, using Oba Super 13 maize variety as test crop, on three major plots, each representing a different tillage method. Each plot has three levels of each of the three soil treatments involved including irrigation deficit, tillage method and NPK Application rate, totaling 27 subplots. The three levels of irrigation treatments were 50%, 30% and 10% management allowable depletion levels; tillage treatments were conventional tillage, conservative tillage and no tillage methods, while the NPK application treatments were 400 kg/ha, 500 kg/ha and 600 kg/ha rates, and experimentally designed using the Central Composite Design (CCD) in Design Expert 11 software. The crop yield for all the subplots were determined, and maximum crop yield of 2540 kg/ha was obtained at conservative tillage with 10%MAD, and 600 kg/ha NPK application rate, while minimum tillage of 1234.67 kg/ha was obtained at no tillage, 50%MAD and 400 kg/ha NPK application rate. Controllable variables were optimized using response surface methodology (RSM) with crop yield for all the subplots. The optimum values based on the run gave irrigation deficit as 11.594%, NPK Application rate as 596.406 kg/ha, best tillage method as conservative tillage, crop yield of 2543.589 kg/ha. The highest maize yield was obtained in conservative tillage and the results confirm the viability of obtaining high yield in the study area using drip irrigation system during the dry season.

Deep-Learning-Based Multispectral Image Reconstruction from Single Natural Color RGB Image—Enhancing UAV-Based Phenotyping

Multispectral images (MSIs) are valuable for precision agriculture due to the extra spectral information acquired compared to natural color RGB (ncRGB) images. In this paper, we thus aim to generate high spatial MSIs through a robust, deep-learning-based reconstruction method using ncRGB images. Using the data from the agronomic research trial for maize and breeding research trial for rice, we first reproduced ncRGB images from MSIs through a rendering model, Model-True to natural color image (Model-TN), which was built using a benchmark hyperspectral image dataset. Subsequently, an MSI reconstruction model, Model-Natural color to Multispectral image (Model-NM), was trained based on prepared ncRGB (ncRGB-Con) images and MSI pairs, ensuring the model can use widely available ncRGB images as input. The integrated loss function of mean relative absolute error (MRAEloss) and spectral information divergence (SIDloss) were most effective during the building of both models, while models using the MRAEloss function were more robust towards variability between growing seasons and species. The reliability of the reconstructed MSIs was demonstrated by high coefficients of determination compared to ground truth values, using the Normalized Difference Vegetation Index (NDVI) as an example. The advantages of using “reconstructed” NDVI over Triangular Greenness Index (TGI), as calculated directly from RGB images, were illustrated by their higher capabilities in differentiating three levels of irrigation treatments on maize plants. This study emphasizes that the performance of MSI reconstruction models could benefit from an optimized loss function and the intermediate step of ncRGB image preparation. The ability of the developed models to reconstruct high-quality MSIs from low-cost ncRGB images will, in particular, promote the application for plant phenotyping in precision agriculture.

Self-organizing map estimator for the crop water stress index

Crop water stress index (CWSI) is a reliable, economic and non-destructive method of monitoring the onset of water stress for irrigation scheduling purposes. Its application, however, is limited due to the need of obtaining the baseline canopy temperatures. This study developed a self-organizing map (SOM) based model to predict the CWSI using microclimatic variables, namely air temperature, canopy temperature and relative humidity. The canopy temperature measurements were made from Indian mustard crop grown in a humid sub-tropical agro-climate during the 2017 and 2018 cropping seasons. Eight levels of irrigation treatments (I1 – I8) based on maximum allowable depletion of available soil water were considered in the study. The CWSI for treatments I2 – I7 was computed using the empirical approach based on the experimentally measured baseline canopy temperatures from treatments I1 and I8. The number of data points used was 1260 and 1350 for model training and testing, respectively. The developed SOM model was evaluated using the error indices Nash-Sutcliffe efficiency (NSE), bias error (BE), absolute error (AE), and coefficient of determination (R2). The SOM predicted CWSI presented a good agreement with the baseline computed CWSI values during model training (R2 = 0.98, NSE = 0.97, AE = 0.018, BE = 0.0004) and testing (R2 = 0.98, NSE = 0.98, AE = 0.018, BE = 0.002). Treatment specific analysis was conducted to evaluate the performance of SOM predicted CWSI for different irrigation levels. Results indicated that the presence of zero CWSI values in a significant proportion in the dataset impacted the model prediction performance at low CWSI (<0.1) values, with an R2 of 0.71 during testing. Nonetheless, the model performed exceptionally well in predicting CWSI values between 0.1 and 0.6 (R2 = 0.93–0.98, NSE = 0.92–0.98, AE = 0.013–0.015, BE = −0.002–0.004), which is the commonly observed CWSI range for irrigation scheduling in field crops. For better understanding, the developed SOM model was also analysed through the component planes, U-matrix, clusters and high-low bar planes in the cluster features.

