Effects Of Tillage Methods And Nitrogen Levels On Soil Microbial Properties And Yield Of Wheat

This experiment was conducted in Qian zhuliu village Longkou City, Shandong Province from 2007 to 2008. The wheat varieties selected was liangxing 99. This experiment was a main field experiment. This experiments studied the effects of conventional tillage, rotary tillage, harrow tillage and no-tillage and nitrogen application at different levels on soil microbial characteristics, physical and chemical properties and yield of wheat. The aim was to clarify the relationships between tillage methods, nitrogen levels and soil microbial characters, enzyme activity, soil nutrients and wheat yield, and to supply academic base for tillage patterns with high efficiency.1. Effects of tillage methods and nitrogen levels on soil microbial properties.Conventional tillage and rotary tillage had higher soil active microbial biomass in 0-20cm soil layer. The average content of soil active microbial biomass of conventional tillage and rotary tillage in 0-10cm soil layer was 19.18mg/kg and it hither than that of harrow tillage and no-tillage by 21.57%. The average content of soil active microbial biomass in the 10-20cm layer was 11.67mg/kg. Harrow tillage and no-tillage tillage had lower soil active microbial biomass, about 9.45mg/kg. And nitrogen can increase active microbial biomass obviously.The content of soil microbial biomass C in 0-10cm layer was higher than that in 10-20cm soil layer in four tillage methods. Conventional tillage increased the soil microbial biomass C in 0-10 cm soil layer,. And soil microbial biomass C can be fixed in conventional tillage. And the content of soil microbial biomass C of harrow cultivation was next to conventional tillage. However rotary tillage and no-tillage had lower soil microbial biomass C. In 10-20cm soil layer, the content of soil microbial biomass C of no-tillage was lower than that of conventional tillage by 12.77%. With the level of nitrogen reducing, the content of soil microbial biomass C declined.In the whole growth period of wheat, soil respiration rate showed a single peak curve. In 0-10cm soil layer, no-tillage had the highest soil respiration rate, and conventional tillage and harrow tillage was next to no-tillage, however rotary tillage had the lowest soil respiration rate. In the 10-20cm soil layer, the soil respiration rate of conventional tillage was the highest and followed harrow tillage, but the soil respiration rate of no-tillage was the lowest. And the soil respiration rate of no-tillage was lower than that of conventional tillage and harrow tillage by 6.07% and 5.51%.In 0-10cm soil, the soil microbial activity of conventional tillage and rotary tillage were higher, at around 5.18mgCO2/kg/h. In 10-20cm soil layer, conventional tillage had the highest the soil microbial activity, it was 2.75 mgCO2/kg/h, it was hither than rotary tillage, harrow tillage, no-tillage, by 4.11%, 12.00%, 8.85%.2. Effects of tillage methods and nitrogen levels on soil physical and chemical properties and soil enzyme activityNo-tillage or minimum tillage had higher water content, and no-tillage or minimum tillage can increase water obviously. in the whole wheat, soil bulk density in 0-40cm increased, especially in 0-20cm soil layer. And the soil bulk of no-tillage was the highest. In 0-10cm soil layer, harrow tillage had higher content of soil available phosphorus, and it was hither than conventional tillage by 5.7%. In 10-20cm soil layer, the content of available phosphorus conventional tillage was higher than other tillage. In 0-10cm soil layer, no-tillage had the highest nitrogen content, and it was hither than conventional tillage by 15.64%. but the nitrogen content of conventional tillage was hither than other tillage in 10-20cm layer. Except rotary tillage, the soil total nitrogen content of conventional tillage, harrow and no-tillage was not different obviously. The soil organic matter content of before planting was hither than that of the wheat harvest, especially the treatments with straw returning. With reducing of nitrogen, available phosphorus, nitrogen, total nitrogen and organic matter reduced.In 0-10cm soil layer, rotary tillage had hither urease activity and sucrose activity. in the 10-20cm soil layer, the no-tillage had hither urease activity, and conventional tillage had higher sucrose activity. With nitrogen reducing, soil urease activity and sucrose activity decreased.3. Effects of tillage methods and nitrogen levels on wheat leaf area and yield.From jointing stage to flowering, no-tillage and conventional tillage had hither green leaf area per plant, and they were hither than cultivator tillage and harrow tillage by 9.00%, 5.52%.No-tillage can maintain green leaf area longer period of time. That is, no-tillage can delay senescence of wheat. The wheat grain-filling rate of rotary tillage faster than other tillage, harrow tillage was next. Wheat green leaf area per plant related positive correlation with the nitrogen level, but it related negative correlation with the nitrogen level. Hither nitrogen level can also delay wheat aging, and make wheat have a long green leaf area time, but, it had lower filling rate.The spike number of no-tillage and rotary tillage was lower, but their 1000-grain was higher. Average yield of rotary tillage and no-tillage was lower than conventional tillage by 10% and 5.52%. But the differences of yield between harrow tillage and conventional tillage was not obvious. Meanwhile, under higher nitrogen level, the difference of yield among the four farming methods was not obvious. However under lower nitrogen level, the differences of yield among the four farming methods was not obvious, the yield of conventional tillage and harrow tillage were hither. With reducing nitrogen levels, hectares spike, grains per spike and yield reduced, but 1000-grain weight increased.