Quantitative Study On Demand Of Active Accumulated Temperature Of Different Cultivars Of Maize

The objective of this study is to determine the demand of maize cultivars of different maturities on active accumulated temperature (T) during growth period and the main growth stages, their process of unfolding leaves, the spike differentiation stages. Different cultivars are selected and carried out with different sowing dates in 2012 and 2013; moreover, we also research maize cultivars of different maturities in regional test in Shanxi Province in 2012 and 2013. The results as follows:1) For days of growing stages, required active accumulated temperature from sowing stage to maturing stage and leaf number, it existed high significant positive correlation between each other. Three factors expressed ripe stage type of cultivars. Among them, days of growing stages and required active accumulated temperatur e from sowing stage to maturing stage were main indexes for ripe stage type expression.56 cultivars were classified into four types according to above three factors by clustering analysis. The result showed that growth period and active accumulated temperature of main growing stage increased with the delay of ripe stage. Difference of active accumulated temperature requirement of different cultivars mainly reflected the requirement during sowing stage and silking stage.2) With the delay of sowing dates, the jointing stage and silking stage and mature stage of cultivars delayed. With the delay of sowing dates, growth period of early-maturing cultivars reduced and growth period of medium-maturing and late-maturing cultivars reduced first and then extended, In generally, when sowing date was delayed by one day, the growth period reduced by 0.34 day. Temperature and sunlight use efficiency was decline with the delay of sowing date. In the range of safe mature sowing date, temperature and light use efficiency of the whole growth period performed as late-maturing cultivar>medium-maturing cultivar>early-maturing cultivar. Sowing date has a great influence on growth period and days of main growing stage and required active accumulated temperature. The difference of growth period and days of main growing stage of different types of cultivars between years was great. Active accumulated temperature between years of whole growing period for all early-maturing cultivars was relatively stable. Moreover, through step-wise regression analysis of active accumulated temperature (X1), sunshine duration (X2) mean daily temperature (X3), precipitation (X4), the optimal regression equation of seedling stage was Y=21.972+0.045X1+0.009X2-1.056X3+0.008X4 (R2=0.993). The optimal regression equation of ear stage was Y=40.34+0.043X1-1.728X3 (R2=0.999).The optimal regression equation of flower stage was Y=51.965+0.031X1+0.039X2-2.310X3+0.009X4 (R2=0.996). The optimal regression equation of whole growing period was Y=128.806+0.044X1-5.698X3 (R2=0.998).3) Along with the delay of sowing dates, the demand of maize cultivars of different maturities on time (in days) and active accumulated temperature (T) during their process of unfolding leaves decreases. The time it takes to unfold one leaf can be as little as 0.3d, and as much as 7.6d, with the corresponding active accumulated temperature to be 8.3℃,140.4℃, respectively. The unfolding of the 1st and the last leaves need the least time and active accumulated temperature, while the 4th-9th leaves need the most. From the normalized number of unfolded leaves and active accumulated temperature for all cultivars in 2012, fitting curves were obtained using Curve Expert 1.4. Among different fitting models, the 3rd degree polynomial fitting model y=a+bx+cx2+dx3 may have the simplest physical meaning and thus adopted. In the model, a is the relative number of unfolded leaves of seedling period, while (a+b+c+d) is the relative number of unfolded leaves of tasseling stage and should be near value one. The model is tested with the data of 2013, and it is found that the accuracy (k) is above 0.9320**, and the precision (R2) above 0.9913**. It is also found that the model of active accumulated temperature obtained from 2-hourly T, daily leave counting is more accurate than that from 6-hourly T,5-day leave counting or min-max T and 5-day leave counting. Sowing dates have significant influence on the unfolding rate of leaves in different cultivars of maize especially those with relatively short maturity. The average unfolding rates of different cultivar group were obtained as Xingnongearly 3>Xieyuearly 1> Zhengdan 958>Xianyu 335> Dafeng 26>Luyu 36. The unfolding rates decelerate and accelerate before and after the jointing stage, respectively.4) With the delay of mature type, the time of entering the spike differentiation stages will be delayed. The start time of the spike differentiation stages will be earlier with the delay of sowing date. The duration of the spike differentiation stages among mature types shows that: early-maturing variety<medium variety<medium-late variety. The sowing dates have larger influence on the early of the spike differentiation.