Modeling the effects of crop management on food barley production under a midcentury changing climate in northern Ethiopia

A crop simulation model was calibrated to (i) identify optimal planting date and quantify the impacts of nitrogen fertilizer and planting date on barley yield, and (ii) evaluate the responses of barley yield to climate change factors at Adigudom area, northern Ethiopia. Response of barley to seven planting dates at 10-days increments from 20-Jun and nine fertilizer rates at 16 kg/ha increments from 0 kg N/ha under five different soil types were evaluated. There were three irrigation treatment levels: I0 (no irrigation application); I1 (deficit irrigation: 4 irrigations); and I2 (full irrigation). Response of barley to midcentury (2040–2069) climate data from three global climate models under higher emission scenario was evaluated. The model simulated the barley biomass, yield, days to flowering and maturity satisfactorily. The optimal planting window for coarse, medium and fine textured soils were July 1 to July 20, July 1 to July 30 and July 20 to August 10, respectively. The optimal N fertilizer for the respective soils was 64, 32 and 32 kg N/ha, respectively. The difference between the simulated rainfed yield under optimal N fertilizer and on farm yield was estimated to be 1.1 Mg/ha. About 0.6 ± 0.4 and 0.5 ± 0.2 Mg/ha of the yield losses were due to nitrogen deficit and inappropriate planting date, respectively. Average barley grain yield is expected to decrease by 6–11% during the midcentury. This study showed that timely planting and N management along with elevated CO2 could contribute to yield enhancement and minimize the risk associated with future climate change.

Effects of Vine Water Status and Exogenous Abscisic Acid on Berry Composition of Three Red Wine Grapes Grown under Mediterranean Climate

Beyond climatic conditions, qualitative performance is led by the intrinsic characteristics of the genotype. The aim of this study was to investigate the relationship between vine water status and exogenous abscisic acid (ABA) application on berry composition of the cultivars Cannonau, Merlot and Sangiovese. The experiment, carried out in 2016 and 2017, consisted of comparing two levels of irrigation treatments, full irrigation versus a non-irrigation treatment. Within each treatment, two sub-treatments were set up: (i) 4 mL L−1 of exogenous ABA applied at veraison to clusters only and subsequently repeated after six days; (ii) a control (untreated vines). The application of different irrigation regimes confirmed that the response to water stress is highly cultivar-dependent. Berry composition was influenced differently among cultivars by water stress. In terms of metabolites, positive influences were observed with Cannonau. No significant effects were observed by spraying exogenous ABA directly on grapes. Moreover, no significant interactions were found between the application of water stress and ABA. Exogenous ABA application did not appear to be a viticultural practice capable of influencing must composition in environments characterized by severe environmental conditions such as heat and drought.

