The crack fertilization technique effectively increases soybean production in upland fields converted from paddies

We have investigated the effectiveness of a new soybean fertilization technique, named crack fertilization, which involves the application of nodule bacteria on biochar to soybean roots through cracks formed between planting rows during midterm tillage. In the present study, the factors and timing of crack fertilization were investigated in an upland field converted from a paddy. The variables investigated were: 1) crack formation without the application of any agricultural materials, and 2) the application of biochar or 3) nodule bacteria on biochar into cracks. The treatment periods were: 1) before sowing, 2) during midterm tillage, and 3) during both periods. The combination of crack fertilization and reduced tillage was also tested. The method of crack fertilization that increased yield was the combination of crack formation and the application of biochar, and the most effective period for the treatment was before sowing in the reduced tillage field. Seed yields in conventional and reduced tillage fields were comparable in the upland field converted from the paddy. These results suggest that the application of biochar into cracks after scratching the soil surface to remove weeds before sowing is a practical method of increasing soybean yield in upland fields converted from paddies.