Cotton Water Use Efficiency Research Articles

Combined application of biochar and partial root-zone drying irrigation improves water relations and water use efficiency of cotton plants under salt stress

Reduced irrigation in combination with biochar application can improve stomatal anatomy, water relations and intrinsic water use efficiency (WUEi), thus having a positive effect on the alleviation of salinity and drought stresses. A split-root pot experiment was executed to explore the effects of two biochar applications (WSP: wheat straw biochar; SWP: soft wood biochar) in combination with three irrigation strategies (FI: full irrigation; DI: deficit irrigation, PRD: partial root-zone drying irrigation) on stomatal anatomy, water relations and WUEi of cotton plants under normal soil (S0, EC=0.36 dS m-1) and saline soil (S1, EC=16.55 dS m-1). The results revealed that both salinity and drought stresses negatively affected plant water relations and reduced stomatal conductance, carbon isotope discrimination (Δ13C), stomatal size (SS) and hydraulic conductance (Kl) while increased leaf abscisic acid (ABA) concentration ([ABA]leaf). However, biochar amendment under salt stress significantly decreased [ABA]leaf while improved leaf water relations, increased Kl, stomatal density (SD), SS, Δ13C and maximum stomatal conductance (gsmax). Meanwhile, compared with FI and DI, PRD plants had greater SD, gsmax, and WUEi but lowered stomatal conductance (gs). Among all treatments, the combined application of WSP and PRD significantly increased SD and gsmax, improved leaf water relations, Kl and [ABA]leaf and WUEi. It is concluded that the altered stomatal features caused by the biochar and irrigation treatments are associated with changes in [ABA]leaf and Kl, and have a major role in affecting plant hydraulic integrity and water use efficiency of cotton exposed to salinity stress.

Growth and Yield Response and Water Use Efficiency of Cotton under Film-Mulched Drip Irrigation to Magnetized Ionized Water and Bacillus subtilis in Saline Soil in Xinjiang

In irrigated agriculture, the combination of multiple regulation measures is an effective method to improve saline soil and promote crop growth. Magnetized ionized water irrigation is considered a promising irrigation water activation technique, while the use of Bacillus subtilis for soil amelioration is environmentally friendly. In this study, magnetized ionized water irrigation and B. subtilis were used to promote cotton growth under film-mulched drip irrigation (FMDI) in saline soil. A two-year field experiment was conducted to investigate the effects of differing B. subtilis amounts under two irrigation water types (non-magnetized-ionized water (NMIW) and magnetized ionized water (MIW)) on the growth (plant height, leaf area index, shoot dry matter and chlorophyll content) and the yield of cotton, as well as the soil water content, salts accumulation, water use efficiency (WUE) and irrigation water use efficiency (IWUE) under FMDI in a saline soil in southern Xinjiang. Five amounts of B. subtilis (0, 15, 30, 45 and 60 kg ha−1) under NMIW (designated as B0, B1, B2, B3 and B4) and MIW (designated as M, MB1, MB2, MB3 and MB4) were applied to the field experiments. The results showed that MIW and B. subtilis increased soil water content and reduced salts accumulation in the 0–40 cm soil layers compared with B0. Moreover, the two measures significantly (p < 0.01) increased cotton plant height, leaf area index, shoot dry matter and chlorophyll content compared with B0. Seed cotton yield, WUE and IWUE were also observed to significantly increase (p < 0.05). Compared with the NMIW treatments, the MIW treatments increased seed cotton yield by 2.1–12.2%, increased WUE by 0.2–9.0%, and increased IWUE by 2.1–12.2%. Under MIW, with the B. subtilis amount as an independent variable, quadratic function relationships with seed cotton yield, WUE and IWUE were established. By taking the first derivative of the quadratic function, the highest seed cotton yield, WUE and IWUE were obtained with the B. subtilis amounts of 51.8, 55.0 and 51.4 kg ha−1, respectively. Based on comprehensive consideration of seed cotton yield, WUE, IWUE and salts accumulation in soil, 51.4 kg ha−1 of B. subtilis under MIW treatment is recommended for cotton cultivated under FMDI in a saline soil of southern Xinjiang, China.

