A Study On Relationships Between Potassiumreleasing Microorganisms And Potassium Use Efficiency In Wheat(Triticum Aestivum L.)

The utilization of potassium resource in typical farmland of Huanghuai Plains is low,the soil potassium cannot be directly absorbed by crops;In order to provide theoretical basis for reducing fertilizer application and improving potassium utilization efficiency,the relationship between potassium release microorganisms and potassium utilization and root activity in rhizosphere soil under different potassium application methods and potassium application amount was investigated.Experiments were conducted with split-split plot design,and the main plots were fertilization(A)with two levels,namely,20% organic fertilizer(chicken manure)+80% chemical fertilizer(A1)and 100% chemical fertilizer(A2).The split plots were potassium fertilization(B)with four levels,namely,no potassium fertilizer(B1),reduced potassium fertilizer 80 kg·hm-2(B2),conventional potassium fertilizer120 kg·hm-2(B3),and increasing potassium fertilizer 160 kg·hm-2(B4).The split-split plots were wheat varieties(C)with two levels,namely,XiˊNong 979(C1)and YuˊNong 202(C2).The main results are as follows:(1)The dynamic changes of potassium releasing microorganisms in the rhizosphere of wheat during the whole growth period showed a trend of first decreasing,then increasing and then decreasing: the number was relatively high before winter,at a low point during winter stage,increased rapidly after returning stage,reached a peak at jointing stage,then decreased gradually,and reached the level of winter stage at maturity.Compared with potassium fertilization,the number of potassium-digestible microorganisms in the rhizosphere increased by 7.59% ~ 32.25% under combined application of organic fertilizer and potassium fertilizer,and the difference was extremely significant.Compared with no potassium fertilization,the number of potassium digestible microorganisms in the rhizosphere gradually increased with the increase of potassium fertilization rate,but the number of potassium digestible microorganisms in the rhizosphere decreased with the increase of potassium fertilization rate,and the overall trend was increasing first and then decreasing.A1B3(organic fertilizer + conventional potassium application)treatment was the best fertilizer combination.Analysis of variance showed that the effects of organic fertilizer and potassium fertilizer on potassium-digestibility microorganisms in rhizosphere reached to extremely significant level,and the differences among cultivars were significant or extremely significant.(2)In the whole growth period of wheat,Bacillus circulans,Bacillus mucilaginosus,pseudomonas and Paenibacillus polymyxa accounted for 27.24%,51.07%,14.31% and 7.38% of the potassium-digestible microorganisms,respectively.With the development of growth in wheat,the contents of soil available potassium,slow available potassium and relatively unavailable potassium were higher before winter,and then gradually decreased to maturity.Further correlation analysis showed that different kinds of rhizosphere potassium releasing microorganisms were significantly positively correlated with different soil potassium forms,among which,Bacillus mucilaginosus was extremely significantly correlated with soil available potassium,and Bacillus circulans was significantly correlated with soil available potassium.(3)Root activity,dry matter weight,potassium accumulation,potassium accumulation rate and potassium use efficiency of wheat were significantly increased under combined application of organic fertilizer and potassium fertilizer compared with potassium fertilization.Compared with no potassium fertilization,root activity,the accumulation of dry matter weight,potassium and potassium accumulation rate,potassium use efficiency increased with the increasing of potassium fertilization,but decreased under the condition of excessive application of potassium fertilizer.It showed that the combination of organic fertilizer and potassium fertilizer was beneficial to the growth and development of wheat and the utilization of potassium,but it had adverse effects with excessive potassium fertilization;Moreover,there are obvious differences in root activity,potassium accumulation and potassium utilization efficiency among different varieties.Correlation analysis showed that there was an extremely significant positive correlation between the number of potassium-releasing microorganisms in the rhizosphere and root activity at different growth stages.(4)The wheat yield under the combined application of organic fertilizer and potassium fertilizer increased by 2.03% ~ 2.97%,and the difference reached to 5%significant level compared with the potassium fertilization.Compared with no potassium application,the increase of the yield of conventional potassium application was highest in the treatments,which was 10.22%.At the same time,combined application of organic fertilizer and potassium fertilizer significantly increased the crude protein content,soluble sugar content,amylose content,amylopectin content,total starch content,and the ratio of amylose to amylopectin decreased in wheat grains.It was concluded that combined application of organic fertilizer and chemical fertilizer could increase the soil potassium releasing microorganisms and soil potassium utilization efficiency,promote the growth and development of wheat,improve the root activity in the late growth stage,increase the grain yield and improve the grain quality.Under the condition of this study,the strategy of potassium application in high-yield wheat fields in Huanghuai Plain was combination of organic and inorganic fertilizers,and the appropriate application of K2O was 120 kg·hm-2.