Increasing Irrigation Frequency Research Articles

Unveiling constraints and cultivating potential: Optimizing spring sugar beet yield through boundary line analysis

To enhance crop yields, narrowing the gap between actual and achievable yields is crucial. One approach involves identifying yield-limiting factors and their optimal levels. Boundary line analysis (BLA), a statistical method, quantifies yield response to environmental or managerial factors while accounting for variable factors. In 2020, a study surveyed 180 spring sugar beet farms in Iran. The findings revealed a 50.7 % yield gap (11.13 t ha−1) between farmers’ average sugar yield (10.84 t ha−1) and potential yield (21.97 t ha−1). BLA implicated low plant density, soil organic content, lack of potassium (K)-containing fertilizers, and non-adherence to crop rotation principles in 81.3 %, 75.5 %, 53.4 %, and 51.1 % of farms, respectively. Optimal levels were estimated at 9.5 plants m−1, 1.15 % soil organic content, 100 kg ha−1 K fertilization rate, and 5–9.8 as the rotation numerical value. Other limiting factors included time from cultivation to thinning and sowing date. The optimal minimum time between planting and thinning stood at 38 days, with the latest sowing date estimated at 94 Julian days (May 5). Achieving attainable yield necessitates limiting root exposure to 4.9 days, keeping disease damage below 15.3 %, and increasing irrigation frequency to over 10 times. In the short term, increasing plant density to optimal levels, promoting K fertilizer use, and adjusting thinning and sowing dates can significantly boost sugar yield per unit area.

Enhanced Cotton Yield and Fiber Quality by Optimizing Irrigation Amount and Frequency in Arid Areas of Northwest China

Optimizing irrigation strategies is crucial for sustaining cotton production in the face of growing water scarcity. The three-year experimental study (2020–2022) focused on the impact of varying irrigation amounts (320, 370, and 420 mm) and frequencies (4-, 8-, and 12-day intervals) on cotton growth, yield, yield components, and fiber quality in southern Xinjiang. Employing a completely randomized design with three replications, the results indicated higher irrigation amounts resulted in numerically 2.5–7.5% higher lint yields compared to those under medium and low irrigation amounts, notably significant in 2021. Boll density emerged as the primary yield component influencing yield loss due to irrigation amount, followed by seed cotton weight boll−1. Increased boll density was associated with a greater total number of fruiting sites. Additionally, the increased seed cotton weight boll−1 could be linked to an increased seed number boll−1 and a decreased boll fraction at the lower fruiting branches with lower seed cotton weight boll−1. Higher irrigation frequency improved lint yield by increasing boll density, though a significant effect was observed only in 2020. Increased irrigation amounts generally led to longer fiber lengths but lower micronaire values, while increased irrigation frequency resulted in longer, stronger fibers and reduced micronaire values. Furthermore, the highest yield stability was observed under the condition of high irrigation amount and high frequency. This study holds certain guiding significance for water resource management in cotton production in arid regions.

Effect of Irrigation Water Salinity on Soil Characteristics and Microbial Communities in Cotton Fields in Southern Xinjiang, China

Irrigation with saline water is a possible solution to alleviate freshwater shortages. The long-term use of saline water for irrigation requires consideration of the influence of salt on the environmental conditions of the soil. The objective of this field study was to determine the effects of three continuous years of saline water irrigation on physiochemical properties and microbial communities in drip-irrigated cotton fields. The three total dissolved solid (TDS) levels of irrigation water treatments were (i) 1 g L−1 (fresh water, FWI), (ii) 3 g L−1 (brackish water, BWI), and (iii) 7 g L−1 (salt water, SWI). After three years, the electrical conductivity (EC), sodium adsorption ratio (SAR), and contents of K+, Na+, Mg2+, Cl−, and SO42− in the SWI treatment were significantly higher than those in the FWI and BWI treatments, but there were no significant differences in EC and K+ between the FWI and BWI treatments. BWI treatment significantly increased microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), urease, and sucrase contents. The diversity and abundance of bacteria and fungi were not affected by saline water irrigation, but the microbial community structure was altered. Saline water irrigation resulted in an elevation in the bacterial abundance of the phylum Chloroflexi and a decline in Proteobacteria and Actinobacteria. For fungi, the abundance of the phylum Ascomycota in the BWI treatment was greater than that in the FWI and SWI treatments. Linear discriminant analysis effect size (NMDS) results indicated clear variation in the microbiota profiles between the FWI, BWI, and SWI treatments for bacteria. Regarding the fungal microbiota profiles, the BWI and SWI treatments had similar microbiota profiles but were different from the FWI treatment. The number of bacterial biomarkers gradually increased with increasing total dissolved solids of irrigation water, while the number of fungal biomarkers gradually decreased. Additionally, cotton yield was significantly and positively correlated with the observed species of fungi, while it was significantly and negatively correlated with EC. Redundancy analysis (RDA) showed that bacterial community structure was regulated by SAR and fungal community structure was regulated by soil salinity and bulk density (BD). Future research will need to look into how the structure of the microbial community and the associated functional microorganisms are gradually changing with increased irrigation frequency under saline irrigation, as well as explore and screen for advantageous functional microorganisms.

