Effects of biochar and NPK on soil microbial biomass and enzyme activity during 2 years of application in the arid region

Abstract

The studies regarding interaction of biochar and fertilizer and their effect on soil microbial biomass and enzyme activity are scarce. This study centers at analysis of soil microbial biomass carbon (MBC), nitrogen (MBN), and phosphorous (MBP) over a period of 2 years under mash bean-wheat cropping system. Overall, six treatments were performed which included (1) B0F0: no biochar no fertilizer; (2) B1F0: 5 tons ha−1 (hectare) biochar with no fertilizer; (3) B2F0: 10 tons ha−1 biochar (B2F0) with no fertilizer; (4) B0F1: no biochar with recommended N:P:K fertilizer (i.e., 23:45:25 kg ha−1 respectively); (5) B1F1: 5 tons ha−1 biochar with recommended fertilizer; (6) B2F1: 10 tons ha−1 biochar with recommended fertilizer. Results elucidated increased soil MBC which increased with increasing biochar concentration. Enzyme activity and microbial biomass were higher initially but decreased in the second year of biochar amendment (both with and without fertilizer) which may be attributed to positive priming effect at the start of the experiment. MBN was observed lowest with fertilizer application but increased with biochar application alone. Seasonal variation in MBC was less in biochar-amended soils suggesting that biochar induced a less extreme environment for microbes throughout the season. The biochar treatment (i.e., B2F0) enhanced the soil microbial biomass, phosphorus, and phosphatase activities while biochar with fertilizer treatment (B2F1) improved urease, dehydrogenase, and alkaline phosphatase activity significantly (P > 0.05) in mash bean crop. In wheat however, this treatment decreased urease activity while dehydrogenase activity remained unchanged. A positive correlation was observed between MBN and dehydrogenase activity with soil organic carbon, dissolved organic carbon, and soil moisture content. These outcomes imply that bagasse biochar improves soil conditions for microbes thereby plummeting temporal variations in carbon dynamics.