This investigation was carried out to elucidated the variations in maturity of foreign maize hybrids grown at Tokachi district. 490 hybrids were grown at the experiment field in Obihiro University from 1978 to 1982. Midsilking date was measured as an index of maturity. These hybrids were introduced from France and U.S.A. and labeled with FAO index of maturity or Relative Maturity (RM). The hybrids with larger FAO index or RM tend to be later in silking date than those with smaller FAO index or RM. However, there were considerable differences in silking date among hybrids which have the same FAO or RM. Some hybrids had therefore the same silking date in spite of different FAO or RM. The order of maturity represented by FAO index or RM was also observed to be reverse.

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Effects of hulling (removal of bracts) on germination improvement of green panic seed were investigated. Generally speaking, hulling increased germination percentage and accelerated germination irrespective of seed age, but rate of improvement decreased with aging of seed. Although the effect of hulling was not comfirmed at 15℃ in light, hulling improved germination at 15℃ in dark and at 30℃ both in light and in dark, and decreased harmful effects of salt solutions and low soil moisture on germination. It was concluded that hulling was a practical method to improve germination of green panic seed. The effect of hulling seemed to be attributed not to increment of water supply or oxygen supply to the inside of seed, but to removal of germination inhibitors contained in bracts.

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Each combination of two of three seed treatments, namely soaking, heating (storage at 30℃) and hulling (removal of bracts), was applied to green panic seed, and seed responses to these combinations were investigated. It was thought that soaking made better germination by leaching water-soluble inhibitors and hulling made better germination by removal of water-soluble and water-insoluble inhibitors in bracts. And so, hulling was a better method than soaking to improve germination. Soaking resulted in worse gerimination with seeds that possibly showed better germination due to heavy rain and a comparatively low temperature during the ripening periods, and the negative effect appeared clearly in the case thta the seed was hulled before soaking. Heating improved germination by different way from soaking or hulling, affecting mainly to a portion of seed except bracts. Combination of heating and hulling improved markedly germination.

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The relationship between attributes of vegetative and reproductive growth was examined in tall fescue and meadow fescue. There was a negative relation between vegetative and reproductive growth in terms of the relative proportion of vegetative and reproductive tillers at flowering time. A greater proportion of reproductive tillers resulted in more efficient seed production but it caused reduced herbage production under frequent cutting. Cultivars generally tended to show a higher proportion of reproductive tillers and thus larger reproductive growth relative to a vegetative one than natural populations in both species.

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A competition diallel experiment was made in five strains of Festuca arundinacea Schreb. (two cultivars and three natural strains) in order to examine the variation of competitive ability and plant characters affecting it. Both cultivars showed higher competitive ability than three natural strains. The competitive ability was closely associated with the shoot DW but not with the root DW under the spaced planting condition. And it also positively correlated with the number of roots. The mixtures were generally more productive than the monocultures probably because of more efficient utilization of light energy by a combination of different plant types.