Impact of deficit irrigation and addition of biochar and polymer on soil salinity and tomato productivity

The aim of this study is to investigate impact of soil amendments (4% biochar, 0.4% polymer, and a combination of them) on soil moisture and salinity distribution, tomato yield, and water-use efficiency (WUE). Open-field experiments were conducted during two successive growing seasons in 2017 and 2018. The experiment consisted of three levels of irrigation treatments: 100%, 80%, and 60% of crop evapotranspiration (ETc); and two different water qualities: fresh 0.9 dS m−1 and saline electrical conductivity 3.6 dS m−1. Results revealed that at 100% of ETc, soil water distribution increased by 12.94%, 37.87%, and 42.21% at depths 0–15, 15–30, and 30–45 cm, with the addition of biochar, respectively, compared with control at same depths under freshwater, but the addition of polymer was increased by 6.35%, 16.56%, and 16.37%, respectively. While combination treatments increased by 15.70%, 24.80%, and 41.26%, at the depths aforementioned. Salt concentration was increased by 59.10% with biochar, whereas decreasing by 7.19% and 57.63% with polymer and mixture treatments, respectively. The results also showed that biochar and mixture treatments improved yield compared with the polymer and control, whereas saline water decreased the yield compared with freshwater. With deficit irrigation, WUE was increased by 28.54%, 40.98%, and 68.93% at 100%, 80%, and 60% of ETc, respectively, indicating it could be used as an irrigation management strategy under arid and semiarid field conditions.

Crop water stress index for scheduling irrigation of Indian mustard (Brassica juncea) based on water use efficiency considerations

AbstractThe study was conducted to determine the feasibility of canopy temperature based crop water stress index (CWSI) for scheduling irrigation of Indian mustard (Brassica juncea). Field crop experiments were conducted in Hamirpur, Himachal Pradesh (India) during three consecutive cropping seasons (2015, 2016 and 2017). The experimental field was divided into five plots with different levels of irrigation treatments based on depletion of total available soil water (TASW) in the crop root zone. The maximum soil moisture depletion (SMD) of TASW at 10%, 30% and 50%, full irrigated (non‐stressed) and extremely dry (full stressed) conditions were maintained in respective plots. Relationships were developed between canopy‐air temperature differential (TC‐TA) and vapour pressure deficit (VPD) for non‐stressed and fully stressed conditions to generate non‐water‐stressed baseline (NWSB) and maximum water‐stressed baseline (MWSB) baselines for Indian mustard crop. The CWSI was computed for different SMD of TASW by using a proven empirical approach based on the baselines. The irrigation treatment corresponding to 30% SMD with a mean CWSI of 0.4 resulted in optimal yield and maximum water use efficiency. Results of the study suggest that established CWSI value can be used to detect stress and schedule irrigations for Indian mustard.

Effects of Irrigation Amount and Irrigation Frequency on Flue-Cured Tobacco Evapotranspiration and Water Use Efficiency Based on Three-Year Field Drip-Irrigated Experiments

This study aimed to determine the effect of irrigation amount and irrigation frequency on drip-irrigated flue-cured tobacco evapotranspiration (ETa), yield, and water use efficiency. Four irrigation treatment levels were imposed: 100% IRT (fully irrigated treatment, no stress), 85% IRT, 70% IRT, RFT (rainfed treatment), and high, medium, and low irrigation frequencies were set. The relationship between irrigation volume and yield is a quadratic curve. The evapotranspiration had a positive relationship with the irrigation amount. The yield of flue-cured tobacco was the highest in 2016 (wet year), and the corresponding ETa was the smallest. The irrigation water use efficiency (IWUE) in the driest year, 2017, was lower than IWUE in the wet years 2015 and 2016, and the crop water use efficiency (CWUE) had similar results for the three years. IWUE increased with irrigation amount. The effect of irrigation frequency on CWUE was not significant. The CWUE had a positive relationship with yield. No significant differences due to irrigation frequency were found for yield.

