| 【 Object 】 The application of drip irrigation technology in wheat production has effectively saved irrigation water and significantly improved water and fertilizer use efficiency of wheat production in Xinjiang Uygur Autonomous Region.However,the traditional drip irrigation layout(one drip tube only supplies 4 rows of wheat,row spacing is 15 cm,and the horizontal distance between the two drip tubes is only 60 cm,denoted as TR4)has many shortages,such as,large amount usage of drip tubes,more water consumption,which makes lower economic return especially in wheat production system,which seriously hinders the enthusiasm of growth wheat for local farmers.At present,expanding the ratio of drip tube to wheat rows(ETR)(increasing the number of wheat rows supplied by single drip tube)is an effective cultivation technique to reduce the input of drip tube.However,because the lateral movement of irrigation water in the soil under drip irrigation is limited,ETR can lead to increased heterogeneity of soil moisture distribution between different wheat rows,then can increased the risk of heterogeneity in yield and water use efficiency(WUE)between rows.This ultimately leads to lower overall yield and economic benefits.Therefore,developing and exploring ETR patterns to reduce drip tube input while keeping high yield levels and WUE in order to support the sustainable development of drip irrigation wheat production and assure food security in Xinjiang.【Methoes】 A field experiment of drip-irrigated wheat was conducted in Shihezi,Xinjiang,involving seven drip-irrigation patterns:(1)Traditional Xinjiang "1 tube supplies 4 rows"(TR4,where one drip tube supplies four rows of wheat,with a row spacing of 15 cm,and a distance of 60 cm between drip irrigation tubes(as control));(2)"Normal 1 tube supplies 6 rows"(TR6,where one drip tube supplies six rows of wheat,with a row spacing of 15 cm,and a distance of 90 cm between drip irrigation tubes);(3)"Normal 1tube supplies 8 rows"(TR8,where one drip tube supplies eight rows of wheat,with a row spacing of 15 cm,and a distance of 120 cm between drip irrigation tubes);(4)"Optimized narrow-row spacing with 1 tube supplies 6 rows"(TR6L,one drip tube supplies 6 rows of wheat,with an inner-row spacing of 10 cm and an outer-row spacing of 35 cm,and a distance of 90 cm between drip irrigation tubes);(5)"Optimized narrow-row spacing and narrow-tube width with 1 tube supplies 6 rows"(TR6S,one drip tube supplies 6rows of wheat,with an inner-row spacing of 10 cm and an outer-row spacing of 25 cm,and a distance of 80 cm between drip irrigation tubes);(6)"Optimized narrow-row spacing with 1 tube supplies 8 rows"(TR8L,one drip tube supplies 8 rows of wheat,with an inner-row spacing of 10 cm and an outer-row spacing of 45 cm,and a distance of 120 cm between drip irrigation tubes);(7)"Optimized narrow-row spacing and narrow-tube width with 1 tube supplies 8 rows"(TR8S,one drip tube supplies 8 rows of wheat,with an inner-row spacing of 10 cm and an outer-row spacing of 25 cm,and a distance of 100 cm between drip irrigation tubes).Additionally,two representative spring wheat varieties were selected,including the Xin chun44(XC44)with small inter-row yield difference and the Xin chun22(XC22)with large inter-row yield difference.Asplit-plot design was adopted in this experiment,with wheat variety as the main plot and drip irrigation patterns as the sub-plot.The optimal drip irrigation patterns for cost-saving,yield-increasing and hight-efficiency in Xinjiang was established by comparing the overall yield,WUE,and economic benefits of the above 7 types of drip irrigation pattern.Based on this,the spatial differences in yield,WUE,soil moisture status,root interception of water(RIW),biomass accumulation and transport,canopy structure and photosynthetic performance,as well as the lodging resistance of plants under these patterns were studied to clarify the physiological mechanisms of yield and WUEunder various drip irrigation patterns.【Results】(1)Comparison of overall yield,water use efficiency(WUE),and economic benefits under different drip irrigation patterns:Compared with TR4,the normal ETR patterns(TR6 and TR8)significantly reduced wheat yield,with a decrease of 5.60%-7.91%(TR6)and 9.72%-13.75%(TR8),respectively.However,the yield reduction of the narrow-row ETR patterns(TR6L and TR8L)was significantly less,with a decrease of 1.85%-4.36%(TR6L)and 4.90%-10.71%(TR8L),respectively.The yield reduction of the narrow-row and narrow-tube ETR patterns(TR6S and TR8S)was further reduced,with a decrease of 0.24%-1.24%(TR6S)(no significant difference with TR4)and 2.09%-4.21%(TR8S),respectively.Compared with TR4,WUE was all increased by all the ETR patterns.Among them,the normal ETR patterns(TR6 and TR8)showed the highest WUE increase,ranging from 3.91% to 13.12%;the narrow-row ETR patterns(TR6L and TR8L)showed a WUE increase ranging from 2.10% to 5.66%;while the narrow-row and narrow-tube ETR patterns(TR6S and TR8S)only showed a WUE increase of 0.12% to 3.40%.In terms of the ultimate economic benefit,compared with TR4,the normal ETR patterns(TR6 and TR8)cut cown the economic benefit by 1.03% to 8.71%,and the narrow-row ETR patterns(TR6L and TR8L)increased the economic benefit by 0.44% to 5.07%;while the narrow-row and narrow-tube ETR patterns(TR6S and TR8S)increased the economic benefit by 3.44% to 5.92%.In addition,the variety XC44 with small differences in inter-row yield had a higher yield than the variety XC22 with large differences in inter-row yield.(2)The grain yield and water use efficiency betweem rows under different drip irrigation patterns:Under the normal ETR patterns(TR6 and TR8),wheat yield showed a significant decreasing trend from the first row near the drip line(R1)outward,increasing the heterogeneity of yield among rows(yield coefficient of variation(C.V)ranging from 3.9 to 14.5).In contrast,under the narrow-row ETR patterns(TR6L and TR8L),the yield reduction of remote rows was mitigated,resulting in a reduction of row-to-row yield heterogeneity(C.V from 1.3 to 11.9).The yield reduction of remote rows(C.V from 1.1 to 8.6)was reduced more by the narrow-row and narrow-tube ETR patterns(TR6S and TR8S).Further studies have shown that yield performance is mainly related to the number of effective spikes and grain,under little influence from thousand-grain weight(the inter-row difference in thousand-grain weight did not reach a significant level).Besides,under the normal ETR patterns(TR6 and TR8),WUE showed a significant increase trend from R1 to the outside,causing a significant increase in the heterogeneity of WUE between rows(C.V was 6.5-13.6).However,the narrow-row ETR patterns(TR6L and TR8L)reduced the increase in WUE in the outer rows,thereby reducing the inter-row heterogeneity of WUE(C.V was 2.9-7.0).The narrow-row and narrow-tube ETR patterns(TR6S and TR8S)further reduced the increase in WUE in the outer rows,resulting in the lowest inter-row heterogeneity of WUE(C.V was 2.2-5.7).(3)Soil moisture conditions and plant interception of irrigation water:The normal ETR patterns(TR6 and TR8)resulted in lower soil moisture content in the distant rows and a significant difference in soil moisture content between distant rows and R1.The narrow-row ETR patterns(TR6L and TR8L)decreased the difference in soil moisture content between the distant rows and R1.Furthermore,the narrow-row and narrow-tube ETR patterns(TR6S and TR8S)showed the smallest differences in soil moisture content between rows.Regarding the differences in RIW between different drip irrigation patterns,the RIW of the normal ETR patterns(TR6 and TR8)showed a gradient decline from R1 to distant rows,with a significant difference in RIW among rows.The optimized ETR patterns(TR6L,TR6 S,TR8L,and TR8S)effectively increased RIW in the far rows,thereby reducing the differences in RIW among rows.Consenquently,the optimized ETR patterns(TR6L,TR6 S,TR8L,and TR8S)had higher soil moisture content and better RIW than their corresponding normal ETR patterns(TR6 and TR8).(4)Characteristics of wheat’ s dry matter accumulation and its translocation:The normal ETR patterns(TR6 and TR8)showed a sharp decrease in dry matter accumulation and its transport from R1 to the outer rows.However,TR6 L,TR6S,TR8 L,and TR8 S significantly alleviated this trend that the dry matter accumulation and the transport of the outer rows were even higher than those of the adjacent inner rows.Ultimately,compared with TR4,normal ETR patterns(TR6 and TR8)significantly reduced dry matter accumulation and its transport.The dry matter accumulation and its transport of the optimized ETR patterns(TR6L,TR6 S,TR8L,and TR8S)were also reduced to some extent,but significantly higher than those of the corresponding normal ETR patterns(TR6 and TR8).In addition,in the drip irrigation patterns with enlarged pipe-row ratio,the transport and contribution of dry matter to grains in the outer rows increased significantly(higher than those in the inner rows).(5)Lodging resistance of wheat:The marginal effect index of grain yield under the drip irrigation patterns with equal row spacing(TR4,TR6,and TR8)are all negative(-0.32 to-19.55),but all positive for the optimized ETR patterns with narrow-row ETR patterns(TR6L and TR8L)and the narrow-row and narrow-tube ETR patterns(TR6S and TR8S),,with the marginal effect index of grain yield for TR6 L,TR6S,TR8 L,and TR8 S ranging from0.95% to 5.77%,-0.42% to 0.73%,3.71% to 5.66%,and 0.38% to 6.45%,respectively.The optimized ETR patterns(TR6L,TR6 S,TR8L,and TR8S)increased the flag leaf height and angle of the far-row wheat,improved the net photosynthetic rate of the flag leaf,and improved the accumulation of endogenous substances in the basal stem,ultimately significantly enhancing the mechanical lodging resistance of the basal stem.Compared with TR4’s lodging rate(7.22% to 42.41%),the normal ETR patterns(TR6 and TR8)significantly increased the lodging rate of wheat(10.82% to 48.21%).On the contrary,the optimized ETR patterns(TR6L,TR6 S,TR8L,and TR8S)effectively reduced the lodging rate(5.62% to 41.73%).【Conclusion】(1)This study successfully estzblished a cost-effective and yield-enhancing drip irrigation pattern with wide row spacing.Taking into account yield,lodging resistance,and economic benefits,the narrow-row and narrow-tube ETR pattern TR6 S is highly recommended in Xinjiang.For cultivar selection,it is suggested to choose varieties with small differences in inter-row yield,such as XC44.(2)The overall yield performance of different drip irrigation patterns is related to the inter-row heterogeneity of wheat yield and WUE.Under the normal ETR patterns(TR6 and TR8),the yield and WUE of the distant wheat vary greatly,which increases the inter-row heterogeneity of yield and WUE,constituting the main reason for the low overall yield.In contrast,the narrow-row ETR patterns(TR6L and TR8L)reduced the decline in yield of far-row wheat,decreased the heterogeneity in yield and WUE among rows,and alleviated the degree of yield decline.The narrow-row and narrow-tube ETR patternss(TR6S and TR8S)were able to further reduce the heterogeneity in yield and WUE among rows and achieve high and stable yields.(3)The optimized ETR patterns(TR6L,TR6 S,TR8L,and TR8S)improved the soil moisture conditions,resulting in a more homogeneous soil moisture and RIW among rows.This played a critical role in reducing the heterogeneity of yield and WUE among rows.(4)The optimized ETR patterns(TR6L,TR6 S,TR8L,and TR8S)maintained higher levels of dry matter accumulation and its transport,improved the rate transport and contribution of dry matter to grains,and partially compensated for the yield loss caused by water deficiency in the far rows.(5)The optimized ETR patterns(TR6L,TR6 S,TR8L,and TR8S)induced marginal effects,optimizing the canopy structure and improving photosynthetic performance,which not only increased the yield of far-row wheat,but also enhanced wheat lodging resistance.This has played an important role in reducing the heterogeneity of yield and WUE among rows,thus achieving high and stable yields.The results of this study can lay a theoretical foundation for further optimizing the pattern of drip irrigation systems for wheat production in arid areas. |
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