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981.
An experiment is described in which S48 timothy seed, direct harvested at 3 stages of ripeness, was dried in layers 6 in. deep, at air temperatures from 75–135° F, immediately after harvest and after periods of from 1 to 3 days conditioning with cold air. Germination results for non-conditioned seed showed good agreement with those obtained in the previous year. The quality of seed hulled during threshing was inferior to that remaining unhulled after threshing, but the latter was more susceptible to high air temperature during drying. The relationship of the seed obtained in this experiment to commercial seed is discussed and a scheme for the practical application of the results will be presented in a subsequent paper. 相似文献
982.
Significant deviations from the ratios expected, according to the single dominant gene hypothesis for resistance to Fusarium wilt, were found in crosses involving several susceptible and resistant tomato lines. The susceptible class was the deficient one in F2 and F3 populations, as well as in backcrosses in which the heterozygotic resistant F1 served as the male parent. The reciprocal backcross, with the F1 as the female and the homozygous susceptible as the male, gave segregations better approximating or consistent with the single gene hypothesis. Reciprocal F1 and F2 generations did not give any evidence of cytoplasmic effects.The results were interpreted assuming preferential fertilization of ovules by pollen grains carrying the dominant I allele for resistance.The practical implications of the phenomenon of preferential fertilization in breeding for Fusarium resistance are discussed. 相似文献
983.
The breeding systems of 12 species and varieties of Trifolium from Africa were investigated. One annual and the three perennial species were allogamous and self-incompatible, the other annuals were autogamous.The effect of temperature on pollen germination and growth was variable. In some species high temperatures (30°C) adversely affected pollen germination and low temperatures (20°C) in others. A high humidity (93–98% R.H.) was essential for good pollen germination and growth.Approach grafts indicated that these species were closely related, however, this method of grafting may not be as reliable as the cleft graft for assessing species relations. From hybridization attempts between seven species, it appears that some interspecific hybrids may be possible within this group. 相似文献
984.
T. D. Johnston 《Euphytica》1967,16(3):365-369
The construction and use of a variable force penetrometer for measuring the woodiness of kale stems is described.The force required to cause penetration of the probe through the xylem tissue was found to bear a close relationship to estimates of quality based on in vitro digestibility determinations, crude fibre content and visual assessment of lignification in stained transverse sections of stems. 相似文献
985.
The improvement of hill land is important to the national economy of the United Kingdom. An increase in the amount of enclosed productive land results in a greater stock-carrying capacity of a hill farm. Improvement is not always possible by conventional implements, and herbicides are being used to kill the old sward. The bipyridyl herbicides offer a means of destroying or modifying the indigenous vegetation. The application of low doses of paraquat or diquat to an association containing Molinia caerulea, Nardus sfricta and Festuca avina resulted in a change in equilibrium in favour of the fescues. The application of 2 lb paraquat per acre practically eliminates all grass species in a sward and it is then possible to establish desirable pasture species after lightly cultivating the dead surface litter. 相似文献
986.
The effects of 4 levels of applied nitrogen, ranging from nil to a maximum of 417 lb N/ acre/annum, in all combinations with 3 frequencies of defoliation, ranging from 2 to a maximum of 10 cuts per annum, on herbage production from a perennial ryegrass/ timothy/meadow fescue/white clover sward were measured. These treatments were operative for 2J years, and in a subsequent year the residual effect of cutting frequency was tested. Dry-matter yields of total herbage and of the clover fraction are quoted, together with N yields of total herbage. Yield response to N was higher than in some other experiments in the U. K. Cutting frequency had a very large effect and, in general, the longer the interval between cuts, the higher was the dry-matter (though not the N) yield. There was a marked interaction between cutting frequency and level of N: at the high cutting frequency, dry-matter yield increased linearly with increasing level of N; at the medium frequency, response tended to fall off at the highest level of N; at the low frequency, yield declined with increasing level of N beyond 139 lb N per acre per anum. 相似文献
987.
988.
Two steers excreting similar quantities of organic matter daily were grazed at pasture during the summer of 1961. The four experiments each involved a preliminary period of five days dosing with Cr2 O3 to reach a fairly constant excretion. The steers received a daily dose of Cr2 O3 either in oil suspension or in shredded paper. The carriers and steers were interchanged for each trial. For two of the trials each steer in turn was harnessed every other day and all its dung collected in a bag. Total faecal excretion of organic matter was measured from the bagged steer and estimated from the Cr2 O3 concentration in a composite sample made up from all dung pats voided during the ten-day collection period. In the other two trials the steers were not harnessed and each dung pat was separately sampled and analysed for Cr2 O3 in the organic matter. The average recovery of Cr2 O3 in the first two trials was 99·1 (oil) or 94·4% (paper). Calculating the faecal organic matter excretion from the concentration of Cr2 O3 in the faeces and the quantity given daily overestimated it by 3·5 to 8·0%. There was no significant difference between shredded paper and oil as carriers of Cr2 O3 for estimating the quantity of organic matter excreted. There were 37% and 22% less variation between dung pats in Cr2 O3 concentration when this was administered in shredded paper than when given in oil suspension. 相似文献
989.
T. Lawrence 《Grass and Forage Science》1963,18(4):292-294
In Saskatchewan, intermediate wheatgrass ( Agropyron intermedium Host. Beauv.) suffered severe winter injury during the 1961–2 winter season, which followed a series of drought years, the most severe being 1961. In two tests, designed to study fertilizer effects, the extent of severe winter injury increased with the rate of application. The killing ranged from 4% where no fertilizer was applied to 90% where 66 lb of N per acre were applied. Slightly more winter-killing occurred after applications of ammonium phosphate/sulphate (16-20-0) fertilizer than after ammonium nitrate (33·5-0-0).
The grass growing in rows 36 in. apart killed out to a greater extent than that growing in rows 18 in apart Less winter injury occurred after spring applications of fertilizer than after application in the fall. 相似文献
The grass growing in rows 36 in. apart killed out to a greater extent than that growing in rows 18 in apart Less winter injury occurred after spring applications of fertilizer than after application in the fall. 相似文献
990.
Because in the past the main emphasis was placed on arable farming, grassland husbandry has played a minor role in East Anglia. Now the increased efficiency exercised in the arable farming of the area is being applied to the grasslands. The main trends are discussed. 相似文献