Changes in Biological Soil Health Properties in Response to Increased Crop Diversity in a Dryland Wheat-Based Cropping System

Diversifying wheat (Triticum aestivum L.)-based cropping systems is important for the sustainability of dryland agriculture. Research has focused on the agronomic benefits of increased crop diversity in semi-arid environments, but less is known about the impacts of increased crop diversity on the soil microbial community. This work compared soil health parameters between a continuous wheat crop sequence to a diverse sequence that included pea (Pisum sativum L.), proso millet (Panicum miliaceum L.), safflower (Carthamus tinctorius, L.), and spring wheat. Respiration was higher (p < .005) in the diverse sequence while activity of N-acetyl-beta-d-glucosaminidase was lower (p < .05) with a mean rate of 26.3 and 16.3 mg rho-nitrophenol kg(-1) soil h(-1) for the continuous wheat and diverse sequences, respectively. The mean net nitrogen mineralized during the growing season was 33.2 +/- 2.5 kg ha(-1) and was not different between treatments (p > .05). No difference was observed in bacterial alpha diversity, while fungal community diversity was 52% lower in the diverse rotation. The results of this work suggest that specific crops in a rotation may impact microbial processes related to nitrogen mineralization and that the soil fungal community may be more sensitive to changes in crop sequence than the soil bacterial community.