Application of UAV Remote Sensing in Monitoring Water Use Efficiency and Biomass of Cotton Plants Adjacent to Shelterbelt.

Tree shelterbelts are crucial for maintaining the ecological environment of oasis, but they may also compete for soil water with adjacent crops, affecting crop yields. To evaluate the impacts of the shelterbelt on water use efficiency (WUE) and normalized water productivity (WP) of adjacent cotton plants, the biomass (B) and WUE of cotton with different distances from the shelterbelt (0.1H, 0.5H, 1H, 2H, and 3H; average tree height = 15 m [H]) were estimated based on unmanned aerial vehicle (UAV) remote sensing data combined with the FAO crop water response model AquaCrop. Besides, the accuracy and universality of the estimation method were also evaluated. The results showed that the method based on UAV remote sensing data and AquaCrop can accurately estimate the impact range and intensity of shelterbelt on WUE, water consumption, and B of adjacent cotton plants. Fierce water competition between shelterbelt and cotton was detected within 0.1H−1H, and the competitiveness of the shelterbelt was weaker in the plots >1H than in the 0.1H−1H. The B, actual evapotranspiration (Tc), and WUE of cotton at 0.1H decreased by 59.3, 48.8, and 23.6%, respectively, compared with those at 3H, but the cotton plants at 2H and 3H were completely unaffected by the shelterbelt. Besides, the B estimated based on WP (root mean square error [RMSE] = 108 g/m2, d = 0.89) was more accurate than that estimated based on WUE (RMSE = 118 g/m2, d = 0.85). This study clarifies the inter-species competition for soil water between crops and shelterbelts under drip irrigation in oases in China.

Magnetic Water Treatment: An Eco-Friendly Irrigation Alternative to Alleviate Salt Stress of Brackish Water in Seed Germination and Early Seedling Growth of Cotton (Gossypium hirsutum L.).

Magnetized water has been a promising approach to improve crop productivity but the conditions for its effectiveness remain contradictory and inconclusive. The objective of this research was to understand the influences of different magnetized water with varying quality on seed absorption, germination, and early growth of cotton. To this end, a series of experiments involving the seed soaking process, germination test, and pot experiment were carried out to study the effects of different qualities (fresh and brackish water) of magnetized water on seed water absorption, germination, seedling growth, photosynthetic characteristics, and biomass of cotton in 2018. The results showed that the maximum relative water absorption of magnetized fresh and magnetized brackish water relatively increased by 16.76% and 19.75%, respectively, and the magnetic effect time of brackish water was longer than fresh water. The relative promotion effect of magnetized brackish water on cotton seed germination and growth potential was greater than magnetized fresh water. The cotton seeds germination rate under magnetized fresh and magnetized brackish water irrigation relatively increased by 13.14% and 41.86%, respectively, and the relative promoting effect of magnetized brackish water on the vitality indexes and the morphological indexes of cotton seedlings was greater than magnetized fresh water. Unlike non-magnetized water, the net photosynthetic rate (Pn), transpiration rate (Tr), and instantaneous water use efficiency (iWUE) of cotton irrigated with magnetized water increased significantly, while the stomatal limit value (Ls) decreased. The influences of photosynthesis and water use efficiency of cotton under magnetized brackish water were greater than magnetized fresh water. Magnetized fresh water had no significant effect on biomass proportional distribution of cotton but magnetized brackish water irrigation markedly improved the root-to-stem ratio of cotton within a 35.72% range. Therefore, the magnetization of brackish water does improve the growth characteristics of cotton seedlings, and the biological effect of magnetized brackish water is more significant than that of fresh water. It is suggested that magnetized brackish water can be used to irrigate cotton seedlings when freshwater resources are insufficient.