Impact of Mole Drains and Soil Amendments Application on Management of Salt Affected Soils

Ameliorating the saline-sodic soil process represents an important target in the agricultural security program of Egypt. In this concern, two field experiment were conducted at El-Serw Agricultural Research Station, Damietta Governorate, Agricultural Research Centre Egypt during two successive growing seasons from (2014 2015).and (2015 )Cultivated crops comprised wheat and sunflower in a consecutive sequence, to study effect of applied alternative gypsum, (it is fabricating from some of sugar industry waste in Egypt, which cause environmental pollution problems by mixing some materials or other wastes in order to maximize the benefit and use it as an alternative gypsum) with mole depth and mole spacing on a possible amelioration for some properties of salt affected soils and its productivity of crops. The experimental design was laid out in split-split plots with three replications was followed. The main plots were three levels of irrigation treatments [field capacity (I1), field capacity +10% (I2) and field capacity +20% (I3)]. The sub plots were five mole drains treatments [ without mole(M0),2m mole space with 30 cm depth (M1), 2m mole space with 50 cm depth (M2), 4m mole space with 30 cm depth (M3) and 4m mole space with 50 cm depth (M4)]. The sub sub plots were three alternative gypsum treatments [ Gypsum (control), alternative gypsum one(AG1) and alternative gypsum two(AG2)] at a rate of 5,71 Mg fed.-1 for each of them. The applied alternative gypsum treatments were uniformly spread on soil surface and thoroughly mixed in the top 15 cm. before sowing. Leaching requirements estimated and then amount of irrigation water applied. The most important findings can be summarized as follows: The effect of the depth, distance of the moles with the addition of alternative gypsum treatments and levels of irrigation treatments [field capacity +20% (I3)]. Reduce salinity, acidity, bulk density, penetration resistances , total porosity,. On the contrary, increase the values ​​of hydraulic conductivity, organic matter, Grain yield (Mg fed. -1), Water productivity (kg/m3) and Water consumptive use efficiency (m3fed-1).The highest values ​​of field crops and water use efficiency occurred when the integration and overlap between increasing the depth of mole to 50 cm, decreasing of the mole to 2 meters and field capacity +20% (I3) with the use of alternative gypsum one (GA1) followed alternative gypsum two (GA2) and gypsum. The achieved amelioration in physio-chemical and hydrological properties of the studied soil positively reflected on the increases of grain yields of crops (wheat and sunflower). Finally, the obtained results suggest that this work is considered as scientific and logic fundamental base for a successful agricultural development of such salt affected area as well as possible to increase unite area income

A Coupled Model for Simulating Water and Heat Transfer in Soil-Plant-Atmosphere Continuum with Crop Growth

Crop growth is influenced by the energy partition and water–heat transfer in the soil and canopy, while crop growth affects the land surface energy distribution and soil water-heat dynamics. In order to simulate the above processes and their interactions, a new model, named CropSPAC, was developed considering both the growth of winter wheat and the water–heat transfer in Soil-Plant-Atmosphere Continuum (SPAC). In CropSPAC, the crop module depicts the dynamic changes of leaf area index (LAI), crop height, and the root distribution and outputs them to the SPAC module, while the latter outputs soil moisture conditions for the crop module. CropSPAC was calibrated and validated by field experiment of winter wheat in Yongledian, Beijing, with five levels of irrigation treatments, namely W0 (0 mm), W1 (60 mm), W2 (110 mm), W3 (170 mm), and W4 (230 mm). Results show that CropSPAC could predict the soil water and temperature distribution, and winter wheat growth with acceptable accuracy. For example, for the 0–1 m soil water storage, the R2 for W0, W1, W2, W3, and W4 is 0.90, 0.88, 0.90, 0.91, and 0.79, and the root mean square error (RMSE) is 17.24 mm, 27.65 mm, 20.47 mm, 22.35 mm, and 12.88 mm, respectively. For soil temperature along the soil profile, the R2 ranges between 0.96 and 0.98, and the RMSE between 1.22 °C and 1.94 °C. For LAI, the R2 varied from 0.76 to 0.96, and the RMSE from 0.52 to 0.67. We further compared the simulation results by CropSPAC and its two detached modules, i.e., crop and the SPAC modules. Results demonstrate that the coupled model could better reflect the interactions between crop growth and soil moisture condition, more suitable to be used under deficit irrigation conditions.

