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1.
Utilized Metabolizable Energy output was calculated and herbage utilization evaluated in two contrasting years on five profitable farms representing a range of soil types.
Annual UME output was 72 GJ ha-1 on average, with a range from 47 to 91 GJ ha-1 . Grazed grass provided 66% of the utilized metabolizable energy, and conserved grass 34%. Higher utilized metabolizable energy output was not always obtained at higher fertilizer N inputs, even when soil moisture conditions favoured herbage growth.
The efficiency of utilization of herbage conserved (almost always as silage rather than hay) was calculated by expressing utilized metabolizable energy output as a proportion of the quantity of herbage cut, measured by swath weighings; the mean value was 64%, with a range from 55 to 73%. Cellulose analyses indicated that mean dry matter losses via CO2 and effluent were 10%; the remaining 26% loss appeared to be due to physical losses in the field, surface waste and wastage at feedout.
For grazed herbage the utilized metabolizable energy output was expressed as a proportion of herbage accumulation measured over 28-day periods. The resultant apparent efficiency of utilization averaged 67%, with a wide range from 51 to 83%. The lowest values were on badly drained farms.
It is suggested that:
(i) there is considerable potential for increasing output from grazing on dairy farms; higher grazing pressure and more flexible management would be needed. Targets should probably be set lower on badly drained soils;
(ii) there is great potential for increasing the efficiency of utilization of conserved forage, by careful application of existing technology;
(iii) on the farms studied the utilized metabolizable energy output from grazed and conserved fields appeared to be similar. 相似文献
Annual UME output was 72 GJ ha
The efficiency of utilization of herbage conserved (almost always as silage rather than hay) was calculated by expressing utilized metabolizable energy output as a proportion of the quantity of herbage cut, measured by swath weighings; the mean value was 64%, with a range from 55 to 73%. Cellulose analyses indicated that mean dry matter losses via CO
For grazed herbage the utilized metabolizable energy output was expressed as a proportion of herbage accumulation measured over 28-day periods. The resultant apparent efficiency of utilization averaged 67%, with a wide range from 51 to 83%. The lowest values were on badly drained farms.
It is suggested that:
(i) there is considerable potential for increasing output from grazing on dairy farms; higher grazing pressure and more flexible management would be needed. Targets should probably be set lower on badly drained soils;
(ii) there is great potential for increasing the efficiency of utilization of conserved forage, by careful application of existing technology;
(iii) on the farms studied the utilized metabolizable energy output from grazed and conserved fields appeared to be similar. 相似文献
2.
Yields of grass were measured on three dairy farms in 1981. Farm 1, on free-draining loamy soil over chalk, produced 10.3 t DM ha−1 using 336 kg N ha−1 . Farm 2, on poorly-drained loam over Oxford clay, produced 12.8 t DM ha−1 using 354 kg N ha−1 . Farm 3, on loam over clay with some free-draining sandy loam, produced 9.5 t DM ha−1 with 169 kg N ha−1 . Allowing for differences in soil nitrogen and summer rainfall these yields were quite close to expectations from experimental results, despite considerable poaching damage to some swards.
Animal production records were kept and all livestock were weighed every 6 months, so as to calculate the utilized metabolizable energy (UME) output from grassland on each farm. These were 73, 62 and 59 GJ ha−1 on farms 1, 2 and 3 respectively.
The UME output, expressed as a proportion of the yield of grass (converted to ME), was taken as the 'efficiency of utilization' of grass. This was 70% on farm 1,44% on farm 2 and 58% on farm 3. Results are presented separately for the summer and winter 6 months. Utilization by grazing appeared to be markedly reduced under very wet soil conditions. Major losses occurred in the conservation of grass.
The results begin to establish a valuable base of data from commercial farms. 相似文献
Animal production records were kept and all livestock were weighed every 6 months, so as to calculate the utilized metabolizable energy (UME) output from grassland on each farm. These were 73, 62 and 59 GJ ha
The UME output, expressed as a proportion of the yield of grass (converted to ME), was taken as the 'efficiency of utilization' of grass. This was 70% on farm 1,44% on farm 2 and 58% on farm 3. Results are presented separately for the summer and winter 6 months. Utilization by grazing appeared to be markedly reduced under very wet soil conditions. Major losses occurred in the conservation of grass.
The results begin to establish a valuable base of data from commercial farms. 相似文献
3.
Records of grassland productivity have been used for 93 farms in 1975–76 (a dry year) and 117 farms in 1977–78 (a wetter year). The samples were selected to contrast well-drained and poorly/ badly drained farms and were further subdivided into dairy and beef. The number of farms in each of the four subsamples for each year was between 19 and 32. In addition the number of days on which the soil was at meteorological field capacity (field capacity days) on each farm was calculated.
The mean utilized metabolizable energy (UME) output within the dairy sample was 45 GJ ha−1 on both well-drained and poorly/badly drained farms. Within the beef sample the output was 41 GJ ha−1 on well-drained farms and 37 GJ ha−1 on the poorly/badly drained farms.
The correlation between fertilizer N and UME output was stronger on well-drained farms than on the poorly/badly drained farms in the wetter year (r = 0.69 v. 0.16 on dairy farms; r = 0.56 v. − 0.12 on beef farms). In the drier year the converse was found (r=0.15 v . 0.49 on dairy farms; 0.13 v. 0.44 on beef farms). The effect of field capacity days on output was inconsistent; only within the dairy sample in the wetter year did increased wetness appear to reduce output.
It is suggested that soil wetness may have only a small effect on utilized output from grassland on a whole-farm basis because (i) most farms have at least some well-drained land, (ii) much of the utilization damage occurs in relatively short periods in spring and autumn and (iii) despite having utilization problems, badly drained land is capable of growing large quantities of grass. 相似文献
The mean utilized metabolizable energy (UME) output within the dairy sample was 45 GJ ha
The correlation between fertilizer N and UME output was stronger on well-drained farms than on the poorly/badly drained farms in the wetter year (r = 0.69 v. 0.16 on dairy farms; r = 0.56 v. − 0.12 on beef farms). In the drier year the converse was found (r=0.15 v . 0.49 on dairy farms; 0.13 v. 0.44 on beef farms). The effect of field capacity days on output was inconsistent; only within the dairy sample in the wetter year did increased wetness appear to reduce output.
It is suggested that soil wetness may have only a small effect on utilized output from grassland on a whole-farm basis because (i) most farms have at least some well-drained land, (ii) much of the utilization damage occurs in relatively short periods in spring and autumn and (iii) despite having utilization problems, badly drained land is capable of growing large quantities of grass. 相似文献
4.
J. H. McADAM 《Grass and Forage Science》1984,39(2):129-138
Forty hill farms in Northern Ireland were surveyed to obtain information on stocking rates and output and to identify factors affecting output. The mean farm area of 194 ha was composed of 155 ha hill land and 39 ha inbye land with a mean stocking rate of 0–7 cow-equivalents ha−1 .
On the average farm most of the grassland (88%) was over 20 years old. The preferred species content of the swards averaged 22% over the whole farm and 42% in cut swards. This latter result may be attributed to the relatively high level of fertilizer N applied to these swards (131 kg ha−1 ) compared to the mean application rate over the whole farm of only 29 kg N ha−1 and 93 kg ha−1 applied to the inbye land.
Output data calculated as utilized metabolizable energy (UME) per unit area for the whole farm and separately for hill and inbye components showed that although only 21% of the farm area was inbye land almost half the annual total metabolizable energy requirements of stock had to be met by grazing inbye. The capacity of herbage to meet stock energy demands was much lower on the hill with supplementary feed having to be provided over the winter.