Do farmers' risk perception, adaptation strategies, and their determinants benefit towards climate change? Implications for agriculture sector of Punjab, Pakistan.

Due to global and regional climatic dynamics for a couple of decades, agricultural productivity, rural livelihood, and food security have been badly affected in Pakistan. This study was conducted in Punjab, Pakistan, to explore the farmers' understanding of the impacts of climate change, adaptation strategies, determinants, and benefits on agriculture using data from 1080 respondents. Perceived risks by the farmers in the rice-wheat cropping system and the cotton-wheat cropping system were weed infestation, seed rate augmented, low-quality seeds, infestation of crop diseases and pests, change of cropping pattern, increase of input use, decrease of cropping intensity and productivity, decreasing soil fertility, increasing irrigation frequency, and increase of harvesting time. To alleviate the adverse influences of climate change, the adaptation strategies used by farmers were management of crop and variety, soil and irrigation water, diversification of agriculture production systems and livelihood sources, management of fertilizer and farm operations time, spatial adaptation, access to risk reduction measures and financial assets, adoption of new technologies, institutional support, and indigenous knowledge. Moreover, the results of Binary Logistic Regression indicate that adaptation strategies are affected by different factors like age, education, household family size, off-farm income, remittances, credit access, information on climatic and natural hazards, information on weather forecasting, land acreage, the experience of growing crops and rearing of livestock, tenancy status, tube well ownership, livestock inventory, access to market information, agricultural extension services, and distance from agricultural input/output market. There is a significant difference between adapters and nonadapters. The risk management system may be created to protect crops against failures caused by extreme weather events. There is a need to develop crop varieties that are both high yielding and resistant to climate change. Moreover, cropping patterns should be revised to combat the effects of climate change. To enhance farmers' standard of living, it is necessary to provide adequate extension services and a more significant number of investment facilities. These measures will assist farmers in maintaining their standard of living and food security over the long term to adapt to the effects of climate change based on various cropping zones.

Amplitude and frequency of wetting and drying cycles drive N2 and N2O emissions from a subtropical pasture

This study investigated the effects of irrigation frequency on N2 and N2O emissions from an intensively managed pasture in the subtropics. Irrigation volumes were estimated to replace evapotranspiration and were applied either once (low frequency) or split into four applications (high frequency). To test for legacy effects, a large rainfall event was simulated at the end of the experiment. Over 15 days, 7.9 ± 2.7 kg N2 + N2O-N ha−1 was emitted on average regardless of irrigation frequency, with N2O accounting for 25% of overall N2 + N2O. Repeated, small amounts of irrigation produced an equal amount of N2 + N2O losses as a single, large irrigation event. The increase in N2O emissions after the large rainfall event was smaller in the high-frequency treatment, shifting the N2O/(N2O + N2) ratio towards N2, indicating a treatment legacy effect. Cumulative losses of N2O and N2 did not differ between treatments, but higher CO2 emissions were observed in the high-frequency treatment. Our results suggest that the increase in microbial activity and related O2 consumption in response to small and repeated wetting events can offset the effects of increased soil gas diffusivity on denitrification, explaining the lack of treatment effect on cumulative N2O and N2 emissions and the abundance of N cycling marker genes. The observed legacy effect may be linked to increased mineralisation and subsequent increased dissolved organic carbon availability, suggesting that increased irrigation frequency can reduce the environmental impact (N2O), but not overall magnitude of N2O and N2 emissions from intensively managed pastures.