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A field study was conducted to evaluate the drought resistance ablities of eight warm season forage species compapreing with their top and root growth, root-top ratio, leaf water potential, stomatal resistance and nutrient uptake. Grass species used in the experiment were Paspalum dilatatum cv. Kyushu 5 (Dallisgrass), Chloris gayana cv. Katambora (Rhodesgrass). Paspalum Notatum cv. Common (Bahiagrass), Sorghum bicolor, cv. Sweet Siox (Sweet sorghum) and cv. Rancher (Rancer), Zea mays cv. Snowdent 1 (Corn), Eleusine coracana, Marketing variety (African millet), Coix lacryma-jobi, Marketing variety (Job's tears). The eight species were grown on the non-irrigated and irrigated field which were regulated to pF 1.7, pF 2.3, pF 2.8 by the automatic irrigation system. The results obtained are summarized as follows ; 1) The relative growth rates of species grown on non-irrigated field to the maximun growth obtained by the most suitable watering were higher as follows ; Dallisgrass Rhodes-grass≧Bahiagrass>Sorghum (Rancher)>Sorghum (Sweet)>Corn>African millet>Job's tears. That is, Dallisgrass, Bahiagrass, Rhodesgrass were most tolerable to water stress, but African millet and job's tears were very sensitive to water stress. 2) Root dry matter weights of Dallisgrass and Bahiagrass were increased in water stress condition, however, the root development of much sensitive species were remarkably suppressed by water stress. The ratios of root weight to top of all species were generally increased by water stress, and especially that of to tolerant species increased higher those of sinsitives. 3) Leaf water potential of all species was decreased as the water stress increased. The order of decrease was as follows ; Dallisgrass<African millet<Bahiagrass<Sorghum (Rancher)<Sorghum (Sweet)<Job's tears<Rhodrsgrass<Corn. The tolerant species maintained relatively higher leaf water potential, but that leaf water potential of Rhodesgrass which was one of the most tolerant species was lower than that of Job's tears. 4) Stomatal resistance of all species was increased by water stress. But, stomatal resistnace of sensitive species remained higher than that of tolerances. 5) The absorption amount of all nutrients of species examined tended to be lowered by water stress, and the absorption of nitrogen and phosphorus were more severely decreased than that of potassium, calcium and magnesium by water stress.

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This study was conducted to evaluate the mechanisms of drought resistance in five warm season species: Dallisgrass (Paspalum dilatatum POIR), Rhodesgrass (Chloris gayana KUNTH) , Sorghum (Sorghum bicolor (L.)), Corn (Zea mays L.) and job's tears (Coix lacrymajobi) by observation of their top and root yields, leaf water potentials, stomatal resistances, nutrient uptakes. The five species were grown on wargner pots, of which soil moistures were adjusted to pF1.7-2.0, pF2.3-2.5, pF2.8-3.0. The results obtained are summarized as follows. 1) Ratio of dry matter weight of each species grown on pF2.8-3.0 to pF1.7-2.0 condition was higher as follows: Dallisgrass>Rhodesgrass>Sorghum>Corn>Job's tears. That is, Dallisgrass, Rhodesgrass were higher resistant to water stress, and Corn, job's tears were very sensitive to water stress. 2) The stomatal resistance of species on pF2.8-3.0 was lower as follows: Job's tears>Corn Sorghum>Rhodesgrass>Dallisgrass. Dallisgrass and Rhodesgrass had the high transpiration rate among species under low soil moisture. And the leaf water potential on pF2.8-3.0 was higher as follows: Job's tears>Corn>Sorghum>Rhodesgrass>Dallisgrass. There was a highly significant correlation between their leaf water potential (Y) and stomatal resistance (X) and their regression equation between X and Y was as follows: Dallisgrass: Y=-1.23X-2.72 (r=0.977) Rhodesgrass: Y=-1.19X-2.50 (r=0.954) Sorghum: Y=-0.90X-2.62 (r=0.933) Corn: Y=-0.69X-3.41 (r=0.989) Job's tears: Y=-0.65X-4.34 (r=0.986) From these linier correlation equation, it was showed that tolerant species to water stress tended to have a lower coefficient of stomatal resistance. 3) Root dry weights of tolerant species such as Dallisgrass and Rhodesgrass were not apparrently suppressed by water stress, however, those of most sensitive species such as Corn and Job's tears were severely lowered the root weight by water stress. 4) The nutrient uptake of species had generally suppressed by water stress, but, sensitive species were suppressed more severely than those of tolerant species. It is concluded from results obtained that mechanisms of drought resistance of warm season forage species might be due to their high water and nutrient absorption abilities from the soil limited moisture by minimyzing the reduction of developing of their root system and by their low leaf water potential comparing with high transpiration rates.