Calculated output from inbye land was 39 GJ ha−1 compared to 7 GJ ha−1 from the hill and 15 GJ ha−1 from the whole farm. UME output of the whole farm was negatively correlated with farm size (r=−0 55) and positively correlated with stocking rate (r = 0 89), applied N level (r = 0 63) 相似文献
On the average farm most of the grassland (88%) was over 20 years old. The preferred species content of the swards averaged 22% over the whole farm and 42% in cut swards. This latter result may be attributed to the relatively high level of fertilizer N applied to these swards (131 kg ha
Output data calculated as utilized metabolizable energy (UME) per unit area for the whole farm and separately for hill and inbye components showed that although only 21% of the farm area was inbye land almost half the annual total metabolizable energy requirements of stock had to be met by grazing inbye. The capacity of herbage to meet stock energy demands was much lower on the hill with supplementary feed having to be provided over the winter.
Calculated output from inbye land was 39 GJ ha
5.
Records of grassland productivity were kept for 2 years on 152 dairy and 179 beef farms. Results were collated for six lowland zones, delineated primarily on the basis of average rainfall, and an upland zone. Contemporary and long-term average meteorological records were also collected.
In most of the lowland zones stocking rates and use of fertilizer N were similar, but utilized metabolizable energy (UME) output from grass varied; it was 25% higher in the wet, cool zone of north-west England and east Wales than in the dry zone of eastern England. The ranking of zones for utilized output corresponded closely with the ranking for summer rainfall.
On upland farms stocking rate was 25% lower and UME output 15% lower than on lowland farms, but this was achieved from little more than half the N input.
The differences between zones were similar to those shown in other published farm data. They also showed a similar trend to that demonstrated in grass cutting experiments. This suggests that farmers were, on average, able to exploit the extra grass grown in wetter climates. The incidence of difficult topography and impeded drainage was similar in dry and wet zones, but did have a more serious effect in the wet zones. The much higher level of concentrate feeding in the driest zone may have reduced the utilization of grass. 相似文献
In most of the lowland zones stocking rates and use of fertilizer N were similar, but utilized metabolizable energy (UME) output from grass varied; it was 25% higher in the wet, cool zone of north-west England and east Wales than in the dry zone of eastern England. The ranking of zones for utilized output corresponded closely with the ranking for summer rainfall.
On upland farms stocking rate was 25% lower and UME output 15% lower than on lowland farms, but this was achieved from little more than half the N input.
The differences between zones were similar to those shown in other published farm data. They also showed a similar trend to that demonstrated in grass cutting experiments. This suggests that farmers were, on average, able to exploit the extra grass grown in wetter climates. The incidence of difficult topography and impeded drainage was similar in dry and wet zones, but did have a more serious effect in the wet zones. The much higher level of concentrate feeding in the driest zone may have reduced the utilization of grass. 相似文献
6.
Use of a systems synthesis approach to model nitrogen losses from dairy farms in south-west England 总被引:2,自引:0,他引:2
Nitrogen (N) budgets were determined for six typical, moderately intensive dairy farms in south‐west England. Proportionately, only 0·12–0·17 of the N input to the farms was recovered in agricultural products, leaving annual N surpluses equivalent to 249–376 kg N ha?1. A sequence of models (MANNER, NCYCLE and SUNDIAL) was used, together with the estimated N balance of the dairy cows and standard ammonia emission factors, to estimate N losses for each farm. Total estimated losses were equivalent to 137–220 kg N ha?1 year?1. Leaching accounted for 0·26–0·45 of the total loss, ammonia volatilization for 0·27–0·39 and denitrification for 0·17–0·36. When residual N from manure applications was included, there appeared to be an annual accumulation of soil N, equivalent to 66–158 kg N ha?1 when averaged over the whole farm area. The amounts of N lost by leaching, volatilization and denitrification, and accumulated as soil‐N, were determined by a combination of farm properties, including N input, soil type, drainage, characteristics of the manure produced and type of fertilizer. The sum of estimated losses and change in N retained on the farm was between 0·85 and 1·11 of the N surplus (input minus output) determined from the farm budget. This suggests that losses and the change in soil‐N were underestimated on some farms and overestimated on others (by up to ?50 and +23 kg N ha?1 respectively). Much of the discrepancy between estimates and the surplus was attributed to difficulties of fully integrating inputs and outputs between the different models and stages of the modelling procedure. 相似文献
7.
