| Summer maize is the main crop in the Guanzhong yellow river irrigation district of Shaanxi Province.In recent years,the technology of maize higher planting density has been vigorously implemented to improve the maize yield.However,the investigation shows that the high density planting resulted in the lodging,premature senescence and aggravation of diseases and insect pests,which seriously affected the yield improvement and economic benefits of farmers,and the enthusiasm of farmers to grow grain.For this reason,8 varieties were selected from local maize varieties,69000 plants/hm~2 were set up for high density test,and 8 different density gradient tests were carried out with 4 primary varieties in Zangcun,Liuqu Town,Fuping County,2016?2017.These main results were as follows.1.A high density comparison tests(8 primary varieties,including Shandan 608,Shandan 606,Shandan 518,Yudan 9,Jundan 20,Shandan 609,Zhengdan 958 and Qinnong11)were conducted to select four varieties(Jundan 20,Shandan 609,Yudan 9 and Zhengdan 95),which were suitable for highdensity and highyield summer maize varieties in this area.The yield was following by 10578.2 kg/hm~2,10486.5 kg/hm~2,10442.5 kg/hm~2 and10264.7 kg/hm~2,respectively.2.A significant difference was recorded in the suitable density among variety;Planting density had significant influence on maize yield.The suitable density ranged from75000 plants/hm~2 to 90000 plants/hm~2 with high yield under the existing palnting techniques in eastern Guanzhong irrigation.The four maize varieties had the highest yield at the density of 82500 hm~2 and 90000 hm~2 in two years.The Shandan 609 and Zhengdan 958 maximum yield was 10625.5 kg/hm~2 and 11181.5 kg/hm~2,respectively,under 90000 plants/hm~2.The Junchan 20 and Yudan 9 got 10413.6 kg/hm~2 and 10828.7 kg/hm~2 under 90000 plants/hm~2.The comparing different density gradients showed that the optimum yield density of Shandan 609 and Zhengdan 958 was 82500?90000 plant/hm~2,and the optimum yield density of Junchan 20 and Yudan 9 was 75000?82500 plant/hm~2.3.Under high density planting,spraying 30%amine fresh ester vinyl and 15%paclobutrazol at 10 leaf stage made plant height decrease by 28?31 cm,the ear height decrease by 20?23 cm,bald tip decrease by 0.3?0.4cm,stem diameter increase by 0.40?0.45 cm,the third node at the stem base shorten by 10.7 cm?11.4 cm,and single plant aerial rooting increase by 4.0?4.5,ans thus significantly improving the plant's ability to resist lobed and field permeability conditions.These tequenologies can increase the yield by 6%?8%.4.The 30 m3/hm~2 of biogas slurry application at the male stage,made the maize leaf color dark green,the function prolong,the maturity delay by 3?4 day,the hundredgrain weight increase by 1.1?4.1g,and the yield increase by 13.7%.5.15?45 million Trichogramma per hectare were released to control corn borers,its preventive effect can reach 47.8%?72.7%during the peak spawning period of maize borer(25 July?2 August).the results showed that 225?450 trap plates were suspended per hectare in the middle and late stages of maize.After 25 day later,the number of leaf spots in maize leaves treated by hanging trap plate was 46.9%?90.1%lower than that of the control. |
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