Optimizing Irrigation Strategies to Improve Water Use Efficiency of Cotton in Northwest China Using RZWQM2

Irrigated cotton (Gossypium hirsutum L.) is produced mainly in Northwest China, where groundwater is heavily used. To alleviate water scarcity and increase regional economic benefits, a four-year (2016–2019) field experiment was conducted in Qira Oasis, Xingjiang Province, to evaluate irrigation water use efficiency (IWUE) in cotton production using the Root Zone Water Quality Model (RZWQM2), that was calibrated and validated using volumetric soil water content (θ), soil temperature (Tsoil°) and plant transpiration (T), along with cotton growth and yield data collected from full and deficit irrigation experimental plots managed with a newly developed Decision Support System for Irrigation Scheduling (DSSIS). In the validation phase, RZWQM2 adequately simulated (S) topsoil θ and Tsoil°, as well as cotton growth (average index of agreement (IOA) > 0.76). Relative root mean squared error (RRMSE) and percent bias (PBIAS) of cotton seed yield were 8% and 2.5%, respectively, during calibration, and 20% and −10.3% during validation. The cotton crop’s (M) T was well S (−18% < PBIAS < 14% and IOA > 0.95) for both full and deficit irrigation fields. The validated RZWQM2 model was subsequently run with seven irrigation scenarios with 850 to 350 mm water (Irr850, Irr750, Irr700, Irr650, Irr550, Irr450, and Irr350) and long-term (1990–2019) weather data to determine the best IWUE. Simulation results showed that the Irr650 treatment generated the greatest cotton seed yield (4.09 Mg ha−1) and net income (US $3165 ha−1), while the Irr550 treatment achieved the greatest IWUE (6.53 kg ha−1 mm−1) and net water production (0.94 $ m−3). These results provided farmers guidelines to adopt deficit irrigation strategies.

Mulch Application and Plant Spacing Influence on Growth Traits, Pests, Insects and Weeds in Cotton (Gossypium hirsutum L.) Varieties

Mulch Application and Plant Spacing Influence on Growth Traits, Pests, Insects and Weeds in Cotton (Gossypium hirsutum L.) Varieties

Irrigation-Water Management and Productivity of Cotton: A Review

A decrease in water resources, as well as changing environmental conditions, calls for efficient irrigation-water management in cotton-production systems. Cotton (Gossypium sp.) is an important cash crop in many countries, and it is used more than any other fiber in the world. With water shortages occurring more frequently nowadays, researchers have developed many approaches for irrigation-water management to optimize yield and water-use efficiency. This review covers different irrigation methods and their effects on cotton yield. The review first considers the cotton crop coefficient (Kc) and shows that the FAO-56 values are not appropriate for all regions, hence local Kc values need to be determined. Second, cotton water use and evapotranspiration are reviewed. Cotton is sensitive to limited water, especially during the flowering stage, and irrigation scheduling should match the crop evapotranspiration. Water use depends upon location, climatic conditions, and irrigation methods and regimes. Third, cotton water-use efficiency is reviewed, and it varies widely depending upon location, irrigation method, and cotton variety. Fourth, the effect of different irrigation methods on cotton yield and yield components is reviewed. Although yields and physiological measurements, such as photosynthetic rate, usually decrease with water stress for most crops, cotton has proven to be drought resistant and deficit irrigation can serve as an effective management practice. Fifth, the effect of plant density on cotton yield and yield components is reviewed. Yield is decreased at high and low plant populations, and an optimum population must be determined for each location. Finally, the timing of irrigation termination (IT) is reviewed. Early IT can conserve water but may not result in maximum yields, while late IT can induce yield losses due to increased damage from pests. Extra water applied with late IT may adversely affect the yield and its quality and eventually compromise the profitability of the cotton production system. The optimum time for IT needs to be determined for each geographic location. The review compiles water-management studies dealing with cotton production in different parts of the world, and it provides information for sustainable cotton production.