Seventy-eight farms in south-west England, originally visited in 1970–72, were revisited in 1983 in order to identify changes in land use and re-seeding over the c. 12-year period; changes in sward composition were assessed on fifty-nine of these farms. The results were also compared with Ministry of Agriculture, Fisheries and Food (MAFF) Census results and MAFF Seeds Branch data.
The proportion of tillage had declined from 29 to 24%. This was in agreement with census results for the south-western counties, but contrasted with those for England and Wales as a whole, which showed an increase from 38.8 to 41.7% tillage. It is indicative of grass becoming more predominant in south-west England as east England has become more dominated by tillage cropping.
There had also been a decline in the amount of short-term grassland. In 1970–72 17% of the grassland was intended to last from 1 to 4 years; in 1983 the proportion was only 10%. That these intentions were being carried out was confirmed by the fact that in 1983 there was more grassland in each of the age categories 5·8,9·20 and over 20 years. The trend towards older grassland confirms that shown by regional and national census data, and the trend away from short-term swards is in line with deliveries of herbage seed which indicate reduced use of Italian ryegrass (Lolium multiflorum).
Botanical composition had changed appreciably, with the proportion of Lolium perenne having increased in swards of all ages, e.g. from 35 to 51% in swards 5–8 years old and from 17 to 31% in those aged over 20 years. Other sown species, predominantly Dactylis glomerata and Phleum pratense , had declined markedly in swards over 4 years old. The proportions of Agrostis spp., Festuca spp. and Poa trivialis had fallen, but Holcus lanatus had increased slightly. There had been a marked reduction in infestations of perennial broad-leaved weeds, particularly Ranunculus , but also Rumex and Cirsium spp. 相似文献
The proportion of tillage had declined from 29 to 24%. This was in agreement with census results for the south-western counties, but contrasted with those for England and Wales as a whole, which showed an increase from 38.8 to 41.7% tillage. It is indicative of grass becoming more predominant in south-west England as east England has become more dominated by tillage cropping.
There had also been a decline in the amount of short-term grassland. In 1970–72 17% of the grassland was intended to last from 1 to 4 years; in 1983 the proportion was only 10%. That these intentions were being carried out was confirmed by the fact that in 1983 there was more grassland in each of the age categories 5·8,9·20 and over 20 years. The trend towards older grassland confirms that shown by regional and national census data, and the trend away from short-term swards is in line with deliveries of herbage seed which indicate reduced use of Italian ryegrass (Lolium multiflorum).
Botanical composition had changed appreciably, with the proportion of Lolium perenne having increased in swards of all ages, e.g. from 35 to 51% in swards 5–8 years old and from 17 to 31% in those aged over 20 years. Other sown species, predominantly Dactylis glomerata and Phleum pratense , had declined markedly in swards over 4 years old. The proportions of Agrostis spp., Festuca spp. and Poa trivialis had fallen, but Holcus lanatus had increased slightly. There had been a marked reduction in infestations of perennial broad-leaved weeds, particularly Ranunculus , but also Rumex and Cirsium spp. 相似文献
8.
A mathematical model of grass production and utilization on a dairy farm is described. Using the model an assessment has been made of the extent to which financial uncertainty arising from year-to-year variability in grass yields, coupled with a preference among farmers for minimizing risks, may explain the relatively low stocking rates and observed nitrogen usages on many dairy farms in England and Wales. The degree of risk has been equated with the probability of profits in a particular year being less than those required to cover the consumption needs and short-term borrowing requirements of the farmer. The results of the analysis indicate that a strategy of minimizing risks may lead to a significantly lower stocking rate than one of maximizing profits. Thus, considerations of risk may lead to stocking rates which are suboptimal from the viewpoint of economic and biological efficiency. However, there is no evidence to suggest that the comparatively low average usage of nitrogen on dairy farms in the UK is determined by risk considerations. On the contrary, increasing nitrogen usage lowers the apparent financial risk at a given stocking rate. 相似文献
9.
