摘要:

AbstractSeedlings ofRumex obtusifoliusL. were grown in gaps (11 cm diameter) in an established sward atLolium perenneL., Root competition from the surrounding sward was controlled by PVC tubes and shoot competition was controlled by cutting the sward frequently. All combinations, with and without root competition and with and without shoot competition, were used.Plants received either 40 or 80 kg N ha−1month−1and 0 or 300 kg K2O ha−1and were harvested 39 d after emergence; a second harvest was made 12 d later, after shading to 20% of full sunlight.The shoot dry weight per plant ofR. obtusifoliuswas much more affected by root competition than by shoot competition, especially at low nitrogen applications. Potassium supply had no effect.More dry matter was allocated to the leaf petioles under shaded conditions and the specific leaf area was greater. This morphological plasticity enabledR. obtusifoliusto grow well under shading and to be affected only slightly by shoot competition fromL. perenne.The results suggest that competition for nitrogen was the main factor limiting the initial grown ofR. obtusifoliusin a ryegrass sward and that the morphological characteristics ofR. obtusifoliusmake it less susceptible to competition for light in the early stages of its develo

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02176.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPopulations of Aberystwyth S23 and S24 ryegrass tillers were individually labelled and harvested at intervals to follow their life histories and productivity in response to the effect of infection with crown rust at two levels of nitrogen fertilization.The number of tillers in a population was reduced as a result of infection with crown rust. Increased rates of tiller death due to the pathogen occurred throughout the population age‐range and were most pronounced in the youngest tillers. Population changes were evident following infection and continued to be apparent in the following spring. The disease caused alterations in sward age structure, leading both to a higher proportion of older tillers in the more rust‐damaged treatments and to a decrease in the weight of the herbage produced. It is concluded that rust infection of a sward may lead to changes in population structure with long‐term yield effects, in addition to the immediate direct yield reductions commonly reported. The significance of these results to the ecological and agronomic balance of grassland is disc

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02177.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractFive experiments were carried out in the years 1980‐1983 and 1986 to study the effect of treating grass at ensiling with sulphuric acid (850 g kg−1) and formic acid (850 g kg−1) additives alone, and in mixtures with or without formalin on the preservation of grass,in vivodigestibility in sheep, in‐silo loss, intake and performance of finishing cattle.Primary growth grass was ensiled in experiments 1 (3–4 June 1980), 2 (12‐15 June 1981) and 3 (31 May‐2 June 1982), primary regrowth grass in experiment 4 (1‐2 August 1983) and secondary regrowth grass in experiment 5 (7‐10 October 1986). During the ensiling period within each experiment, approximately 60 t of unwilted, double‐chopped, additive‐treated or untreated grass was packed into covered concrete‐walled 60‐t capacity silos. The dry matter (DM) contents of the ensiled grass in experiments 1, 2 and 5 ranged from 155‐180 g kg−1and were lower than those recorded in experiments 3 and 4 (214 g kg−1). With the exception of grass ensiled in experiment 2, where water‐soluble carbohydrate (WSC) contents were low, at 104 g kg−1DM, grass in all other experiments contained relatively high WSC contents ranging from 140‐154 g kg−1DM.In experiments 1, 3 and 4 all silages were well‐preserved. However, in experiment 2 the 450 g kg−1sulphuric acid‐treated and formic acid‐treated silages displayed significantly lower pH, buffering capacity (Bc) and ammonia nitrogen contents than the untreated silage. In experiment 5, the sulphuric acid‐treated and formic acid‐treated silages displayed significantly lower pH, Bc, ammonia nitrogen, butyrate and volatile fatty acid (VFA) contents than the untreated silage.Each of the silages was offered daily with various levels of a supplementary concentrate for approximately 70‐d periods to twelve animals of mixed breed in experiments 1, 3, 4 and 5 and to fifteen animals in experiment 2. All animals weighed between 380‐470 kg at the start of the experiments.In experiments 1, 2 and 3 there were no significant differences between silages for any of the intake or animal performance parameters. In experiment 4, cattle fed the formic acid‐treated silage displayed significantly higher silage DM intakes and daily liveweight gains than those fed the sulphuric acid‐treated and untreated silages; in experiment 5, cattle fed the formic acid‐treated silage displayed significantly higher silage DM intakes than those fed the untreated silage. It was concluded that formic acid was a more effective silage additive than sulphuric acid.Increasing the level of supplementation significantly decreased silage DM intakes in cattle in experiments 3 and 4, and significantly increased daily liveweigh