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The characters and yearly changes in root growth of forage crops and soybean were examined for 4 years in conversion from paddy field of ill-drained cleyey soil into upland field. Species used were corn, sorghum, rhodesgrass, green panic and soybean. The methods of cultivation were same descrived in the former papper. The results are summarized as follows ; 1) In the first year of the conversion, the depth of root penetration was shallow and most of roots were confined to the upper 10cm layer of soil in all species. The root penetration rate was gradually improved with a lapse of time. 2) After the second year from the convertion, sorghum roots could penetrate through the traces of roots of rice which was planted before conversion, and the two tropical grasses roots could grow through there after three years, so the roots of such species distributed uniformly under the plow layer. Corn and soybean roots could grow through only the cracks of the soil. 3) In all years, sorghum roots could penetrate most deeply followed in decreasing order two tropical grasses, corn and soybean, and the soil oxidation was followed by development of root system. On the other hand, the depth of cracks in the soybean fields was deepest. 4) Water absorption from soil by the crops was measured with tensiometer. Sorghum absorped water strongly from lower soil. In bare ground, the soil moisture was kept higher than the ground by cultivation of upland crops.

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Macroptilium atropurpureum cv. Siratro and Stylosanthes guianensis cv. Schofield were grown in Red-Yellow acid soil under four levels of liming (0, 0.4, 0.8, and 1.2t/10a)×four levels of phosphorus application (0, 5, 10, and 15kg/10a) and in Redish-Brown alkali soil under six levels of phosphorus application (0, 1.5, 3.0, 6.0, 9.0, and 12.0kgp/10a). Dry matter yields obtained were discussed with soil chemical properties changed with liming and phosphorus application. Results. Red-Yellow acid soil. DM of Siratro and Schofield increased with P-application. With liming of 400-800kg/10a DM of Siratro increased showing an additive effect of P-application, however, DM of Schofield decreased indicating an optimal liming level to this species ca. 200kg/10a. Available soil P increased with both liming and P-application but decreased with liming which increased soil pH above 7. With liming above 800kg/10a, exchangeble Al^<+++> and H^+ significantly decreased. The DM data above obtained were discussed in relation to the change in soil chemical properties induced and the physiological characteristics of the legumes tested. Red-Brown alkali soil. Soil available P increased with P-application, however, any significant change in DM of the legumes were not observed, possibly due to the higher soil pH for the growth of the legumes tested.

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Tropical pasture legumes; Macroptilium atropurpureum cv. Siratro and Stylosanthes guianensis cv. Endeavour, and grasses; Panicum maximum cv. Gatton and Chloris gayana cv. Boma were grown in Red-Yellow acid soil [pH(H_2O) 4.3] and in Dark-Red alkali soil [pH(H_2O) 7.2] applied with five levels of P-fertilizer (0, 100, 200, 400, and 600mgP/pot). The growth response to the P-fertilizer application was greater in Guinea grass than in Rhodes grass, but the difference was not recognized in the legumes. Soil available-P should be maintained at 15, 40, and 25ppm in the acid soil for producing more than 90% of the maximum yield in the legumes, Rhodes grass, and Guinea grass, respectively. The levels of soil available-P required in the alkali soil for the optimum plant growth were lower than in the acid soil. Dry matter yield of the tested plants were greater in the alkali soil than in the acid soil, however, the difference disappeared in Guinea grass when higher levels of P-fertilizer were applied. This is probably due to the increased levels of P uptake by the increased root mass of Guinea grass which showed increased efficiencies in dry matter production per unit of P uptake. Comparing with Siratro, Stylo showed higher levels of DM production at lower levels of soil available-P, probably due to the efficient P uptake by the root system of Stylo.

