摘要:

AbstractSPOT high‐resolution visible (HRV) multispectral data were used to estimate the biomass of an improved pasture near Clare in South Australia. The study examined the effects of trees, senescent vegetation, surface wetness, herbage composition and management practices including the age of the pasture and stocking rate, on reflectance. This was undertaken by a comparison of spectral responses and through the use of partial correlation analyses. Changes in biomass had the greatest influence on reflectance, though the presence of trees and senescent vegetation influenced reflectance significantly in all wavebands. These areas were excluded from the model developed to estimate pasture biomass. The regression model was inverted and applied to a normalized difference SPOT HRV image. The accuracy of the biomass estimation was 43–81% at the 95% confidence level, or ±57.0 gm−2of dry grass. This technique provides resource managers with a tool for routinely assessing pasture condition over large

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01945.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractForage production based on summer annual crops is a common agricultural practice in many areas of the world where the growing season is favourable.0An investigation was conducted over 3 years to compare the dry matter (DM) yield and quality of four annual crops; maize (Zea maysL.), sunflower (Helianthus annusL.), sudangrass (Sorghum bicolor L.Moensch) and sorghum (Sorghum bicolorL. Moensch) x sudangrass; in two rainfed locations with different summer temperatures in north‐west Spain (Galicia). The crops were compared at three harvest dates; first weeks of August and September and, except for sunflower, at a later silage stage.The comparative forage yields of each crop varied depending on location and harvesting date, reflecting their suitability for the climate of the location.At Mabegondo, with relatively mild summer temperatures (16.5 °C), maize throughout summer and sunflower until September produced higher DM yields than sudangrass and sorghum × sundangrass. At this location the silage DM yields for maize, sorghum × sudangrass and sundangrass were respectively 15.2, 9.92 and 7.79 t ha−1. At Puebla de Brollón, where the average temperature from June to September was about 2 °C higher than at Mabegondo, the DM production of the sudan‐type crops were similar to maize, while sunflower was significantly lower at the September harvest. The silage DM yields were: maize 14.07 t ha−1sorghum x sudangrass, 14.05 t ha−1, sudangrass 12–26 t ha−1.Thein vitrodry matter digestibility (IVDMD) of maize was always higher than that of the other crops, with an average value of 700 g kg−1.It is concluded that, in north‐west Spain, maize is the most suitable summer crop for maximum yield of good quality forage from the first week of August through to the normal s

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01946.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe benefits of reducing competition from the surrounding grass sward against slot‐seeded clover were measured in terms of white clover dry matter production following applications of two grass‐suppressing herbicides, propyzamide and carbetamide.Clover was slot‐seeded in early June 1983 and herbicides were applied in September and October 1983. The later application was more damaging to the surrounding sward. Generally, the September spraying was more effective in encouraging white clover, especially from July of the following year. Only by September 1984 did the October applications result in higher clover yields than the September applications.Propyzamide had the greater stimulatory effect on white clover production but it also damaged the grass more than carbetamide. Increasing the dose of each herbicide increased grass damage. However, with treatments applied in September, the loss was more than compensated for by an increase in clover and in total dry matter production at the end of the year.The results suggest that either of these herbicides, but especially propyzamide, can be used to increase both total dry matter production from the sward and the contribution from slot‐seeded white

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01947.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe use of brine in plastic pipes inserted into the ground is now an established technique for sampling leatherjackets in grassland. Three sequential sampling plans were compared with a standard twelve‐pipe sample for the probability of a recommendation to spray and the number of sample units necessary before a decision over a range of population densities. Data derived from field studies showed a good fit with the expected outcomes. All four plan models were applied to leatherjacket distribution data from Northern Ireland, This shows the number of samples required before a decision was reduced with sequential sampling and that the use of single sequential samples would increase the risk of error. The results are discussed in the context of the physical limitations of the brine sampling procedure and it is concluded that a sequential scheme based upon groups of four pipes would reduce average sampling time by 36% without increasing erro

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01948.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA total of 1009 samples of silage made in bunker silos on commercial farms between 1972 and 1978 was analysed to investigate the effect of herbage water‐soluble carbohydrate content (WSC) and weather conditions at ensilage on fermentation as measured by ammonia‐N concentration and pH of first‐cut grass silages.Silage dry matter (DM) content had the major effect on fermentation. Factors influencing silage DM were rainfall and hours of sunshine during silage making, and DM content of the grass cut. WSC content of herbage ensiled also had a significant effect on subsequent fermentation. The major influences on herbage WSC were hours of sunshine and rainfall during the growing season.The effect of chemical additives, albeit at poorly defined and often inadequate rates, was small in comparison to that of silage DM.The minimum DM necessary to produce well‐fermented silage without additive was approximately 260 g kg−1. Use of formic acid significantly reduced this requirement to 240 g kg−1and to 252 g kg−1for sulphuric add + formalin. The results indicate that the minimum herbage WSC necessary to prevent a clostridial fermentation developing in silage with a DM content of 230 g kg−1is approximately 37 g kg−1without additive and 30 g kg−1with formic acid.It is concluded that on commercial farms, weather conditions i.e. amount of rainfall and sunshine prior to and at ensilage, have a greater effect on subsequent silage fermentatio