Using an integrated crop water stress index for irrigation scheduling of two corn hybrids in a semi-arid region

Different thermal-based plant feedback systems have been used for irrigation management of cotton and grain crops in the Texas High Plains region, producing yields that are similar or better than irrigation scheduling using the neutron probe. However, there are limited studies using plant feedback systems to actively scheduling irrigations for corn. In this 2-year study, a drought tolerant and a conventional hybrid were managed under a variable rate center pivot irrigation system. The main treatments were manual and plant feedback irrigation scheduling based on weekly neutron probe readings and an integrated crop water stress index (CWSI), respectively. In each main treatment, three irrigation treatment levels were established. Crop responses were compared between irrigation methods and levels. Results demonstrated that overall grain and biomass yields and grain WUE for the plant feedback-control plots were similar to those from the manual-control plots for both years. These results indicate that a plant feedback system using a CWSI could be used to manage corn in a semi-arid region and over a large-sized field. The plant feedback system could provide convenience and time savings to farmers who manage multiple center pivot fields.

Evaluation of FAOAqua Crop model for wheat under different irrigation regimes

The experiment was conducted at the research farm of the Water Technology Centre, IARI, New Delhi during rabi seasons of 2010-11and 2011-12. Irrigation treatments include irrigation applied at 50% deficit (W1) and 25 % deficit (W2) and full irrigation (W3) under recommended fertilization levels with split doses of N-fertilizer. Fullirrigation treatment was based on irrigations to meet the soil moisture deficit up to the field capacity (FC) level and deficit irrigation treatments of 25% and 50% were imposed with respect to the full irrigation.The model was calibrated with experiment generated data sets of rabi 2010-11 and validated using the data set of rabi 2011-12. It was observed that the validated model performed well for grain yield prediction with absolute prediction error of 2.9%, 0.91% and 7.85% for full, 25% deficit and 50% deficit irrigation levels, respectively. Also, for prediction of biomass yield the prediction error ranged from 11.81% to 28.96% for all three irrigation treatments. Moreover, the validated model was observed to predict the water productivity with absolute prediction errors of 43.57%, 13.87% and 12.8% for full, 25% deficit and 50% deficit irrigation treatment levels, respectively. Nonetheless, it was observed from this study that the AquaCrop model can be used to simulate the grain and biomass yield for wheat crop with acceptable accuracy under different irrigation regimes in a semi-arid enviroment.

Dynamic prescription maps for site-specific variable rate irrigation of cotton

A prescription map is a set of instructions that controls a variable rate irrigation (VRI) system. These maps, which may be based on prior yield, soil texture, topography, or soil electrical conductivity data, are often manually applied at the beginning of an irrigation season and remain static. The problem with static prescription maps is that they ignore spatiotemporal changes in crop water status. In a two-year study (2012 and 2013), a plant feedback system, including a wireless sensor network of infrared thermometers (IRTs), was used to develop dynamic prescription maps to accomplish adaptive irrigation scheduling for cotton (Gossypium hirsutum L.). One-half of a center pivot field was divided into manually and plant feedback-controlled irrigation treatment plots. Irrigation treatments were at three levels, 75, 50 and 25 percent of full as defined by either replenishment of crop water use to field capacity or by the equivalent threshold of the IRT sensed crop water stress. The system accepted user input to control irrigation for the manual treatment plots (I75M, I50M, and I25M), and calculated and compared a thermal stress index for each plant feedback-controlled treatment plot (I75C, I50C and I25C) with a pre-determined threshold for automated irrigation scheduling. The effectiveness of the plant feedback irrigation scheduling system was evaluated by comparing measured lint yield, crop water use (ETc), and water use efficiency (WUE) with the manually scheduled treatment plots. Results for both years indicated that average lint yields were similar between the manual and plant feedback-control plots at the I75 level (181 and 182gm−2, respectively, in 2012; 115 and 103gm−2, respectively, in 2013) and I50 level (146 and 164gm−2, respectively, in 2012; 95 and 117gm−2, respectively, in 2013). At the I25 level, average lint yield was significantly greater for the plant feedback-compared with the manual-control treatment plots (142gm−2 and 92gm−2, respectively), but the mean amount of irrigation was twice that of the manual-control plots. Mean water use efficiencies (WUE) within the same irrigation treatment levels were similar between methods. Importantly, the automatic plant feedback system did not require the time consuming and expensive manual reading of neutron probe access tubes that was required to schedule the manual treatments. These results demonstrate that the integration of a plant feedback system with a commercial VRI system could be used to control site-specific irrigation management for cotton at higher irrigation treatment levels, i.e., I75 percent and I50 percent of full. Such a system can facilitate the use of a VRI system by automating prescription map coding and providing dynamic irrigation control instructions to meet variable crop water needs throughout the irrigation season. As of yet, further research is required to maintain automatic deficit irrigation at a level equivalent to 25 percent replenishment of crop water use relative to field capacity.

Assessment of drip and flood irrigation on biomass production, nutrient content and water use efficiency of maize (Zea mays L.)

An experiment was conducted in wooden boxes to assess flood, surface and sub-surface drip irrigation on biomass production, nutrient content and water use efficiency of maize (Zea mays L.). Four levels of irrigation treatments were applied: (i) SD1 = Drip irrigation pipe was set up on the surface of the soil ; (ii) SSD2 = Drip irrigation pipe was buried up to 5 cm depth; (iii) SSD3 = Drip irrigation pipe was buried up to 7.5 cm depth and (iv) FI = Flood irrigation was practiced without any drip irrigation pipe. Leaf area, leaf area index and biomass production of maize were significantly (p &lt; 0.05) higher in SSD3 than SSD2 and FI treatments. Biomass production was 37.2, 41.1, 54.2 and 35.2 g in SD1, SSD2, SSD3 and FI treatments, respectively. Water use efficiency (WUE) was also significantly (p &lt; 0.05) higher in surface and sub-surface drip irrigation than flood irrigation. Values for WUEs were 0.248, 0.298, 0.430 and 0.156 kg/m3 in SD1, SSD2, SSD3 and FI treatments, respectively. As a result, all three drip irrigation treatments enhanced water use efficiencies than flood irrigation. Comparing the three drip irrigation treatments, significantly (p &lt; 0.05) higher nitrogen was found both in leaf and stem (3.3 and 3.8%) in sub-surface drip irrigation at 7.5 cm depth than flood irrigation (2.2 and 1.4%). Although, potassium contents in leaf and stem were not significantly different between the treatments, but had a tendency to be higher in drip irrigation treatments. Above all, drip irrigation performed better with higher water use efficiency.&#x0D; Dhaka Univ. J. Biol. Sci. 22(1): 47-54, 2013 (January)

Grain Sorghum Response to Irrigation Scheduling with the Time-Temperature Threshold Method and Deficit Irrigation Levels

Studies using the time-temperature threshold (TTT) method for irrigation scheduling have been documented for cotton, corn, and soybean. However, there are limited studies of irrigation management of grain sorghum (Sorghum bicolor, L.) with this plant-feedback system. In this two-year study, the TTT method was investigated as an automatic irrigation control algorithm for a late-maturing grain sorghum hybrid (Pioneer 84G62) grown in 2009 and an early maturing hybrid (Moench, NC+ 5C35) grown in 2010. The method was evaluated by comparing grain sorghum responses of biomass and dry grain yields, crop evapotranspiration (ETc), water use efficiency (WUE), and irrigation water use efficiency (IWUE) between automatic and manual control methods of irrigation scheduling at different deficit irrigation treatments (i.e., 80%, 55%, 30%, and 0% of full replenishment of soil water depletion to 1.5 m depth). Irrigation scheduling using the TTT method produced mean response variables of yield (biomass and grain), WUE, and IWUE that were similar or better than those from the manually scheduled method in both years. Water use efficiency was highest at the 80% and 55% levels in 2009 and 2010, respectively. Average IWUE was highest at the 55% level in 2009 and at the 30% level in 2010. For both of these responses, differences among irrigation treatment levels were not always significant. Crop production functions were curvilinear in both years as dry grain yields began to plateau between water application amounts delivered from irrigation treatments at the 55% and 80% levels. Results from this study indicate that both late and early maturing hybrids of grain sorghum are responsive to the TTT method of irrigation scheduling. Irrigation management with this algorithm can produce biomass and dry grain yields, ETc, WUE, and IWUE levels that are similar to those achieved with an accurate irrigation scheduling method based on direct soil water measurement.