The Effects of Different Irrigation Scheduling Approaches on Seed Yield and Water Use Efficiencies of Cotton

This study was conducted in the Aegean region conditions of Turkey in 2020. It was carried out on May-505, a local cotton variety. The study examined the variation of seed yield, water use efficiency (WUE), and irrigation water use efficiency (IWUE) of cotton with different irrigation programs and water levels. The field trial, which was designed as two factors and three replications, was designed according to the randomized complete block trial design. Four different irrigation levels (IL) (100%, 67%, 33%, and 0%) and two different irrigation scheduling approaches (gravimetric and pan evaporation) were investigated in the study. Seasonal water use values in treatments varied between 215 (0%) and 746 (100% - Pan evaporation approach) mm during the production period. The average yield values obtained with irrigation levels, which have essential effects on cotton seed yield, are listed as follows; 2057 kg ha-1 (IL-0%), 3471 kg ha-1 (IL-33%), 3771 kg ha-1 (IL-67%), and 5083 kg ha-1 (IL-100%). It was determined pan evaporation applications performed higher yields than gravimetric applications. WUE values were between 0.63 – 1.04 kg m-3. The gravimetric method’s yield response factor (ky) was 0.73, and the pan evaporation method’s yield response factor (ky) was 0.89. These results show that cotton is tolerant of water stress. In conclusion, although the pan evaporation approach with 100% treatment is suggested for cotton production in the parts of the Aegean region within the semi-arid climate zone, while water resources are sufficient. When the results are evaluated in terms of seed cotton yield for a deficit irrigation strategy, IL-67% treatment with a gravimetric approach can be used.

Effects of deficit irrigation on cotton growth and water use efficiency: A review.

Cotton is one of the most important crops in the world. With the increasing scarce of global water resources, irrigation water will become a major limiting factor in cotton production. Deficit irrigation is an irrigation method which consumes less water than the normal evapotranspiration of crops. It is an effective water-saving method due to improved water use efficiency without sacrificing cotton yield and fiber quality. We summarized the effects of deficit irrigation on the growth and water use efficiency of cotton. The results showed that deficit irrigation promoted the transformation from vegetative growth to reproductive growth, reduced plant height, leaf area, and total biomass of cotton, and subsequently improved the harvest index, stem diameter and water use efficiency. Finally, based on the current research and combined with cotton production reality, the application and future development of deficit irrigation were proposed, which might provide theoretical guidance for the sustainable development of cotton plantation in arid areas.

The response of photosynthetic capacity and yield of cotton to various mulching practices under drip irrigation in Northwest China

Mulched drip irrigation is regarded as an effective water-saving irrigation technique that is adopted widely in dryland regions. However, due to the lack of efficient mulch film recovery, residual plastic film fragments accumulating in soil nowadays pose a risk to agricultural production sustainability. To mitigate the pollution result from polyethylene (PE) film mulching and demonstrate the relationship between soil microenvironment, photosynthetic capacity, yield, and water use efficiency of cotton (Gossypium hirsutum L.) in various mulching practices, a two-year field experiment was carried out to test five mulching practices (sprayable degradable film mulching; biodegradable transparent film with an 80-day induction period mulching; biodegradable transparent film with a 100-day induction period mulching; conventional transparent polyethylene film mulching; no film mulching) in Xinjiang, Northwest China. The results showed that mulching significantly increased soil water content and temperature by 23.83% and 15.01% (average on two years) in topsoil compared to the bare soil surface, associated with a higher plant height, leaf area index, photosynthetic rate and aboveground biomass accumulation. Soil moisture, temperature, and crop height all significantly influenced cotton leaf photosynthetic rate, and soil moisture had the most significant impact (the direct path coefficient was 0.450). The highest cotton yield and WUE were observed in PE film mulching (5480.59 kg ha−1 and 1.35 kg m−3, respectively, average on two years) and the biodegradable transparent film with a 100-day induction period was comparable with PE film in yield increased and reduction of water loss (yield and WUE was 5357.51 kg ha−1 and 1.29 kg m−3, respectively, average on two years). The sprayable biodegradable film also had good wetting and warming effects on soil, but notably, sprayable film performances were still weaker than that in solid films. Compared to solid degradable films mulching, soil moisture, soil temperature, photosynthetic rate, yield, and WUE in sprayable film mulching was decreased by 5.55%, 7.19%, 31.41%, 5.31%, and 8.58% on average, respectively. In general, biodegradable transparent film with a 100-day induction period could significantly improve soil water-heat status, enhance cotton development, reduce water evaporation, increase cotton yield and WUE, which provides a cotton-cultivation option to control residual PE fragments pollution and maintained cotton yield.

