Rational application of nitrogen （N） fertilizers is an important measure to raise N fertilizer recovery rate and reduce N loss.A two-year field experiment of rice-wheat rotation was employed to study the effects of ...Rational application of nitrogen （N） fertilizers is an important measure to raise N fertilizer recovery rate and reduce N loss.A two-year field experiment of rice-wheat rotation was employed to study the effects of N fertilization modes including a N fertilizer reduction and an organic manure replacement on crop yield,nutrient uptake,soil enzyme activity,and number of microbes as well as diversity of microbes.The result showed that 20% reduction of traditional N fertilizer dose of local farmers did not significantly change crop yield,N uptake,soil enzyme activity,and the number of microbes （bacteria,actinomycetes,and fungi）.On the basis of 20% reduction of N fertilizer,50% replacement of N fertilizer by organic manure increased the activity of sucrose,protease,urease,and phosphatase by 46-62,27-89,33-46,and 35-74%,respectively,and the number of microbes,i.e.,bacteria,actinomycetes,and fungi by 36-150,11-153,and 43-56%,respectively.Further,organic fertilizer replacement had a Shannon＇s diversity index （H） of 2.18,which was higher than that of other modes of single N fertilizer application.The results suggested that reducing N fertilizer by 20% and applying organic manure in the experimental areas could effectively lower the production costs and significantly improve soil fertility and biological properties.展开更多
Oxalic acid plays an important role in improving the bioawilability of soil nutrients.Batch experiments were employed to examine the influences of oxalic acid on extraction and release kinetics of potassium (K) from s...Oxalic acid plays an important role in improving the bioawilability of soil nutrients.Batch experiments were employed to examine the influences of oxalic acid on extraction and release kinetics of potassium (K) from soils and minerals along with the adsorption and desorption of soil K^+.The soils and minerals used were three typical Chinese soils,black soil (Mollisol),red soil (Ultisol),and calcareous alluvial soil (Entisol),and four K-bearing minerals,biotite,phlogopite, muscovite,and microcline.The results showed that soil K extracted using 0.2 mol L^(-1) oxalic acid was similar to that using 1 tool L^(-1) boiling HNO_3.The relation between K release (y) and concentrations of oxalic acid (c) could be best described logarithmically as y=a+blogc,while the best-fit kinetic equation of K release was y=a+b t^(1/2),where a and b are the constants and t is the elapsed time.The K release for minerals was ranked as biotite>phlogopite》muscovite>microcline and for soils it was in the order:black soil>calcareous alluvial soil>red soil. An oxalic acid solution with low pH was able to release more K from weathered minerals and alkaline soils. Oxalic acid decreased the soil K^+ adsorption and increased the soil K^+ desorption, the effect of which tended to be greater at lower solution pH, especially in the red soil.展开更多
基金supported by the National Basic Research Program of China (973 Program,2007CB109308)the National High-Tech R&D Program of China (2007AA06Z332)a special grant of Application of Nuclear Techniques in Agriculture from the Ministry of Agriculture of China (200803034)
文摘Rational application of nitrogen （N） fertilizers is an important measure to raise N fertilizer recovery rate and reduce N loss.A two-year field experiment of rice-wheat rotation was employed to study the effects of N fertilization modes including a N fertilizer reduction and an organic manure replacement on crop yield,nutrient uptake,soil enzyme activity,and number of microbes as well as diversity of microbes.The result showed that 20% reduction of traditional N fertilizer dose of local farmers did not significantly change crop yield,N uptake,soil enzyme activity,and the number of microbes （bacteria,actinomycetes,and fungi）.On the basis of 20% reduction of N fertilizer,50% replacement of N fertilizer by organic manure increased the activity of sucrose,protease,urease,and phosphatase by 46-62,27-89,33-46,and 35-74%,respectively,and the number of microbes,i.e.,bacteria,actinomycetes,and fungi by 36-150,11-153,and 43-56%,respectively.Further,organic fertilizer replacement had a Shannon＇s diversity index （H） of 2.18,which was higher than that of other modes of single N fertilizer application.The results suggested that reducing N fertilizer by 20% and applying organic manure in the experimental areas could effectively lower the production costs and significantly improve soil fertility and biological properties.
基金the National Natural Science Foundation of China (No.29777021).
文摘Oxalic acid plays an important role in improving the bioawilability of soil nutrients.Batch experiments were employed to examine the influences of oxalic acid on extraction and release kinetics of potassium (K) from soils and minerals along with the adsorption and desorption of soil K^+.The soils and minerals used were three typical Chinese soils,black soil (Mollisol),red soil (Ultisol),and calcareous alluvial soil (Entisol),and four K-bearing minerals,biotite,phlogopite, muscovite,and microcline.The results showed that soil K extracted using 0.2 mol L^(-1) oxalic acid was similar to that using 1 tool L^(-1) boiling HNO_3.The relation between K release (y) and concentrations of oxalic acid (c) could be best described logarithmically as y=a+blogc,while the best-fit kinetic equation of K release was y=a+b t^(1/2),where a and b are the constants and t is the elapsed time.The K release for minerals was ranked as biotite>phlogopite》muscovite>microcline and for soils it was in the order:black soil>calcareous alluvial soil>red soil. An oxalic acid solution with low pH was able to release more K from weathered minerals and alkaline soils. Oxalic acid decreased the soil K^+ adsorption and increased the soil K^+ desorption, the effect of which tended to be greater at lower solution pH, especially in the red soil.
