Supplemental Irrigation Treatments Research Articles

Stem characteristics and yield of wheat is regulated to improve planting efficiency and reduce lodging risk by fertilizer rate and irrigation stage

Stem characteristics and yield of wheat is regulated to improve planting efficiency and reduce lodging risk by fertilizer rate and irrigation stage

Different supplemental irrigation methods result in discrepant water use efficiency and yield by changing steps of water use process in dryland wheat

Different supplemental irrigation methods result in discrepant water use efficiency and yield by changing steps of water use process in dryland wheat

Sorghum Response to Supplementary Irrigation at Different Growth Stage in Rain-Fed Agriculture for Increasing Yield and Water Productivity at Raya Valley

In arid and semi-arid ecosystems, the efficient use of water becomes increasingly important because water is a crucial limiting factor for increased food and fibre production to supply an ever-growing number of people. A field experiment was conducted in three consecutive seasons three year in Mekhoni Agricultural Research Centre, Raya valley, to investigate with the objective of to evaluate the influence of supplemental irrigation applied at different growth stages on the yield, to prevent sorghum failure caused by less rain water and to maximize the water productivity of the sorghum. The experiment was laid out in a random complete block design (RCBD) consisting of eleven supplemental irrigation treatments (one supplemental irrigation during initial stage, one supplemental during development stage, one supplemental during mid-stage, one supplemental during Late stage, one supplemental during initial and development stage, one supplemental during initial and mid stage, one supplemental during initial and late stage, one supplemental during development and late stage, one supplemental during development and late stage and rain-fed (with no SI) as a control treatment with three replications. The result was showed a significant difference on plant height, panicle length, grain, biomass yield and water productivity sorghum. The highest grain yield was obtained from the treatment supplement one SI at development and mid stage and followed by one SI at mid stage and at late stage. Whereas, the lowest grain yield of sorghum was observed from treatment with rainfed (non-supplementary). It is concluded that in the study area the rain fed amount were very inadequate and supplementary irrigation will help to increase crop productivity, minimize crop failure due to the low rainfed. The experiment showed that supplementary irrigation offers a great potential for improving crop production in Raya valley.

Effect of Supplemental Irrigation on Wheat Performance Grown in Semi-Arid Environment

This study was carried out to determine the effects of different supplemental irrigation (SI) treatments on yield, yield components, and some drought-related traits in eight wheat varieties grown in the semi-arid environment of Jordan. Two SI treatments were used in addition to the control (i.e. rainfed treatment with 262.8mm accumulated rains): partially SI treatment (PSI=262.8mm rains+220mm irrigation at anthesis stage) and continuous SI treatment (CSI= 262.8mm rains + 377.5mm at 2-3 weeks intervals during different stages of wheat growth). Seven durum wheat varieties; namely Sham1, Omqais, Acsad65, Bani Suef6, Bani Suef4, Horani Nawawi, and Dairalla6 in addition to one bread wheat variety (Ammon) were included in this study. Yield and yield components were significantly increased and the time required to anthesis and maturity were delayed by SI. PSI treatment significantly increased grain yield by 50.2%, while CSI increased yield by 121% as compared to the control treatment. Considerable variations among varieties were observed under different irrigation treatments. Sham1 (2266.7 kg ha-1), Omqais (2253.3 kg ha-1), and Acsad65 (1963.3 kg ha-1) gave the highest grain yield under control treatment with low drought susceptibility indices, implying their low grain yield losses under control as compared with SI treatments with high genetic potentials for drought tolerance. The top-yielding varieties under CSI were Acsad65 (4716.7 kg ha-1), Dairalla6 (4586.7 kg ha-1), Bani Suef6 (4460 kg ha-1), and Omqais (4360 kg ha-1). Under PSI, Sham1 (3303 kg ha-1) followed by Dairalla6 (3193.3 kg ha-1), Horani Nawawi (3130 kg ha-1), and Bani Suef6 (3026.7 kg ha-1) gave the highest grain yield. All yield components (number of kernels per spike, number of tillers, and grain size) significantly contributed to increasing grain yield under SI. In conclusion, SI under rainfed conditions improves yield-attributing traits, which led to a substantial increase in grain yield. It would be possible to increase GY by more than 3 and 4 tonnes ha-1 with PSI and CSI, respectively.

Effects of phosphorus application rates on photosynthetic and senescence characteristics and yield of diffe-rent stems and tillers of wheat under water-saving supplementary irrigation

To clarify the physiological mechanism underlying grain yield of different stems and tillers of wheat in response to phosphorus application under water-saving supplementary irrigation and to determine the suitable phosphorus fertilization rate, we set water-saving supplementary irrigation (irrigation to the soil water content of 0-40 cm soil layer shall be supplemented to 70% of the field saturation capacity during the jointing stage and flowering stage, W70) and no irrigation (W0) on wheat variety 'Jimai 22', and three phosphorous application rates, low (90 kg P2O5·hm-2, P1), medium (135 kg P2O5·hm-2, P2), and high (180 kg P2O5·hm-2, P3), with no phosphorus application as the control (P0). We examined the photosynthetic and senescence characteristics, the grain yield of the different stems and tillers, as well as water and phosphorus use efficiency. The results showed that under both water-saving supplementary irrigation and no irrigation, the relative content of chlorophyll, net photosynthetic rate, sucrose content, sucrose phosphate synthase activity, superoxide dismutase activity, and soluble protein content of flag leaf of the main stem and tillers Ⅰ and Ⅱ (first degree tillers arising from axils of the 1st and 2nd true leaf of the main stem) under P2 were significantly higher than those under P0 and P1, which contributed to the higher grain weight per spike of main stem and tillersⅠ and Ⅱ, but did not differ from P3. Under water-saving supplementary irrigation, P2 increased grain yield of main stem and tillers Ⅰ, Ⅱ and Ⅲ (first degree tillers arising from axils of the 3rd true leaf of the main stem) compared with that under P0 and P1, and increased grain yield of tillers Ⅱ and Ⅲ compared with P3. Grain yield per hectare under P2 was 49.1%, 30.5% and 8.9% higher than that under P0, P1 and P3, respectively. Similarly, water use efficiency and phosphorus fertilizer agronomic efficiency under P2 were the highest among the phosphorous treatments under water-saving supplementary irrigation. Under no irrigation condition, P2 increased grain yield of main stem and tillers Ⅰ and Ⅱ compared with P0 and P1, yet grain yield of tiller Ⅱ was higher than that of P3. Furthermore, under P2, the grain yield per hectare, water use effi-ciency, and phosphorus fertilizer agronomic efficiency were higher than those under P0, P1 and P3 under no irrigation. Under each phosphorous application rate, grain yield per hectare, phosphorus fertilizer agronomic efficiency, and water use efficiency of water-saving supplementary irrigation treatment were higher than those of no irrigation treatment. In conclusion, medium phosphorus application rate (135 kg·hm-2) under water-saving supplementary irrigation would be the optimal treatment for both high grain yield and efficiency under the experimental condition.

Enhancing Grain Yield and Zinc Content in Bread Wheat Using Zinc and Nitrogen Application under Supplementary Irrigation Treatments

Wheat (Triticum aestivum L.) is one of the crops that has great importance in human and animal nutrition. Nutrient management can improve the nutritional value and grain yield in bread wheat. Therefore, this study was conducted to assessment the effect of Zinc (Zn) levels as well as the interactions with Nitrogen (N) and irrigation regimes on yield, yield components and Zn content in bread wheat grain. To this purpose, an experiment was performed in a split-split plot design with four replications, which supplementary irrigation (no irrigation, irrigation at stem elongation and irrigation at the stage of grain filling) as the main plot, Zn levels as split-plot (no spraying of Zn and Spraying Zn with a concentration of 5%) and nitrogen consumption levels (nitrogen-free, half the normal dosage and normal nitrogen consumption) as split-split factors. The results showed that the grain yield and yield components affected by the applied treatments. The highest grain yield (646 g/m2 ) and Zn concentration (32.69%) observed in spraying Zn at 5% concentration supplemented with irrigation at the grain filling stage with normal N application. Also, Zn content of grain was increased by Zn foliar application. Furthermore, the grain yield significantly correlated with Zn content, Harvest index (HI), seed filling rate (SFR), thousand seed weight (TKW) and seed number per spike (SNS) traits. The highest grain yield was obtained in supplementary irrigation in grain filling stage indicating importance of supplementary irrigation in this stage. In general, the results of this study showed that the grain yield and quality in bread wheat could be increased by supplementary factors.

Effects of Supplementary Irrigation and Nitrogen Fertilization on Characteristics of Sun Cured Tobacco in Semi-Arid Conditions

ABSTRACT Nitrogen and water should be applied at the right time and amount to obtain optimum crop yield in arid and semi-arid regions. The study was carried out in 2017–2018 to investigate the effects of different supplementary irrigation levels applied after harvests, and different nitrogen sources on water use efficiency (WUE), yield and quality characteristics of sun-cured tobacco. The study included five different nitrogen sources (N1: zero-nitrogen, N2: ammonium nitrate, N3: ammonium sulfate, N4: calcium ammonium nitrate, and N5: urea) and four different irrigation treatments (I0:No irrigation; I33:66% deficit, I66:33% deficit and I100:100% full irrigation). The effects of nitrogen sources and supplementary irrigation treatments on plant height, leaf number, leaf width, leaf height, yield, quality grade, sugars, nicotine, phenolics, WUE and irrigation water use efficiency (IWUE) were statistically significant. Seasonal crop evapotranspiration values ranged between 117.7 and 235.3 mm. The highest WUE 1.65 kg m−3 and IWUE: 10.48 kg m−3 were recorded in I33 treatment. Plant characteristics were different between nitrogen sources; however, the results did not indicate a prominent nitrogen form. The results for supplementary irrigation revealed that the I100 treatment in semi-arid conditions increased the sun-cured tobacco yield by 22% with acceptable quality improvements. The gross income increased 1705 $ ha−1 with the increase in tobacco yield and sale price per hectare.

Integrated on-site & off-site rainwater-harvesting system boosts rainfed maize production for better adaptation to climate change

Solving the disparity between rainwater supply and crop water demand is a fundamental issue in semiarid rainfed agriculture. Over the last decades, the ridge-furrow-plastic-mulching (RFM) farming system has been widely used as an on-site (in-situ) rain-harvesting farming strategy, providing a partial solution to the supply-demand mismatch of rainwater. The off-site rain-harvesting system (ex-situ water cistern) for supplemental irrigation has been little used. We established an integrated ex-situ rain-harvesting system incorporated into maize RFM in a semiarid site of northwest China from 2018 to 2019. Five treatments were designed as: (1) CK-1, flat planting without mulching and irrigation, (2) CK-2, RFM without irrigation, (3) RFM60, RFM with 60 mm irrigation, (4) RFM105, RFM with 105 mm irrigation, and (5) RFM150, RFM with 150 mm irrigation. We found that supplemental irrigation treatments significantly increased grain yield, total biomass, and crop water productivity compared to CK-1 and CK-2 (P < 0.05) across two growing seasons, suggesting that ex-situ rain-harvesting irrigation can significantly promote field productivity based on widely used RFM system. The differences mentioned above were the greatest in RFM105 and RFM150, significantly greater than those of RFM60. No significant difference was observed between RFM150 and RFM105. Greater output in RFM150 and RFM105 was closely associated with improved soil water storage and thermal state in two growing seasons. Particularly, RFM150 and RFM105 harvested the highest soil organic carbon and total nitrogen after the second fallow period. The highest economic benefit was found in RFM105, followed by RFM150 and RFM60, the least in the two control groups. Our findings provided a critical case to solve the rainfall supply-demand mismatch. The ex-situ rainwater-harvesting supplemental irrigation can act as a promising solution to upgrade the current widely-used RFM farming system for better adaptation to climate change in the semiarid region.

Effects of supplemental irrigation on the accumulation, partitioning, and remobilization of nitrogen, yield and water use efficiency of wheat cultivars

In the Mediterranean, unbalanced precipitation distribution causes drought stress in rainfed wheat cultivation. Under such conditions, supplemental irrigation (SI) is a highly efficient practice to reduce the adverse effects of drought stress and improve yield. The present study aimed to assess the effects of SI on traits related to N accumulation and remobilization, chlorophyll concentration, yield and yield components, and water use efficiency (WUE) in different cultivars. Two field experiments with four irrigation levels (I0= rainfed, I1= SI at booting stage, I2= SI at booting and anthesis stages, I3= SI at booting, anthesis, and grain filling stages) and five cultivars (Rejaw, Sardari, Homa, Azar2, and Sirwan) was conducted during the 2015–2016 and 2016–2017 wheat growing seasons. Overall, results showed that SI notably had a positive effect on chlorophyll concentration, N content of plant parts, N remobilization (NR), grain number per spike, 1000-grain weight, biological yield, and grain yield in cultivars. Although the grain yield in the three SI treatments was 237.1 kg ha−1 and 630.4 kg ha−1 more than the other two (I2) and one (I1) SI, respectively, but the WUE was slightly lower in this treatment. The cultivars exhibited apparent differences in their responses to SI. The Sirwan cultivar showed a higher reaction to SI amongst cultivars. The highest N remobilization efficiency (NRE) was observed in I1 (73.69%) and I0 (73.34%) irrigation treatments. Sardari (74.03%) and Azar2 (73.60%) cultivars had higher NRE than other cultivars. The minimum contribution of NR to grain appeared in the I3 treatment (74.54%).

The Effect of Plant Density and Supplementary Irrigation on Nutritional Value of Two Safflower (Carthamustincturius L.) Forage Crops

ABSTRACT Safflower (Carthamustinctorius L.) is an important forage. An experiment was carried out to investigate the effects of planting density and supplementary irrigation on quantitative and qualitative forage yield of two safflower cultivars as a split-factorial at the research farm of the Agricultural Faculty of Ilam University, Iran during 2015–2017. The main factor was irrigation at two levels (supplementary irrigation and dry-land) and sub–factors included density levels (20, 30, 40, 50, and 60 kgseed/ha) and cultivars (Goldasht and Faraman) in three replications. In both growing seasons, supplementary irrigation (SI) increased Ash, neutral detergent fiber (NDF), Phosphorus (P) and fresh forage yield (FFY), while rain-fed (RF) increased crude protein (CP), ethereal extract (EE) and potassium (K). Faraman had better FFY, Ash, EE and K in terms of these traits, while Goldasht was better than Faraman. Improving FFY through increasing in plant density per unit area was considered appropriate, so that the densities of 50 and 60 (kg/ha−1) in SI treatment in both cultivars were concluded as more effective, while in RF treatment for having better nutritional value (in terms of protein and fat content) lower density was observed as more appropriate and in order to have less NDF higher density was more suitable. Due to the two-year data of nutritional values and yields, it was concluded that the crop had the ability to adapt to and tolerate drought condition and increase yield in semi-arid regions. Also, it is suitable in terms of nutritional value and forage production in dry-land areas of experiment.

Effects of supplemental irrigation on winter wheat starch structure and properties under ridge-furrow tillage and flat tillage

Supplemental irrigation (SI) is an important strategy to improve the water-use efficiency (WUE) of crops without compromising the yield. However, such strategy can influence the starch and grain quality. Hence, the effects of SI on winter wheat starch structure and functionality were studied on ridge-furrow (RF) and flat tillage (FT) treated fields. Flat irrigation was set as control. RF+SI significantly increased the grain yield throughout the study period (2016-2018). SI decreased the amylose content and the content of amylopectin chains with DP 13-24 but increased the proportions of amylopectin chains with DP 6-12 and 25-36. The starch granule relative crystallinity decreased, and more B-type granules were produced by SI treatment. SI significantly increased the resistant starch content in both raw and cooked starch systems. Flat tillage enhanced the effect of SI on granule specific surface area (SSA) and viscosity, which increased starch paste viscosity, while SI+RF showed the opposite effects. Our study demonstrates important combined effects of SI and tillage on wheat starch quality.

Economic Indices for the Application of Irrigation to Enhance Cactus Pear Fruit Yield

Aims: Cactus pear cultivation for fruit production is under rainfed conditions, mainly. Hence, irrigation uses for this purpose is expensive in arid and semi-arid agricultural lands. The objective of this study was to derive agro-economic indicators associated with supplemental irrigation to improve fruit yield of commercial cactus pear cultivars grown in a semiarid agroecosystem of Mexico.&#x0D; Study Design: The irrigation treatments tested were fully irrigated (FI) and supplemental irrigation (SI), with non-irrigated as a control (NI).&#x0D; Place and Duration of Study: The experiment was set up at the Campo Experimental Zacatecas, Calera, Zacatecas, Mexico from 2011 to 2013.&#x0D; Methodology: Five-year-old cactus pear plants of ‘Cristalina’ (O. albicarpa Scheinvar; white-pulped fruit) and ‘Roja Lisa’ [O. ficus-indica (L.) Mill.; red-pulped fruit] were included. The experiment was conducted in a split-block design. There were three blocks; each included both cultivars, randomly allocated to each irrigation treatment. The response variables were: fruit yield (FY), cultivation costs (CC), gross return (GR), net return (NR), benefit-cost ratio (BC), irrigation use efficiency (IUE), gross water productivity (GWP), net water productivity (NWP), labor productivity (LP), break-even-point (BEP), and credit vulnerability (CV).&#x0D; Results: In all years but 2013, FI ‘Cristalina’ plants had the highest CC, reflected in their greater GR and NR; however, BC values were similar between SI and FI plants or greater in SI plants for 2013. Therefore, SI plants had the highest IUE, GWP, NWP, LP, EP, and equal or greater credit vulnerability than FI plants. The NI plants produced positive values for BEP and CV. The economic indices for ‘Roja Lisa’ were similar to those of ‘Cristalina’.&#x0D; Conclusion: The SI treatment produced the best agricultural economic indices and it is also a feasible water-saving irrigation strategy for cactus pear cultivation in semiarid agroecosystems worldwide.

Supplemental irrigation to save water while growing cactus pear in semi‐arid regions*

AbstractClimate change will compromise food access by causing water shortages for agricultural purposes. Supplemental irrigation (SI) was explored for its effect on crop water use, fruit yield, water use efficiency, water productivity, mean fruit mass and fruit size distribution of four cactus pear cultivars. The irrigation treatments were: non‐irrigated (NI) rainfed control, SI and full irrigation (FI). The cultivars were: ‘Cristalina’ (Opuntia albicarpa Scheinvar), ‘Amarilla Olorosa’ (O. spp.), ‘Roja Lisa’ (O. ficus‐indica L. Mill.), and ‘Dalia Roja’ (O. spp.). The experiment was conducted in a split‐block design. The SI treatment saved water, in a 3‐year‐average, by 52% for ‘Cristalina’, 51% for ‘Roja Lisa’ and 52% for both ‘Amarilla Olorosa’ and ‘Dalia Roja’. This resulted in a reduction in crop water use by 38% for ‘Cristalina’, 42% for ‘Roja Lisa’, 39% for ‘Amarilla Olorosa’ and 40% for ‘Dalia Roja’. For SI, plant‐relative water content and fruit growth were similar to the FI plants. SI plants maintained fruit yield, mean fruit mass and marketable fruit size at the level of FI plants, while it improved efficiencies of water use and water productivity. SI is therefore a feasible irrigation strategy for cactus pear for those areas where water availability is limited for agricultural activities.

Rate of Nitrogen Rather Than Timing of Application Influence Yield and NUE of Canola in South Australian Mediterranean Environments

Canola has a high nitrogen requirement and optimal nitrogen (N) management in environments with variable rainfall is a challenge. This study investigated the impact of timing of N as a single or split application at different growth stages on seed yield, N uptake and water-use efficiency in canola. Nitrogen rates of 100 and 200 kg ha−1 were applied after sowing when two leaves were unfolded or equally split between the rosette, green bud and first flower stages. The experiments were conducted at two sites with contrasting rainfall and a supplementary irrigation treatment at the low rainfall site, generating a third environment. Nitrogen application increased seed yield by up to 20% at a high rainfall site and by up to 77% at a medium rainfall site, but the timing of N did not significantly affect the yield response to N. Seed yield was closely associated with total dry matter production and seed m−2. N-use efficiency was influenced more by N recovery and uptake efficiency, rather than physiological efficiency, which highlights the importance of soil moisture availability and the ability of the crop to exploit soil water and N reserves. The results suggest that better use of subsoil moisture by overcoming some of the subsoil constraints may be an avenue for further improvements in yield and nitrogen-use efficiency (NUE) of canola in this environment.

Quality and storability of cactus pear fruit as improved by supplemental irrigation

This research evaluated some fruit quality attributes at harvest and after two storage conditions [i.e., room temperature and cold storage] of four cactus pear cultivars previously exposed to non-irrigated (NI) treatment as the control, supplemental irrigation (SI) and commercial irrigation (CI). The cultivars responded differently to irrigation treatments and among evaluations. SI and CI plants had the highest fruit and pulp mass at harvest and maintained at both storage conditions, although these results were not always significant. Flesh firmness tended to be the highest in SI and CI fruit at harvest in all cultivars. The latter response was maintained occasionally at both storage conditions in all cultivars. Both dry mass concentration and total soluble solids concentration tended to be the highest in NI fruit of all cultivars. Fruit mass loss was minimized by SI and CI treatments in both storage conditions, and in relation to room temperature storage, cold storage increased the fruit storage life of all cultivars. At the start of the experiment, NI fruit at room temperature storage had the highest decay incidence; after that, this fruit deterioration problem was observed occasionally in both storage conditions. It was concluded that the amount and occurrence of rain was an important factor in the statistical inconsistence of the response variables. However, the SI and CI treatments minimized fruit mass loss in both storage conditions and extended the fruit storage life of all cultivars in cold storage, which is important for transportation, marketing, and consumers. Additionally, SI, on a three-year-average, saved irrigation water by 51% compared to CI, therefore, SI may be recommended to similar agro-ecological regions.

Calibration and evaluation of the DSSAT/Canegro model for sugarcane cultivars under irrigation managements

ABSTRACT Model calibration is a fundamental factor to obtain high accuracy in the estimation of crop growth and yield. This study aimed to parameterize the genetic and ecotype coefficients of the DSSAT/Canegro model for five sugarcane cultivars kept under three water managements, besides evaluating the accuracy of the model in predicting sugarcane stalk yield, sugar yield and height. Experimental field data were obtained from two years (2016 and 2017) of cultivation at FCAV/Universidade Estadual Paulista, Jaboticabal, SP, Brazil. The cultivars were maintained under supplementary irrigation, deficit irrigation and no irrigation. Data of the supplementary irrigation treatment (without stress) were used for the parameterization of each cultivar. Model accuracy was assessed by Pearson correlation (r), root mean squared error (RMSE), mean bias error (MBE), index of agreement (d) and confidence coefficient (c). The DSSAT/Canegro model is highly accurate in predicting stalk and sugar yields of sugarcane grown under water regimes, presenting itself as a viable alternative in sugarcane yield simulation. For better performance of the DSSAT/Canegro model, it is necessary to parameterize the variables related to the ecotype of the cultivars, besides the specific coefficients of the cultivars.

Effects of deficit irrigation combined with rainwater harvesting planting system on the water use efficiency and maize (Zea mays L.) yield in a semiarid area

The ridge and furrow rainfall harvesting planting system (RFRHP) where runoff is collected by plastic mulched ridges can improve the crop productivity in the semiarid areas of northwest China. During 2012–2014, we performed a field evaluation of the influence of RFRHP with supplementary irrigation (RI) on the water irrigation use and water use efficiency by maize in a semiarid climate using the following treatments: (1) no supplementary irrigation (RN); (2) irrigation during the trumpeting stage (RB); (3) irrigation during the blooming stage (RF); (4) irrigation during the trumpeting and blooming stages (RBF); and (4) traditional flat planting with border irrigation (CK). We found that although the irrigation volume was double under CK, the soil water content in the 0–120 cm soil layer did not differ significantly between the RFRHP with supplementary irrigation treatments and CK. The RFRHP with supplementary irrigation treatments reduced the irrigation water volume required (750–1125 m3 hm−2) and alleviated drought stress during key maize growth periods. The biomass, grain yield, and water use efficiency were significantly higher under RFRHP with supplementary irrigation, i.e., 6.0–8.7%, 15.4–25.8%, and 34.9–39.2% higher compared with CK, respectively, and 3.8–6.4%, 4.8–14.2%, and 9.2–12.7% higher compared with RFRHP with no supplementary irrigation. Under RFRHP with supplementary irrigation treatments, the irrigation water use efficiency was 1.5–3.9 times higher than that under CK. The irrigation water productivity levels under the RFRHP with supplementary irrigation treatments were ranked as follows: trumpeting stage > trumpeting and blooming stages > blooming stage. Compared with CK, RFRHP with supplementary irrigation significantly increased the out/input ratio and net income by 13.1–26.9% and 2600–3762 Chinese Yuan hm−2, respectively.

Time and amount of supplemental irrigation at different distances from tree trunks influence on morphological characteristics and physiological responses of rainfed fig trees under drought conditions

Abstract This study was carried out to identify the effects of time and amount of supplemental irrigation (SI) at different distances from tree trunks on morphological characteristics and physiological responses of mature rainfed fig trees in Estahban County, Fars Province, Iran. The two-year experiment was conducted in a split-split plot statistical design with four replications. SI treatments consisted of 1) irrigation position treatments in a micro-catchment close to tree trunks, 1–1.1 m from tree trunks inside of canopy, and 2.1–2.2 m from tree trunks outside of canopy 2) irrigation time treatments in early spring and in mid-summer, and 3) irrigation water amount treatments of no supplemental irrigation (control), 1000 liters, and 2000 liters of irrigation water per tree. The results showed a positive effect of SI on some morphological traits of rainfed fig trees. SI increased the leaf gas exchange parameters, including net photosynthesis rate (An), transpiration rate (Tr), and stomatal conductance (gs). The highest An and gs occurred in leaf water potential (LWP) around -1 MPa and the air temperature of 20 °C. The LWP equal to −2 MPa could be considered as a threshold for stomatal closure of rainfed fig trees, which put this plant among drought-tolerant trees. The higher correlation coefficient between An and gs compared with that obtained for An and Tr implied the higher dependence of the An variation on the gs than that of Tr. The highest leaf scale water use efficiency for trees irrigated with 2000 liters of water, out of the canopy, indicated higher increase of An compared with Tr after irrigation. Applying SI with 2000 liters of water per tree (200 m3 ha−1), outside of canopy in early spring could improve some of the morphological traits and physiological responses of rainfed fig trees, under drought conditions. However, under water resources limitation, 1000 liters of irrigation water per tree (100 m3 ha−1) could be recommended for rainfed fig orchards.

Comparisons of WUE in twelve genotypes of winter wheat and the relationship between δ 13C and WUE.

Twelve winter wheat (Triticum aestivum) genotypes were examined for differences in grain yield, water use efficiency (WUE), and stable carbon isotope composition (δ13C) in flag leaves. The plants were subjected to rain-fed treatment and supplemental irrigation at the jointing and anthesis stages, during the 2015–2016 and 2016–2017 winter wheat growing seasons. The relationships between δ13C with grain yield and WUE were analyzed under two different water environments. The results indicated that there were significant differences in δ13C, grain yield, and WUE among wheat genotypes both under rain-fed and supplemental irrigation conditions. The δ13C values increased with grain-filling proceeding, the δ13C being lower under supplemental irrigation treatment than that under rain-fed treatment. The relationships between the average of δ13C with grain yield and WUE were significantly positive during three measurement periods (R2 = 0.5785 − 0.8258), whether under rain-fed or irrigation environments. This suggests that δ13C might be associated with the grain yield and WUE in winter wheat under rain-fed and supplemental irrigation conditions in the climate region of the northwest Huang-Huai-Hai Plain of China.

Effects of supplemental irrigation on yield and yield attributes of chickpea (Cicer arietinum L.) in western Ethiopia

Terminal moisture stress is one of the major factors that reduce the yield of chickpea when it is grown using residual moisture. Field experiment was conducted for two consecutive years (2015/16 and 2016/17) at Teda research site, northwestern Ethiopia to investigate the effect of Supplemental Irrigation (SI) on yield and yield attributes of chickpea ( Habru variety). The treatments comprised of six SI levels (no SI/rain-fed, SI at: 50% flowering, 50% pod setting; vegetative + 50% flowering, vegetative + 50% pod setting stages). The treatments were laid out in randomized complete block design with three replications. Data were analyzed using SAS software, and means were separated by least significant difference test. The result showed that the effect of SI on water use efficiency, yield and most yield components of chickpea such as weight of 100-seed, biomass yield, number of secondary branch, pods and seeds plant -1 was significant. SI generally decreased the water use efficiency of chickpea compared to rain-fed condition. Based on two-year result, SI twice at vegetative + pod setting produced maximum seed yield (30.02 q ha -1 ), which was at par with that of SI twice at vegetative+ flowering (29.30 q ha -1 ) and once at vegetative stages (29.17 q ha -1 ). SI once at vegetative, twice at vegetative + flowering and twice at vegetative + pod setting stages increased seed yield by 12, 17 and 19% in 2015; and by 35, 24 and 36 % in 2016, respectively, compared to rain-fed condition. SI once at vegetative stage provided maximum net benefit (45880.40 ETB ha -1 ), with a marginal rate of return (477%) greater than minimum acceptable level (100%). Moreover, it had the highest water use efficiency among SI treatments. Therefore, SI once at vegetative stage can be recommended as the best management option for chickpea production in the study area.