摘要:

AbstractChanges in the chemical composition of pasture samples from five dairy farms were observed over a 2‐year period. Many of the minerals were at their lowest concentration in samples taken in the spring and early summer. At these times the concentrations of P, Mg and Na were often less than sufficient to meet the calculated requirements of the dairy cow fed on pasture alone. Cu and Co concentrations in the herbage were also generally low relative to the needs of the dairy co

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01450.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractPerennial ryegrass tillers were collected from intensively used set‐stocked and zero‐grazed leys and from an old permanent pasture, grown on and compared at 30 cm spacing. All swards except the permanent pasture had been sown with cv. S23 and were of known age, ranging from 6 months to 11 years from sowing.Each genotype was scored for date of inflorescence emergence, and subsequentlyin vitrodry matter digestibility (DMD), D‐value of green leaf and the ratio of leaf dry weight: stem dry weight were determined.Both DMD and D‐value declined significantly in green leaf samples of populations from the older zero‐grazed swards but no significant changes were detected in populations from set‐stocked swards. In set‐stocked populations there was a shift towards later flowering.In zero‐grazed populations there was a consistent increase in the amount of leaf relative to stem with the age of the sward from which the plants were sampled. The survivor plants were more prostrate and leafier and it is suggested that under zero grazing, where cutting was to a uniform height, plants of this form were less severely defoliated and thus at a sele

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01451.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractTwo methods were adopted of measuring sward output, following the prevention of bracken frond growth, with differing results. Accumulated growth estimation, corresponding to production under a system of open‐range grazing, showed that asulam used for frond control had no effect on herbage yield in the year of application and large increases were observed in succeeding years compared with untreated control plots. In measuring production by sward regrowth after cutting, corresponding to intensive pasture utilization systems, asulam reduced yields in the year of treatment and increases were not observed until 2 years later. The inhibition of growth could be overcome by applying ground mineral phosphate at rates of 300 or 500 kg ha‐1before spraying but the 500 kg ha‐1rate showed no advantage over 300 kg ha‐1. Applications of ground mineral phosphate after spraying had no effect on sward output.It is concluded that indigenous pasture plants in bracken‐infested areas of western Scotland cease growth by mid July unless subjected to major earlier defoliation or severe soil moisture deficits and the removal of the frond canopy does not change this pattern significantly. Obtaining the full benefit of bracken clearance depends on making use of the resulting production of extra herbage and limiting as far as possible frond regrowth in trea

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01452.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractGrass silage made in May from S24 perennial ryegrass was offeredad libitumto twelve Ayrshire cows in a 12‐week feeding experiment. The silage had a DM concentration of 217 g kg‐1, contained 147 g crude protein per kg DM and had a D‐value of 64·6. In addition each cow consumed 1 kg hay per d plus concentrate supplements of dried sugar‐beet pulp with (A) soya bean meal, (B)‘Pruteen’, a single‐cell protein (C) groundnut cake. The three concentrate supplements each contained 250 g crude protein per kg DM and were offered at the rate of 2·9 kg per 10 kg milk. The daily intakes of silage DM were 8·38, 7·94 and 7·49 kg on treatments A, B and C, respectively, with the extreme values being significantly different. The mean daily yields of milk on treatments A and B were both 16·2 kg per cow, and were significantly higher than the yield of 15·2 kg per cow on treatment C. The fat and lactose contents of the milk on the three treatments were not significantly different, but the CP content on treatment C was significantly lower than that on the other treatments. It is concluded that soya bean meal and‘Pruteen’were superior to groundnut cake as a protein supplement

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01453.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractA cutting experiment was carried out on a sward of S23 perennial ryegrass to study the effect of different defoliation regimes on regrowth and the factors affecting regrowth. The defoliation frequencies and intensities encompassed the range commonly found on continuously stocked pastures. The defoliation regimes produced swards of contrasting growth form with regrowth characteristics which differed in respect of senescence loss, fall in water‐soluble carbohydrate concentration, residual leaf area index, photosynthesis per unit leaf area index and photosynthesis per unit area of land. Regrowth was most closely related to the latter. These results were used to interpret data for net canopy photosynthesis of continuously grazed pasture