Applying plant-based irrigation scheduling to assess water use efficiency of cotton following a high-biomass rye cover crop

BackgroundThis study addressed the potential of combining a high biomass rye winter cover crop with predawn leaf water potential (ΨPD) irrigation thresholds to increase agricultural water use efficiency (WUE) in cotton. To this end, a study was conducted near Tifton, Georgia under a manually-controlled, variable-rate lateral irrigation system using a Scholander pressure chamber approach to measure leaf water potential and impose varying irrigation scheduling treatments during the growing season. ΨPD thresholds were − 0.4 MPa (T1), − 0.5 MPa (T2), and − 0.7 MPa (T3). A winter rye cover crop or conventional tillage were utilized for T1-T3 as well.ResultsReductions in irrigation of up to 10% were noted in this study for the driest threshold (− 0.7 MPa) with no reduction in lint yield relative to the − 0.4 MPa and − 0.5 MPa thresholds. Drier conditions during flowering (2014) limited plant growth and node production, hastened cutout, and decreased yield and WUE relative to 2015.ConclusionsWe conclude that ΨPD irrigation thresholds between − 0.5 MPa and − 0.7 MPa appear to be viable for use in a ΨPD scheduling system with adequate yield and WUE for cotton production in the southeastern U.S. Rye cover positively impacted water potential at certain points throughout the growing season but not yield or WUE indicating the potential for rye cover crops to improve water use efficiency should be tested under longer-term production scenarios.

The Effects of Biodegradable Mulch Film on the Growth, Yield, and Water Use Efficiency of Cotton and Maize in an Arid Region

Plastic residual film pollution in China is severe, and the use of degradable mulch film instead of plastic mulch can effectively alleviate this situation. The substitution of common polyethylene plastic mulch film with biodegradable mulch film in the agricultural production of cotton and maize in an arid region was investigated in the present study. Using bare soil as the control, we compared the effects of common polyethylene plastic film and biodegradable mulch film on crop growth, yield, and water use efficiency (WUE) in maize and cotton. The results indicated that: (1) the biodegradable mulch film in this region remained intact for 60 days after being laid down, significantly degrading after 120 days, and was associated with increased soil temperature, moisture conservation, and degradability in comparison to a bare soil control; (2) Both the biodegradable mulch film and the polyethylene plastic film significantly increased various physiological parameters, such as crop height, stalk diameter, and leaf area; (3) The biodegradable mulch film had a significant effect on crop yield by 69.4–76.2% and 65.2–71.9%, respectively, compared to the bare soil control. (4) Compared to the bare soil control, the biodegradable mulch film effectively increased WUE in the crops by 64.5–73.1%. In summary, biodegradable mulch film had comparable results to the common polyethylene plastic film in increasing crop growth, yield, and WUE. As the biodegradable mulch film causes no residual pollution, it is thus preferable to common plastic mulch film for agricultural applications in arid regions and supports the sustainable development of agroecosystems. Therefore, the use of degradable mulch films in agricultural production is more environmentally friendly and more conducive to the sustainable development of agricultural systems.

