LAUSR

Abstract Buckwheat is a rapidly growing cover crop with the potential to improve soil quality and health. In this study, the impact of buckwheat plant material (BPM) as a soil amendment on seedling emergence and suppression of damping-off and root rot of radish (Rhizoctonia solani) and cucumber (Pythium ultimum) was investigated in pot assays. Fresh BPM grown in a greenhouse potting mix for 4 weeks was chopped in small 1–2 cm long pieces and incorporated into field soil containing 0–10% of R. solani or P. ultimum inoculum produced on sterilized rye seed. The infested soil was then incubated for 0–8 weeks prior to planting radish or cucumber seed. The effects of BPM on plant growth and disease development were determined 2 weeks after planting. There was no disease protection if radish and cucumber seeds were planted within 1–2 weeks after soil incorporation of BPM. Disease protection was evident when planting was delayed for 3 weeks after BPM amendment to soil. BPM soil amendment provided protection of radish plants from Rhizoctonia damping-off and protection of cucumber plants from Pythium damping-off and root rot. BPM amendments had no effect on promoting plant growth but slightly increased soil pH. In amended soil receiving 4% and 10% of BPM planted with radish or cucumber seeds 0, 3 and 8 weeks later, total populations of indigenous fungi were 0.66–2.01 log units higher and bacteria were 0.53–0.92 log units higher compared with the populations in the non-amended soils. Buckwheat soil amendment offers a potential option to improve plant and soil health.