Dung pats were artificially deposited in a bahiagrass pasture rotationally grazed by Holstein heifers in June (JD sward) and in August (AD sward). The dung-deposited and surrounding places of JD and AD swards gave different energy flow through the producer from the dung-free place (ND sward) as follows. (1) The dung-deposited places of both JD and AD swards took larger litter production (LP) than ND sward in the first periods after the dung deposition, which indicated some plant killing by the dung pat cover. However, bahiagrass was found to be considerably tolerant to the dung pat cover since the net primary production (NPP) in those places was not reduced. (2) The dung-deposited and surrounding places of AD sward in the first period after the dung deposition showed a tendency of higher NPP than ND sward mainly because of the higher storage in plant (ST). This was considered to be primarily caused by the increment in the leaf area index rather than the increment in the leaf nitrogen percentage. (3) Then, in the next year over winter, both JD and AD swards tended to be lower than ND sward in NPP chiefly because of the lower ST and LP. In case of AD sward, the reduction in photosynthesis due to the shading by large standing dead and the rise in respiration due to the large non-photosynthetic organs are regarded as the main reasons. However, in case of JD sward, no reason was found for the smaller NPP.

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Digestion trials with sheep and nylon bag were carried out using with timothy hay, reed canarygrass silage, alfalfa hay, mixed grass hay, corn silage, soybean meal, cottonseed meal and wheat bran. In vivo digestion of feeds has shown the amount of digestible organic cellular contents (OCC), cellulase digestible cell wall fraction (Oa) and cellulose contained in low digestible cell wall designated as Ob fraction were highly correlated to their contents in dry matter. In comparison with cell wall digestibility, 72 hr nylon bag digestion has shown higher values generally than those of in vivo trials. However, both values were similar in the case of alfalfa hay.

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A mathematical method was evaluated to manage herd reproduction stably and efficiently in a large scale cow-calf operation. This method is based on the model with discrete time intervals and overlapping generations, which is called the LEWIS-LESLIE matrix model in population dynamics study and contains terms describing age-specific fecundity and survival rate. Using this matrix, the population age structure at a given time can be predicted, and the finite rate of natural increase, the stable age distribution and the reproductive values of a population can be calculated. In the present study, this model was applied to a series of 13 year data of Japanese Black Cattle population reared at Alpine Region Branch, National Grassland Research Institute. The matrix constructed for this cattle population showed the population decrease, suggesting that the operation could not be carried on. Here, the finite rate of natural increase, equivalent to the largest latent root of the matrix, could be used for evaluation of feeding and management, because it was a indicator of population growth. It is clarified that the minimum condition for sustaining herd reproduction is attainable when the finite rate of natural increase of the herd equals to unity. Under this condition, the relationship between fecundities and survival rates was calculated for three different durable periods of years. The number of calves to be admitted into a herd for maintaining its population is equivalent to the number of the female calves in the stable age distribution of the herd. The calves to be admitted to the herd and the surplus stocks produced from the herd were calculated for several levels of fecundity, survival rate and durable year. The relationship between surplus stocks and durable years was discussed in connection with the three different types of survivorship curve and the number of cattle to be kept.

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In order to evaluate the role of phosphorus nutrition in drought tolerance of warm season forage crops, Chloris gayana and Coix lacryma-jobi var. mayuen which had been classified to the most tolerant and the weakest species to water stress, respectivily, grown under various levels of phosphorus were subjected to drought. The leaf water potential (Ψl), stomatal resistance (Υs), leaf area, shoot and root dry weights, root development, nutrient concentration of leaves, stems and roots were determined. Shoot and root dry weights of both species decreased with the increment of phosphorus deficiency and water stress. Water stress markedly decreased shoot and root dry weights in plants, but the decrease was lessened in phosphorus sufficient plants. The root development of phosphorus deficient plants was severely inhibited by the stress. The penetration and development of roots in phosphorus deficient plants was not depressed in deeper soil layers under the water stress condition. Phosphorus application enhanced leaf area expansion, leading to an increased total leaf area in both species under water stress. Leaf water potential Ψl decreased and Rs increased under water stress condition. Assuming the maximum stomatal resistance of 10 s/cm in Chloris gayana, 50% stomatal closure occurred at the Ψl of -0.8 〜 -1.0 MPa for phosphorus deficient plants and -1.4 〜 -1.6 MPa for phosphorus sufficient plants. The values for Coix larcryma-jobi var. mayuen was -0.7 〜 -0.9 MPa for phosphorus deficient plants and -1.2 〜 -1.4 MPa for phosphorus sufficient plants. Phosphorus deficiency increased the stomatal sensitivity and decreased the photosynthetic activity under the stress condition. However, phosphorus sufficient plants maintained higher photosynthetic rates than phosphorus deficient plants under low water potential condition.

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The rolling land of marginal mountain area in Japan, actually used for extensive forestry, is considered to be promising area to develop pastures for the cow-calf program of beef-cattle. However, the cost of pasture establishment is very expensive mainly because of the high application rate of chemical fertilizers. The objective in a series of the experiments is to develop the low-input method of pasture establishment by the effective use of tree litter sources. In this report, the effect of litter layers on the establishment and overwintering of D. glomerata oversown in the cutover land of deciduous broad-leaved forest without chemical fertilizers is presented. L, F and H layers on the forest floor were perfectly remained in the experimental field just after clear-cutting. Three kinds of seed-bed preparation plots were conducted with different degrees of disturbance of litter layers : I ; Removing the whole litter layers, II ; Removing L and F layers, III ; No disturbance. In August of 1982, one week after seed-bed preparations, D. glomerata was oversown without fertilizers in each plot. Results are summarized as follows : 1. Physical factor of litter layers negatively influenced on the emergence of D. glomerata. But the individual growth of the seedling was stimulated by chemical factor of litter layers. At the beginning of winter, the population numbers of D. glomerata in the I, II and III plots were 240, 152 and 184 no./m^2, respectively. 2. Land F layers, only remained in the III plot, prevented winter killing of the seedlings by their physical factors, so that the population number of D. glomerata in the III plot approximated to that of the I plot in next spring. The lowest number was obtained in the II plot. 3. The invasion of native plants was obviously inhibited by physical factor of litter layers. Particularly winter annual plants, which had a stiff competition with D. glomerata after spring, rarely appeared in the II and III plots. 4. The growth of D. glomerata was the highest in the III plot due to low copetition and high nutrients released from litter layers. In June of 1987, 10 months after sowing, the maximum standing crop weight of D. glomerata was obtained in the III plot (58.2 DM g/m^2), which was about 5 times more than that in the I plot. From these results, it was evident that litter layers of deciduous broad-leaved forest should be remained as much as possible in the seed-bed at the phase of pasrture establishment of D. glomerata. Furthermore the effective use of the litter sources opens possibility for the pasture establishment without application of chemical fertilizers.

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A series of field experiments was carried out in cutover land of forest, in order to develop the low-input method of pasture establishment with effective use of tree litter sources. In this report, the effect of litter layers on the productivity of Dactylis glomerata pasture established on the cutover land of deciduous broad-leaved forest without chemical fertilizers is presented. L, F and H layers on the forest floor were perfectly remained in the experimental field just after clear cuting. Fresh tree leaf litter was 0.69 DM kg/m^2 in Land F layers, and decayed one with soil particles was 2.24 DM kg/m^2 in H layer. Three kinds of seed-bed preparation plots were conducted with different degrees of disturbance of these litter layers : I ; Removing the whole litter layers, II ; Removing Land F layers, III ; No disturbance. On August 14 of 1982, one week after seed-bed preparations, D. glomerata was oversown without chemical fertilizers in each plot. Nitrogen mineralization activity under incubating condition was also compared among the three types of tree leaf litter in each layer to know the effect of their nitrogen sources on the growth of D. glomerata. Results are summurized as follows : 1. The maximum plant height and tiller number per plant of D. glomerata were obtained In the III plot. In June of 1983, 10 months after sowing, standing crop weights of D. glomerata were 12.2, 23.6 and 58.2 DM kg/m^2 in the I, II and III plots, respectively. 2. Fresh tree leaf litter in Land F layers, only remained in the III plot, had higher contents of N, P_2O_5, K_2O, MgO and CaO than those of decayed one in H layer. The uptake amounts of those minerals in the top of D. glomerata in the III plot were 4 to 6 times more than in the I plot. 3. The amounts of inorganic nitrogen released from tree leaf litter after 8 weeks of incubation were 1.56, 0.92 and 0.62 mg/g litter in L, F and H layers. On a per hectare basis, those amounts were 3.6, 4.2 and 13.9 kg N/ha, respectively. However, nitrogen mineralization activity of the surface soil was much lower than that of tree leaf litter. Litter sources remained in the cutover land of deciduous broad-leaved forest was considered to be very useful for the growth of D. glomerata, especially in the case of fresh tree leaf litter in L and F layers. Low-input method of pasture establishment was discussed in relation to the comparison of yields between the two pastures of D. glomerata establised on the cutover land with or without chemical fertilizers.

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