Abstract
In the cold region, as in Nemuro-Kushiro district, we have not a lot of days in year to graze cattle on the grassland, because period of frost free is for only 120 days a year. So, it is necessary to prolong the period of grazing which results in a cut down the cost of dairy and beef production. There are two methods to prolong the grazing period: One is to make the beginning of grazing in spring as early as possible and the other is to finish grazing as late as possible in autumn. Although it has been usually recommended to apply fertilizers as early as possible in spring, the deeply frozen soil makes much trouble on the operation of farm tractor and forces to apply fertilizer too late in earlier spring. In this study, we tried application of fertilizer in autumn to hasten the regrowth of grasses in the following spring. The experiment was carried out on humic volcanic ash soil in Nemuro-Kushiro district by using orchardgrass (Dactylis glomerata) and timothy (Phleum pratense) from 1969 to 1970. The results were summarized as follows: 1. Some part of elements of the fertilizers applied in autumn was absorbed by grasses even in late autumn. Absorbed elements were assimilated to the growing leaves when the fertilizing time was the middle of October, whereas the elements absorbed in_ late autumn were stored at the storage organs such as leaf base, stem base, young shoots, corm and roots of plants. 2. The other part of fertilizers applied in autumn remained in the soil without leaching until the following spring, particularly urea remained more than ammoniumsulfate and ammoniumchloride. Potassiumsulfate remained as much as potassiumchloride. 3. Compared with fertilization in spring, autumnal fertilization was favorable for regrowth of grasses in early spring of the following year and caused some increases of the yield of grasses in May, but showed no more difference in the yield in June. This was because the effects of autumnal fertilization extended no longer, while the same amount of fertilizers applied in early spring become more effective in June when the forages were growing rapidly. 4. The effects of fertilization in autumn were a little of difference between orchardgrass and timothy. Namely, by the application of nitrogen in early autumn, orchardgrass was accelerated more in growth and its leaf color got more green in autumn and also in spring. On the other hand, timothy was not so much accelerated by the application of three elements (N, P and K) in autumn, but it reserved these elements more at storage organs before wintering and its growth was accelerated in spring largely. The reason for mentioned above would be explained by some difference in the growing habit in autumn. 5. The contents of total available carbohydrate (TAC) in storage organs of grasses at late autumn decreased by the autumnal fertilization, particularly in orchardgrass fertilized at early autumn. This tendency was accelerated by nitrogen application, but not by potassim. Accordingly, it is necessary to take care of grasses from winter-killing by the reasonable fertilization in autumn.