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To examine the relative importance of genotypic and environmental effects in determining differences in life-history traits such as survival rate, plant size and fecundity within a pasture population of timothy, the tiller- and seedling-transplanting experiments were carried out in a small area (40×45m). The adjacent subpopulations of timothy were transplanted in each experiment. The survival rate and the size of plants were examined among the tiller-transplants for three years, and among the seedling-ones for two years. The results were as follows: 1. The survival rate and the plant size were different among the transplanting plots. These variations were closely related to those for grazing pressure and vegetational structure. 2. Life-history traits were different between the tiller-transplants and the seedling-ones. The plant size and the seed reproduction in first year were lower in the seedling-transplants than the tiller-ones. 3. No differences in life-history traits were found among the adjacent subpopulations in both transplanting experiments. 4. These facts suggest that environmental differences were much more important than genotypic ones in determining differences in life-history traits of timothy in this pasture.

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Landsat multispectral scanner (MSS) data acquired on May 22 in 1979, over Northern Tochigi district (Figs.1 and 2) was analyzed using the Image Information Processing System at Chiba University to evaluate the utility of satellite data for land-use classification. A flow chart of the basic steps taken to perform this analysis is shown in Fig.3. In addition to the original four Landsat MSS bands (500-600nm, 600-700nm, 700-800nm and 800-1100nm), two rationing treatments using bands 5 (red) and band 7 (infrared) were applied in this analysis (Table 1). Fourteen cluster classes were identified as exhibiting spectrally separable characteristics and they merged finally into nine types of land-use groups. The number of cases classified into each cluster class and land-use group for training data is shown in Table 2. More than 90% performance in every group, and an average of 94.0% performonce for overall were attained. Difficulties were encountered in classifying groups such as "Forest"-"Grassland" or "Urban"-"Bare soil" correctly. These difficulties have currently been resolved by using Landsat data from different seasons. A land-use maps with six groups represented in different symbols covering the Nishinasuno Town was produced (Fig.4). The accuracy of the Landsat estimates were examined by contrasting them with the Real Estate Records in Municipal Offices of one city and two towns in Northern Tochigi Prefecture (Table 3). The general patterns of the classifications were found to be acceptable when we incorporate proper corrections for discrepancies which occurred because of differences between the present actual state of land-use and the registered land classification (Table 4).

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Pasture yields often fluctuate with differences in management, because pasture is usually cultivated for a number of years under the pressure of grazing or cutting several times a year. However, pasture has wide areas of non-uniform growth distributions in contrast to row crops such as rice or wheat. Therefore a grasp of pasture productivity is difficult to ascertain at present which complicates the inevitable need to build plans for the renovation of pasture and/or the purchasing of supplemental forage on a farm. A study was undertaken for estimating pasture yields using Landssat multispectral scanner (MSS) data. In the previous paper, six land-use groups including a "Grassland" group are identified using Landsat MSS data acquired over Northern Tochigi Prefecture. In this study, multiple regression models were created using first cutting yield data collected from 26 pasture plots in Nishinasuno Town (Table 1) and combining this information with Landsat spectral reflectance data (CCT count) of the six channels appearing in Table 2. Flow of analysing process is shown in Fig.1. Results obtained are as follows ; 1) Band 6 (infrared) had the highest correlation with yield (r=0.823) when it used single band. 2) Multiple regression coefficients improved in accordance with the increment of number of channels entered in the model, however, this increase was retarded when four channels were exceeded (Table 3). The equation used in the best four channels (R=0.923) is expressed as, Y_<est>(kg/ha)=-177.7X_1+132.5X_3+99.9X_4-216.216+10642.5 Here, estimated yield (Y_<est>) is expressed as a function of Xs, and X_1 to X_6 in the equation corresponds to the CCT or computer compatible tape counts of Ch 1 to Ch 6, respectively. 3) Yield estimation by a multiple regression model using the best four channels was applied to our study area, and the magnified Shiobara-Nishinasuno area appeared in a yield map of Fig.4. In the map, four yield classes for the first cutting were indicated with numbering, 1 for 0-1.9ton, 2 for 1.9-4.1ton, 3 for 4.1-5.7ton, and 4 for over 5.7ton per hectare. 4) Because of a lack of reference information, accuracy had to be confirmed by field checks, however the general classification patterns were found to be acceptale.

