摘要:

ABSTRACTA model is described which can be used to synthesize dairy systems under various price environments and sets of decision rules.The potential use of the model is illustrated with reference to the seasonal calving pattern as an economic decision.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01246.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe DM production from INRA 200, an early maturing hybrid maize grown for silage, was 10±6 and 14 5 t/ha in mid‐October 1972 and 1973 (4±2 and 5±8 tons/ac). The plant population in both years was approximately 112,000/ha (45,320/ac). Whole‐crop and cob DM percentages were 18±2 and 21±3 for 1972 and 39±9 and 53±0 for 1973, respectively. The cob yields were 49 and 10±4 t/ha (2±0 and 4±1 tons/ac) in 1972 and 1973 and cob in the two years accounted for 46 and 72% of total yield. At harvest the 1973 crop was 4–6 weeks more mature than the 1972 crop. These differences were attributed to the difference in accumulated temperature recorded from May till October, which was 567°C days in 1972 and 817 in 1973. Whole‐crop DM content, yield of cob and yield of cob as a percentage of total yield were studied against seasonal temperature accumulation. In the case of DM percentage there was a highly significant linear regression which showed that 627°C days were needed to mature maiz

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01247.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTACTIrrigated plots of a mixed sward of four grasses and white clover were cut to a height of 3 cm in either June, August, October, December or February. The plots cut at each commencement date were harvested when the height of growth of the pasture was either 10, 18, 25, 32, 40, 48 or 55 cm. At each harvest, the pasture was cut at 7 to 8 cm intervals down to a height of 3 cm. DM production, botanical composition,in vitrodigestibility (DOM) and CP of each layer was determined.DM production declined from the lower to the upper layers for pastures shorter than 32 cm. For pastures taller than 32 cm, DM production declined from the lower to the middle layers, then increased in the upper layers, due mainly to the presence of seed heads.Maximum percentages of DOM and CP were observed for the middle layers of the pastures taller than 25 cm. For pastures shorter than 25 cm, DOM and CP percentages increased from the lower to the upper layers, for all commencement dates. The percentages of DOM and CP of each layer decreased as the height of growth increased.The percentage of DOM showed a positive correlation with the percentages ofLolium perenne, Bromus unioloidesandTrifolium repens, and a negative correlation with the percentages ofPaspalum dilatatumand chlorotic material. The percentage of CP showed a positive correlation with the percentages ofPaspalum dilatatum, Dactylis glomerataandTrifolium repensand a negative correlation with the percentages of chlorotic material and the total of the four grasses within the pasture layers.The lower layers of the pasture produced large quantities of DM and, despite the lowerin vitrodigestibility of these layers, they produced more DOM than the other pasture layers. The DOM production of the pasture increased with increasing height of growth, but decreased as the commencement date was altered from winter through to the end of summer.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01248.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTNewly‐sown S24 perennial ryegrass at Hurley and old established ryegrass‐dominant mixed pasture at Rothamsted were treated with several pesticides, singly and in combination, over the period 1969–73. Yields were either unaffected or increased by up to 30% in any one year, depending on the treatment, the newly‐sown sward giving the more consistent response from year

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01249.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTDifferent grazing treatments applied to pastures in which perennial ryegrass was dominant had little influence on DM production during the main reproductive growth period in late spring and early summer. Lax and infrequent grazing at this time did, however, reduce tiller density. During the dry summer period lax infrequent grazing increased production by 20%, while in the vegetative growth period in autumn those pastures which were alternately lax‐ and hard‐grazed outyielded those which were hard grazed by 63%.In all treatments, initial recovery growth resulted almost exclusively from the production of leaf tissue. The rate of leaf growth declined three to five weeks after grazing, depending on treatment and season, and subsequent yield increase was dominated by sheath and stem gro

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01250.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe liveweight gain was measured of beef cattle on pastures stocked at 5.9 to 11.8 cattle/ha and receiving 50, 182 or 329 kg N/ha in a 12‐week season. N levels and stocking rates were so adjusted that similar yields of herbage per animal were expected. Results showed that similar liveweight gains per animal, averaging 1.03 kg/day, occurred at all N levels. Liveweight gain/ha ranged from 547 to 1037 kg in 12 weeks and the corresponding quantities of metabolizable energy utilized were 9890 and 17590 Meal. The results confinn earlier work (4, 7

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01251.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTExperiments were carried out with different depths of added topsoil, with different methods of cultivation and with different rates of application of fertilizers on an ash disposal site near Newark. Good yields of hay and wheat were obtained and were shown to vary systematically with the treatment of the plots. Good yields of wheat were obtained with a top dressing of 125 kg N/ha even on bare ash but, in contrast with the yields of DM from grass, yields of grain tended to increase with increasing depth of added soil. This pattern appeared to be influenced by the variations in spring rainfall. There appeared to be no adverse effects of uptake of trace elements from the ash.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01252.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTThe DM and N contribution of S184 white clover in mixed ryegrass/clover swards was recorded at Pant‐y‐dwr Hill Centre (305 m) for 4 years, 1967–70. By direct comparison with fertilized grass swards it was estimated that the clover N contribution on peaty gley soil averaged 100 kg N/ha per year (89 Ib N/ac) under cutting and 98 kg N/ha (87 ib/ac) under grazing with faecal return. On more fertile acid brown earth the corresponding contributions were 81 and 90 kg N/ha (72 and 80 Ib/ac). Full replacement of clover by N fertilizer would require average annual applications of 268, 229, 156 and 128 kg fertilizer N/ha, respectively (239, 204, 139 and 114 Ib

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01253.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

ABSTRACTData are presented demonstrating the effects of applying fertilizer N at 59, 118 or 177 kg/ha on 16 Apr. on uptake of K, P. Ca, Mg and Na in primary growth (PG) harvested 8, 12, 16, 23, 29, 45 and 57 days afterwards, and residual effects in two successive regrowths (RG1 and RG2) harvested on 12 June and 13 Aug., respectively.Significant residual responses as uptake of K, P, Ca, Mg and Na were shown in RG1 and RG2 after all dates of harvesting PG. The residual responses compensated for poor uptake in PG. Thus, low uptakes to the second increment of N were followed by high residual responses in both regrowths; and low uptakes in PG harvested shortly after applying the fertilizer N were followed by high residual responses.Averaged over the seven dates of PG harvest, the sum of responses (PG+RG1+RG2) to the second N increment was greater than total response to the first increment in P and Mg, considerably greater in Ca and Na and slightly lower in K. These marked residual responses to the second N increment were most noticeable where PG was harvested 23 days after applying fertilizer N and became less marked as date of PG harvest was advanced.Percentage K, P, Ca, Mg and Na in DM of the PG and of RG1 increased as N application was raised. By RG2, the residual effects of fertilizer N on percentage K. P and Mg were reversed to give reduced percentages with increased N application to PG. indicative of deficiencies in availability of these elements.The application of 177 kg N/ha to PG resulted in the release of additional soil N and of other mineral elements which could lead to their depletion.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01254.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1974.tb01255.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY