Effects Of Different Fertilization On The Growth Of Sorghum And The Functional Diversity Of Rhizosphere Microorganisms

This paper was based on the long-term field test of sorghum / corn rotation,combined with the pot experiment of artificial greenhouse.Five treatments of NPK,PK,NK,NP and CK(no fertilizer treatment)were set up.In order to understand the response of sorghum growth and rhizosphere microbial stress on nitrogen,phosphorus and potassium,and provide a theoretical basis for nutrient management of different soil nutrients under conditions of sorghum.The effects of long term fertilization on the growth of sorghum,nutrient uptake and transport and microbial functional diversity in rhizosphere soil were studied.The results of the study show that:(1).Nitrogen fertilizer is the primary limiting factor affecting the biological yield of grain sorghum,grain yield and its components,and the effect of phosphorus fertilizer and potassium fertilizer is the second.The nutrient supply capacity of soil nitrogen,phosphorus and potassium were 64.24%,96.21% and 93.44% respectively after 6 years of continuous positioning test.Low nitrogen stress promoted seedling growth of upper sorghum,after jointing stage began to inhibit its growth,and the inhibition is more and more obvious.Low phosphorus stress significantly inhibited the growth of sorghum,and low potassium stress has little effect.Treatment of lack fertilizer on the jointing stage of plant height and stem diameter,inhibition of leaf number,leaf area and visible the aboveground biomass showed no fertilizer > no P fertilizer > no N fertilizer > no k fertilizer trend,spike flowering showed the trend of no fertilizer > no inhibition of N fertilization > no P fertilizer > no k fertilizer.It indicated that the effect of low nitrogen or low phosphorus stress on the growth of aerial parts of sorghum was greater than that of low potassium stress,and in the early growth stage,sorghum was more sensitive to phosphorus and more sensitive to nitrogen at later stage.(2).When nitrogen is insufficient,sorghum can absorb more nitrogen by increasing total root length,root surface area and fine root ratio.However,root distribution is shallow,which is not conducive to the absorption and utilization of deep nutrients.Compared with NPK,the total root length of sorghum increased by 18.29%,the total root surface area increased by 3.47%,and the proportion of fine roots of the diameter was less than 0.5 mm increased significantly,but the roots were mainly distributed in 0~10 cm soil layer under long-term PK application.No phosphorus fertilizer(NK)significantly inhibited root growth,total root length,total root surface area,total root volume and total dry weight of sorghum significantly decreased by 24.03%,27.48%,41.29% and 19.81% compared with NPK.No potassium fertilizer(NP)had an obvious inhibitory effect on the growth of fine roots.Removal of either N,P or K decreased the accumulation of the corresponding element in sorghum.It was recommended not to induce N or limit N and K translocation from vegetative organs to grains.Both the combinations NK and NP inhibited the transfers of N,P and K to grain from vegetative parts.The accumulation and translation of N,P and K were regulated by root morphology.There were significant relationships between both N and K accumulation and individual root parameter(total root length,total root surface area and total root volume).Compared with P and K accumulation,N accumulation in sorghum had an obviously correlation with both N translocation from vegetative organs to grains and aboveground biomass.Therefore,although no phosphate fertilizer could significantly inhibit the growth of root system,the yield reduction of no nitrogen fertilizer was significantly greater than that of no phosphate fertilizer.(3).BIOLOG ECO microplate method was used to study the effects of different fertilization treatments on the microbial functional diversity of the rhizosphere of Sorghum in panicle flowering stage.The results showed that the field test was in agreement with the pot experiment.PK increased the metabolic activity of microorganisms in the rhizosphere,improve the utilization of amino acids,carboxylic acids,amines,sugars and polymers,reducing the use of amphiphilic compounds,the diversity index,richness index and dominance index were higher than other treatments.NK and NP on the effects of rhizosphere microbial functional diversity was not significant,but NK treatment reduced the late culture rhizosphere microbial metabolic activity.CK treatment significantly decreased the rhizosphere microbial utilization of carbon sources,the diversity index,richness index and dominance index were lower than other treatments,evenness index were higher than other treatments.Principal component analysis showed that the field test of NPK and NP in rhizosphere soil microbial carbon utilization ability are not significant differences,but there was a significant difference between the rest of the treatment.There was no significant difference in carbon source ability and type between NPK,NK and NP in pot experiment,and the difference between the other treatments was significant.In conclusion,fertilization is beneficial to the improvement of soil microbial characteristics.The rhizosphere microorganisms of sorghum had different responses to low nitrogen,low phosphorus and low potassium stress.Low nitrogen stress had greater influence on sorghum,and enhanced microbial activity in rhizosphere might be the reason of nitrogen tolerance in sorghum.