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The effects of slope aspects on the root growth of bahiagrass, Paspalum notatum Flugge, during eary growth stage were investigated in order to get informations concerning topographic functions in terms of exposure differences for establishing bahiagrass pasture on lowland hills in southern part of Kyushu. Bahiagrass was grown from July, 1981 to September, 1982 on each of north (shady)-and south (sunny) aspect of artificial slopes with gradient of 30 degrees. Shoot density, daily herbage regrowths, numbers of nodal root, rate of root elongation and root weight in each soil layer were investigated periodically. Changes of daily solar radiation, mean soil temperature and soil moisture percentage were measured on each aspect throughout the experiment. The results obtained are summarized as follows: 1) Shoot density increased more significantly on sunny slope from early March to early May, 1982 than on shady slope. 2) On sunny slope, there was a large increase in daily herbage regrowths through growing seasons. 3) Numbers of nodal root on sunny slope increased in autumn and early spring, while those on shady slope were less and changed a little during the experimental period. 4) In 1982, root elongation on sunny slope started early in March. Roots on shady slope, however, began to elongate nearly two months later, that is from the beginning of May. 5) Comparing with shady slope, root weight in the upper 5-10cm soil layer increased significantly on sunny slope during May to August, 1982. 6) The delay in growth on shady slope seems to be brought about by less solar radiation, followed by lower soil temperature during autumn to spring. From these findings, it is suggested to be necessary to take slope exposures into account as one of the main topographic functions for establishing bahiagrass pasture.

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The differences in cell wall digestibility using cellulase were compared among several warm-season forage crops. Greenpanic, bahiagrass, fall panicum, finger millet and rhodesgrass were sampled at three different growth stages while maize and sorghum were sampled two growth stages. 1) A high amount of cell wallconstituents (CWC) decreased digestibility of them (CWC D) and in vitro dry matter digestibility (IVDMD) of all the warm-season forage crops. 2) CWCD of all forage crops decreased with late growth stage. CWCD of fall panicum was the highest of all the grasses and that of rhodesgrass was the lowest at all growth stages. 3) Increases in the proportion of lignin to CWC between young and old growth stages were found in all grasses. The greatest increase of lignin in the CWC was seen in fall panicum (52.9%) and the least increase was in bahiagrass (1.2%). 4) Differences in CWCD between various grasses were seen even when the proportion of lignin to CWC was similar. These results mean that differences in CWC among warm-season forage crops were influenced by other factors in the CWC as well as the proportion of lignin.

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The effect of planting density on cell wall synthesis and its digestilibility by cellulase was investigated using two sorghum cultivars (Sendachi & Hiromidori) of different tillering habit. Planting densities, inter-and intra-row space, were planned as 30×5cm, 60×10cm and 90×30cm 1) The increase of cell wall constituents (CWC) and the reduction of CWC digestibility (CWCD) by cellulase were investigated in Sendachi. Indigestible CWC increased with maturating to the dough stage, while digestible CWC decreased. This phenomenon accelerated the formation of (indigestible constituents such as) lignin and hemicellulose. 2) A major portion of dry matter substance was distributed in to the abundant tillers of the cultivar Sendachi, while it was found in the main stem of Hiromidori. With increasing planting density the leaf proportion decreased and the maturation advanced in both cultivars. A decreasing of in vitro dry matter digestibility (IVDMD) and CWCD was seen when planting density increased. There was little or no differences in these variations between the two sorghum cultivars. 3) High planting density reduced CWCD in tillers as well as in the main stems of Sendachi. This means that high planting density causes the decreases of IVDMD and CWCD in sorghum regardless of its varietal tillering habits. 4) With the increasing of planting density, dry matter yield increased, but digestible dry matter yields was almost unchanged (especially in Hiromidori.) These results suggest that high planting density promotes cell wall synthesis and maturation in sorghum. It is concluded that an optimal planting density would supply the highest digestible dry matter production in sorghum, even though, it has a tillering habit or not.

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For the purpose of investigating the efficient method of utilizing the ensiled NaOH-treated rice straw, two digestion and nitrogen balance trials were carried out, in which the four rations: ensiled NaOH 6%-treated rice straw ; ensiled NaOH 6%-treated rice straw and ryegrass hay (expt. 1) or ryegrass silage (expt. 2) mixed at the time of feeding to approximate 50:50 or 25:75, respectively, on a dry matter basis ; and ryegrass hay (expt. 1) or ryegrass silage (expt. 2) were fed to four goats in a 4×4 Latin square design. The digestibilities of dry matter, organic matter, NFE, crude fiber, NDF, ADF, hemicellulose and cellulose were significantly higher for the ensiled NaOH 6%-treated rice straw than both for the ryegrass hay and the ryegrass silage. The digestibilities of all the constituents actually determined for the 50:50 and 25:75 rations significantly higher than those calculated by the combining ratios assuming constant digestibilities of both the ensiled NaOH 6%-treated rice straw and the hay (or the grass silage) rations, namely combining NaOH 6%-treated rice straw with hay or grass silage resulted in associative effects on digestibility of verious constituents. The digestibilities of all the constituents for the ensiled NaOH 6%-treated rice straw portion in the 50:50 and 25:75 rations calculted by an indirect method assuming constant digestibility of hay or grass silage increased with increasing level of hay or grass silage in the rations. The TDN contents of ensiled NaOH 6%-treated rice straws mixed with ryegrass hay ware 57.2, 59.7 and 62.5% of dry matter for the 100:0, 50:50 and 25:75 rations, respectively, and those of them mixed with ryegrass silage were 57.4, 59.9 and 62.7% for the 100:0, 50:50 and 25:75 rations, respectively. Much more nitrogen were retained with the mixed rations of ensiled NaOH 6%-treated rice straw and ryegrass silage than with the ryegrass silage ration. From these results it was suggested that the ensiled NaOH-treated rice straw could be efficiently used in combining with other feeds, especially with grass silage for fully attaining potential digestibility in the NaOH-treated rice straw.

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This study was undertaken to investigate the significance and the adequate level of urea supplementation as a source of nitrogen for fully attaining potential digestibility in the ensiled NaOH-treated rice straw. Either untreated or NaOH 6%-treated ensiled rice straw was supplemented with two levels of urea, namely 0 or 2% of the straw dry matter, and with these four rations a digestion and nitrogen balance trial was conducted with four goats in a 4×4 Latin square design in the experiment 1. In the experiment 2, the ensiled NaOH 6%-treated rice straw was supplemented with four levels of urea, namely 0, 1, 2 or 2.5% of the straw dry matter and a digestion and nitrogen balance trial was conduted in the same way as in the experiment 1. In the experiment 1, for the untreated non-supplemented, the untreated 2% urea-supplemented, the NaOH-treated non-supple mented and the NaOH-treated 2% urea-supplemented straws, the dry matter digestibilities were 37.0, 37.7, 53.0 and 59.0%, respectelviy, the TDN contents were 34.7, 36.4, 46.6 and 52.6% on a dry matter basis, respectively and the dry matter intakes were 1.15, 1.15, 0.86 and 1.26% of live weight, respectively. In the experiment 2, for the 0, 1, 2 and 2.5% urea-supplemented NaOH-treated straws, the dry matter digestibilities were 43.4, 55.1, 56.2 and 58.7%, respectively, the TDN contents were 38.6, 48.4, 51.9 and 53.8% on a dry matter basis, respectively and the dry matter intakes were 0.95, 1.26, 1.26 and 1.52% of live weight, respectively. These results indicated that although the treatment of rice straw with NaOH resulted in increased energy digestibility, nitrogen was a limiting nutrient, namely an adequate supply of nitrogen was necessary to increase the rate of microbial digestion and thus the voluntary consumption of the NaOH-treated straw by the animal.

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[in Japanese]

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[in Japanese]

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