Growth Dynamics And Optimum Harvest Stage Of Two Forage Maize Varieties

SAUMZ1 and SAUMZ2 are two forage maize varieties reproduced by hybridizing inbred lines of cultivated maize with the chromosome substitution line derived from the cross between cultivated maize and tetraploidy and diploidy perennial teosinte. These two hybrids have strong heterosis and high vegetative yield, resulting from the advantage complement between the productivity of cultivated maize and the stress adaptability of perennial teosinte. As forage species,the harvest stages of forage maize varieties are not as crutial as cultivated maizes. However, the investigation and analysis of the growth dynamics can help us to find the optimum harvest period, and gain the maxmium yield, find the appropiate technology for different new varieties.SAUMZ1 and SAUMZ2 were planted in a random block design with three replications.Relative feed value, growth periods, effective tempeatature summations and leaf ages were used to predict the optimum harvest period with fresh matter and dry matter yields,nutrition,length and tillering number data. The main results are as follows:(1) The yield growth dynamics of two forage maize varieties. conform to Logistic model.SAUMZ1 began to have higher rate in the growth dynamics of fresh matter at 17th leaf,dry matter at 20th leaf,and the maximum rate in 20th leaf and 24th leaf,6.43 t/hm~2 per leaf age and 1.62 t/hm~2 per leaf age,and began to have lower rate at 23rd leaf and 27th leaf.SAUMZ2 began to have higher rate in the growth dynamics of fresh matter at 13rd leaf,drymatter at 15th leaf age,and the maximum rate at 16th leaf age and 19th leaf age,6.53 t/hm~2 and 0.86 t/hm~2 per leaf age,and began to have lower rate at 19th leaf and 23rd leaf.(2) The changes of Grading Index of forage maize varieties conform to linear model.Both SAUMZ1 and SAUMZ2 decline.The decline rate are -0.4266 and -0.2743.So,as the fields increase with growth of leaf,the rate of digested nutritions decline,However,the optimum harvest period is not the leaf age that the maximum field gained ,nor the leaf age that the field began to decline.To predict the optimum harvest period of the SAUMZ1 and SAUMZ2 need to consider both yield and nutrition,according to the digested enegy changes per hectare.(3) The Grading Index changes of forage maize varieties per hectare conform to(?) and (?)indicating the energy of SUAMZ1 digested gained by cows per hectare,x for leaf age. SUAMZ1 has a growth in energy before 25th leaf age,the maximum growth rate appear at 21st leaf age(84th day,971℃, effective temperature summation), 3227.5 MJ/hm~2 per leaf age. The energy began to decline at 25th leaf age. We can gain the maximum energy 26075MJ/hm~2, at 25th leaf age. SUAMZ2 has a growth in energy before 22th leaf age, the maximum growth rate at 17th leaf age(72th day, 815℃), 2056 MJ/hm~2 per leaf age. The digested energy began to decline at 22th leaf age. We can gain the most energy 20973 MJ/hm~2, at 22th leaf age.So,the optimum harvest period of SUAMZ1 should be at 25th leaf age, the effective temperature summation at 1160℃, SUAMZ1 at 22th leaf age, the effective temperature summation at 1097℃.