Abstract
The application of organic matter to arable land is important in promoting soil fertility. Excessive application of organic matter, however, causes adverse effects on the nutrient condition of the soils and ground water pollution. We propose subsoil application of cattle manure composts (CMC) to strongly acidic andisols in which elongation of crop roots are inhibit, since CMC have ameliorate ability of acid injury soil. It's probable that the CMC have a slowly decomposing character when mixed with water treatment residuals (WTR) containing aluminum (Al). Aluminum cattle manure composts (AlCMC) having a slowly decomposing character were expected to have an organic sequestration effect when they were applied to subsoil. This study was carried out to confirm the nitrogen and carbon mineralization characteristics of A1CMC, and also the effect of AlCMC application on soil chemical properties and sorghum growth. 1) Incubation at 50℃ after mixing CMC with WTR accelerated oxidation of manganese ion (Mn^<2+>) which is otherwise harmful to plants. Exchangeable manganese decreased to one-tenth of the initial amount over ten days. The available phosphorus in CMC was fixed by Al contained in the AlCMC (containing 50% WTR) and decreased to 33% of that in CMC. Exchangeable potassium in CMC was not fixed by AlCMC. 2) The carbon dioxide (CO_2) emission from CMC mixed with WTR was compared with the sum of CO_2 emissions from unmixed CMC and WTR. When the mixing rate of WTR : CMC was 1:1 or 1:2, CO_2 emission decreased to 87% or 71% respectively of that from the unmixed treatment after 86 d. The nitrogen mineralization in the 1:1 mixing treatment after 70d decreased to 75% in comparison with the unmixed treatment. 3) The acid soil used in the pot culture experiment was ameliorated. Soil pH increased to more than 5.7. The available phosphorus after the pot experiment was lower in the AlCMC treatment compared with that of the CMC treatment. The exchangeable manganese was sufficiently low to prevent harm. The cation exchange capacity increased after treating with Al compost. 4) The applications of the AlCMC increased the dry matter of sorghum compared to non-treated compost, owing to soil acidity amelioration. Sorghum growth in the AlCMC treatments was equivalent to that of CMC treatment. In conclusion, the rate of the mineralization of carbon and nitrogen, and the amount of available phosphorus of CMC was suppressed by mixing with WTR. Application of AlCMC to soil improved soil acidity, cation exchange capacity and soil nutrient status.
