Influence of medium-term application of rhizobacteria on mustard yield and soil properties under different irrigation systems

Abstract

The dynamic interaction of factors such as soil, environment, microbe and plant plays a pivotal role in the growth and productivity of the plant. Hence, we conducted a field experiment to evaluate the medium-term (three years) application of rhizobacterial inoculants viz., Bacillus spp. MRD-17, Bacillus aryabhattii NSRSSS-1 and Bacillus casamanscensis MKS-6 on soil parameters, and growth and productivity of mustard under varied irrigation levels. After three years of application of rhizobacteria, the impact on soil characteristics was assessed. Chlorophyll content (a, b and total chlorophyll) and relative water content were more in the rhizobacterial inoculated treatments; interactive effect was noted only on total chlorophyll content. Inoculation with MKS-6 led to an increase in the proline content in leaves compared to uninoculated treatments under all irrigation levels. Reduced catalase activity was observed in the inoculated treatments, especially under rainfed and one-irrigation condition. Soil biological activity (Dehydrogenase, Fluorescein diacetate hydrolysis and Microbial Biomass Carbon) was also positively influenced with rhizobacterial inoculation under all irrigation levels. Higher percentage (∼53%) of large macro aggregates (>2mm) was obtained in the soil samples from MRD-17 and NSRSSS-1 inoculated treatments. Inoculation with these cultures also significantly increased the total soil carbohydrates in all the soil fractions [bulk soil (∼15%), large-macro (∼6-8%), small-macro (∼9-20%) and micro-aggregates (∼4%)] as well as glomalin content in large-macro-aggregates. Inoculated treatments had 11.7-19.7% more yield than uninoculated plots. The positive influence of rhizobacterial inoculation was clearly reflected in the plant growth, yield and soil biological activities; medium-term application of rhizobacteria improved soil characteristics.