A mathematical model of the production, harvesting and utilization of maize and grass silage on a dairy farm with an autumn-calving herd is described. Using the model the comparative costs and benefits of growing and feeding maize in place of grass silage are examined for three sites in southern England. It is concluded that a winter milk production system based on maize rather than grass should improve profits by at least £30, and possibly by as much as £80 cow-1 . This financial improvement is attributable to higher feed intakes and lower harvesting and fertilizer costs with maize silage. Simulating the results over a 10-year period also revealed that the switch from grass to maize should lower the risks in terms of the annual variability of silage yields and herd profits. Furthermore, it would appear unnecessary to completely turn over from grass to maize production to realize a significant financial benefit. Setting aside just 25% of the conservation area to maize and feeding a mixture of maize and grass silage is projected to increase profits from winter milk production by £30 to £45 cow-1 . 相似文献
10.
P. Creighton E. Kennedy L. Shalloo T. M. Boland M. O’ Donovan 《Grass and Forage Science》2011,66(2):251-264
The objective of this study was to identify and understand grassland management practices employed on dairy farms in the Republic of Ireland, including grazing‐season length, concentrate‐feed input, uptake of new grassland‐management technologies and frequency and methods of sward renewal. The sample population for the survey was chosen from a proportionate representation of all milk suppliers taken from three of the largest dairy processors in the Republic of Ireland. The sample was subsequently broken down into three stocking rate (SR) and three size categories of milk quota (Qcat) to investigate their effects on the survey variables. Both SR and Qcat had significant effects on the proportion of participants adopting grass‐based technologies and on the amount of supplementary feed offered. Grazing‐season length increased from 228 d in Qcat1 to 249 d in Qcat 3 but was unaffected by SR (241 d; s.d. 3·05). The proportion of the grazing area reseeded annually was significantly affected by SR, increasing from 0·044 to 0·095 of the grassland area as SR increased from SR1 to SR3, with no effect of Qcat (0·068). The results show that on‐farm grass utilization is low, with significant potential for expansion and increased efficiency through increased SRs, greater adoption of grassland‐management technologies and higher levels of sward renewal. 相似文献
11.
Soil samples taken from one- to four-year-old swards of white clover and perennial ryegrass at 34 sites, and from older clover/grass swards at 56 sites in England and Wales, were examined for plant parasitic nematodes. Stolons of white clover from 46 of these sites were examined for nematodes. Clover cyst nematode ( Heterodera trifolii ) and white clover stem nematode ( Ditylenchus dipsaci ) were found in 62% and 41% of sites respectively. The grass cyst nematode ( Punctodera punctata ) was present in 56% of 71 sites examined, and other grass cyst nematodes ( H. bifenestra and species of the H. avenae group) occurred in 13% and 17% of sites. Two root-knot nematodes were found, Meloidogyne naasi and M. hapla, in 15% and 4% of the samples examined. Migratory nematodes were extracted from 63 samples, and spiral, pin and lesion nematodes were found in more than 90%. Stunt nematodes were less frequent (65%) and criconematids (19%) were found relatively infrequently. The significance of these observations to grassland productivity is discussed. 相似文献
12.
A. HOPKINS 《Grass and Forage Science》1986,41(3):237-246
Grassland in England and Wales accounts for nearly 60% of the enclosed agricultural land and approximately 50% is at least 20 years old. Botanical composition, especially amongst older grassland, is extremely variable.
A survey of 502 grassland farms was conducted in the 1970s. Factors affecting botanical composition of individual fields have been investigated using correlation and regression analyses and swards of similar botanical composition grouped using cluster analysis. Lolium perenne, Agrostis spp. and Holcus lanatus were numerically the most important species, contributing, on average, 35%. 21% and 10%, respectively. Most older swards contained Lolium perenne and Agrostis spp. in varying proportions depending on drainage, soil fertility and management. Swards containing a significant proportion of Trifolium repens were associated with adequate drainage, good soil nutrient status, low inputs of fertilizer nitrogen and hard grazing. Of the other common species Holcus lanatus was associated with poor drainage, low soil fertility, hay cutting, short-season grazing and low fertilizer N. Festuca rubra was mainly in older swards, at higher elevations and with low fertilizer N but heavy stocking. Swards containing Rumex spp., Poa trivialis and other sown grasses were associated with mowing together with reasonably high soil fertility. 相似文献
A survey of 502 grassland farms was conducted in the 1970s. Factors affecting botanical composition of individual fields have been investigated using correlation and regression analyses and swards of similar botanical composition grouped using cluster analysis. Lolium perenne, Agrostis spp. and Holcus lanatus were numerically the most important species, contributing, on average, 35%. 21% and 10%, respectively. Most older swards contained Lolium perenne and Agrostis spp. in varying proportions depending on drainage, soil fertility and management. Swards containing a significant proportion of Trifolium repens were associated with adequate drainage, good soil nutrient status, low inputs of fertilizer nitrogen and hard grazing. Of the other common species Holcus lanatus was associated with poor drainage, low soil fertility, hay cutting, short-season grazing and low fertilizer N. Festuca rubra was mainly in older swards, at higher elevations and with low fertilizer N but heavy stocking. Swards containing Rumex spp., Poa trivialis and other sown grasses were associated with mowing together with reasonably high soil fertility. 相似文献
13.
J. R. B. Tallowin R. E. N. Smith J. Goodyear† J. A. Vickery‡ 《Grass and Forage Science》2005,60(3):225-236
The contention that agricultural grassland within the UK is spatially and structurally uniform across wide differences in livestock farming intensity is examined. Total nitrogen (N) input was used as a surrogate for management intensity. Farms with average annual N inputs of >200 kg ha?1 were categorized as highly intensive, those with N inputs of 50–200 kg N ha?1 as moderately intensive and those with inputs of <50 kg N ha?1 were categorized as extensive. Four farms within each management category were selected in two discrete regions: one in south‐west England, typifying a landscape dominated by agricultural grassland, the other in south‐east England with a more mixed‐farming landscape. Specific N input and management data, and sward botanical composition and structure, were obtained on four fields per farm. The south‐west region had a higher proportion of farms with dairy cattle than in the south‐east England region. The average N input and stocking rates were higher within the intensive‐management category farms in south‐west England than in south‐east England. Old permanent grasslands contained variable amounts of sown species, such as Lolium perenne, and were dominated by a few (generally <5) non‐sown grass species. Grassland that received >75 kg N ha ?1 year?1 contained <7 plant species and <3 forb species m?2. Grassland communities with >12 plant species and >5 forb species m?2 were only found in study fields that received <50 kg N ha?1 year?1. Grasslands with >10 forb species m?2 were found only in sites receiving <15 kg N ha?1. Of importance at a landscape scale was ubiquity of species‐poor and similar grassland plant communities across the management intensity range within and between livestock farms. Grassland in the extensive management category was similar in structure in terms of sward height and/or sward density to more intensively managed grasslands. This study revealed, albeit in two lowland sample regions in the UK, the ubiquity of grass‐dominated, species‐poor and structurally uniform grasslands, irrespective of apparently broad differences in farming intensity. The consequences of this spatial uniformity on grassland biodiversity are likely to be profound. 相似文献
14.
Harvesting techniques, which involve simultaneously preserving and upgrading mature crops of whole cereals using an alkali, have been developed. When treated crops have been fed to sheep and cattle, satisfactory intakes and growth rates have been observed. With the possibility of falling cereal prices, such an end-use for grain crops may be attractive in the future. Accordingly, a mathematical model of the production, harvesting and utilization of whole-crop wheat and grass silage has been developed to examine the economic implications. Using the model, the comparative costs of growing and feeding alkali-treated whole-crop wheat in place of grass silage for winter milk production have been examined.
