Effects of Organic Amendments on Microbial Biomass Carbon and Nitrogen Uptake by Corn Seedlings Grown in Two Purple Soils

An incubation experiment and a pot experiment were carried out to investigate the effects of organic materials on microbial biomass carbon (MBC) and nitrogen (MBN) content, dry weight, and nitrogen uptake of maize seedlings grown in an acidic purple soil and a calcareous purple soil. The organic materials used included pig manure biogas residue (PM), cattle manure biogas residue (CM), sludge compost (SC), compost from rural domestic waste both with and without 20% sludge (RWC1 and RWC2, respectively). The results showed that MBC content in the acidic and calcareous purple soils increased by 53.63%-102.91% and 12.14%-137.00%, respectively. The slower the decomposition of organic materials and the higher the C/N ratio, the bigger the MBC content of the soils. Furthermore, MBN contents, which were affected by the different forms of organic, increased by 23.37%-150.08% and 35.02%-160.02%, respectively. The MBC/MBN contents of both soils decreased with the increase in the C/N ratio of the organic materials, but a higher C/N ratio was beneficial for maintaining a higher MBN content over an extended period of time. With the exception of CM, the addition of organic materials improved the biomass of maize seedlings, and their nitrogen uptake and utilization rate in both soils were also significantly enhanced, although these effects were less than that achieved through conventional fertilization. The uptake and utilization of nitrogen followed the order of SC>PM>RWC2>RWC1. The inhibiting effect of CM was related to its higher C/N ratio, while the promoting effect of the other materials on nitrogen uptake by the corn seedlings increased as soil MBC/MBN content decreased. Therefore, the influence of organic materials on the change and supply of soil nitrogen was not only related to their properties but also to their effects on soil MBC/MBN content. © 2019, Science Press. All right reserved.