Investigation of concentration of nitrate in the crop field fertilized with shochu distiller's by-product, 2: Experimental field research

Summary: Field plots fertilized with shochu distiller's by-product at rate of 0 and 23 kg/square m were grown with corn, and changes in some chemical properties of soil (0-210 cm depth) were monitored to evaluate the impact of the by-product on the environment. Fungi appearing in the soil after the by-product application were also identified to determine their origin. The by-product contained 94.4 % moisture, 2.44 % total carbon and 0.17 % total nitrogen, with a C/N ratio of 14.33 and pH 3.9. The liquid portion of the by-product contained 0.90 % total carbon and 0.07 % total nitrogen, with a C/N ratio of 12.54. The fertilizer rate for the application plot was thus equivalent to 390 kg N/ha, which was almost twice the rate recommended by Miyazaki prefecture. Changes in soil pH were similar between the nil-application and the application plots. Nitrate-N concentration and electric conductivity (EC) of the top soil in the application plot remained higher than those in the nil-application plot, peaking 14 days after application (8.33 mg/1OO g dry soil and 0.33 dS/m, respectively) and gradually decreasing thereafter. In contrast, the subsoil of the 2 plots showed similar nitrate-N concentrations and EC values. The nitrogen content of the corn used for the cultivation test was 1.5 % in the application plot and was 0.8 % in the nilapplication plot. The recovery rate of nitrogen by the corn was 21.2 %. Three types of fungi were observed in the soil after the by-product application, and they were identified to belong to genera different from that of the fungus used for shochu production. The results show that application of shochu distiller's by-product to a crop field at a conventional rate by farms in Miyazaki prefecture (10kg/square m) does not accumulate nitrate-N in subsoil.