Complex of soil tillage, organic and biological fertilization for improving soil microbial activity and nitrogen transformation efficiency in intensive cropping on Calcaric Luvisols

Abstract

Intensive cropping is, mainly, based on the cultivation of monocultures and highly relying on the use of mineral fertilizers and pesticides. Those can reduce soil microbial activity (SMA) and decrease the nitrogen transformation efficiency (NTE). However, we can expect that the capacity of the SMA and NTE will be recovered when all the reducing soil tillage, the using organic fertilizers or crop residues and the applying of biological stimulants carried out in complex. To evaluate the SMA and NTE response to the complex of soil tillage, organic and biological fertilization, two sites in the vicinity of Kaunas district were selected in the intensive cropping experiments. In both experiment sites continuous winter wheat (Triticum aestivum L.) cropping was dominant and wheat straw was returned as organic fertilizer for soil organic matter improvement. Thus, the soils were different tilled in both experiment sites. In first site the deep ploughing was used once per season with straw incorporation by disking. In site two reduced and no-tillage systems in complex with straw retention and different biological preparations was evaluated. The results showed, that applying biological stimulants and nitrogen fertilizers in complex with deep ploughing in experimental site one, the SMA was not significantly increasing but the significantly higher content of N-NH4 (N-NH4 – 118 mg kg-1) in soil was obtained. Additionally, the transformation to N-NO3 in soil was consistent and intensified (N-NO3 were in 32–50 mg kg-1).However, in second experimental site with straw different application technology by different intensity soil tillage the SMA was not significantly affected but the content of N-NH4 was decreasing even the biological stimulants were applied (from 216 N-NH4 mg kg-1 to 100 N-NH4 mg kg-1). Despite that, the nitrogen transformation to N-NO3 in soil (in some cases reached more than 120 N-NO3 mg kg-1) was higher than the N-NH4 content.