Abstract
Purpose of these studies were to establish a method by which the highest yield would be secured as well as well balanced high production throghout a year would be expected. On October 12, 1961, orchard grass, Ladino clover, red clover and Italian ryegrass were sown (reseeding being made in autumns of the following years) under treatments of irrigation, water table, amount of fertilizer applied and cutting height to test their effect on yield and botanical composition for tow years. The results obtained were as follows: (1) In Kanto area where dry condition continues in early spring, irrigation was effective in that season, particularly to Italian ryegrass. But in the summer when water table went up high (average 32cm), the favorable effect of irrigation disappeared. (2) Moreover when water table came up too high (average 22cm), orchardgrass and red clover faded away damaged by high humidity, and single vegetation of Ladino clover appeared thereafter was due to this fact. (3) High producing effect by heavy fertilizer application was observed only when Italian ryegrass occupied main part of the botanical composition. But since summer, withered plants produced naked spots in the field and weeds invaded to those spots. Instead of heavy fertilization plots, forage yield was higher in standard fertilization plots (total amount of annual top-dressing being N:P_2O_5: K_2O=2: 2: 5kg/a) and effect of heavy fertilization was not observed in total annual forage yield. (4) By low cutting (5cm), Italian ryegrass and Ladino clover gave higher yield but in orchardgrass and red clover, high cutting (10 and 15cm) gave higher yield. As to total annual forage yield, lower cutting produced high yield but low cutting also induced monopolization of Ladino clover, bringing reduced production in summer and autumn seasons. (5) When water table was low, though low yield in summer and autumn seasons could be somehow controled by standard fertilization instead of heavy one and by high cutting instead of low one, their range of control was very narrow, the total annual green forage yield being about 1,000kg/a.