Water use efficiency of green gram (Vigna radiata L.) impacted by paddy straw mulch and irrigation regimes in north-western India

A multilocation field experiment was conducted at Students’ Research Farm, Department of Agronomy, Punjab Agricultural University (PAU), Ludhiana and PAU, Regional Research Station (RRS), Bathinda, during summer 2019. The experiment was conducted in RCBD with 15 treatment combinations with 3 replications. The treatments comprised of 3 mulch levels i.e., M0, M6, and M12 i.e., no mulch, 6 and 12 t ha−1, respectively, and 5 irrigation schedules i.e., I10, I20, I30, and I40 with 10%, 20%, 30% and 40% depletion of available soil water (ASW), respectively, and IR (PAU recommendation as 4 irrigations). The growth parameters (plant height, dry matter accumulation and leaf area index), yield attributing characters namely pods per plant, number of seeds per pod and thousand-grain weight, seed and straw yield were significantly higher in M12 than M6 and no mulch (M0). The growth parameters, yield attributes, seed and straw yield were significantly higher for I10 due to increased irrigation frequency (5–6 irrigations). Both M0I10 (seven irrigations without mulch) and M6I30 (3 irrigations with straw mulch (6 t ha−1)) treatments observed comparable seed yield (1.06 t ha−1). Therefore, the substantial increase in seed yield with lower crop water use with the usage of straw mulch saves a considerable amount of water. Subsequently, the use of 6 t ha−1 of straw mulch with 3 irrigations (30% depletion from available soil water) facilitated a higher seed yield. The crop water use (CWU) was highest for M0 as due to bare soil, resulted in more evapotranspiration. The bio-physical productivity (BPWP) and water use efficiency was found to be maximum for mulch treatments. The I10 reported maximum CWU, whereas, Bio-physical water productivity (BPWP) were higher for I40 treatment where only one irrigation was given in this treatment. The WUE was maximum in I30 treatment at Ludhiana and in I20 at Bathinda location.

Hybrid Bermudagrass and Tall Fescue Turfgrass Irrigation in Central California: II. Assessment of NDVI, CWSI, and Canopy Temperature Dynamics

As the drought conditions persist in California and water continues to become less available, the development of methods to reduce water inputs is extremely important. Therefore, improving irrigation water use efficiency and developing water conservation strategies is crucial for maintaining urban green infrastructure. This two-year field irrigation project (2018–2019) focused on the application of optical and thermal remote sensing for turfgrass irrigation management in central California. We monitored the response of hybrid bermudagrass and tall fescue to varying irrigation treatments, including irrigation levels (percentages of reference evapotranspiration, ETo) and irrigation frequency. The ground-based remote sensing data included NDVI and canopy temperature, which was subsequently used to calculate the crop water stress index (CWSI). The measurements were done within two hours of solar noon under cloud-free conditions. The NDVI and canopy temperature data were collected 21 times in 2018 and 10 times in 2019. For the tall fescue, a strong relationship was observed between NDVI and visual rating (VR) values in both 2018 (r = 0.92) and 2019 (r = 0.83). For the hybrid bermudagrass, there was no correlation in 2018 and a moderate correlation (r = 0.72) in 2019. There was a moderate correlation of 0.64 and 0.88 in 2018 and 2019 between tall fescue canopy minus air temperature difference (dt) and vapor pressure deficit (VPD) for the lower CWSI baseline. The correlation between hybrid bermudagrass dt and VPD for the lower baseline was 0.69 in 2018 and 0.64 in 2019. Irrigation levels significantly impacted tall fescue canopy temperature but showed no significant effect on hybrid bermudagrass canopy temperature. For the same irrigation levels, increasing irrigation frequency slightly but consistently decreased canopy temperature without compromising the turfgrass quality. The empirical CWSI values violated the minimum expected value (of 0) 38% of the time. Our results suggest NDVI thresholds of 0.6–0.65 for tall fescue and 0.5 for hybrid bermudagrass to maintain acceptable quality in the central California region. Further investigation is needed to verify the thresholds obtained in this study, particularly for hybrid bermudagrass, as the recommendation is only based on 2019 data. No CWSI threshold was determined to maintain turf quality in the acceptable range because of the high variability of CWSI values over time and their low correlation with VR values.