The combination of limited irrigation and high plant density optimizes canopy structure and improves the water use efficiency of cotton

Increasing plant density under insufficiency or deficit irrigation is considered a new water-saving technique in cotton production, especially in Xinjiang, China, an arid area with a short growing period. Increasing plant density reduces light intensity within the canopy; therefore, we hypothesized that resource use efficiency may be the main factor affecting cotton yield and water use efficiency under limited irrigation conditions. To test this hypothesis, 2-year field experiments were conducted to explore the effects of two irrigation patterns (I500, conventional irrigation; I425, limited irrigation) and three planting densities (D12, 12; D24, 24; D36, 36 plants m−2) on cotton yield, fiber quality, light interception rate, canopy photosynthesis and irrigation water use efficiency (IWUE). I425D36 raised yield and IWUE by 1.40–22.4% and 13.4–34.5%, respectively, but it did not affect fiber quality compared with other treatments. Further, I425D36 increased the leaf area index and the top- and middle-canopy light interception rates after 105 days after sowing, which improved the canopy apparent photosynthetic rate. Seed cotton yield was associated with leaf area index and the top- and bottom-canopy light interception rates. We conclude that irrigation of cotton with limited irrigation at a 425-mm level and a plant density at 36 plants m−2 had significant benefits in terms of economized irrigation without reducing yield in arid areas.

Presowing fertigation effects on soil moisture absorption and consumption of cotton in arid regions

To increase the yield and water-use efficiency of cotton in arid regions, irrigation and fertilizer management must be optimized. This study evaluated the effects of two irrigation levels (i.e., with (W80) and without (W0) presowing irrigation) combined with two basal fertilization methods (i.e., surface application (F10) and deep application (F30)) on soil water absorption and transport, and relationships with water-use efficiency. Our results showed significantly positive relationships between water-use efficiency and the root surface area in the 0–30 cm soil layer (RSA-30), root vigor in the 0–30 cm soil layer (RV-30), root vigor in the 60–80 cm soil layer (RV-80), the leaf transpiration rate, stomatal conductance, sap flow, and water productivity. Principal component analysis showed that the W80F10 treatment initially positively influenced RSA-30, RV-30, and RV-80 and that these parameters affected the leaf transpiration rate, stomatal conductance, sap flow, and leaf area (i.e., the main transpiration area), which finally influenced water productivity and water-use efficiency. In addition, the W80F10 treatment increased the ability of aerial parts to compete for water after 69 days after emergency. These findings indicate that the combination of presowing irrigation and basal fertilizer surface application can enhance the ability of aerial parts to compete for water and increase water-use efficiency by promoting water absorption and consumption after the full flowering stage. This research provides valuable information on agricultural management in aridregions.

Spatio-temporal variation of water requirement and meteorological impact factors of cotton in North Xinjiang, China.

Based on daily data of 25 meteorological stations in North Xinjiang during 1961-2013, the FAO Penman Monteith equation and crop coefficient method were used to estimate water requirements as well as irrigation water demands of cotton during all growth stages. The results suggested that cotton water requirement in each growth period had been decreasing in the past 53 years. Besides, crop water demand declined most significantly at the blossing and boll forming stage, with change rate of -0.15 mm·a-1. Furthermore, there were various multiscale cycle changes during the growth period. the water demand of crops in each growth period roughly changed as 'high low high' in the large periodic scale around 30 a and, as 'low high low' in the 15-17 a of the mesoscale cycle, but had no obvious cyclical characteristics on the interannual scale. Average crop water demands decreased roughly from west to east across North Xinjiang. The mutation results showed that the crop water demand decreased significantly in each growth period, especially in the northwest and southwest of North Xinjiang. In addition, cotton water demand was positively correlated with ave rage wind speed, sunshine hours and average temperature during each growth period, and negatively correlated with relative humidity. The results would provide basic data for timely quantitative irrigation and improving water use efficiency of cotton in North Xinjiang.

Rational Water and Nitrogen Management Improves Root Growth, Increases Yield and Maintains Water Use Efficiency of Cotton under Mulch Drip Irrigation.

