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101.
Sampling of the benthic fauna showed that dredging operations produced relatively short-term effects on invertebrate population levels. The behaviour of the animals was immediately affected, the differences between species were noted and the implications of dredging at different times of year are discussed. 相似文献
102.
DM yield and N uptake data are presented from primary growth and two successive regrowths of perennial ryegrass treated with combinations of three N treatments for the primary growth viz. 0, 50 and 100 kg N/ha (PN) and four N treatments applied for the second growths, viz. 0, 33, 66 and 100 kg N/ha (SN). Primary growth gave a response of 24·2 kg DM/kg applied N to PN50 with only a further l±0 kg DM/kg applied N from the second PN increment. A significant interaction between PN and SN treatments was shown in second growth. The residual DM response to PN was highest at SN0 and reduced as the level of SN was raised. Substantially greater residual responses to PN treatments were shown in the third growth. Third growth DM responses to SN treatments were high. High apparent recovery of fertilizer N reached 111% of primary N where SN66 followed PN50. High available soil N is partly responsible for both high apparent recovery of N and high DM response. The latter appears to be associated with inclusion of growths given no fertilizer N so that the full residual effects of fertilizer N and ‘priming’ of available soil N can be realised. 相似文献
103.
D. V. H. Rees 《Grass and Forage Science》1974,29(1):47-55
Experiments to determine the exposed layer drying rate of cut leaves and stems of a tetraploid (Sabel) and diploid (S23) ryegrass are described. Drying was achieved by passing air through the crop; the changes in weight were monitored continuously. Airflow was fixed throughout the experiments at 37·5 ft/min (0·190 m/s) and the temperatures were controlled in the range 25°C to 50°C. Comparisons were also made of the drying rates at different stages of maturity. Drying curves were determined and moisture content was shown to decay exponentially with time, the relationship approximating closely to a two term exponential. 相似文献
104.
I. V. Hunt 《Grass and Forage Science》1973,28(3):171-180
The effects of 59, 118 or 177 kg N/ha were measured on 7 occasions from 8 to 57 days after application to a perennial ryegrass sward in terms of changes in composition. The first increase Dt of N significantly raised percentages of CP, non-protein N, K, P, Ca, Na and Mg and significantly depressed percentages of DM, OM and OM digestihility. The second increment of N resulted in a further rise in the percentages of CP, true protein, non-protein N, K, P, Ca, Na and Mg; the percentages of DM and OM were further depressed but OM digestihility was not significantly depressed. Percentages of P and Na showed increased responses for the more mature herbage; while percentage non-protein N showed a more marked response in younger herbage. As herbage matured percentages of OM and Na rose, the latter only from days 16 to 45. All other attributes showed falling percentages to levels which could be inadequate for a 500 kg dairy cow yielding 15 kg milk. CP percentage reached this critical level (1.4% N) at days 37, 45 or 56 given 59, 118 or 177 kg N/ha; P percentage became critically low (< 0.36%) at days 27, 35 or 38, respectively; Mg percentage fell to the critical level (0.12%) at days 23, 35 and 46. Na percentage showed the reverse trend, being deficient (< 0.13%) in the earliest samples and becoming satisfactory from days 23 or 27 at 118 and 177 kg N/ha but it remained inadequate at 59 kg N/ba. 相似文献
105.
The capacitance meters available in the past for estimating herbage yields have lacked sensitivity at the extremes of their range of measurement. The preliminary evaluation of a highly sensitive capacitance meter described here indicates that accurate measurement is possible in the range 0.1100 kg DM/ha. The implications of this development for the measurement of herbage of low availability are discussed. 相似文献
106.
107.
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
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