The effect of microhabitat features, anthropogenic pressure and spatial structure on bird diversity in southern Tunisian agroecosystems

AbstractIn southern Tunisia, oases and olive orchards are the two main agroecosystems, hence the importance of investigating their value for native fauna. Using generalised linear mixed models, we assessed the relative value of oases and olive plantations over the wintering and the breeding periods by comparing their avifauna diversity using the Shannon diversity index. We also used data on a series of microhabitat features, anthropogenic pressure and spatial parameters to identify the best predictors of bird diversity. In total, 32 species belonging to 18 families were recorded. Sedentary birds accounted for 47% of the counts. Our results showed that bird diversity depends on habitat type, being higher in oases than in olive plantations, but not on the season as no difference was recorded during the two periods of wintering and breeding. The assessment of the effects of microhabitat features, anthropogenic pressure and spatial structure revealed that bird diversity was positively influenced by the cover of trees in oases and olive orchards, negatively affected by distance to edge and that to the paved road in the olive orchards and spatially structured in both agroecosystems. Variation partitioning analysis revealed that the pure effect of microhabitat features (tree cover) was important in explaining the bird diversity both in oases and olive orchards. The identification of factors affecting bird diversity is of great importance for the efficient management of these agroecosystems. Special attention should be paid to keeping a good tree cover. This cannot be performed without: (a) increasing irrigation frequency, (b) adequate tree maintenance (pruning) and (c) reduction of pesticide application. Also, the synergy among owners, farmers, managers and researchers is recommended for the conservation of bird diversity in this North African arid agricultural region.

Alternate furrow irrigation improves grain yield and nitrogen use efficiency in winter wheat

The objective of this study was to determine whether grain yield and nitrogen (N) use efficiency (NUE) in winter wheat (Triticum aestivum L.) could be improved by alternate furrow irrigation (AFI). During the 2009–2010 and 2010–2011 crop seasons, the effects of AFI on grain yield, NUE (and its components), the recovery of 15N-labeled fertilizer, N uptake and distribution, and soil nitrate-N were evaluated under field conditions. The irrigation regimes were: W0, non-irrigated; W2, every furrow irrigated at jointing and anthesis; W3, every furrow irrigated before wintering and at jointing and grain filling; and AFI, each of two neighboring furrows irrigated either before wintering or at grain filling, and every furrow irrigated at jointing. Our results show that grain yield, above-ground nitrogen uptake (AGN; including N from fertilizers and soil), and NUE were lowest in the W0 treatment and tended to increase with increasing irrigation frequency. Grain yield, AGN (including N from fertilizers and soil), NUE, nitrogen uptake efficiency (UPE), 15N-recovery efficiency, and N accumulation in grains were significantly higher in the AFI treatment than in the W2 treatment. AGN increased due to a higher amount of N derived from both fertilizers and soil. More N was derived from soil than from fertilizers; thus, the proportion of N derived from fertilizers decreased. No significant differences in grain yield and NUE were observed between the AFI and W3 treatments. AGN decreased when soil N luxury uptake and N accumulation in stems and leaves decreased. Greater N utilization efficiency and a higher N harvest index were observed in the AFI treatment compared with the W3 treatment. In addition, AFI increased nitrate-N contents in the upper soil layer (0–60 cm) and reduced nitrate-N movement to deeper soil compared to the W2 and W3 treatments. Therefore, AFI may be an appropriate irrigation method for improving NUE and decreasing water consumption in winter wheat without reducing yield.

Optimizing irrigation frequency and amount to balance yield, fruit quality and water use efficiency of greenhouse tomato

Vegetable production in many countries relies on irrigation. While increasing irrigation amount normally improves yield, too much water could jeopardize fruit quality and comprise profit. Optimizing irrigation frequency and amount is thus essential to ensuring yield increase without compromising fruit quality. This paper presents a three-year (2011–2013) experimental study on responsive changes in yield, fruit quality and water use efficiency (WUE) of tomato grown in greenhouse to different irrigation frequency and amount under drip irrigation. The irrigation scheduling was based on accumulative evaporation (AE) measured from a standard 20 cm pan. Three irrigation frequencies were considered in which irrigation was resumed when AE was 10 mm (I1), 20 mm (I2) and 30 mm (I3) respectively. Each frequency was associated with four irrigation amounts, which were 50% (Kcp1), 70% (Kcp2), 90% (Kcp3) and 110% (Kcp4) of AE respectively. Water consumption, yield characteristics and fruit quality of the plants in each treatment were measured. The three-year results show that for each irrigation amount, increasing irrigation frequency led to an increase in yield and WUE. Visual fruit-quality traits, including average weight, longitudinal and transverse diameter, increased with irrigation amount but not with irrigation frequency. It was found that a reduction in irrigation amount increased all other fruit quality characteristics except the sugar-organic acid ratio in 2013. Both yield and WUE increased asymptotically with irrigation amount before approaching their plateau when the irrigation amount reached 90% and 70% of AE respectively. While the yield was positively related to fruit size and negatively to soluble solid content, it was independent of WUE. The results from technique for order preference by similarity to ideal solution analysis revealed that among all treatments, I1+Kcp2 was the optimal in terms of best balancing yield, fruit quality and water use efficiency. Principal component analysis found that the comprehensive fruit quality score was closely related to the total soluble solids content.

Optimized micro-sprinkling irrigation scheduling improves grain yield by increasing the uptake and utilization of water and nitrogen during grain filling in winter wheat

The North China Plain (NCP) is the main wheat production area in China; however, irrigation water and nitrogen fertilizer use in this area is relatively inefficient, and must be optimized to attain higher yield and resource use efficiency for winter wheat. In this study, a four-year field experiment was conducted during the 2012–2016 growing seasons. Under quota irrigation conditions, an experiment with various micro-sprinkling frequencies (S2, irrigation at jointing and anthesis; S3, irrigation at jointing, booting and filling; and S4, irrigation at jointing, booting, anthesis and filling) was conducted in 2012–2014. In 2014–2016, different nitrogen application rates (150, 195, and 240 kg N ha−1; denoted as S4N1, S4N2, and S4N3, respectively) under the S4 condition were tested. The local traditional flood irrigation pattern was designated as the control (CK) in 2012–2016. The grain yield, leaf area index of the population (LAI), flag leaf senescence during gain filling, accumulation and distribution of dry matter and nitrogen, and water and nitrogen use characteristics were investigated. The results showed that, no significant difference was observed in grain yield between the CK and S2, whereas S4 and S3 showed increased grain yields of 5.7–22.2% and 4.6–19.1%, respectively, compared with the CK. The increase of yield in micro-sprinkling treatments was mainly due to a significant increase in the 1000-grain weight. With increasing irrigation frequency, the LAI at the filling stage improved significantly; the flag leaf chlorophyll content decreased slowly; and the total dry matter accumulation, dry matter after anthesis, and its contribution to grain yield increased significantly. Meanwhile, the total water consumption of S4 (N2) decreased significantly, and the water use efficiency increased by 10.0–27.8% compared with the CK. In addition, micro-sprinkling irrigation with frequent application of a small amount of water with optimized nitrogen application (S4N2) yielded the highest nitrogen fertilizer use efficiency. Water consumption and nitrogen accumulation during grain filling were significantly increased in S4, which could explain the higher yield and resource use efficiency of S4. Overall, a suitable micro-sprinkling irrigation frequency (S4) and nitrogen application (195 kg N ha−1) can achieve higher grain yields and resource use efficiencies in the NCP.

Sprinkler Irrigation Frequency Affects Maize Yield Depending on Irrigation Time

Core Ideas Plant Na+ content doubled with daytime sprinkler irrigation. Plant Na+ content increased by 30% with high irrigation frequency. Irrigation frequency was not relevant for nighttime sprinkler irrigation of maize. High irrigation frequency during daytime reduced maize yield and water use efficiency. Sprinkler irrigation with solid‐set systems easily allows changing irrigation frequency. We studied, under field conditions and during 3 yr, the effects of irrigation frequency (two events per week or daily) and daytime vs. nighttime irrigation on microclimatic changes, soil matric potential, growth, yield, and water use of maize (Zea mays L.). Microclimatic changes (decrease of air temperature and vapor pressure deficit, and of canopy temperature) were slightly larger and lasted for more time after the irrigation event with low frequency irrigation. Increasing irrigation frequency during daytime resulted in a lower soil matric potential. Irrigating at nighttime resulted in higher maize height (+3%) and yield (+10%) than irrigating at daytime. The high irrigation frequency decreased maize height (−7%) and yield (−5%) compared with the low irrigation frequency when irrigation was performed at daytime but not at nighttime. The Na+ content of the plant was doubled with daytime sprinkler irrigation compared with nighttime irrigation, and was increased by 30% when the irrigation frequency was increased. Water use efficiency (WUE) was not affected by irrigation frequency when irrigating at nighttime, but it decreased with the increase of irrigation frequency when irrigation was applied during daytime. Sprinkler irrigation with solid‐set must be applied at night to obtain the maximum maize yield and WUE. Irrigation frequency is not relevant for sprinkler irrigation of maize applied at night, but high irrigation frequency should be avoided when maize is sprinkler irrigated during daytime to avoid yield and WUE decreases.

Assessing the performance of different irrigation systems on winter wheat under limited water supply

The rapid decline of groundwater table is threatening sustainable irrigation agricultural development in the North China Plain (NCP). Optimized irrigation scheduling and water-saving irrigation technologies need to be developed to reduce irrigation water use and maintain the grain production potential for the region. This study was conducted at Luancheng experimental station in the NCP during 2012–2015 to evaluate the effects of different irrigation methods (basin irrigation, BI; tube-sprinkler irrigation, SI; pillow irrigation, PI and drip irrigation, DI) with various irrigation amount/frequency on yield, economic returns and water use efficiency (WUE) of winter wheat. Under the same limited irrigation amount (90mm/season), two irrigation applications (45mm/application) conducted using DI significantly increased the yield and WUE as compared with the BI using one single application. Increasing the seasonal irrigation amount to 160mm, the increase in the application frequency by reducing the irrigation amount per application didn’t significantly affect the yield using either PI or SI. Results showed that soil water depletion (SWD) contributed 40–60% of the seasonal evapotranspiration (ET) under limited water supply. The smaller root length density (RLD) in deep layers of the soil restricted the soil water uptake by the crop. Therefore, increasing irrigation frequency would maintain the top soil layers with higher soil water contents where RLD was greater that improved crop water use and yield under limited water supply. However, when irrigation water was plentiful, micro-irrigation methods did not increase yields. Due to the high cost in installation of the three micro-irrigation systems, their net income was reduced by 30% as compared with the BI method. The economic water productivity ratio (EWPR) was only 3–4 for the three micro-irrigation systems, much less than the basin irrigation method, which had an average value of 16. Currently, the basin irrigation method is more economic for growing winter wheat in the NCP.

Productivity and Profitability of Tomato Due to Irrigation Frequency and Mulch

ABSTRACTThe scarcity of water requires its judicious application and conservation for Tomato (Solanum lycopersicum L) production. Tomato was grown during Nov.–Mar. 2003–2005 under the following irrigation regimes: rainfed or irrigation when cumulative pan evaporation (CPE) reached 50 mm (CPE50) or 25 mm (CPE25) and the following mulch treatments: none, rice straw, and white or black polyethylene. Fruit yield increased with increased irrigation frequency. Mulch enhanced fruit yield by 23%–58% over no mulch. The cost–benefit (CB) ratio increased with an increase in irrigation frequency. Rice straw, which is less costly and easily available, had the highest CB ratio (1:3.1) in all moisture conditions, followed by black polyethylene (1:2.9). Use of black polyethylene when water is scarce (rainfed, CPE50) has the potential to increase income compared to plants in bare soil when water is plentiful.