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02178.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA total of eighty‐nine big‐bale (BB) silages made on commercial farms in South Wales during the autumn in 1983‐87 were analysed to discern the effect of dry matter (DM) content on fermentation. Silages were made predominantly in late September, during fine weather from permanent pasture or perennial ryegrass pastures, which had not been grazed for 9 weeks. On average 7·8 ha of pasture were cut; most farmers attempted to pre‐wilt grass for an average of 36 h prior to ensilage in individual plastic bags. Silage making was usually completed within 4 d of starting to cut. Silage ammonia‐N content was inversely correlated with DM content. The results indicated that a DM content of about 280 g kg−1was needed to produce well‐preserved silage with an ammonia‐N content of 100 g (kg total N)−1. Silages were, therefore, generally poorly preserved because the DM increase from wilting was

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02179.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA trial was carried out over two harvest years to assess the effect of sheep grazing and closing date on stolon density and seed yield components of two contrasting white clover varieties and to determine the potential for producing clover seed from mixed swards in an integrated livestock/seed production system.Overall, the small‐leaved cv. S184 had a higher stolon density at closing and harvest than the large‐leaved cv. Olwen, but only significantly so in 1987. Stolon density at closing was generally increased by delaying closing. Varieties also differed in their response to closing date. Stolon density of cv. S184 in both harvest years, generally increased with later closing whilst cv. Olwen was less influenced by closing date and at all dates in 1987, and all but one date in 1986 was not significantly different from the ungrazed treatment.Delay of closing significantly increased stolon density at harvest on all closing dates in 1987 but had no effect in 1986. Varieties responded similarly to a delay in closing but the magnitude of increase of cv. Olwen was less than that of cv. S184.The seed yield components of both cv. S184 and cv. Olwen were influenced by closing date, but the effect differed between years. Although there was some initial increase in inflorescence production, delaying closing after inflorescence buds appeared on the stolon reduced inflorescence number of cv. Olwen in both years but reduced inflorescence number in cv. S184 in 1986 only. However, inflorescence size, seed yield per inflorescence and the proportion of ripe inflorescences at harvest was reduced in both years. Cultivar S184 produced more inflorescences than cv. Olwen in both years and in both years tolerated later closing than cv. Olwen.The effect of sheep grazing and closing date is discussed in relation to stolon removal and the suitability of particular leaf types for this system of seed product

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02180.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe productivity of permanent swards of mixed species composition was compared with that of sownLolium perenne, cv. Melle at five fertilizer‐N rates (0, 150, 300, 450 and 900 kg N ha−1) and withL. perenne/Trifolium repens, cv. Grasslands Huia at 0 kg N ha−1. The investigation was conducted under two cutting frequencies at sixteen sites in England and Wales, representing a range of grassland environments.Annual total herbage dry matter (DM) production from both permanent and reseeded swards increased with successive increments of fertilizer‐N up to 450 kg N ha−1. Herbage DM production from reseeded swards in the first year after sowing was signficantly higher than from the permanent swards, at all fertilizer‐N treatments. In subsequent years the production advantage of theL. perennereseeds was maintained only at the higher N rates, though sownL. perenne/T. repenswas the most productive sward type at 0 N. Average differences in modified acid‐detergent fibre suggested small advantages in herbage quality to the reseeded swards.It is concluded that, while reseeded swards are more productive in the year after sowing, many permanent swards are capable of high levels of production and that reseeding to aL. perennesward cannot always be justified, particularly for grassland receiving low or moderate inputs of

