Abstract
An Italian ryegrass-corn-corn triple cropping, which consists of conventional-tillage (overall-tillage) cultivation of Italian ryegrass as a winter crop and minimum-tillage (partial-tillage) cultivations of corn as summer crops, is a forage production system that has a potential to maximize annual yield of quality feed with minimal labor requirements for corn establishment. Manure is applied only at the time of conventional tillage for Italian ryegrass (single application), while chemical fertilizer is applied at the tillage times for all the crops (3 applications). We tested whether an increase in the manure application level in autumn can reduce the annual use of chemical fertilizer, assuming that manure applied in autumn remains effective until the corn cropping seasons in the next year due to low mineralization and leaching of nutrients during the cool, dry winter-early spring seasons. Annual forage yield in the heavy manure plot [900kg/a manure and 2.25kg/a N, P_2O_5 and K_2O as chemical fertilizer (0.6-0.75-0.9kg/a for ryegrass-corn-corn)] was equivalent to that in the conventional manure plot [300kg/a manure and 3.7kg/a N, P_2O_5 and K_2O as chemical fertilizer (1.0-1.5-1.2kg/a for ryegrass-corn (conventional tillage)-corn)], showing the effectiveness of applying manure for the 3 crops as a single autumn application.