A milk production system based on whole-crop wheat rather than grass silage is estimated to improve profits by up to £130 per cow. However, the improvement in profitability is very sensitive to assumptions about the uses for surplus land or silage arising from such a switch. Furthermore, for physiological reasons it may be prudent to restrict the quantity of whole-crop wheat fed to about 50% of the total forage intake. Thus, whole-crop cereals may best be seen as a complement to rather than a substitute for grass silage. However, in the absence of data on feeding dairy cows with treated wheat silage, research is required before the computer simulations can be corroborated. 相似文献
A milk production system based on whole-crop wheat rather than grass silage is estimated to improve profits by up to £130 per cow. However, the improvement in profitability is very sensitive to assumptions about the uses for surplus land or silage arising from such a switch. Furthermore, for physiological reasons it may be prudent to restrict the quantity of whole-crop wheat fed to about 50% of the total forage intake. Thus, whole-crop cereals may best be seen as a complement to rather than a substitute for grass silage. However, in the absence of data on feeding dairy cows with treated wheat silage, research is required before the computer simulations can be corroborated. 相似文献
15.
Twenty-four British Friesian cows were allocated between six grazing treatments (two levels of herbage mass x three levels of daily herbage allowance) in a balanced change-over design with four periods of 12 d each at monthly intervals. Herbage OM mass ranged from 3790 to 5770 kg ha-1 measured to ground level and daily herbage DM allowances were 30, 60 and 90 g per kg animal live weight. Herbage OM intake was lower at high than at low herbage mass (24·6 vs 26·3 g per kg LW), and was 26·9, 26·6 and 22·9 g per kg LW respectively at daily herbage DM allowances of 90, 60 and 30 g per kg LW. Milk yield was not affected by herbage mass but was depressed at the low herbage allowance. 相似文献
16.
A. HOPKINS JOANNE WAINWRIGHT P. J. MURRAY P. J. BOWLING MORAG WEBB 《Grass and Forage Science》1988,43(2):185-198
A sample of 10000 ha of grassland in seven upland districts originally surveyed in 1970–72 was re-surveyed in 1986. Forty percent of the area was above 240 m elevation, 38% had gradients above 81/2°, 29% had poor or bad drainage and 54% was classified as having difficult or severe limitations to management. Twelve percent had been reseeded within the previous 5 years and 39% within 20 years; 6% was classified as arable grassland (in rotation with crops). Thirty-four percent was usually mown, two-thirds of it for silage. In most years 72% of grassland received fertilizer N (average application 123 kg N ha−1 ) and 35% received organic manure; nearly 20% received neither. Older swards tended to receive lower rates of fertilizer N than reseeds, hay fields and grazed fields less than silage fields, and fields on beef/sheep farms less than those on dairy farms. The proportion of sown species in swards averaged 35%, of which Lolium perenne accounted for 23%. A good contribution of Trifolium repens was recorded in 15% of the grassland. Herb species were recorded in 30% of the grassland, mostly in situations with low fertilizer N under hay or grazing. Agrostis spp., Poa spp., Holcus lanatus and Festuca rubra were the main unsown grasses. The average contribution of L. perenne had increased since 1970–72; it was also present in two-thirds of the area from which it was absent in 1970–72, whilst the contribution of T. repens had decreased. The incidence of Cirsium arvense and Ranunculus spp. had also decreased, whilst that of Pteridium aquilinum had increased. 相似文献
17.
18.
R. S. SMITH† H. BUCKINGHAM†‡ M. J. BULLARD†§ R. S. SHIEL† A. YOUNGER¶ 《Grass and Forage Science》1996,51(3):278-291
The results are reported from an experiment on the effects of cutting date (14 June, 21 July and I September), fertilizer application (none or 80 kg ha?1 N plus 40 kg ha?1 P and K) and grazing treatments (none, autumn or autumn plus spring) on the vegetation of an upland mesotrophic grassland in Upper Teesdale. northern England, UK. Effects on plant species number and cover are reported for 4 years (1989–93) of treatment. Effects on ‘species -attributes’ are given for the fourth year. The cessation of grazing combined with the use of fertilizer progressively reduced species number by about 25%. Under traditional management (no fertilizer, cutting date on 21 July, autumn and spring grazing) the species number and cover remained relatively static over the 4 years. Comparison between treatments in the fourth year showed a reduction in species number under the fertilizer application, cutting date on 1 September and no-grazing treatments. Fertilizer use together with cutting date on 1 September particularly lowered species number and cover. Analysis of variance was used to assess the effect of treatment on species that occurred frequently in the sward. A cutting date of 1 September favoured Agrostis capillaris. Alopecurus pratensis, Poa trivialis, Phleum pratense and Trisetum flavescens, The absence of grazing favoured Dactylis glomerata and Holcus lanatus. The use of fertilizer particularly favoured A. pratensis and H. lanatus. Ordination methods were used to assess the effect of treatment on the less frequent species. These were primarily associated with the treatment combination that matched ‘traditional’ management. Deviations from this ‘traditional’ regime acted separately, rather than in combination, and favoured different grass species. Traditional management was associated with ruderal, stress-tolerant ruderal and competitive ruderal strategists and with longer seed germination times, heavier seeds, some of which needed scarifying or chilling to break dormancy, and transient seed banks that germinated in the autumn. The original sward was an Anthoxanthum odora-turn-Geranium sylvatirum grassland, Briza media subcommunity (MG3b). After 4 years, Festuca ovina-Agrostis capillaris-Galium saxatile grassland, Holcus lanatus-Trifolium repens subcom-munity (U4b) and Lolium perenne-Alopecurus pratensis-Festuca pratensis grassland (MG7c) were found in many of the fertilized and late-cutting treatments. 相似文献
19.
