Effect of Alternative Dryland Crops on Soil Microbial Communities

Soil microbial community composition associated with novel rotation crops could contribute to increased yield to subsequent crops and an important factor influencing the composition of the rhizosphere microbiome. However, the effect of alternative dryland crops on soil microbial community composition is not clear in the northern Great Plains (NGP). The objective of this study therefore was to evaluate the effects of oilseed crops Ethiopian mustard (Brassica carinata A.) or camelina (Camelina sativa L.) or a 10-species forage/cover crop (CC) mix and fallow on soil microorganisms. A field study was conducted from 2014 to 2020 in the northern Great Plains, USA and was designed as a randomized complete block with three replications in a no-tillage system. Results showed that total bacterial proportion was significantly higher in camelina and fallow compared to CC and carinata. Total fungal proportion was significantly higher under CC mix compared to camelina and fallow. Fungal to bacterial ratio was significantly higher in CC and carinata compared to fallow. Fungi are often considered a good indicator of soil health while bacteria are crucial in soil functions. The changes in specific microbial communities due to crop-related alterations might play a key role in the yield of subsequent crop. Mechanisms responsible for these differences will be discussed.