| A field experiment was conducted using the Jimai 22 wheat cultivar under standard field conditions in the Shiwang village?35°40?N,116°41?E?,Yanzhou district,Jining city,Shandong Province,northern China,during the 2014-2019 wheat-growing seasons.The aim of this experiment was to study the characteristics of soil and winter wheat plants under various tillage practices and the physiological basis of high yield and water saving in wide-range sowing of wheat.Successive years of rotary tillage resulted in shallower plough layer,harder plow pan and poor soil water and air permeability,thus hindering the growth of crop root system.And successive years of plowing tillage lead to soil erosion,excessive energy consumption and reduced benefits.Therefore,the research team established a water-saving cultivation technology of wheat with subsoiling and reduced tillage,and studied its effect on soil and plant characteristics in wheat field,so as to provide a theoretical basis for water-saving and high-yield cultivation of wheat.During the 2014-2015 and 2015-2016 growing seasons,four tillage treatments were tested,namely rotary tillage?RT?,strip rotary tillage?ST?,strip rotary tillage with a two-year subsoiling interval?STS?,and conventional plowing tillage?PT?.All tillage treatments were replicated three times and followed a randomized block design.Conventional drilling sowing was crowded in a single line,which led to lack of seedlings,clumps of seedlings,low nutrient area per plant,poor individual development,unreasonable canopy structure and poor ventilation and light transmission in the field.And wide-range sowing was a kind of decentralized seed sowing with wide sowing.Therefore,we studied the effect of wide-range sowing on water consumption characteristics and yield of wheat,in order to clarify its physiological basis of water-saving,yield increasing and efficiency increasing,and provide a theoretical basis for water-saving and high-yield cultivation of wheat.During the 2017-2018 and 2018-2019 growing seasons,the experiment was set up as a split-plot design with three replicates.The main-plot treatments consisted of three row spacings,namely 20 cm?20?,25 cm?25?and 30 cm?30?.The sub-plot treatments consisted of two sowing patterns:wide-range sowing?K?and conventional drilling sowing?T?.The wide-range seeder adopts the socket-roller seeding device,double row seed tube,and the sowing width is 8 cm.The conventional drilling seeder adopts the outer groove wheel seeding device,single row seed tube,and the sowing width is 3 cm.1 Effects of various tillage practices on the characteristics of soil and wheat plants1.1 Effects of various tillage practices on soil physicochemical and microbial properties in wheat fieldsThe soil bulk density of the 15-45 cm soil layers,and the soil water content of the 40-60cm soil layers in STS treatment were significantly lower than in the RT and ST treatments.The soil porosity,soil organic matter,and total nitrogen content in the 15-45 cm soil layers were significantly higher in the STS treatment than in the RT and ST treatments.The soil respiration rate in the 15-45 cm soil layers and the soil microbial biomass carbon content in the 0-30 cm soil layers under treatment STS were significantly higher than under RT and ST treatments.These results indicate that treatment STS reduced soil bulk density and increased soil porosity,which improved the soil micro-ecological environment and soil fertility.1.2 Effects of different tillage practices on soil enzyme activity and soil fertility in wheat fieldsDuring the 2014-2015 growing season,the soil gaseous phase ratio and soil particle macro-aggregation in the 15-45 cm soil layers were higher in soils in the STS treatment than in soils in the PT,RT,and ST treatments.The soil penetration resistance of the 15-45 cm soil layers in the STS treatment was significantly lower than that of the 15-45 cm soil layers in the PT,RT,and ST treatments.Soil urease,invertase,phosphatase,and catalase activities in soils in the STS treatment were higher than those of soils in the PT,RT,and ST treatments.The hydrolysable nitrogen content in the 15-30 cm soil layers was higher in soils in treatment STS than in soils in treatment PT,and the lowest values were recorded in soils in the RT and ST treatments.In the 30-45 cm soil layer,the hydrolysable nitrogen content was significantly higher in soils in treatment STS than in soils in treatments PT,RT,and ST.In the 15-45 cm soil layers,soil available phosphorus and available potassium content were significantly higher in soils in the STS treatment than in soils in the PT,RT,and ST treatments.These results indicate that treatment STS enhanced the stability of soil aggregates,improved soil enzyme activities,and increased the content of soil available nutrients.1.3 Effects of various tillage practices on photosynthetic characteristics and dry matter production of wheatDuring the two wheat growing seasons,the highest photosynthetically active radiation?PAR?capture ratios post-anthesis were obtained in wheat plants grown in the STS treatment,followed by wheat plants grown in the PT and then RT treatments,with wheat plants grown in the ST treatment having the lowest PAR capture ratios.At 7,14,21 and 28 days after anthesis?DAA?,the highest leaf area index?LAI?was recorded in wheat plants in the STS treatment,followed by wheat plants in the PT treatment,whereas the lowest LAI was recorded in wheat plants in the RT and ST treatments.At 14,21 and 28 DAA,the highest chlorophyll content and net photosynthetic rate?Pn?in winter wheat flag leaves were observed in treatment STS,followed by treatment PT,and the lowest chlorophyll content and Pn were observed in treatments RT and ST.At maturity,dry matter?DM?accumulation was the highest in wheat plants in the STS treatment,followed by wheat plants in the PT,and then RT,and ST treatments.At 7,14,21 and 28 DAA,the sucrose content and sucrose phosphate synthase activity in winter wheat flag leaves were greatest in treatment STS,followed by treatment PT,and the lowest values corresponded to treatments RT and ST.These results demonstrate that treatment STS resulted in a high light energy interception rate during the grain filling stage,improved the photosynthetic assimilation capacity of flag leaves during the middle and late grain filling stages,extended the duration of high photosynthetic value,promoted the dry matter accumulation at maturity,and provided the foundation for obtaining high yields.During the two wheat growing seasons,at 14,21,and 28 DAA,the superoxide dismutase?SOD?activity and soluble protein concentrations in winter wheat flag leaves were highest in treatment STS,followed by treatment PT,with the lowest SOD activity and soluble protein concentrations recorded in treatments RT and ST.Malondialdehyde?MDA?concentrations in winter wheat flag leaves did not differ among treatments PT,RT,and ST,but were higher in these treatments than in treatment STS.These results indicate that treatment STS enhanced the scavenging capacity of superoxide free radicals,reduced cell damage,improved cell metabolism,and delayed flag leaf senescence.1.4 Effects of various tillage practices on root distribution and physiological characteristics,grain yield and water use efficiency of wheatDuring the two wheat growing seasons,at jointing,anthesis,and 20 DAA,the root weight density?RWD?,root length density?RLD?,root volume density?RVD?,root surface area density?RSAD?,root TTC reduction activities?RTRA?,root total absorption area?RTAA?,and root active absorption area?RAAA?in the 15-30 cm soil layers did not differ between treatments STS and PT,and were higher in treatments STS and PT than in treatments ST and RT.In the 30-45 cm soil layer,RWD,RLD,RVD,RSAD,RTRA,RTAA,and RAAA in treatment STS were significantly higher than in treatments PT,RT,and ST.These results indicate that the STS treatment promoted the growth and development of wheat roots,and improved the absorption and utilization of soil water and fertilizer by the wheat plant roots.During the two wheat growing seasons,at jointing and 20 DAA,the root indoleacetic acid and trans zeatin riboside content in the 0-45 cm soil layers was highest in the STS treatment,followed by the PT treatment,and the root indoleacetic acid and trans zeatin riboside content were lowest in treatments RT and ST.At jointing,the highest root abscisic acid content in the 0-45 cm soil layers was obtained in treatment ST,followed by treatment RT,and then treatment PT,with the lowest trans zeatin riboside content recorded in treatment STS.However,at 20 DAA,the trans zeatin riboside content was highest in treatments ST and RT,followed by treatment PT,and then treatment STS,and there was no significant difference between treatments ST and RT.After anthesis,the root soluble protein content,SOD,and catalase activity in the 30-45 cm soil layer under the STS treatment were significantly higher than those of the soil under PT,RT,and ST treatments.The root MDA content in the 30-45 cm soil layer did not differ among PT,RT,and ST treatments,and was significantly higher in these treatments than in treatment STS.These results indicate that treatment STS improved the antioxidant capacity of wheat roots,promoted root cell division,improved cell metabolism,and delayed root senescence.During the 2014-2015 growing season,the highest grain yield?GY?,spike number,and1,000-kernel weight were observed in treatment STS,followed by treatment PT,whereas the lowest values were observed in treatments RT and ST.Water use efficiency?WUE?did not differ between treatments PT,RT,and ST,but was lower in these three treatments than in treatment STS.During the 2014-2015 growing season,the highest GY and 1,000-kernel weight were obtained in treatment STS,followed by treatment PT and then treatment RT,with treatment ST having the lowest values.The spike number in treatments STS and PT was higher than that in treatments RT and ST,and the spike number in treatment RT was higher than that in treatment ST.WUE did not differ among treatments PT,RT,and ST,and was lower in these treatments than in treatment STS.These results indicate that treatment STS resulted in the highest grain yield and water use efficiency,and as such could be considered the optimum tillage treatment for high yield and water saving wheat cultivation under the experimental conditions of our study.2 Effects of wide-range sowing on water consumption and photosynthetic characteristics of wheat2.1 Effects of wide-range sowing on water consumption characteristics of wheatUnder row spacings of 25 cm and 30 cm,the amount of irrigation at jointing and anthesis,and the total amount of irrigation of plots with wide-range sowing?K?were significantly lower than those of plots with conventional drilling sowing?T?.Furthermore,the amount of soil water consumed and the ratio of total water consumption were significantly higher in treatment K than in treatment T.The soil water consumption from jointing to anthesis and anthesis to maturity,and water consumption,daily water consumption,and consumption percentage from anthesis to maturity were significantly higher in treatment K than in treatment T.Furthermore,the evaporation at the jointing and anthesis stages in treatment K was significantly lower than in treatment T.These results indicate that treatment K improved the absorption and utilization of soil water by wheat plants,and resulted in reduced use of irrigation water.The water consumption characteristics of wheat plants in treatment K were significantly better at 25 cm row spacing than at 30 cm row spacing.2.2 Effects of wide-range sowing on flag leaf photosynthetic and senescence characteristics of wheatUnder row spacings of 25 cm and 30 cm,at 0,14 and 28 DAA,the PAR capture ratios were higher in treatment K than in treatment T.At 25 cm row spacing,at 14,21,and 28 DAA,the Pn,transpiration rate?Tr?,and stomatal conductance?Gs?in winter wheat flag leaves of wheat plants under treatment K were significantly greater than those of winter wheat flag leaves of wheat plants under treatment T.At row spacing of 30 cm,at 7,14,21 and 28 DAA,the Pn,Tr,and Gs of winter wheat flag leaves in treatment K were significantly greater than those of winter wheat flag leaves in treatment T.At row spacings of 25 cm and 30 cm,the DM accumulation and single stem weight of wheat at the anthesis and maturity stages,and the distribution amount and contribution rate of DM accumulation post-anthesis to grains were significantly higher in treatment K than in treatment T.The13C distribution amount and ratio in grains of winter wheat were significantly higher in treatment K than in treatment T.These results indicate that treatment K improved the photosynthetic assimilation capacity of flag leaves during the middle and late grain filling stages,prolonged the duration of high photosynthetic value,and promoted dry matter accumulation and the amount of dry matter distributed directly to the grains after anthesis.The photosynthetic capacity of the flag leaves during the middle and late grain filling stages,dry matter production capacity,and the ability to transfer dry matter to the grains in wheat plants grown under treatment K were significantly better at 25 cm row spacing than at30 cm row spacing.At row spacing of 25 cm,at 14,21,and 28 DAA,the SOD activity and soluble protein content in winter wheat flag leaves were significantly higher in wheat plants grown in treatment K than those of wheat plants grown in treatment