There is a need to optimize water-nitrogen (N) applications to increase seed cotton yield and water use efficiency (WUE) under a mulch drip irrigation system. This study evaluated the effects of four water regimes [moderate drip irrigation from the third-leaf to the boll-opening stage (W1), deficit drip irrigation from the third-leaf to the flowering stage and sufficient drip irrigation thereafter (W2), pre-sowing and moderate drip irrigation from the third-leaf to the boll-opening stage (W3), pre-sowing and deficit drip irrigation from the third-leaf to the flowering stage and sufficient drip irrigation thereafter (W4)] and N fertilizer at a rate of 520 kg ha-1 in two dressing ratios [7:3 (N1), 2:8 (N2)] on cotton root morpho-physiological attributes, yield, WUE and the relationship between root distribution and dry matter production. Previous investigations have shown a strong correlation between root activity and water consumption in the 40–120 cm soil layer. The W3 and especially W4 treatments significantly increased root length density (RLD), root volume density (RVD), root mass density (RMD), and root activity in the 40–120 cm soil layer. Cotton RLD, RVD, RMD was decreased by 13.1, 13.3, and 20.8%, respectively, in N2 compared with N1 at 70 days after planting (DAP) in the 0–40 cm soil layer. However, root activity in the 40–120 cm soil layer at 140 DAP was 31.6% higher in N2 than that in N1. Total RMD, RLD and root activity in the 40–120 cm soil were significantly and positively correlated with shoot dry weight. RLD and root activity in the 40–120 cm soil layer was highest in the W4N2 treatments. Therefore increased water consumption in the deep soil layers resulted in increased shoot dry weight, seed cotton yield and WUE. Our data can be used to develop a water-N management strategy for optimal cotton yield and high WUE.

Effects of deficit irrigation and plant density on the growth, yield and fiber quality of irrigated cotton

Deficit irrigation is a new strategy to increase water use efficiency of cotton in arid areas, but it is not clear if it interacts with plant density. The objective of this study was to determine the effects of deficit irrigation and plant density as well as their interaction on the growth, yield and fiber quality of irrigated cotton. Two field experiments were conducted at three sites in 2013 and one site from 2014 to 2015 in an arid area of Xinjiang. A randomized complete block design with three replicates was used to determine the effects of 6 irrigation regimes on seedcotton yield in the first experiment, while a split-plot design was used in the second experiment with the main plots assigned to irrigation regime (saturation, regular and deficit) and the subplots to plant density (high, medium and low) to examine cotton yield, fiber quality and water productivity as affected by plant density under deficit irrigation. Averaged across the three sites, drip irrigation ranging from 3650 to 4700m3/ha did not significantly affect cotton yield, but seedcotton yield under 3650m3/ha in S1 was 6.3% lower than that under 4000m3/ha. Thus, it is quite appropriate to regularly drip-irrigate at 4000m3/ha in the experimental area. Deficit irrigation at high plant density also maintained a relatively higher leaf area index (LAI) and net assimilation rate (NAR), particularly at late stages of plant growth and development, than saturation or regular irrigation. Plant density ranging from 18 to 24 plants/m2 produced more seedcotton than 12 plants/m2 under regular irrigation. Increasing irrigation to saturation levels had little effects on cotton yield regardless of plant density; saturation irrigation at high plant density even reduced cotton yield compared with regular irrigation at medium plant density. Under deficit irrigation, the high plant density produced 9.1-17% greater yield and 9.3-16.8% higher irrigation water productivity (IWP) than low or medium plant density, and comparable yield to medium or high plant density under regular irrigation. This high yield under deficit irrigation at high plant density was due to increased plant biomass occasioned by high plant population and improved harvest index. Deficit irrigation did not affect fiber quality in 2014, but reduced fiber length and increased fiber micronaire value in 2015. Conclusively, use of high plant density under deficit irrigation can be a promising alternative for water saving without compromising cotton yield under arid conditions.

