Sustaining vulnerable agroecosystems with compost: Lasting benefits to soil health and carbon storage in semiarid winter wheat (Triticum aestivum, L.)

Abstract

Wheat agroecosystems provide one of the most important crops worldwide yet are often threatened by land degradation and climate change, making it vital to find practices that sustain soil health. Organic amendments can regenerate degraded soils, provide plant-available nutrients, and sequester carbon (C), and have long-lasting impacts in semiarid regions. This project evaluated the legacy of compost (0–50 Mg ha⁻¹) in an organic winter wheat-fallow rotation by comparing soil health and plant growth either 1–2 or 5–6 years after compost application, with or without cover crops. We assessed soil chemistry, structure, labile organic matter pools, microbial activity (by extracellular enzymes), and microbial community composition (by phospholipid fatty acids). We aimed to understand how compost application and cover cropping contribute to long-term soil health and C storage in semiarid regions, and how these practices impact soil microbiology. Compost resulted in sustained increases in organic matter pools, but only marginally benefitted plant growth and soil structure. Compost did not impact microbial community composition or activity, possibly because cold and dry conditions inhibited microbial functioning and compost decomposition. Cover crops did not impact soil organic matter or microbiology. Overall, we found that compost can contribute to long-term soil C storage in semiarid degraded soils such as these, despite having no measurable impacts on soil microbial biomass or activity.