Microwave Soil Treatment Increases Soil Nitrogen Supply for Sustained Wheat Productivity

Herbicide-resistant weeds have prompted the development and adoption of new non-chemical weed management technologies for sustainable food production. Considering this, pre-sowing microwave (MW) soil treatment has potential to reduce weed pressure in no-till farming systems. However, the effects of this transient heat disturbance on the soil nutrient profile and on the uptake and accumulation of nutrients in plant biomass warrant further study. In this study, we examined the effect of MW soil treatment on the recovery and accumulation of nitrogen (N) in wheat dry biomass using a 15 N pool dilution technique over two years. Further, temporal changes in wheat yields were assessed by running sequential residual trials. The pre-sowing MW treatment achieved a temperature of 75°C to 85°C. MW soil heating increased the dry biomass and grain yields of the wheat crop over two years of study regardless of the initial N application. Furthermore, MW soil treatment did not significantly increase the N derived from fertilizer (N dff , %). The maximum N dff achieved for the untreated control soils at the higher N dose was 13%, while it was only 8% for the MW-treated soil. Despite this, the total N accumulation in the dry biomass increased by 17% because of MW soil heating, compared to the untreated control soils, revealing the uptake of N from indigenous sources. Consequently, the grain yield supported by indigenous soil N was significantly higher with MW soil treatment at 160, 440, and 740 days after heating. In summary, MW soil treatment appeared to be effective for sustaining the soil fertility over the long term, regardless of initial labeled N application. Keywords: Long-lasting effect, Microwave energy, Nitrogen accumulation, Soil temperature, Wheat yields.