Effect of Super Absorbent Polymer and Irrigation Deficit on Water Use Efficiency, Growth and Yield of Cotton

Sustainable use of water resources in agriculture is a necessity for many arid countries. In order to investigate the effect of water deficit, irrigation after 120 (control), 155 (moderate water stress) and 190 mm (sever water stress) pan evaporation and super absorbent polymer rates (SAP) (0, 30, 60 and 90 kg ha-1) on growth, yield and water use efficiency of cotton, an experiment was conducted as split plot based on a randomized complete block design with three replications. Moreover, the effect of water quality (distilled water and solutions of 0.25, 0.5, 0.75, 1 and 1.25% NaCl) was investigated on water holding capacity by SAP. Results revealed that moderate water stress (irrigation intervals of aprox. 15 days) along with 60 kg ha-1 SAP application was the best treatment in terms of growth and yield indices of cotton. The results for plant height, plant dry weight, boll number per plant and fiber yield in this treatment were 16, 28, 42 and 10% higher than control treatment, respectively. Water deficit and SAP application improved the water use efficiency (WUE) of cotton. The amount of WUE in moderate water stress treatment along with consumption of 60 or 90 kg ha-1 SAP was 26% higher than for control treatment. In addition, water holding capacity by SAP in distilled water treatment was 7 times higher than in the case of 1.25% NaCl solution. The overall results showed that irrigation deficit and SAP application are two appropriate strategies for crop production in areas affected by drought stress, especially if low saline water sources are used.

Effect of Super Absorbent Polymer and Irrigation Deficit on Water Use Efficiency, Growth and Yield of Cotton

Sustainable use of water resources in agriculture is a necessity for many arid countries. In order to investigate the effect of water deficit, irrigation after 120 (control), 155 (moderate water stress) and 190 mm (sever water stress) pan evaporation and super absorbent polymer rates (SAP) (0, 30, 60 and 90 kg ha-1) on growth, yield and water use efficiency of cotton, an experiment was conducted as split plot based on a randomized complete block design with three replications. Moreover, the effect of water quality (distilled water and solutions of 0.25, 0.5, 0.75, 1 and 1.25% NaCl) was investigated on water holding capacity by SAP. Results revealed that moderate water stress (irrigation intervals of aprox. 15 days) along with 60 kg ha-1 SAP application was the best treatment in terms of growth and yield indices of cotton. The results for plant height, plant dry weight, boll number per plant and fiber yield in this treatment were 16, 28, 42 and 10% higher than control treatment, respectively. Water deficit and SAP application improved the water use efficiency (WUE) of cotton. The amount of WUE in moderate water stress treatment along with consumption of 60 or 90 kg ha-1 SAP was 26% higher than for control treatment. In addition, water holding capacity by SAP in distilled water treatment was 7 times higher than in the case of 1.25% NaCl solution. The overall results showed that irrigation deficit and SAP application are two appropriate strategies for crop production in areas affected by drought stress, especially if low saline water sources are used.

Effect of irrigation regime and method of strip irrigation system on yield, yield components and water use efficiency of cotton under drought stress conditions of Orzouiyeh region of Kerman province in Iran

Deficit irrigation is one of the most important methods of management of irrigation to save irrigation water without much damage to plants. Field experiment was conducted in 2010 to study the effect of irrigation deficit and method of irrigation on yield and yield components and water use efficiency of cotton in Orzouiyeh region of Kerman province of Iran. Treatments consisted of three levels of water requirement: 100, 80 and 60% as main factors and two systems of irrigation: surface drip irrigation and subsurface drip irrigation as sub factors. The study showed that under subsurface irrigation method treatment of 80% water requirement compared to treatment of 100% water requirement, there is increased water use efficiency by 4.9% with a saving of 1500 m3ha-1 water. However, 80% water treatment lead to decrease of 12% in yield, 11% in the number of bolls per plant and 2.5% in boll weight. The 60% water treatment saved 3200 m3ha-1 water (40% less consumption of water), but it resulted in a decrease of 38% in cotton yield, 37% in the number of bolls per plant and 24% in boll weight. In general use of 80% water deficit method in cotton cultivation using subsurface irrigation could help in saving of irrigation water and increasing water use efficiency under drought conditions prevailing in Orzouiyeh region of Kerman province of Iran. Key words: Cotton, irrigation deficit, irrigation strip, Kerman, water use efficiency, yield.