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01949.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe numbers of lactic acid bacteria (LAB), as measured by Rogosa SL agar, on lucerne (Medicago sativa) chopped for ensiling were predicted using two methods. The first prediction method consisted of regression equations developed from two previous harvesting seasons and required inputs of wilting time between mowing and chopping, average wilting temperature and moisture content of the lucerne at chopping. The second method simulated the growth of LAB on the lucerne during wilting and needed similar inputs. The former method predicted LAB counts within one order of magnitude more than 95% of the time except for lucerne samples drier than 60% dry matter. The prediction of the simulation model had more variation than those of the regression equations, but the simulation model was applicable over a wider range of conditions. These results, together with earlier studies, provide a preliminary basis for determining when a silage inoculant containing LAB will be most beneficial.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01950.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAn experiment was carried out during 1984 to study the effect of treating grass at ensiling with three commercially available inoculant‐type additives (H/M Inoculant, Grass Sile and Siron), formic acid (850 g kg−1; Add‐F) or no additive on grass preservation, in‐silo loss, intake and animal performance. Primary growth grass ensiled from 28–29 May into concrete‐walled covered silos was of high dry matter (DM, 234 g kg−1), water‐soluble carbohydrate content (WSC. 212 g kg DM−1) and digestibility (MADF, 250 g kg DM−1).The untreated silage displayed good preservation and with the exception of the Sirontreated silage which showed significantly lower buffering capacity (Be) and volatile fatty acid (VFA) contents than the untreated silage, the application of inoculant‐type additives did not improve silage preservation or decrease in‐silo DM losses. The formic acid‐treated silage displayed significantly lower Be, water‐soluble carbohydrate, ash, ammonia nitrogen (g kg total N−1) and lactate contents than the untreated silage.After a 133 d storage period, silages were offered to finishing beef cattle for an 84‐d period. Cattle offered the silages displayed similar and non‐significant daily DM intakes, daily liveweight gains, dressing proportions and daily carcass gains. From this experiment it appears unlikely that any of the additives evaluated will improve animal performance relative to

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01951.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractLittle bluestem (Schizachyrium scoparium (Michaux) Nash), a perennial bunchgrass, is a potentially valuable species for use in restoring ground cover in shallow range sites that are subject to drought. However, there are no data on the nutritive quality of the diverse phenotypes of little bluestem found in the north central USA and south central Canada, and there are no cultivars of little bluestem that are adapted to these areas. The objectives of this study were to measure the nutritive quality of little bluestem clones sampled on different dates and to determine whether clones differed sufficiently to facilitate selection efforts to improve forage quality. Whole plant samples of little bluestem were clipped on 8 August and 8 September 1983 and 5 July and 6 August 1984 from a field nursery at Mandan, North Dakota, containing plants originating from Minnesota and North and South Dakota in the USA. Significant differences between sampling dates were found each year for in vitro digestible organic matter (IVDOM), crude protein, lignin, calcium, phosphorus (P) and potassium (K). In order to minimize the effects of maturity on chemical composition, data were statistically evaluated for clonal differences, using only the August sampling dates. Clones were further separated into north and southeast groups according to stage of maturity and latitude and moisture conditions where the clones originated. Clones were significantly different with respect to IVDOM and P in both the north and southeast groups for the August 1983–1984 data. IVDOM and P among clones averaged over years for the August sampling date ranged from 374to 521 g kg−1and from O‐9to l‐6g kg−1, respectively, for the north group and from 456 to 538 g kg−1and from 1–2 to 2–0 g kg−1, respectively, for the southeast group. The range in IVDOM and P suggests that selection to improve little bluestem quality components, especially later in the season, may be warranted. However, it is important that these results be corroborated under conditions where the effects of maturity are f

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01952.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn two field experiments acetylene (C2H2) reduction by white clover in mixed swards was compared to N2‐fixed measured by15N dilution. In both experiments, samples for C2H2reduction were 7.5 cm diameter turves taken from plots within which microplots of 24 cm diameter were delimited and to which15N was applied as ammonium sulphate (15NH4)2SO4). C2H2reduction was assayed every 6–7 d. The rate of C2H2reduction per unit length of stolon was applied to the estimated stolon length within the appropriate microplot at the time of assay, and the amount of C2H2that would have been reduced within the microplot was estimated by integration.In experiment 1, turves taken from grass/clover swards to which 0, 1·5, 3·0, 4·5 or 6·0 g N m−2had been applied were incubated in sealed chambers (10% C2H2, 90% air). The mean ratio of C2H2 reduced to N2 fixed during 5 weeks was 0.74:1. Application of N fertilizer lowered the proportion of assimilated N derived from N2fixation from 95% in unfertilized swards to 83% in those receiving 6 g N m−2(60 kg N ha−1). In experiment 2, clover roots and stolons from plots that previously had been grazed were dissected from turves and incubated in a stream of C2H2and air (i.e. the open system). The maximum rate of ethylene (C2H4) produced during the first 12 min was taken as a measure of true nitrogenase activity. The relationship between C2H2reduced and N2fixed was significant (r=0.80**). The mole ratio was 0.55:1 for the 6 weeks duration of the experiment, the low ratio possibly being due to disturbance of the nodules adversely affecting acetylene reduction. Mole ratios from both experiments were well short of the theoretical 4·3:1. Using the open system does not, therefore, overcome the shortcomings of the acetylene reduction technique for measuring N2fixation of white clover i

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01953.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb01954.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY