Effects Of Different Fertilization Depth On Growth,Development And Yield Of Summer Maize In Guanzhong Area

In order to explore the effects of different fertilization depths on the growth of summer maize,a field experiment was carried out in Yang ling,Shaanxi Province for two consecutive years from 2019 to 2020.Taking Zheng dan 958 as the experimental material,five different fertilization depth treatments were set,namely:surface fertilization（D0）,5 cm depth fertilization（D5:normal fertilization）,15 cm depth fertilization（D15）,25 cm depth fertilization（D25）and 35 cm depth fertilization（D35）.By studying the effects of different fertilization depths on agronomic characters,canopy light transmittance,photosynthetic characteristics,grain filling,yield and yield composition of summer maize,the following main research conclusions are obtained:（1）Effects of different fertilization depth on Agronomic Characters of Summer MaizeDifferent fertilization depth had significant effects on plant height,stem diameter,leaf area index and dry matter accumulation of summer maize.The agronomic characters of D0treatment were significantly lower than those of other fertilization depth treatments;Compared with D5 treatment,applying fertilizer deep to 15 cm can significantly increase plant height,stem diameter,leaf area index and dry matter accumulation;When the fertilization depth was further increased to 25 cm,the indexes related to agronomic characters of summer maize did not show obvious increasing advantage;In addition,if the fertilization depth is too deep（D35）,the agronomic characters of summer maize will be reduced.（2）Effects of different fertilization depths on canopy transmittance and photosynthetic indexes of Summer MaizeDifferent fertilization depths had significant effects on canopy light transmittance of summer maize.With the increase of fertilization depth,the canopy transmittance of panicle layer and bottom layer decreased first and then increased,which was D0>D35>D5>D25>D15.Compared with D5 treatment,the decline of canopy transmittance of bottom layer under D15 treatment was greater than that of panicle layer;The chlorophyll content and net photosynthetic rate increased first and then decreased with the increase of fertilization depth,and reached the maximum under D15 treatment.The results showed that applying fertilizer deep to 15 cm can significantly reduce the light transmittance of the lower layer of the population,make the light evenly distributed in the canopy structure,ensure that more light can be intercepted by the leaves,delay the senescence of the leaves after tasseling and prolong the photosynthetic time by increasing the chlorophyll content.In terms of net photosynthetic rate,D15 increased by 33.38%,11.75%,3.01%and 11.34%respectively compared with D0,D5,D25 and D35.Therefore,applying fertilizer deep to 15 cm is beneficial to promote the utilization of light energy by leaves and improve the photosynthetic characteristics of plants in the later stage of growth.（3）Effects of different fertilization depth on Grain FillingThe maximum grouting rate among different treatments was D25>D15>D5>D35>D0.The maximum grouting rate of D15 and D25 treatment was 1.74%and 2.83%higher than that of D5 treatment,while the maximum grouting rate of d0 and D35 treatment was 30.34%and 1.47%lower than that of D5 treatment.The average grouting rate of different treatments was as follows:D15>D25>D5>D35>D0.The average grouting rate of D15 and D25treatment was 9.15%and 0.88%higher than that of D5 treatment,while the average grouting rate of D0 and D35 treatment was 20.29%and 1.40%lower than that of D5 treatment.It shows that when the fertilization depth is adjusted by 15 or 25 cm,it is more conducive to grain filling and promote grain development.（4）Effects of different fertilization depth on summer maize yieldThe results showed that the fertilization depth had a significant effect on the yield of summer maize.The yield of summer maize increased first and then decreased with the increase of fertilization depth.When the fertilizer is applied deep to 15 cm,the yield of summer maize reaches the highest（the grain yield in 2019 and 2020 are 8803.74 kg ha-¹ and 8985.77 kg ha-¹,respectively）.Compared with D5 treatment,the output of D15 treatment increased by 19.63%and 16.56%in 2019 and 2020,D25 treatment increased by 8.79%in 2019,decreased by 1.25%in 2020,D0 treatment decreased by 42.27%and 39.10%respectively,D35 treatment increased by 1.31%in 2019 and decreased by 8.12%in 2020.On average,the number of grains per ear in D15 and D25 treatments increased by 4.77%and 1.92%respectively compared with D5treatment;The 100^-1 grain weight of D15 and D25 treatment increased by 8.86%and 1.76%respectively compared with D5 treatment.It shows that the deep application of fertilizer can increase the number of grains per ear and 100 grain weight of summer maize,and the yield increase effect is the best under D15 treatment.The fitting results show that the theoretical depths of maximum yield in 2019 and 2020 are 21.05 cm and 19.62 cm respectively.In conclusion,combined with the actual production,through reasonable deep application of fertilizer（about 15 cm）,the agronomic properties and canopy transmittance of summer maize are improved,the photosynthetic capacity of plants is improved,the accumulation of assimilates and the transportation to grains are promoted,which is conducive to the increase of grain number and grain weight per ear,so as to improve the yield of summer maize.