摘要:

SummaryVernalized and unvernalized perennial ryegrass (Lolium perennecv. Gremie) tillers planted in microplots in a glasshouse in April 1974 and 1975 were exposed to natural daylength thus inducing vernalized plants to produce reproductive, and unvernalized plants vegetative growth. Nitrogen was applied at 0–30 g m−2(to 24 g m−2in 1975) to both types of herbage. At the first defoliation in each year yields from vernalized grass were greater than those from unvernalized grass; subsequently differences were minimal or reversed. Vernalization had no significant effect (P>0.05) on total yields over four defoliations in either year.Apart from the first cut in 1974 nitrogen application increased dry matter yields of both types of herbage. Tiller numbers were usually increased by the lowest level of nitrogen application but at higher levels the effect was variable.There was no evidence of an interaction effect of level of nitrogen application and vernalization on dry matter y

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00813.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractIn two 4 × 4 Latin Square experiments, one with dry cows and one with sheep, animals were givenad libitumearly‐cut ryegrass silages prepared using formic acid (2.31 t−1) as an additive. The silages were offered either untreated or partially neutralized with either a low (8 g kg−1fresh weight) or high (16 g kg−1) level of sodium bicarbonate or with sodium bicarbonate solution (50 g kg−1) given as an intraruminal infusion at a rate sufficient to provide bicarbonate at a rate similar to that provided by the high level of dietary addition.In cows the bicarbonate treatments were associated with a depression in the intake of organic matter which at the high level of addition of bicarbonate was statistically significant (P0.05). In both species water intake increased directly with the quantity of bicarbonate ingested.In both experiments the bicarbonate treatments increased rumen pH but there were no significant treatment effects on the concentration of ammonia or of total or individual short‐chain fatty acids in the rumen fluid. In sheep, bicarbonate addition or infusion had no effect on the digestibility of organic matter but at the high levels of bicarbonate supplementation there was a tendency for the digestibility of nitrogen to be depressed.In two further experiments each with two dry cows determinations were made of the effects on food intake of (a) the insertion of water‐filled bags into the rumen and (b) the removal of digesta from the rumen. Treatment (a) produced consistent and significant (P<0.05) depressions in dry matter intake and treatment (b) increased (P<0.05) dry matter intake in one cow but not in the other.The lack of significant improvement in silage intake through the addition of sodium bicarbonate to the diet indicated that the acidity of the silage was not a major factor limiting appetite. On the other hand, the effects of the insertion of water‐filled bags into the rumen and of the removal of digesta from the rumen on feed intake were consistent with appetite being controlled through a ru

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00814.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe effects of applying nitrogen at different growth stages to S24 and S23 perennial ryegrass grown for seed were investigated in a series of field experiments from 1971 to 1976. These varieties of ryegrass were found to be insensitive to timing of nitrogen application from apex initiation to the stage when ears first emerged. However, if nitrogen application was delayed until about 30% or more of the ears had emerged, yields were lower compared with earlier applications, this effect being significant when nitrogen was delayed until 70–80% ear emergence because of a decrease in both numbers of fertile tillers and number of seeds per unit area. No advantages were found for splitting nitrogen applications between apex initiation and ear emergenc

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00815.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractOven‐ and freeze‐dried samples of the separated green material ofTrichophorum caespitosum, Molinia caerulea, Eriophorum vaginatum, Erio‐phorum angustifolium, Juncus acutiflorusandJ. squarrosuscollected in May, July and September were analysed for dry matter digestibility (DMD) using anin vitroprocedure and for structural carbohydrate content.Results were affected by method of drying, oven‐dried (45°C) samples in general giving lower estimates of quality than freeze‐dried samples. Low DMD values were obtained forJ. squarrosusfor all sampling dates. The remaining species had DMD values above 60 in May; some maintained these levels until July but all had low values by September.A comparison was made betweenin vitroDMD and predicted DMD using the data from the structural carbohydrate analyses and the summative equation of Van Soest (1965a). Two species,J. acutiflorusandJ. squarrosus, showed poor agreement between values obtained by the two methods. The other species showed good agreement between values in May and July but poor agreement in September.The data are discussed in relation to the quality and seasonal patterns of growth of species of hill

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00816.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe effect of defoliation and nitrogen application on the cold tolerance of four varieties of Italian ryegrass was assessed using controlled environment chambers. Both defoliation and nitrogen fertilizer markedly reduced overall cold tolerance and this closely matched changes in winter hardiness induced by similar treatments applied to the same varieties in a field experiment. However, the relative response of individual varieties differed from that found under field conditions. Thus, RvP showed high levels of tolerance to low temperatures in the controlled environments and was also winter‐hardy under field tests; by contrast Bb 1430, although previously shown to be winter hardy in the field, exhibited low tolerance of cold stress in growth chambers. Thus, results obtained in controlled environment tests cannot be entirely equated to winter hardiness in the field.Water‐soluble carbohydrate (WSC) levels were reduced by both defoliation and nitrogen application and there were significant overall differences between varieties. It was not possible, however, to detect any clear relationship between these differences in WSC levels and cold tolerance.The significance of these results in relation to the use of controlled environment chambers for selecting for improved winter hardiness is discus