Water Deficit Irrigation and Nitrogen Response of Sudan Grass under Arid Land Drip Irrigation Conditions

AbstractThe present study evaluated the interactive effect of water deficit irrigation (WDI) and nitrogen application on Sorghum sudanense growth, biomass accumulation, nitrogen content and water productivity for two consecutive seasons and three cuts. The WDI of 50, 30 and 10% depletion ratios (different application rate and frequency) along with four levels (0, 100, 200 and 300 kg ha−1) of nitrogen fertilizer were applied in three splits. The WDI of 10% depletion ratio recorded significantly higher (15–17%) fresh and dry biomass accumulation of both leaf and stem as compared with WDI of 50%. Nitrogen application improved all growth traits irrespective of the applied levels of WDI, season and cut number. The interaction of WDI of 30% depletion ratio and N200 outcompeted all other treatments for plant nitrogen and protein contents, as the resulting increment was 10–22% higher as compared to control. Of the different cut numbers, the first cutting ascribed the maximum value for plant protein contents and stated up to 32% improvement over second and third cuttings. By increasing the rate of nitrogen application, a significant increment in crop water productivity was also measured that attributed at least a threefold higher value for stem over leaf. In essence, WDI of 10% depletion ratio and nitrogen rate of 200 kg ha−1 were the optimum levels that improved Sudan grass growth, biomass and water use efficiency; moreover, the 30% depletion ratio favoured plant nitrogen content. By using a WDI approach, we can improve our forage yield with a limited amount of water by increasing irrigation frequency. Copyright © 2017 John Wiley & Sons, Ltd.

Nitrous Oxide Fluxes, Soil Oxygen, and Denitrification Potential of Urine- and Non-Urine-Treated Soil under Different Irrigation Frequencies.

Despite increased use of irrigation to improve forage quality and quantity for grazing cattle ( Linnaeus), there is a lack of data that assess how irrigation practices influence nitrous oxide (NO) emissions from urine-affected soils. Irrigation effects on soil oxygen (O) availability, a primary controller of NO fluxes, is poorly understood. It was hypothesized that increased irrigation frequency would result in lower NO emissions by increasing soil moisture and decreasing soil O concentrations. This would favor more NO reduction to dinitrogen (N). We examined effects of high (3-d) versus low (6-d) irrigation frequency with and without bovine urine addition to pasture. Nitrous oxide fluxes were measured daily for 35 d. Soil O, temperature, and water content were continuously measured at multiple depths. Inorganic nitrogen, organic carbon, and soil pH were measured at 6-d intervals. Measurements of denitrification enzyme activity with and without acetylene inhibition were used to infer the NO/(NO + N) ratio. The NO/(NO + N) ratio was lower under high- compared with low-frequency irrigation, suggesting greater potential for NO reduction to N with more frequent irrigation. Although NO fluxes were increased by urine addition, they were not affected by irrigation frequency. Soil O decreased temporarily after urine deposition, but O dynamics did not explain NO dynamics. Relative soil gas diffusivity (/) was a better predictor of NO fluxes than O concentration. On a free-draining soil, increasing irrigation frequency while providing the same total water volume did not enhance NO emissions under ruminant urine patches in a grazed pasture.

THE EFFECT OF IRRIGATION FREQUENCY AND RATE UNDER TRICKLE IRRIGATION MANAGEMENT ON YIELD GREEN BEAN GROWN IN CLAY LOAM SOIL

This study was conducted over 2 years (2013 and 2014) to establish the optimal combinations between irrigation frequency and rate for trickle-irrigated green bean using water production functions and water use– yield relationships. A field experiment was conducted using a randomized complete block design with three irrigation frequencies (F1, F2 and F3, irrigation events once every 1, 2and 3 days, respectively) and three trickle irrigation rates (I1: 1.00, I2: 0.80, and I3: 0.60 of the estimated evapotranspiration, ET). Our results show that yield variables and water use efficiencies (WUEs) increased with increasing irrigation frequency and rate, with non-significant differences between F1 and F2 in yield variables and between I1 and I2 in WUEs. Moreover, the combination between various irrigation frequencies and rates had an important effect on yield variables and WUEs, with the highest values being found with F1I2 and F2 I1 and the lowest for F2I3 and F3I3. The F1I3 treatment had grain yield and yield components values similar to those obtained for the F2I3 treatments and WUEs values similar to those obtained for the F2I3 and F3I1 treatments. Production functions of yield versus seasonal crop ET were linear for all combinations of irrigation frequency and rate and for all irrigation frequency treatments with the exception of the F1 treatment, which instead showed a second order relationship. In conclusion, we identified the optimal coupling combinations between irrigation frequency and water application rate to achieve the maximum yield and WUEs.

