| With the change of the food consumption structure of Chinese residents,the demand for animal food such as meat,eggs and milk increases gradually,resulting in the rising proportion of livestock and poultry feed grains in the total food consumption.Sweet Sorghum is a C4 plant with high light efficiency,rapid growth,large biomass,strong adaptability,strong stress resistance and other excellent characteristics.In recent years,the research of sweet sorghum used as silage in agricultural areas has been increasing,but there is still a lot of detailed work to be done in fertilization.Field experiment was conducted with four nitrogen application levels(0,100,200 and 300 kg·hm-2)to study the effects of nitrogen application in plant growth,leaf net photosynthetic rate,biomass,growth rate,nitrogen accumulation and nitrogen utilization rate.Furthermore,the effects of nitrogen application on nitrogen distribution in leaves and its relationship with biomass and net photosynthetic rate were also analyzed.The main conclusions are as follows:1.Reasonable nitrogen application can effectively increase aboveground biomass:(1)When nitrogen applicatio1 is less than 200 kg·hm-2,plant height and tiller number were increased with increasing in nitrogen application;(2)The net photosynthetic rate,stomatal conductance and carboxylation efficiency of sweet sorghum increased with the increase of nitrogen application;(3)The dry weight of leaf,stem(including leaf sheath)and biomass of sweet sorghum increased with the increase of nitrogen application;(4)The growth rate of sweet sorghum increased with the increase of nitrogen application;(5)There was a significant positive correlation between plant height,tiller number,net photo synthetic rate and growth rate and biomass.2.Reasonable nitrogen application can effectively increase nitrogen accumulation and nitrogen utilization rate:(1)At each growth stage,the nitrogen concentration in the leaves and stems of sweet sorghum increased with the increase of nitrogen application,and reached a significant level;(2)Nitrogen accumulation in the leaves,stems and plants of sweet sorghum increased with the increase of nitrogen application.Nitrogen accumulation gradually increased with the extension of growth period.There was no significant difference between nitrogen application of 200 kg·hm-2 and 300 kg·hm-2;(3)At different growth stages and nitrogen application levels,nitrogen uptake in different organs was characterized as leaf>stem;(4)The dry matter production efficiency,dry matter production efficiency and nitrogen utilization rate were higher when the nitrogen application amount was 200 kg·hm-2,and the overall performance was better than other treatments.3.Nitrogen application affects nitrogen distribution in leaves:(1)The content of inorganic nitrogen in leaves decreases with the increase of nitrogen application,but their proportion of nitrogen content in leaves was not high(not exceeding 2%),so its impact on nitrogen allocation in leaves was small;(2)The content of photosynthetic nitrogen increased with the increase of nitrogen application,and there was no significant difference in the proportion of photosynthetic nitrogen in leaves;(3)Free amino acids increased with the increase of nitrogen application.4.The distribution of nitrogen components in leaves influenced the net photosynthetic rate and biomass:(1)There was a significant positive correlation between the ratio of chlorophyll nitrogen to leaf nitrogen and net photosynthetic rate.Increasing the proportion of chlorophyll nitrogen was beneficial to the increase of net photosynthetic rate of leaves and the yield of sweet sorghum;(2)There was a significant positive correlation between soluble protein,chlorophyll nitrogen,free amino acid content and sweet sorghum growth rate at 80 days after sowing.(3)There was a significant positive correlation between the content of chlorophyll nitrogen content and the biomass,which is an important factor affecting the biomass of sweet sorghum. |
PDF Full Text Request