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01454.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractNine varieties of Italian ryegrass were subjected to two generations of selection for cold tolerance using a controlled environment test. Selection led to a significant overall improvement in average tiller survival from 39·8 to 47·7%, even though the selection intensity achieved was not more than 20%. Although individual varieties varied in initial tolerance from 31·1 to 71·4%, the cold room tests were not sufficiently sensitive to attach significance to differences in response to selection which varied from 0·3 to 17·6%. Agronomic assessment of spaced plants indicated that the winter and spring growth potential of all nine varieties was unaffected by selection for cold tolerance. Although some of the selected populations showed a significant decline in their total yields and persistency, others showed no significant change in these characteristics. The plant breeding implications of these results are disc

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01455.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractAn apparatus in which shoot and root CO2exchange and acetylene reduction can be simultaneously measured in specific white cloverrhizobium associations is described. In mature stolonating clover there was a fairly constant ratio between net photosynthesis, root respiration and acetylene reduction. Of the net carbon fixed daily (12 h light of 80 W m‐2, 400–700 nm; day/night temperature 15°C) 12% was lost during the dark period by the shoot and 17% by the nodulated root. Changes in the rate of acetylene reduction by nodulated root systems occurred more slowly than those in rates of root respiration in response to reduced irradiance. In 21·5 h continuous darkness the rate of acetylene reduction remained constant. Responses to increased irradiance were more immediate in both root respiration and acetylene reduction. In plants maintained at 15°C in a 12‐h, 80‐W m‐2photoperiod there was no significant diurnal variation in acetylene reduction or root respiration. Acetylene depressed root respiration by 20%. Assuming the energy requirement of the nitrogenase system to be the same when reducing acetylene and N the depression can be used as an indication of the energy requirement of fixed N assimilation, metabolism and export in the nodulated root. Of the net carbon fixed daily 3·4% was utilized in this way in plants growing in a 12‐h photoperiod (80 W m‐2, 40

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01456.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractScots timothy was harvested three times a year for 3 years under four harvesting patterns and at all combinations of three levels of application of nitrogen and four of potassium. Harvesting patterns, H1, H2, H3 and H4, comprised cutting primary growth on 27–29 May or 14, 28 or 42 d later followed by cutting a first regrowth 8 weeks afterwards and a second regrowth on 15–16 October. N treatments, N0, N1 and N2, involved annual totals of 0,108 and 216 kg ha‐1N in three equal doses. K treatments, K0, K1, K2 and K4, involved annual totals of 0, 54, 108 and 216 kg ha‐1K also in three equal doses.Mean herbage DM yields in successive years were 8·90, 9·54 and 9·61 t ha‐1containing92·4%, 93·1% and 94·5% timothy, respectively. Systems H3 and H4 had 24% higher yields than H1 and H2. The superiority of the late systems derived from higher yields of primary growth. Mean response to 108 kg ha‐1N at 36·7 kg DM per kg N was significantly higher than the response to an additional 108 kg ha‐1N. Response in primary growth to successive increments of 36 kg ha‐1N averaged 53·9 and 27·5 kg DM per kg N. The first regrowth gave linear responses up to 72 kg ha‐1N. The possibility is discussed of more effective use of N by increasing the proportion applied to regrowth. Response to K was low except in the third year when there was a marked response at N2. It was calculated that to maintain soil potash it is necessary to apply 23·9, 47·7 and 86·6 kg ha‐1fertilizer K for each harves

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01457.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe drying of Italian ryegrass (RvP) tillers under controlled conditions at three stages of growth is described. The rate of water loss was dependent on tiller morphology as well as on water content. Leaf laminae dried faster than stems and also aided the loss of water from stems. Drying time was shortest for vegetative tillers despite their high water content, and longest for reproductive tillers shortly before ear emergence. The practical implications in relation to haymaking are discussed.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01458.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe crude protein concentration, amino acid composition and protein quality of sainfoin (Onobrychis viciifolia) forage was compared to that of lucerne(Medicago sativa).The amino acid analyses showed that sainfoin contained higher amounts of lysine, histidine, proline, cystine, glycine, alanine, valine, leucine, tyrosine, phenylalanine and tryptophan than lucerne, whereas lucerne contained more aspartic acid, methionine and isoleucine than sainfoin; the limiting amino acid in both legumes was methionine. The protein score, an estimation of protein quality for nonruminants, was 68 for sainfoin forage and 71 for lucerne forage compared to 100 for an ‘ideal protein’. The similarity of protein quality of sainfoin forage to that of lucerne indicates that, where conditions permit, sainfoin could be grown for the production of protein as an alternative to other cr

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1979.tb01459.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY