Effects Of Conservation Tillage On Soil Microbiomass

The field experimental research was conducted at the station of dry land farming of Gansu Agriculture University. The two rotation series (the rotation of spring wheat—field pea and the rotation of field pea—spring wheat) have being studied for 2 years. The results are as follows:1.Compared with conventional tillage, the soil microbial biomass is higher in the no-till and mulch treatments. The soil microbial biomass is increased by 14.9 percent in the rotation of spring wheat—field pea, and by 38.4 percent in the rotation of field pea—wheat. In the rotation of spring wheat—field pea, covering straw made the biomass of bacteria and fungi increased by 56.7 percent and 12.5 percent, made the biomass of actinomyces decreased 28.2 percent, mulching plastic made the biomass of bacteria and fungi increased by 90 percent and 43.8 percent, made the biomass of actinomyces decreased 2.9 percent. In field pea—spring wheat rotation , covering straw and mulching plastic made the biomass of bacteria increased by 48.3 and 22.3 percent, However both of covering straw and mulching plastic made the biomass of fungi and actinomyces decreased.2.The variance of MBC was very significant between different treatments in soil surface and sub-surface. In the depth of 0-5cm, the tillage effect was very significant and the cover effect was significant. In the depth of 5-10cm, the cover effect was very significant but the tillage effect was not significant. The reciprocal effect of tillage and cover was not significant in soil surface and sub-surface. The sequencing of means MBC was NTS>NTP>TS>NT>TP>T. The variance of MBC was significant between NTS and TP, NTS and T. In 5-10cm depth layer, the sequencing was TS>NTS>NT>NTP>T>TP. The variance of MBC was significant between TS and T,TS and TP,NTS and T,NTS and TP.MBC under no-till was larger than that of tillage in soil surface. MBC under straw cover was larger than that under no straw cover. 3. The seasonal dynamics of MBC showed that all treatments were the highest in Mar accept the treatments of TS and NTS which were the highest in Aug and lowest in Nov. However NTP was the highest in Mar and the lowest in Aug.4. The variance of MBN was not significant between different treatments .The cover effect was significant, but the effects of tillage and interaction of tillage and cover were not significant in soil surface. All factors, effects were not significant in soil sub-surface. The sequencing of means MBN was NTS>TP>TS>NTP>NT>T, The variance of MBN was significant between NTS and T. In 5-10cm depth layer, the sequencing was TP>TS>NTS>NT>NTP>T. The variance of MBN was significant between TP and T. The variance of cover effect was significant in soil surface. 5.The seasonal dynamics of MBN showed that all treatments were the highest in Aug and lowest in Nov.6. The variance of MBP in different treatments showed that it was significant in the depth of 0-5cm,and it was very significant in the depth of 5-10cm. The variance of straw cover was significant in soil surface, but was not significant in soil sub-surface. The effect of plastic cover was not significant in both soils. The sequencing of MBP was TS>NTS>NTP>NT>TP>T in the depth of 0-5cm and NTP>TS>NTS>NT>T>TP in the depth of 5-10cm. The variance of MBP was significant between NTS and T, between TS and T in soil surface .In the depth of 5-10cm, The variance of MBP was significant between NTP and T, NTP and TP.7.The seasonal dynamics of MBP near the soil surface showed that all treatments were the highest in Nov and lowest in Mar.8. soil microbial biomass, MBC ,MBN and MBP in soil are negatively related to the depth of the soil accept NTP of MBP.