Development of crop water stress index of wheat crop for scheduling irrigation using infrared thermometry

This study was conducted to develop the relationship between canopy–air temperature difference and vapour pressure deficit for no stress condition of wheat crop (baseline equations), which was used to quantify crop water stress index (CWSI) to schedule irrigation in winter wheat crop ( Triticum aestivum L.). The randomized block design (RBD) was used to design the experimental layout with five levels of irrigation treatments based on the percentage depletion of available soil water (ASW) in the root zone. The maximum allowable depletion (MAD) of the available soil water (ASW) of 10, 40 and 60 per cent, fully wetted (no stress) and no irrigation (fully stressed) were maintained in the crop experiments. The lower (non-stressed) and upper (fully stressed) baselines were determined empirically from the canopy and ambient air temperature data obtained using infrared thermometry and vapour pressure deficit (VPD) under fully watered and maximum water stress crop, respectively. The canopy–air temperature difference and VPD resulted linear relationships and the slope ( m) and intercept ( c) for lower baseline of pre-heading and post-heading stages of wheat crop were found m = −1.7466, c = −1.2646 and m = −1.1141, c = −2.0827, respectively. The CWSI was determined by using the developed empirical equations for three irrigation schedules of different MAD of ASW. The established CWSI values can be used for monitoring plant water status and planning irrigation scheduling for wheat crop.

Tree Irrigation Levels for Optimum Chemical and Sensory Properties of Olive Oil

A comparative study was conducted to evaluate the influence of seven different levels of irrigation applied to `Arbequina I-18' olive (Olea europaea L.) trees grown in a super-high-density orchard (1,656 trees/ha) in the Sacramento Valley of California. Water was applied differentially by drip irrigation at rates of 15%, 25%, 40%, 57%, 71%, 89%, and 107% evapotranspiration (ETc) in 2002, and 28%, 33%, 55%, 74%, 93%, 117%, and 140% ETc in 2003. Each treatment was replicated three times. Olives were harvested on two different dates each year from each of 21 plots. Three of four harvest dates showed a decrease in maturity index with increasing irrigation levels. Oils were made from olive samples collected from each plot and analyzed for oil quality parameters. Total polyphenol levels and oxidative stability decreased as the trees received more water, especially for the three lowest irrigation treatment levels in 2002, but few differences were noted between treatments in 2003 when all the trees were irrigated more heavily. Average oxidative stability was correlated very closely with total polyphenol content with r2 = 0.98 in 2002 and 0.94 in 2003. In 2002, free fatty acid levels increased and peroxide levels were unchanged, but in 2003, free fatty acid levels were unchanged and peroxide levels decreased in treatments receiving more water. Saturated fatty acids did not significantly change in 2002, due to tree irrigation level. The mono-unsaturated fatty acid levels and oleic–linoleic relationship declined while poly-unsaturated fatty acid levels increased in 2002 with increased irrigation. In 2003, there was no notable difference in the ratio of mono to poly unsaturated fatty acid levels. The individual fatty acid most consistently affected by more irrigation water was stearic, which decreased in both years. Total sterol content (mg·kg–1), percentages of cholesterol and erythrodiol were significantly influenced by tree irrigation levels, but increased in one year and either decreased or were unchanged the next. Oil sensory properties of fruitiness, bitterness, and pungency all declined in oils made from trees receiving more water. The lowest irrigation levels produced oils that were characterized by excessive bitterness, very high pungency, and woody, herbaceous flavors. Intermediate irrigation levels (33% to 40% ETc) produced oils with balance, complexity, and characteristic artichoke, grass, green apple, and some ripe fruit flavors. Higher irrigation levels lowered oil extractability and produced relatively bland oils with significantly less fruitiness and almost no bitterness or pungency.

