Crop yield gaps can be partially overcome by soil sanitation strategies such as fumigation; however, there are fewer suitable fumigants available in the marketplace and growing concerns about chemical impacts in the environment and human food chain. Therefore, thermal soil sanitation has been considered for some time and microwave soil treatment has some important advantages over other thermal soil sanitation techniques, such as steam treatment. It is also apparent that microwave soil sanitation does not sterilize the soil, but favors beneficial species of soil biota making more nutrients available for better plant growth. From these perspectives, microwave soil treatment may become an important pre-sowing soil sanitation technology for high value cropping systems, allowing agricultural systems to better bridge the crop yield gap.

Pre-sowing microwave (MW) irradiation (2.45 GHz) of soil for 120 s was investigated for sustainably enhancing wheat yield. A two-factor factorial glasshouse experiment was conducted to explore the bio-stimulation effect of MW energy on wheat crop growth and yield. The 175% increase in dry biomass and 96% incremental increase in grain yield of wheat were obtained through the application of 2.45 GHz MW energy to soil at N₁ (0 mg N pot ^–1) compared to non-microwave treated soil. The MW irradiation of soil holds potential to significantly enhance wheat productivity.

Herbicide-resistant weeds have prompted the development of non-chemical weed-control techniques for sustainable crop production. We examined the potential of pre-emergence microwave (MW) soil treatment to suppress weeds and enhance grain yield in rice (Oryza sativa L.) cropping in two agro-ecological zones of Australia. An experimental MW weed killer, which has four, independently controlled, 2-kW MW generators operating at 2.45 GHz, was used to treat the soil before cropping under field conditions. A once-off MW soil treatment (duration 60 s) and an untreated control were assigned in a randomised complete block design with five replicates at two study locations: Dookie (Victoria) and Jerilderie (New South Wales). Simpson’s numerical surface integral approximation estimated the applied energy density of ~500 J cm–2. This energy increased the soil’s temperature up to 70–75°C in top soil horizon (0–6 cm) as depicted by infrared thermal imaging. No statistically significant difference was detected for weed control between MW and untreated control plots at either study location. At Dookie, grain yield did not significantly increase in response to MW soil treatment, whereas at Jerilderie, grain yield was 20% higher (P < 0.05) with MW soil treatment than in control plots. At Jerilderie, the irrigation water use efficiency (t ML–1) was 21% higher in MW plots than control plots. In summary, MW exposure of 60 s appeared to be an insufficient heating duration for seedbank depletion. This suggests further treatment modification followed by rigorous testing under different soils conditions using the MW prototype.

Two barley varieties (California Mariout and Gustoe), differing in putative salt tolerance, were grown in lysimeter tanks containing 1 m³ of sandy loam soil in a greenhouse experiment in Tucson, Arizona. The varieties were subjected to three salinity treatments (0, 150, and 250 mol/m³ NaCl) and two leaching fractions (LF) (0.2 and 0.4). Mariout, a reportedly salt‐tolerant, high straw variety, yielded more grain and biomass than the semi‐dwarf variety, Gustoe, across salinity treatments, but slopes of growth responses to salinity were similar. Mariout grain yields on control solution were the equivalent of 4.8–5.3 t/ha, similar to good open field yields of this variety. Gustoe yields were lower, 3.5–4.1 t/ha. Salinity reduced Mariout yields to 4 t/ha on 150 mol/m³ and this was judged to be the highest irrigation salinity which will produce economic yields of this variety. The saturated soil extract (ECe) in the root zone at this salinity was 11.8 dS/m. For both varieties, biomass and grain yields were reduced by 2.4–3.1% for each 1 dS/m increase in ECe, and ECe's producing 50% yield reduction of biomass or grain ranged from 17–21 dS/m. Increasing the LF increased biomass and grain production by both varieties, especially on 150 mol/m³ treatment, but did not reduce ECe as much as expected. Adding additional water as a LF increased the amount of evapotranspiration rather than reducing ECe.