Effects Of Sowing Date And Sowing Rate On Grain Yield And Utilization Efficiency Of Different Spike Winter Wheat

In order to study the effects of sowing date and sowing rate on population dynamics ofwheat, yield and yield components, nitrogen accumulation and transportation, root lengthdensity of different soil depth、15N-labelled urea N absorption and nitrogen utilizationefficiency of winter wheat. Under field conditions,use varieties of Tainong18(T18) andShannong15(S15) as materials, set different planting densities (135×10~4(T1),270×10~4(T2)and405×10~4(T3) plants ha-1for T18;172.5×10~4(S1),345×10~4(S2) and517.5×10~4(S3)plants ha-1for S15), three sowing dates(Otc.4th(D1),Otc.9th(D2) andOtc.14th(D3)), and inject15N-labelled urea in the20,60,100cm at emerging and jointing. Thefollowing are the main research results:1Effects of sowing date and sowing rate on population dynamics of wheatThe number of tillers of two wheat varieties have a trend that first increased and thendecreased during the growth period, the number of tillers is decreased with the delayedsowing date, but the rate of tillering significantly improved as the delay of sowing date; thenumber of tillers is increased as density increased, tillering rate has dropped significantly.The dry matter of two wheat varieties present “S” shape curve trend during the growthperiod, dry matter at earlier stage is decreased as the sowing date delayed, the later is risedwith the sowing date delayed; the dry matter is increased as the density increased, but thesecond density of D1gradually exceeds the maximum density after anthesis.The leaf area index of two wheat varieties shows a trend that first increased and thendecreased during the growth period, with the sowing date delayed the variation of leaf areaindex becomes easing, and the leaf area index of later sowing date is less than the earliersowing date. But leaf area index of later sowing date exceeds earlier sowing date and maintaina longer time at late growth stage. The leaf area index is increased as the density increased,but the second density of D1gradually exceeds the maximum density after anthesis.The plant height and Percentage of internodes (1+2) length of total intenode length of two wheat varieties are reduced significantly with the sowing date delayed, and increasedwith the density increased.2Effects of sowing date and sowing rate on grain yield and its components of wheatThe components of yield: spikes, kernels,weight per103kernels is influenced significantby sowing date and sowing rate. As the delay of sowing date, spikes decrease and kernels,weight per103kernels increase; as the decreasing of density spikes increase, kernels, weightper103kernels decrease. Grain nitrogen concentration decreases as sowing date and sowingrate. The yield is influenced by sowing date and sowing rate, and except the second density ishigher than the other tow at D1, grain yield increase as delayed sowing date and increasingsowing rate at other treatments.The interaction between sowing date, sowing rate and grainyield reach a significant level。3The effect of sowing date and sowing rate on nitrogen accumulation andtransportation of wheatFrom emerging to jointing, nitrogen accumulation of both wheats decrease with the delayof the sowing date and increase with the increasing of the density. Jointing toanthesis,nitrogen accumulation of TN18and SN15reaches maximum in second densityduring D1；there is no difference between D2、D3of TN18, on the other hand, SN15increaseswithin the increasing density; however, there is significant difference between S1and S2、S3during the D2, the difference between S2、S3is minor. The accumulation of nitrogen inTN18and SN15from anthesis to maturity increases with the delay of sowing date, and decreaseswith the increasing density. At maturity, the accumulation of nitrogen of the second densityreaches maximum in D1, others increasing with the growing density and delay of the sowingdate.4The effect of sowing date and sowing rate on root length density of wheatDuring the jointing, the root length density of TN18and SN15increases with theincreasing density of both sowing dates, except0-40cm is the increasing ratio of maximumdensity, the40-80cm and80-120cm all shows the second density is the maximum. Duringanthesis and middle grain filling, no matter it is early sowing or late sowing date, the rootlength density both increase with the increasing density, proportion increasing of the highestdensity takes the highest. Under the early sowing date, the proportion increasing of rootlength density decreases from jointing step by step, however after the delay of sowing date, the proportion increasing of root length density increases from jointing.5The effect of sowing date and sowing rate on nitrogen utilization efficiency of wheatThe15N-labelled urea N absorption of TN18and SN15both increase with the increasingof sowing rate, and the highest proportion increasing in the highest density. The proportionincreasing of the15N-labelled urea N absorption increases significantly with the increase ofmarking depth. The highest proportion increasing of the15N-labelled urea N absorption of allmarking depths is highest in D3, no matter what sowing date thatTN18and SN15are using.Except D1, the Above-ground N uptake increases with the delay of sowing date and theincrease of sowing rate, this results the increasing efficiency of both nitrogen-uptakeefficiency and nitrogen-use efficiency.Comprehensive thinking, it is possible to realize the improvement of both grain yield andnitrogen-use efficiency by properly delay the sowing date and increase sowing rate. Underthis experiment, the best sowing date forTN18and SN15to get higher yield and andnitrogen-use efficiency is October14; the sowing rate should be405×10~4(T3) plants ha-1and517.5×10~4(S3)plants ha-1.