Effect of Soil Moisture on Relative Leaf Water Content, Chlorophyll, Proline and Sugar Accumulation in Wheat

The responses of four wheat (Triticum aestivum L.) varieties to soil moisture were determined by measuring plant parameters such as relative leaf water content (RLWC) and the chlorophyll, proline and sugar contents of the leaf over two seasons. Two levels of irrigation treatments were adopted: irrigated and rainfed. The rainfed plants had consistently higher amounts of proline and sugar but lower RLWC and chlorophyll content. As drought intensified, differences between the irrigated and the rainfed plants with respect to all of these characters increased. The RLWC values of the irrigated plants were significantly higher in the morning but lower values were found at noon, showing some recovery in the afternoon.

Growth and Adaptation of Soybean Cultivars under Water Stress Conditions. III. Yield response and dry matter production.

Yield and dry matter production were examined under water-stress conditions. Two cultivars (Zhengzhuta 2 and Heinong 33) were grown in a concrete-framed field. From the flowering to the pod-filling stage, four levels of irrigation treatments were carried out (Treatment I, II, III and IV-from the severst, Treatment I to the non water stressed, Treatment IV). The growing periods were shorter with increasing amount of irrigation. Zhengzhuta 2 had larger shoot dry weight than Heinong 33 in every irrigation treatment. Dry weight of each organ tended to increase with increasing amount of irrigation during the treatment. Shoot dry weight ceased to increase in Treatment IV, but increased in the other treatments after the treatment. Percentage dry weight were higher in leaf and root of Zhengzhuta 2, and in pod of Heinong 33. Crop growth rates (CGRs), leaf area indices (LAIs), net assimilation rates (NARs) and pod growth rates (PGRs) were generally higher with increasing irrigation for both cultivars. CGR was closely related to LAI during the treatment. Pod, seed number and seed yield were greater in the plots with greater amount of irrigation. Zhengzhuta 2 had 540O kg ha-1 in Treatment IV. It's high-yielding potential seemed to be related to it's efficient leaf epansion and radiation interception ability.

Crop Water Stress Index Models for Bermudagrass Turf: A Comparison

AbstractA field study assessed the accuracy and consistency of crop water stress index (CWSI) estimates determined by two empirical models and one theoretical model for evaluation of bermudagrass [Cynodon dactylon (L.) Pers. cv. Midiron] water status. The simplest empirical model, describing canopy temperature minus air temperature (Tc — Ta) of well‐watered turf as a linear function of air vapor pressure deficit, was inadequate for estimating CWSI, since seasonal averages of CWSI for well‐watered, moderately stressed, and stressed turf had corresponding coefficients of variation of 1170, 160, and 86, respectively. The CWSI values were also highly influenced by net radiation, as indicated by coefficients of determination for regressions of calculated CWSI on net radiation of 0.68, 0.76, and 0.33 for the three levels of irrigation treatments, respectively. The second empirical model included net radiation in the regression analysis of of Tc — Ta. The inclusion of net radiation in the equation for the unstressed baseline increased the coefficient of determination from 0.76 to 0.90 as compared with Model 1. The coefficient of determination for the upper baseline (which included net radiation) was 0.872, indicating a strong dependency of CWSI on net radiation. The theoretical CWSI model yielded the most accurate estimates of turfgrass water stress, as indicated by coefficients of variation for seasonal averages of CWSI for well‐watered, moderately stressed, and stressed turf of 76, 3, and 86, respectively. Midday estimates of CWSI were related to percent available extractable water, with coefficients of determination for a regression of midday CWSI on percent available extractable water of 0.988, 0.989, and 0.991 for the empirical, modified empirical, and theoretical models, respectively. The theoretical CWSI appears to be the most promising approach for a turfgrass crop water stress index for irrigation scheduling.