《Field Crops Research》2001,72(1):51-66
Pearl millet (Pennisteum americanum L.) is an essential crop in farming systems of the dry areas of the semi-arid tropics and its tillering habit is an important adaptive feature. This is the first paper in a series aiming at developing and validating a pearl millet simulation model that recognises tillers as functional entities, analogous to intercrops. The objective of this paper is to quantify the effects of total leaf number per axis (TLN), cultivar, plant density and axis number on parameters that are used to simulate potential leaf area per plant. Four cultivars with different phenology and tillering habit were grown under well-watered and well-fertilised conditions at two locations in India, covering a range of daylengths and plant densities. For selected plants, the area of fully expanded leaves was measured non-destructively. A bell-shaped function adequately described the relationship between individual leaf area and leaf position on an axis. Its shape was determined by the position (X0) and area (Y0) of the largest leaf and by the breadth and skewness of the leaf area profile curve. TLN affected all four parameters, although the association with Y0 was weak. Cultivar only affected Y0, suggesting that parameterising new cultivars is straightforward. The observed density effect confirmed that competition for light between axes started during stem elongation. The results highlighted the consistent differences between leaf area profiles of main shoots and tillers. For a high-tillering crop like pearl millet, modelling leaf area dynamics through individual leaves is justified, as this approach can potentially deal with cultivar and environmental effects on tillering. 相似文献
20.
The plant species number and composition, iind yield of herbage biomass of an agriculturally improved hay meadow were assessed after 4 years under various combinations of grazing, fertilizer applicution. cutting date and seed addition treatments in a replicated split-plot design. Grazing treatments consisted of either autumn grazing with cattle and sheep, spring grazing with sheep or both regimes. Fertilizer application treatments consisted of either 25 kg ha?1 N plus 12–5 kg ha?1 P and K or no fertilizer. Cutting date treatments consisted of cuts on either 14 June, 2i July or 1 September. Seed addition treatments consisted of either no addition or sowing with a range of meadow species in the autumn. Data analysis was by correspondence analysis and analysis of variance. Species number decreased with fenilizer use and when the cutting date was 1 September. A range of species was affected by the main treatments and there were some first-order interactions, mainly between cutting date and fertilizer application. Rhinanthus minor was particularly favoured by the seed addition treatment. Species attnbutes in the regenerative and established phase were related to treatments and their effect on species composition. The National Vegetation Classification communities were associated with particular treatment regimes. The 21 July cutting date favoured ‘improved’ over ‘unimproved-traditional’ swards, with spring grazing favouring ‘unimproved-traditional’ swards. Lowest yields of herbage biomass were associated with autumn and spring grazing, the 14 June cutting date and no fenilizer treatments. The fenil-izer, 1 September cutting date and auiumn grazing treatments gave the highest yields. The implications of these results are discussed in terms of the conservation management required to return agriculturally improved mesotrophic grassland to a species composition similarto that of traditionally managed grassland. 相似文献