T.The MDA content in winter wheat flag leaves was lower in wheat plants grown in treatment K than in wheat plants grown in treatment T.At row spacing of 30 cm,at 7,14,21,and 28 DAA,the SOD activity and soluble protein content in winter wheat flag leaves in treatment K were significantly greater than those of winter wheat flag leaves in treatment T.At 14,21,and 28 DAA,the MDA content in winter wheat flag leaves in treatment K was lower than that in winter wheat flag leaves in treatment T.These results indicate that treatment K enhanced the scavenging capacity of superoxide free radicals,reduced cell membrane structure damage,and delayed flag leaf senescence.The ability to delay flag leaf senescence of wheat plants in treatment K was significantly better at 25 cm row spacing than at 30 cm row spacing.2.3 Effects of wide-range sowing on wheat nitrogen accumulation and soil nitrate nitrogen transportAt row spacings of 25 cm and 30 cm,the amount of nitrogen accumulated at the anthesis and maturity stages,nitrogen accumulated in grains at maturity,and the amount of nitrogen translocated and the contribution rate from vegetative organs to grains were significantly higher in wheat plants in treatment K than in wheat plants in treatment T.These results indicate that treatment K promoted the accumulation of nitrogen during the anthesis and maturity stages,as well as the transport of nitrogen stored in vegetative organs to grains,which promoted the accumulation of nitrogen in grains at the maturity stage.During the 2017-2018 growing season,at a row spacing of 25 cm,the nitrate-nitrogen content at maturity in the 60-160 cm soil layers was much lower in treatment K than in treatment T.At a row spacing of 30 cm,the nitrate-nitrogen content in 60-180 cm soil layers was significantly higher in treatment T than in treatment K.During the 2018-2019 growing season,at row spacing of 25 cm,the nitrate-nitrogen content in 40-140 cm soil layers at maturity was significantly lower in treatment K than in treatment T.At row spacing of 30 cm,the nitrate-nitrogen content in 40-160 cm soil layers was significantly higher in treatment T than in treatment K.These results indicate that treatment K was beneficial for the absorption and utilization of soil nitrate nitrogen by wheat plants,and reduced the leaching of nitrate nitrogen into the deeper soil layers.The accumulation of nitrogen,transport of nitrogen stored in vegetative organs to grains,and absorption and utilization of soil nitrate nitrogen by wheat plants grown in treatment K were higher at 25 cm row spacing than at 30 cm row spacing.2.4 Effects of wide-range sowing on root physiological characteristics,grain yield and water use efficiency of wheatAt row spacings of 25 cm and 30 cm,at jointing,anthesis,and 20 DAA,the root weight density,root length density,and root TTC reduction activities in the 0-40 cm soil layers were significantly higher in treatment K than in treatment T.At 0,10 and 20 DAA,the root SOD activity and soluble protein content in the 0-40 cm soil layers were significantly higher in treatment K than in treatment T.The root MDA content in the 0-40 cm soil layers was significantly lower in treatment K than in treatment T.These results indicate that treatment K improved the antioxidant capacity of wheat roots,delayed root senescence,and promoted the absorption and utilization of soil water and fertilizer by roots.The root activity and antioxidant capacity of wheat grown in treatment K were significantly higher at 25 cm row spacing than at 30 cm row spacing.At row spacings of 25 cm and 30 cm,the GY,WUE,and irrigation water use efficiency of wheat plants grown under treatment K were markedly greater than those of wheat plants grown under treatment T.These results indicate that wide-range sowing resulted in better GY,WUE,and irrigation water use efficiency than conventional drilling sowing.The GY,WUE,and irrigation water use efficiency of wheat plants grown under treatment K were significantly higher at 25 cm row spacing than at 30 cm row spacing.As such,treatment K under the condition of 25 cm row spacing resulted in the optimum treatment for water-saving and high yield cultivation of wheat under the experimental conditions of this study.The GY and irrigation water use efficiency under both treatments K and T were significantly lower at 20 cm row spacing than the GY and irrigation water use efficiency of treatment K at 25 cm and 30 cm row spacing. |
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