Maintaining adequate soil fertility and health is a challenge in dryland organic wheat systems. This research examines the short-term impact of a one-time addition of compost on the soil health in a rainfed dryland organic winter-wheat (Triticum aestivum L.) fallow system. Field plot experiments were established in 2015 in a semiarid dryland organic wheat field in Snowville, Utah with the following treatments: control (C), compost at 12.5 Mg/ha dry weight (CM1), 25 Mg/ha (CM2), 50 Mg/ha (CM3), positive control 25 Mg compost + 40 lb N feather meal (PC), and 2 Mg chicken manure (CMU). Soil samples were taken in May 2016 at a depth of 0-10 cm from the plots in the wheat phase of the rotation. Indicators of soil health and fertility were determined such as microbial biomass C, enzyme activities involved in the cycling of C and P, total organic carbon and nitrogen determined.

The application of compost appeared to promote microbial activities with the greatest effect at CM3. Acid and alkaline phosphatase enzyme activities significantly increased by as much as 61 % and 47 % respectively. Microbial biomass carbon, dehydrogenase enzyme activity, readily mineralizable carbon, total organic carbon and total nitrogen were highest at CM3.

Based on our findings so far, compost addition stimulated soil microbial activities and boosted organic C and N in the surface layers of the soil. Outcomes of this study will contribute to the overall goal of enhancing productivity and sustainability of rainfed dryland organic winter-wheat.