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00817.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe regrowth of Italian ryegrass was studied at weekly intervals from 2 to 14 weeks after a cut in late April when 140 kg ha‐1N was applied. Reduction in digestibility with delay in date of harvest was due to both an increase in the proportion of cell wall and a reduction in the digestibility of the cell wall, particularly the former from week 2 to about week 5 and particularly the latter after week 5. The reduction in the digestibility of the cell wall was about equally attributable to reduction in digestibility of cellulose and to reduction in digestibility of hemicellulose. The proportion of lignin in cell wall was highly correlated with both digestibility of cellulose and digestibility of hemicellulose. The proportion of digestible cell wall in dry matter was not as constant as has sometimes been noted, increasing by about 5 percentage units from week 2 to week 5 and decreasing by about 10 percentage units from week 5 to week 13. During the latter period the decline in digestible cell wall in dry matter accounted for nearly half the decline in true digestibility of dry matter. The ratio of cellulose:hemicellulose averaged 1:0.89 and hemicellulose was more digestible than cellulose. Rate of increase in yield of cell contents appeared to diminish from about the third week of regrowth onwards, whereas the rate of increase in yield of dry matter did not begin to diminish until about the seventh week.In vitrodry matter digestibility was not increased by adding extra N to the digestion tubes, even with samples containing only 1% N in dry matte

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00818.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractMoisture and mineral concentrations and calorific values of cattle dung pats were studied under field conditions. The rate of moisture loss from dung pats varied according to the season but the dung was rarely re‐wetted by rainfall. Soluble mineral ions were only leached from pats by prolonged rainfall. Magnesium was particularly resistant to leaching. In the summer months about 15% of the organic matter in the dung was lost over 2 months. The calorific value of the dung decreased by 18% in the same period. The loss of organic matter resulted in a concentration effect in calcium, iron, magnesium and nitroge

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00819.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractA reproducible method of causing tiller death on individual ryegrass (Lolium perenneL., cv. S23) plants is described. This was achieved by subjecting whole plants grown previously for 7 weeks in full light (100%) and full nutrient (100%) to either light stress (17.5% or 2.5%) or nutrient stress (10% or 0%) or various combinations of light and nutrient stress. Detailed records were made of tiller appearance, position and weight, and the probability of tiller death was calculated. Analysis of each plant indicated that the smallest tiller, which was often, but not always the youngest, was the most vulnerable when the whole plant was stressed. Tiller position was relatively unimportant in determining survival. The results are discussed in relation to tiller mortality in natural populations and crop communities.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00820.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe causes of tiller death in a 2‐year‐old perennial ryegrass sward were examined between April and August 1977. Physiological causes accounted for most tiller deaths and grazing by slugs and rodents was more important than the damage caused by stem‐boring larvae. Tillers which died were mainly small and vegetative, although some flowering tillers died prematurely. Low nutrient status delayed but did not prevent tiller death.Using14CO2it was shown that small tillers fixed relatively less radiocarbon than did larger tillers and they did not receive much support for their carbon economy. Selective defoliation showed that in April defoliated tillers imported radiocarbon from undefoliated tillers but that in July at anthesis an undefoliated reproductive tiller retained most of the carbon it fixed, despite its vascular association with defoliated tillers. It appears that much of the tiller death during the period April‐August is due to the failure of the more favourably placed tillers to support other tillers which are heavily

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00821.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractFive experiments were conducted to determine the effect of pre‐harvest treatment with steam or formic acid on the moisture concentration (MC) in crops of lucerne, two varieties of perennial ryegrass, tall fescue and Italian ryegrass. In each experiment, plots were treated with a mixture of hot gases and steam (S) or sprayed with an aqueous solution of formic acid (F). In the tall fescue experiment the F treatment was applied to the cut swath but in all other instances the F and S treatments were applied to the swards before cutting and the MC changes after treatment compared with those in untreated cut swaths (W 1). Twenty‐four hours after initial treatment all S plots, and those F plots other than tall fescue, were cut and the subsequent water loss compared with that from (i) untreated material cut at the same time (W 2) and (ii) the W 1 plots cut the previous day.In all five experiments the change in the MC of the S plots was similar to that of the W 1 plots both before and after cutting. The reduction in the MC of the F plots before cutting was less than that of the S and W 1 plots, and in three of the five experiments water loss from cut F plots was apparently restricted in comparison with that from untreated cut material (W2).Neither desiccant treatment showed great promise as a pre‐treatment to cutting for hay making although formic acid may have limited value when a crop is to be harvested directly for silage or artificial dehydration.In an appendix, the efficacy of using accumulated vapour pressure deficit as a basis for comparing the water loss from the untreated cut crops drying under different conditions is demonst

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1978.tb00822.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY