Effects Of Ridge-furrow System With Supplemental Irrigation On Growth,Yield And Water Use Efficiency Of Winter Wheat Under Simulated Rainfall Conditions

The ridge-furrow?RF?rainwater harvesting system is an efficient way to enhance rainwater accessibility for crops and increase winter wheat productivity in semi-arid regions.However,the RF system is mainly applied to dry-land farming system and has not been popularized and applied in irrigated dry-land farming system.To exploit its efficiency on a large-scale,the RF system needs to be tested at different amounts of supplemental irrigation under simulated rainfall conditions.Therefore in during the 2015-16 and 2016-17 winter wheat growing seasons,we examined the effects of two planting patterns:?1?the RF system and?2?traditional flat planting?TF?with two supplemental irrigation levels?150,75 mm?under three simulated rainfall intensity?1:275,2:200,3:125 mm?were set up,to determined the effects of different treatments on soil moisture,water consumption,grain filling rate,biomass,yield and net economic benefit.The main findings are as follows:1.Impacts of rainwater harvesting on soil moisture,temperature,respiration and wheat productivityThe topsoil?from 5–25 cm?temperature and ET were significantly higher under TF planting than the RF system,which increased soil water content at 0 to 200 cm and soil respiration rate at each growth stage.The RF2₁₅₀ treatment exhibited fast and stable seedling establishment due to its high soil moisture,regulating soil temperature and respiration rate,reduced ET and prolonged the period of water accessibility which led to longer growth duration,and thus significantly enhanced grain yield?19%?and WUE?76%?compared to TF2₁₅₀ treatment.Simulated rainfall and supplemental irrigation has significant effects on leaf area per plant and total biomass per plant at different growth stages,but there were no significant increases in moisture contents,soil temperature,soil respiration rate,ET,WUE,crop development,or grain yield,as precipitation increased from 200 to 275 mm under both planting models.2.Effects of rainfall harvesting irrigation on photosynthetic characteristics,dry matter accumulation and water use efficiency of winter wheatUnder the RF cultivation technique with 150 mm supplemental irrigation and 200 mm simulated rainfall level can efficiently improve moisture content,thus significantly increased the average net photosynthetic rate?Pn??10.4%?,stomatal conductance?Gs??27.2%?,transpiration rate?Tr??9.3%?,intercellular CO₂ concentration?Ci??4.0%?,dry matter translocation?31.6%?,translocation efficiency?15.2%?,pre-flowering assimilate translocation to grain?10.6%?,grain yield?18.9%?,WUE?75.8%?and economic return(12197 Yuan ha^-1)of winter wheat,while significantly reduce?32.7%?ET rate compared with F cultivation technique.The photosynthetic characteristics of winter wheat were positively correlated with the dry matter translocation,soil water content and grain yield.3.Effect of rainfall harvesting on grain filling and hormone balanceThe results indicated that RF₁₅₀ treatment with 125 mm rainfall,a significantly improved seed filling rate was observed in the basal and upper seeds.The RF₁₅₀ treatment with 200 mm precipitation also significantly improved the single seed weight and seed filling rate in the basal and upper seeds.In contrast,the RF system with 275 mm precipitation showed no significant influence on the seed filling rates and seed weight of basal and upper seeds under either supplemental irrigation level.The RF system increased?IAA?indole-3-acetic acid and?Z?zeatin+?ZR?zeatin riboside contents at 125 and 200 mm simulated rainfall level.The RF system under150 mm supplemental irrigation showed decreased?ABA?abscisic acid and gibberellic acid?GAs?in the basal and upper seeds.At 275 mm precipitation,the RF system had no significant effect on IAA,Z+ZR,ABA and GA contents in the basal and upper seeds of panicles.The IAA,Z+ZR,ABA and GAs in the seeds were positively correlated with the maximum and mean seed-filling rate and the maximum seed weight.4.Effect of rainfall harvesting with supplemental irrigation on anti-oxidative defence system and photosynthesis of flag leaves under simulated rainfall conditionsThe RF2₁₅₀ treatment increased soil water content at jointing and stages and increased flag leaf photosynthetic pigment content and net photosynthetic rate?Pn?due to decreased MDA content and oxidative damage at different growth stages of winter wheat.The RF2₁₅₀ treatment significantly improved the activities of superoxide dismutase?SOD?,peroxidise?POD?,catalase?CAT?,ascorbate peroxidase?APX?and soluble protein content?SP?at different growth stages of winter wheat,and attained a highest value at flowering stage,while significant reducing the contents of proline,MDA,H₂O₂ and O₂ in flag leaves.The free H₂O₂ and O₂ scavenging ability and better anti-oxidative enzymes activities under the RF2₁₅₀ treatment were due to the lower level of lipid peroxidation,which effectively protected the photosynthetic machinery.The contents of chlorophyll ab,SOD,POD,CAT,APX and SP were negatively correlated with the content of proline,MDA,H₂O₂ and O₂.The results showed that RF2₁₅₀ treatment in semi-arid areas of China was an ideal water-saving management measure,which could significantly delay flag leaf senescence and increase SWC,chlorophyll ab,Pn and antioxidant enzyme activities of flag leaf.