| The experiments were conducted in 2013-2014 at the Maize Technological Innovation Center of the north China plain(NCP), located at Shandong Agriculture University(36°09′N, 117°09′E, 128 m above sea level) in Taian and state key laboratory of crop biology. Using different maize varieties as materials, one is Zheng Dan958(ZD958), and another is Denghai 661(DH661), which were planted in the fields at three nitrogen fertilization depths(0 cm, 20 cm, 40 cm). By studying the influence of different fertilization depth on time and space distribution characteristics of root, leaf development, photosynthetic performance, grain development and the characteristics of plant nitrogen uptake in high- yielding corn, ascertain the effects of different fertilizer application depth on root distribution and the yield formation of corn.The main results were as follows:1. Effect of different fertilizer application depth of nitrongen on grain yields in summe r maizeNitrogen deeply fertilizated significantly increased the grain yield of two varieties. The biggest increase of yield is fertilization depth at 20 cm. Compared with surface broadcasting, the grain yield of ZD958 on 20 cm fertilization depth and 40 cm fertilization depth treatments increased by 19.13% and 15.63% at R6 stage, respectively. And, the grain yield of DH661 of 20 cm fertilization depth and 40 cm fertilization depth increased by 20.95% and 18.06% at R6 stage, respectively. For the yield components, because the planting density was same of each treatment, so there was no significant difference among ear harvested per hectare of different treatments.While, grains per ear and kernel weight significantly increased after deep fertilization. Compared with surface broadcasting, the grains per ear and kernel weight of ZD958 in 20 cm fertilization depth and 40 cm fertilization depth treatments increased by 7.11%, 4.25%(20 cm) and 4.56%, 3.74%(40 cm), respectively. The grains per ear and kernel weight of DH661 in 20 cm fertilization depth and 40 cm fertilization depth treatments increased by 12.61%, 9.62%(20 cm) and 10.71%, 6.51%(40 cm), respectively.2. Effect of different fe rtilizer application depth of nitrogen on characteristics of summe r maize rootsAfter nitrogen deeply fertilized, the root traits(including the root dry weight, root length density, root surface area, TTC reducing quantity, absorbing area and active absorbing area) and their proportion in the deep soil(60-100 cm) of ZD958 and DH661 are all significantly higher than those of surface broadcasting. Compared with surface broadcasting, root length density, root surface area, TTC reducing quantity, absorbing area and active absorbing area of ZD958 in 20 cm deep fertilization and 40 cm deep fertilization treatments increased by 19.67%, 14.07%, 21.16%, 11.23%, 59.67%(20 cm) and 23.58%, 4.59%, 17.97%, 8.59%, 22.37%(40 cm) at VT stage, respectively. Root length density, root surface area, TTC reducing quantity, absorbing area and active absorbing area of DH661 on 20 cm fertilization depth and 40 cm fertilization depth treatments increased by 15.37%, 3.67%, 53.08%, 27.53%, 43.76%(20 cm) and 11.56%, 14.99%, 47.73%, 20.64%, 24.06%(40 cm) at VT stage, respectively. Reasonable deep fertilization(in our experiment is 20 cm fertilization depth) made summer maize have a larger root number, more root in deeper la yer, more rational root distribution and longer duration of root functional period. All of these could ensure the nitrogen uptake and making for its material production.3. Effect of different fertilizer application depth of nitrogen on leaf photosynthetic characteristics in summe r maizeAfter nitrogen deeply fertilizated, leaf area index, leaf area duration, chlorophyll contents of ZD958 and DH661 were all significantly higher than those of surface broadcasting, respectively. Compared with surface broadcasting, leaf area index, leaf area duration, chlorophyll contents of ZD958 on 20 cm fertilization depth and 40 cm fertilization depth treatments increased by 3.14%, 3.48%, 23.51%(20 cm) and 2.03%, 4.03%, 13.98%(40cm) at VTstage, respectively. Leaf area index, leaf area duration, chlorophyll contents of DH661 on 20 cm fertilization depth and 40 cm fertilization depth treatments increased by 6.71%, 1.61%, 10.54%(20 cm) and 3.33%, 2.04%, 7.56%(40cm) at VT stage, respectively. All of these demonstrated that summer maize have strong photosynthetic function and delayed leaf senescence after nitrogen deeply fertilizated, which would benefit for plant growth, development and yield formation of summer maize.4. Effect of differe nt fertili zer a pplicati o n de pt h of nit roge n o n t he acc u mul ati o n, dist ri buti o n a nd t ra nslocati o n of dry matter a nd nit roge n i n s u mmer mai zeAfter nitrogen deeply fertilizated, the dry matter accumulation, dry matter accumulation amount in different organs(stems, leaves, grains), total nitrogen accumulation, nitrogen accumulation in different organs of two varieties are all significantly higher than those of surface broadcasting. Compared with surface broadcasting, the total amount of dry matter accumulation and nitrogen uptake amounts of ZD958 on 20 cm deep fertilization and 40 cm deep fertilization treatments at R6 stage increased by 20.16%, 32.11% and 9.62%, 14.21%, respectively. The total amount of dry matter accumulation and nitrogen of DH661 on 20 cm fertilization depth and 40 cm fertilization depth treatments at R6 stage increased by 17.4%, 27.20% and 12.16%, 24.60%, respectively. In addition, throughout the reproductive period, the proportion of stems, leaves and the total nitrogen accumulation of those organs decreased in two varieties after the nitrogen deeply fertilizate, while the proportion of grain is significantly higher than that of surface broadcasting. After nitrogen deeply fertilizated, the accumulation amount, translocation amount, translocation rate and contribution rate of dry matter and nitrogen in ZD958 and DH661 became higher than those of surface broadcasting, which ultimately achieve high yield and efficiency purposes. |
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