Impact of Irrigation Intervals and Fertilization on Actual Evapotranspiration and Wheat Production

FIELD experiments were conducted in clay loam soil during two …. successive seasons 2010/2011 and 2011/2012 at the Agricultural Experimental station, Faculty of Agriculture, Cairo University to investigate the impact of 4 irrigation frequencies combined with three fertilizers as well as control treatment (without fertilizer) on actual evapotranspiration (ETa), grain yield (Triticum aestivum, L. Sids1) and water use efficiency (WUS) of wheat under furrow irrigation system and Giza region conditions. The results clearly revealed that increasing irrigation frequency significantly decreased seasonal ETa values during studied growing seasons. While the addition of inorganic and organic fertilizers to the studied soil significantly increased seasonal ETa compared to the control treatment (without fertilizers). The wheat crop irrigated by short irrigation interval ≤ 14 days with fertilization by combined between inorganic and organic fertilizers increased seasonal ETa values. While the wheat crop irrigated by the long irrigation interval of 18 days with separately organic fertilizer decreased seasonal ETa value. The results revealed that irrigation interval every 10 days with combined fertilizers treatment had the highest seasonal ETa value (44.56 cm) while the irrigation interval every 18 days with separately organic fertilizer had the lowest seasonal ETa value (37.79 cm) compared to the control treatment (without fertilizers) during studied growing seasons. The results noticed that

Water balance and migration for maize in an oasis farmland of northwest China

Water balance and migration characteristics are vital to the establishment of an efficient irrigation management system. Based on the observed data including microclimate and growing parameters of maize from 2009 to 2012, actual evapotranspiration during the growth period was estimated by a combination of the FAO-56 crop coefficient approach and the Penman–Monteith model; the changes in soil water storage were estimated through the monitored water content at different depths from 0 to 3 m; the water content monitoring zone was divided into three sub-zones according to the water-balance characteristics of different soil layers and water monitoring data. On these bases, in combination of water-balance model, three aspects were analyzed: water-balance characteristics at different growth stages; water-balance characteristics in the three different sub-zones; and water-migration characteristics of ten sunny days following irrigation. These analyses revealed severe deep leakage under present irrigation management, which could be remedied by limiting one-time irrigation practices and increasing irrigation frequency. Additionally, some practical suggestions are provided for different growing stages.

A PRELIMINARY STUDY OF THE EFFECT OF DRY WINTER IRRIGATION ON LITCHI PRODUCTION

The traditional perspective implies that water stress during winter is required for floral induction of fruit on litchi (Litchi chinensis Sonn.). We hypothesized that correct timing for moderate irrigation during a dry winter benefits floral induction, fruit set and yield in ‘Guiwei’ and ‘Nuomici’ litchi. Canopy covers were used to simulate the natural drought process, intercepting any rainfall. ‘Guiwei’ litchi trees (average crown size 4×4 m) under cover or in an open field were irrigated for two consecutive winters during 2009-2010 and 2010-2011. During the winter of 2010-2011 ‘Nuomici’ litchi trees were irrigated in an open field. For all treatments except the drought/moisture control 150 L/tree/irrigation were used. The effects of winter irrigation on litchi fruit production were investigated. The results indicated that dry winter irrigation, including manual watering and natural events, improved the flowering rates of ‘Guiwei’ litchi trees and increased the final fruit yields for ‘Guiwei’ and ‘Nuomici’ litchi trees. There was a positive association between increased irrigation frequency and improved flowering rates and fruit yield. In combination with efficient cultivation and water conservation (via irrigation), the best regime for increased flowering and fruit set during dry winters was to irrigate four times during the coldest time in winter.