| Nitrogen and phosphorus are essential for plant growth and development.The content of available nutrient elements in soil is low,which affects plant growth and yield.Fertilization is a common measure to increase agricultural production.However,excessive nitrogen and phosphorus content in soil is caused by a large amount of fertilization,which results in a series of environmental problems.Winter wheat is one of the important food crops in China,and its yield is of great significance to China’s food security.Therefore,improving the P-utilization efficiency is very important for winter wheat.In this study,we took loess soil as the test soil and winter wheat as the test crop,and carried out a greenhouse pot experiment by adding different levels of inorganic phosphorus(0,6.25 and 25 mg P kg–1)in the form of calcium superphosphate,organic phosphorus(0,25 and 100 mg P kg–1)in the form of sodium phytate,and nitrogen(0,50,200 mg N kg–1)in the form of ammonia nitrate to the soil to grow wheat.The seedling samples were collected at different time periods of wheat growth（45d,60d and 75d）,mainly to determine plant biomass and phosphorus concentration,as well as soil p H,total P and Olsen-P,alkaline phosphatase and phytase activity.The main results are as follows:（1）For winter wheat,the addition of exogenous nitrogen and phosphorus had a significant effect on its dry mass and promoted plant growth.The responses of wheat shoot and root to N and P were different.Shoot dry mass increased with the increase of N and P level,while root dry mass and root mass ratio decreased with the increase of N and P level.The change of the relative growth rate of wheat with the change of N and P level was not obvious.（2）No matter adding inorganic or organic P,the P level had a significant effect on the P concentrations of shoot and root,the plant P concentration increased with the increase of soil P level.The level of soil inorganic P had no significant effect on P-utilization efficiency.Organic P level had a significant impact on P-utilization efficiency,which decreased with the increase of soil P level.（3）No matter adding inorganic or organic P,the concentration of soil Olsen-P increased with the increase of P level,and reached the maximum at the highest P level;total P decreased with the increase of P level.（4）The effects of different types and levels of P on alkaline phosphatase activity were inconsistent.When adding inorganic P,alkaline phosphatase activity increased with the increase of P level,and reached the maximum at 25P.When adding organic P,alkaline phosphatase activity first increased and then decreased with the increase of P level,and P level had a significant effect on alkaline phosphatase activity.（5）The results showed that there was a significant positive correlation between in shoot and root P concentrations,plant P accumulation,and soil total P and Olsen-P concentrations.The addition of exogenous N and P changed the composition of P pool in soil,improved the availability of P in soil,and then promoted the absorption and utilization of P by plants.The results showed that the addition of exogenous N and P promoted the growth of wheat and the absorption and utilization of P.It also affected the concentrations of soil total P,Olsen-P,and phosphatase activity,and further affected the absorption and utilization of P by wheat.The results of this study showed that in order to promote wheat growth and achieve the maximum P-utilization efficiency,the fertilization measures of high P and low N should be taken when applying N and P fertilizers together to the loess soil. |
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