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02181.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractRed fescue (Festuca rubraL.) cvs Reptans, Dawson and Ruby, perennial ryegrass (Lolium perenneL.) cvs Perma and Sprinter, crested dogstail (Cynosurus cristatusL.) cv. Southlands, smooth meadow‐grass (Poa pratensisL.) cvs Parade and Arena, Yorkshire fog (Holcus lanatusL.) commercial types I and II, creeping bent (Agrostis stoloniferaL.) cv. Penncross and rough meadow‐grass (Poa trivialisL.) cvs Omega Øtofte, Dasas and Sabre were each sown with white clover (Trifolium repensL.) cv. Donna and the productivity of the fourteen mixtures assessed under simulated grazing (six harvests per year) for 3 years. A single fertilizer‐N rate (50 kg ha−1) in early spring was applied to all treatments each year.Over the 3 years, mean annual dry matter (DM) production of the swards ranged from 5·25 t ha−1(creeping bent) to 8·71 t ha−1(red fescue cv. Reptans), with the species ranking order of: red fescue>perennial ryegrass>crested dogstail>smooth meadow‐grass>Yorkshire fog>creeping bent. Rough meadow‐grass only persisted over the first harvest year. Mean annual organic matter digestibility (OMD) values of the swards ranged from 0·712 (creeping bent) to 0·782 (ryegrass cv. Sprinter). Mixtures with the lowest proportion of grass (crested dogstail and smooth meadow‐grass) generally gave the highest proportions of white clover. The creeping bent mixture had exceptionally low production of both components.Red fescue, crested dogstail and smooth meadow‐grass showed compatibility with clover and, therefore, have potential for use in grass/clover swards. Yorkshire fog had lower compatability with clover. Some breeding effort to improve selected characteristics of promising species, e.g. improvement of low OMD in red

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02182.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractRates of N accumulation were studied on sheep grazed grass swards maintained at a constant height of 5 cm for two growing seasons (1985 and 1986) and receiving no N fertilizer using a tiller tissue turnover technique. Grazing with normal excretal returns resulted in an 85‐105% increase in the estimated rates of N accumulation by laminae compared with similarly grazed swards where excretal returns were prevented. Generally, increases in tiller numbers in plots receiving excreta were mainly responsible for the increased rates of N accumulation, rather than increased rates of N accumulation per tiller. Rates of N remobilization from laminae and senescence (flux of N to standing‐dead litter pool) per tiller, and rates of leaf extension and leaf appearance/disappearance were unaffected by excretal returns, in urine patches increased tiller numbers and increased rates of accumulation per tiller both resulted in greater estimates of N accumulation compared with tillers not visibly affected by excreta. However, at any one time only about 11% of the plot area was affected by excreta and increases in N accumulation in excreta patches could not account for the overall plot increases in rates of N accumulation.The increased tillering in plots receiving excreta may have increased exploitation of the soil N. With an average stocking rate of 15 sheep ha−1, soil nitrate‐N, but not total N (Kjeldahl) nor bulk density, was increased during the winter of the second year as a result of excretal

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02183.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAn experiment was carried out during 1986 and 1987 to examine the effects of mid‐season slurry injection and fertilizer‐nitrogen (N) application on herbage dry matter (DM) yield and N recovery. Cattle and pig slurry were injected at 56 and 112 m3ha−1into an established sward. Five rates of fertilizer‐N, as calcium ammonium nitrate, ranging from 0 to 120 kg ha−1in 30‐kg increments, were superimposed on these treatments, and in both years DM yield was measured in one cut after 70 d regrowth. Slurry treatments increased herbage DM yields significantly (P<0‐001). The efficiency of slurry total N compared with calcium ammonium nitrate‐N averaged 53% in 1986 and 86% in 1987. The mean apparent recovery of slurry total N in herbage was 55% in 1986 and 40% in 1987. Fertilizer‐N application increased (P<0.001) the mean yields of herbage in both years but when combined with some of the slurry treatments, DM yields over the five N‐levels did not differ significantly, giving rise to interactions in 1986 (P<0‐001) and 1987 (P<001). It is concluded that mid‐season injection of slurry can be an effective means of utilizing slurry‐N in terms of herbage DM produc

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02184.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe drying rates of grasses and lucerne, following treatment with 1% formic acid, were compared with those of untreated crops. Material was fully exposed to a flow of air in a ventilated laboratory oven set at 23 °C. Treatment with formic acid initially enhanced the rate of drying of grass, but this was followed by retardation. This reduction in the rate of drying was caused by the rapid desiccation of laminae, which reduced their effectiveness in providing a pathway for water loss from the stem. The rate of water loss directly from the stem surface was not increased by formic acid treatment, probably because the enveloping leaf sheaths acted as a protective layer. In contrast, formic acid increased drying rate in lucerne. whose stems have no such protective layer. The results suggest that chemical desiccants. which have a contact action are unlikely to have any application in making hay from grass

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02185.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY