This experiment was made to clear the influence of Rhodesgrass reseeding on preventing summer depression of cool season type pastures and to get the more ballanced forage production throughout a year. Rhodesgrass was sown on mixed pasture-orchard grass, Ladino clover, red clover, perennial ryegrass-after 3rd cutting (July. 3) in 1965. Treatments of pasture soil surface before Rhodesgrass reseeding were made following three kinds ; no treatment (containing no seeding and seeding), harrowing-reseeding and plowing-reseeding. Every experiment section was cut 6 times a year. The results obtained were summerized as follows : 1. In no seeding pasture, total 5, 000kg/10a green yield was gained in a year and about 80% of the yield were produced in spring season. While, in pastures sown with Rhodesgrass the yields during summer and autumn seasons and the total yearly green yields increased in amount 2, 000〜5, 000kg/10a more than in no seeded pasture. By reseeding of Rhodesgrass the seasonal yield distribution was able to lead more ballanced production than no reseeding. 2. Not treated, harrowed and plowed pastures were gained by reseeding Rhodesgrass 6, 700〜7, 800kg, 8, 500kg and 9, 500kg/10a of total green yields, respectively. In other words, the heavier pastures were treated, the more total green yields were gained. However, Rhodesgrass occupied the more part of the botanical composition during summer and autumn, but cool season type forages, especially legumes decreased remarkably, orchardgrass being not to such an extent. 3. After the 5th cutting, Rhodesgrasses were almost dead out and naked spot which suggested decreasing of the next year production appeared in pastures, and there were observed relation between the growth amount of Rhodesgrass during summer and autumn and the naked spot area after the 5th cutting. 4. Throughout winter, the area of naked spot did not changed in slightly damaged spot, however, in spring, it decreased through the regrowth of cool season plants. As survived plants in heavily damaged spot more withered, regrowth of them were more limited than in slightly damaged spot, and it was observed that the larger the naked spot area was, the more difficult was to decrease them. 5. From the evidence above mentioned, it was confirmed that both heavy treatment of soil surface for reseeding and luxuriant growth of Rhodesgrass were injurious for obtaining well ballanced prodution in future.

View full abstract

On account of remarkable difference between summer and winter temperatures and monsoon-like atmospheric condition, the productive structure of forage crops in warm areas in this country are much different from that of stockfarming countries, such as Europe, America and NewZealand. In this country the forage crop production are concentrated in spring season, especially in rainy June and July, and during this period forage crop are produced 70〜80% of total yearly yield. This experiment were carried out to establish a culture method of forage crop which would be secured ballanced and efficient production throughout a year as possible. This paper deals with change of botanical composition from Italian ryegrass (cool season annual grass) community to Rhodesgrass (warm season annual grass) community by reseeding Rhodesgrass after clipping of Italian ryegrass in spring season. The results were shown as follows : 1. This experiment were consisted of 3 treatments, each of them were sown in last decade of a month in April, May and June respectively. In "section 1st" which were clipped and sown in latter part of April, the regrowth of Italian ryegrass were vigorous and their community were clipped twice during the period about 50 days after the reseeding of Rhodesgrass. On the other hand, during this period the growth of Rhodesgrass suffered from extreme shading under the community of Italian ryegrass, and growth of the seedling retarded. After 50 days, with mean temperature ascending over 20℃, Italian ryegrass ceased to regrow, and the growth velocity of Rhodesgrass seedling become larger. And during the period of 50〜90 days after the treatment, exchange of botanical compositions from Italian ryegrass to Rhodesgrass were recognized. 2. In "section 2nd" which were clipped and sown in latter part of May, the regrowth of Italian ryegrass was not so vigorous and almost consisted of small culm, namely it entered reproductive growth. After clipping of them, with ascending mean temperature over 20℃, and ceasing of reproductive development of grass, regrowth was scarcely recognized. Then, the growth of Rhodesgrass seedling became vigorous, and during the period of 30〜60 days after the treatment, exchange of botanical composition from Italian ryegrass to Rhodesgrass were shown. 3. In "section 3rd" which were clipped and seeded in latter part of June, Rhodesgrass seedling did not suffer from any oppression from Italian ryegrass community. Under the optimum temperature, they grew rapidly, and 35 days after reseeding, they could be able to establish a pure stand. 4. When Rhodesgrass were sown in early spring, seedling of them frequently suffered from extreme shading under the community of Italian ryegrass, and the growth of seedling were retarded or obstructed. Whenever green weight of Italian ryegrass community reached to 2,500〜3,000g/m^2, growth retardation of Rhodesgrass were found, and then the green weight decreasing of the seedling began. 5. Early or late the seeding dates of Rhodesgrass might be, the exchange of botanical compositions from Italian ryegrass to Rhodesgrass happened during the period of the range of 20〜24℃ of temperature, and establishment dates of Rhodesgrass pure stand were confined during the period from late July to early Aug. 6. On the other hand, early seeding caused severe competition between the both grasses, but efficient use of light could be made. The forage production velocity during these experiments were larger in the early seeding section than in the late seeding one. These phenomenon seemed to indicate that the productive structure of earlier seeding was able to secure the more efficient exchange process of botanical composition.

View full abstract

Contribution of the existence of tap root for the foliage production of white clover was estimated by growing the plants under various ways. In a glass house, observation was made on the growth of Ladino clover seedlings whose root systems were allowed to develop in one of three ways ; one group of plants was prevented from establishing a system of nodal roots ; the tap roots of second group were removed after the nodal roots were established ; a third group was allowed to grow normally with both tap root and nodal roots system intact. The intact group showed the greatest total leaf growth throughout the experiment. In earlier stage, the growth of plant grown on tap root only was quite similar to the intact plants, but it decreased gradually toward the end of the experiment, which indicates that the physiological activity of the tap root seems to cease by summer month of the second growing season. In the plants whose tap roots were removed, a large denuded area occurred around the center of the plant immediately after removing and the plant formed a doughnut shape in appearance. This indicates that the tap root plays some role on the growth of this plant even after establishment of nodal root system. This role was also observed in the tracing of the seasonal changes of the development of the root system cultivated in a big glass-sided root box, in which the root system without tap root was not distributed evenly in the soil. In the field experiment, the tap roots of Ladino clover sward were removed in June, July and August, respectively to ascertain how the yield of this plant response to the tap root removing. The swards were harvested four times in the second growing year and three times in the third. Annual green yield was quite the same in all treatments. The yield, however, next to the time of removing was decreased by this treatment and this decrease was most obvious in the sward whose tap roots were removed in June. So the authors suppose that the role of tap root on the poductivity is played by July of the second growing season and the nadal root system takes place the role thereafter.

View full abstract

The effects of irrigation, amount of fertilizer, row spacing, plant population, cutting frequency and cutting height on growth and forage yields of New-sorgo (interspecific hybrid between Sorghum vulgare PERS. and S. sudanense (PIPER) STAPF.) were investigated in 1963 and 1964. The results obtained are summarized as follows : 1. Irrigation increased forage yields by the increase of growth rate in fresh weight per unit area. The interaction between irrigation and cutting frequency was significant in 1964, that is, the effects of irrigation increased strikingly when cutting period was short. Short cutting period augmented the effects of irrigation because these cutting procedures mitigated the retard of regrowth after cutting. 2. Heavy fertilization increased forage yields by the increase of plant height, but the interactions between heavy fertilization and other treatments were not significant. Heavy fertilization increased remarkably the forage yields of first cutting, but lessened the increases of these on second and following cuttings as a result of the retardation of regrowth. 3. Narrow row spacing and dense population increased forage yields in consequence of the increase of number of stem per unit area and the promotion of growth rate. The interactions between these treatments and cutting frequency were significant, that is, the effects of narrow row spacing and dense population increased remarkably when the period of cutting was short. In narrow row spacing and dense population the growth rates after cuttings were rapid but when the next time of cutting was too late the retard of regrowth came out. On the contrary when the period to next cutting was short the retardation of regrowth was mitigated. 4. As described above short cutting period increased forage yields by mitigating the retardation of regrowth. The interactions between cutting period and row spacing or plant population were significant. In the practices such as narrow row spacing, dense population and irrigation the retard of regrowth after cutting were liable to happen. In these cases it is desirable to cut in short period. 5. High cutting decreased slightly forage yields by the increase of remaining parts after cutting. Amounts of remaining parts after cutting influenced little on subsequent regrowth ; there-fore it is not necessary to make high cutting in New-sorgo culture.

View full abstract

Vegetative growth of white clover grown under long and short day was compared in order to make clear the cause of seasonal production of this clover, especially of low production in summer. Results of 4 experiments were reported. In the Exp. 1, treatments of long and short day were made on young plants, sown in small wooden boxes. The experiment was carried out from autumn to spring in a glasshouse. In Exp. 2, the same treatments were made on transplanted stolons in pots during the same season with Exp. 1. In Exp. 3, treatments were made on young plants the same as Exp. 1, but during in warm season, from summer to autumn. In those experiments a number of clipping was done to examine the yields of regrowth. In Exp. 4, ten treatments of different daylength were made on young plants sown in pots. Plots changing from long day to short day at four different number of days after beginning treatment were provided. Similarly four plots of changing from short day to long day were provided. Together with those plots, continuous long and short day plots were prepared as a control. The following results were obtained : 1. There was a little difference in day length responses between Ladino type white clover (Italy) and common type white clover (Nolins), as well as between young plants and a sod made up by transplanted stolons. Whereas, significant differences were found in vegetative growth between short and long day plots. 2. The long day plot produced higher green yield than short day from the beginning of treatment up to early flowering stage, however, produced lower yield after that (Fig.s 1 and 5, Tables 3 and 6). A transition of superiority in the yield from the long day plot to short day plot, corresponding with growth stage, seemed to be very much important to understand the seasonal production in the field. 3. The superiority of the long day plot in yield at the early stage was appeared due to large leaves (Fig. 6, A.B.) and high rate of leaf appearance. The superiority of the short day plot at the later stage was appeared due to a large number of leaves, a large leaf area (Table 1), a large amount of healthy root and stolon, high activity of root and high rate of leaf appearance. 4. The main reason of growth depression in the long day plot was assumed to be deterioration of the structure for regrowth, which was formed by decreased weight of storage organs, such as root and stolon and number of growing points. The structure for regrowth seems to play an important role to reproduce new leaves after clipping. Long day plants were vigorous in top growth, while poor to built up a structure for regrowth (Tables 2, 3 and 5) and this seems to give explanation for occurrence of production cycle. 5. The death and decay of roots and an old part of stolons, sometimes even a death of stumps (Fig. 6, C.D.) were observed in long day plants in an experiment of summer. Whereas, this was never observed in short day plants. The death and decay of those was due to the diseases and it was assumed that decreases of resistance to diseases occurred at the flowering stages, at which growth of roots and stolons were severely depressed. This fact was thought to be important in regard to summer depression in the field, since some evidence proved that the death and decay of roots and stolons was a direct cause of summer depression. 6. These findings were obtained from the continuous long and short day experiments. But it was indicated in the Experiment 4. that changing from short day to a long day or from a long day to a short day, which used to occur in natural condition, influenced more severely than the continuous long day or continuous short day (Fig. 8). 7. A schema of the developmental phase of Ladino clover in a year at Chiba is presented as Table 7, according to the growth response to changing daylength and the field observations reported previously. 8. Causes of summer depression is understood i

(View PDF for the rest of the abstract.)

View full abstract

The two grass-legume mixtures composed of orchardgrass and Ladino clover (O-L sward), orchardgrass and alfalfa (O-A sward), respectively, which differently respond to moistureand cutting method, were used to observe the trend of botanical composition and yield under different soil moisture conditions and cutting height treatments. Varieties used for the mixtures were ; Frode orchardgrass, Du Puits alfalfa and an unknown variety of Ladino clover. Eight concrete pots of 1m×1m×0.5m were filled with the Narugo andosoil (acidic volcanic ash) with river sand at the bottom. Before seeding, basic fertilizers of each 340g CaCO_3, 11.4g N, 17.0g P_2O_5 and 11.4g K_2O were dressed mixing with the upper soil layer, and furthermore, a half amount of the above fertilizers except CaCO_3 was top-dressed in early spring and each one fourth of them was applied after each cut. The following treatments were given, each being composed of one pot : H-W, H-D, L-W and L-D, where H and L denote the cutting height of 10cm and 5cm, respectively, and W and D the soil moisture condition with a constant water table 15 to 20cm below the ground surface and with no irrigation except natural rain, respectively. Only the initial crop was harvested at hay stage and the subsequent cuts were made when the plants reached about 50cm high. In the regime of this trial, soil moisture had a little effect on the growth of orchardgrass, whereas produced a great change in the legume growth ; humid soil was favourable for Ladino clover and checked alfalfa, instead, dry soil being favourable for the latter and depressing the former. The growth of orchardgrass was thought to be influenced more by cutting height than by soil moisture. In the rchardgrass-Ladino clover mixture, the clover played the leading part in determining the yield, and the highest fresh yield was obtained in the low cut-wet soil treatment, followed by the high cut-wet soil, whereas, the highest dry matter was obtained in the high cut-wet soil, as a result of better grass-legume balance where the legume of higher water content decreased and the grass of less water content increased in ratio, as compared with the low cut-wet soil condition. In the orchardgrass-alfalfa sward, the growth of alfalfa dominated the sward resulting in the highest yield by low cut on dry soil, followed by high cut on the same soil condition, where the growth of grass was improved by higher cut, but the alfalfa growth was fairly depressed. There was little yield difference in terms of dry matter production found between the O-L and O-A swards when the soil condition and cutting height were favourable for each mixture, respectively, whereas under the condition of higher water table with much soil moisture, the former considerably outyielded the latter. In fresh weight yield, the sward containing Ladino clover was always more productive than the one containing alfalfa.

View full abstract

In order to trace the yearly change of both plant numbers and tiller numbers per pant and area, and also to find out their relations to the yield with more accuracy than the previous trials, orchardgrass seedlings propagated from one original plant derived from var. Frcde, were transplanted during the fall to establish the two kinds of swards, that is the high density sward with 400 plants per 10a (HD-sward) and the low density sward (LD-sward) with 100 plants per 10a. The size of each plot was 4m^2 (2m×2m). These swards were differentially fertilized in level of nitrogen with the same amounts of other elements ; HN (40kg N per 10a), MN (20kg N) and LN (10kg N), respectively. Furthermore, two cutting systems were employed ; the 4-cut system which took the initial harvest at the early boot stage and the 3-cut system in which the first cut was taken at the maturing stage of the plant. In both systems the subsequent cuts were made when the plant reached around 50cm high. The cutting height was 5cm above ground surface. Plant height and emergence or death of tillers per plant were measured on 20 plants at one or two week intervals. 1. Generally, the height of plant and canopy increased with the increased application of nitrogen, whereas under hot and dry summer conditions high nitrogen retarded the regrowth. High density with high nitrogen depressed the elongation of the plant in the early heading stage resulting in the lowest height at the maturing stage. Plant weight was greater in the low density plant and became greater with increased application of nitrogen (Figs. 1, 2). 2. The percentage of dead plants over a year increased with the increased nitrogen application and in the high density sward, it was greater when the initial cut was taken later at the maturing stage (3-cut system) than when cut at the early boot stage (4-cut system) (Fig. 3). 3. Tillers of each plant emerged rapidly at the three periods, that is, from early spring to prior to the boot stage, after flowering to the early August and in the fall with short day-length and low temperature. The death of tillers, on the contrary, occurred at the two periods, from early head to full bloom and after cutting during hot and dry weather (Fig. 4), and the former death was caused in the younger tillers emerged April to May because they became weaker under the thick mutual shading (Table 1). The total tiller numbers per plant over a year emerged or died were always greater in the LD plants than in the HD plants. The yearly emerged numbers of the HD sward were greater in the 4-cut system (Table 2). Generally more tillers emerged with increased nitrogen application, but with the 3-cuts of the LD sward, medium nitrogen produced more tillers than high nitrogen. With the low level of nitrogen, the numbers of bath emerged and died tillers were small (Table 2). 4. In the LD sward, the number of live tillers per plant when cut 3 times reached three peaks in one season ; the first was the heading stage at the end of May, the 2nd was at the middle August after the initial cutting, and the 3rd was in the fall. When cut 4 times, the first peak was about 10 days later but the other two were at almost the same dates as with the 3-cuttings. In the HD sward, the first peak occurred 10 days earlier but the other two at almost the same dates as in the LD sward. The variability in tiller numbers was always less in the HD sward as compared with the LD sward (Fig. 6). 5. The total number of live tillers per area was greater and reached a peak earlier in the HD sward by the middle May, but decreased earlier due to the death of many tillers, as compared with the LD sward. The latter sward gradually increased in number. It reached the first peak a month later with the 4-cuttings, and half a month later in the 3-cuttings. During the summer, however, the difference between the two swards in terms of live tiller number almost disappeared. In the

(View PDF for the rest of the abstract.)

View full abstract