The Characteristics Of Soil Nutrients And Microenvironment In Super High Yield Summer Corn Field

Studying the super high yield summer corn field is very important to solve the problem of the cultivated land resources intensity and the food security which are brought about by population explosion. We chose the field that the yield was over 15 000 kg?ha-1 in the continuous 4 years as our research base to study the characteristics of the soil nutrients, soil microbial number and soil enzyme activities in different soil layers compared with the conventional farmland. Main results and conclusions are as followings:1 The characteristics of the soil total nutrients in the super high yield summer corn fieldThe soil organic matter, total N and total P showed the decline trend as the soil layer became deeper. In every growth stage the soil organic matter contents of the super high yield summer corn field and conventional field were not different in every soil layer. The soil organic matter contents of the super high yield summer corn field and conventional field were not different in 0-20cm soil layer. In 20-40cm soil layer the soil organic matter in the super high yield field was higher than that in the conventional field in every stage except the 31st. day after sowing. In the soil layers below 40cm the contents of the soil organic matter in super high yield field were lower than those in conventional field. In 0-20cm soil layer the total N changed significantly. After flowering stage the total N content in the super high yield field was higher than that in the conventional field. In the soil layers below 20cm it did not show the same trend. In 0-40cm soil layer the total P content in the super high yield field was significantly higher than that in the conventional field. In the soil layer below 40cm the total P content in the super high yield field was not different with that in the conventional field.2 The characteristics of the available nutrients in the super high yield fieldAfter flowering stage the contents of soil available N and K in 0-20cm soil layer of the super high yield field were higher those in those in the conventional field. In the soil layers below 20cm the soil available N and K contents in the super high yield field were not different with those in the conventional field. The soil available P contents were higher than those in the conventional field in each soil layer. In the later stages NH4+-N contents in 0-20 cm soil layer of the super high yield field were significantly higher than those in the conventional field and in 20-40cm NH4+-N contents in the super high yield field were higher. In the soil layers below 40cm the NH4+-N contents were lower or equivalent compared with the conventional field. The soil NO3--N in the conventional field mainly accumulated in 0-40cm soil layer. The soil NO3--N contents in the super high yield field were higher than those in the conventional field in each soil layer. It showed that to achieve super high yield high content of the available nutrients in 0-20cm should be maintained.3 The soil microorganism characteristics in the super high yield fieldIn 2006 the number of bacteria, fungi and actinomycete first increased and then declined in the super high yield and conventional field soil. From the 31st day after sowing the number of bacteria and actinomycete in the super high yield was lower than that in the conventional field. The number of fungi did not change obviously. From the 107th day after sowing the number of fungi in the super high yield was significantly lower than that in the conventional field. In 2007 the trends of bacteria, fungi and actinomycete number in 0-20cm soil layer were like those in 2006. At every stage the number of bacteria, fungi and actinomycete in 20-40cm were not different with that in the conventional field. At harvest stage the average B/F of 2006 and 2007 in the super high yield field was 55.6% higher than that at sowing stage. At harvest stage B/F in the super high yield field was 278 % higher than that in the conventional field. At harvest stage B/F in the conventional field was 89.2% higher than that at sowing stage. In 0-20cm soil layer the soil microorgnism number were correlated negatively with soil available N, P and K. The number of actinomycete was significantly correlated negatively with soil available N, P and K. And the correlation coefficients were -0.755, -0.779 and -0.849.4 The soil enzyme characteristics in the super high yield fieldIn 2006 the urease activity in the super high yield field was lower than that in the conventional field after jointing. Invertase activity in the super high yield field decreased rapidly and was distinctly lower than in the conventional field after silking. In 2007 the urease and invertase activities showed the same trend with those in 2006 in 0-20cm soil layer. The urease and invertase activities in the super high yield field were lower than those in the conventional field. In the soil layers below 20cm the urease and invertase activities in the super high yield field were not different with those in the conventional field. The soil enzyme activities were correlated negatively with soil available nutrients. The invertase activity was significantly correlated negatively with soil available K. And the correlation coefficient was -0.761.