摘要:

AbstractAn experiment is described in which the amount of nitrogen fixed by the white clover component of a surface‐sown hill sward was determined using small quantities of15N‐labelled ammonium sulphate. Between 11 July and 22 August 1974 25 kg ha−1N was fixed. No evidence of a transfer of N from clover to the associated perennial ryegrass was detectable over this period although the N content of the grass growing with the clover was higher. The relative advantages of the isotope technique and the acetylene reduction assay are disc

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01414.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractIn a small drainage basin in the Peak District rates of soil erosion were measured between October 1966 and September 1968. The vegetated margins of ground denuded of vegetation (scars) were retreating by 9.3 mm per annum and rills and sheet wash removed annually from these scars up to 34 t ha−1soil. Erosion was taking place primarily withinAgrostis‐Festucaswards and also in heather moor, but not on peat‐covered slopes under cotton grass (Eriophorum vaginatum) moor. TheAgrostis‐Festucasward supported a higher sheep population than did the other vegetation types. In May 1974 most scars had been colonized by vegetation; this was related to a marked decrease in sheep numbers in 1969 and not to climatic

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01415.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe drying pattern of grass swaths was monitored using microclimate techniques during a 48 h summer wilting period of good drying conditions. Swath drying pattem, which is dependent upon the swath energy relations, water relations and resistances to evaporation, was explained in terms of changes in the balance of available energy, ambient vapour pressure deficit and swath internal resistance to water vapour transfer throughout the drying period. A typical drying pattern showed limited swath evaporation between sunrise and 09.00 hours, and rapid evaporation between 09.00 hours and 12.00 hours when available energy and vapour pressure deficit were high and swath resistance to water loss low. Between 12.00 and 18.00 hours, because of a decrease in available energy and increase in swath resistance, swath evaporation was reduced. Between 18.00 hours and sunset swath evaporation was near zero.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01416.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe dry matter and crude protein production of the perennial ryegrass varieties S24, S23, Premo, Houba, Barlenna, Melle and Sceempter Pasture at annual nitrogen application rates of 212, 425, 637 and 1062 kg ha−1were studied for the years 1972–74 inclusive. The DM and CP response curves for the variety Melle were steeper than those for other varieties tested and levelled off at a higher N application rate. The results suggest that Melle is a variety with a genotype capahle of utilizing N more efficiently at higher rates than the other varieties tes

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01417.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractRyegrass swards at fourteeo widely separated sites in England were assessed for yield, botanical composition and invertebrate populations, with and without insecticide treatment during a 4‐year period. Treatment with insecticide reduced the numbers of almost all invertebrate groups sampled and increased grass growth at some time at all but one site. Annual DM output was increased by 0–32% depending upon the site concerned. Evidence is presented which suggests that the yield increases were due to the suppression of aphids, plant‐sucking bugs, stem‐boring fly larvae, and perhaps ne

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01418.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractExcised S24 perennial ryegrass leaves were dried in controlled and measured conditions of temperature (28°C), relative humidity (22%) and airspeed (40 cm s−1), without treatment or after treatment with petroleum ether (4O–60°C boiling point) applied in various ways. Subsequent increase in the drying rate of the leaves varied greatly with method of application of petroleum ether, and the results indicate that the modification of the waxes on the leaf surfaces, which results in reduced cuticular resistance to water loss, requires the presence of liquid petroleum ether on the leaf surface. This effect increases with temperature, and the increase is due to the enhanced activity of the petroleum ether in dissolving waxes, rather than to direct thermal effect on tissue resistance. The practical implications of employing such a technique are disc

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01419.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractRelationships between readings of the electronic (capacitance) pasture meter and descriptions of pasture yield were examined over the yearly growth cycle in grazed pastures ofSetaria ancepscv. Nandi, with or withoutMacroptilium atropurpuremcv. Siratro andDesmodium intortumcv. Greenleaf. There was a poor relationship between meter reading and pasture dry matter yield (r =+0.574 pooled over pastures and seasons) but this relationship was improved tor=+0.750 by inclusion of other regressors describing pasture height and proportion of inert material. Meter reading was more closely related to fresh pasture yield (r =+0.830), water yield (r =+0.885) or dried green yield (r =+0.830), although inclusion of a pasture height term still improved the relationship slightly. Suggestions are made about using the meter to estimate dried green yield rather than total dry matter yield, and taking more consideration of the proportion of inert material when relating the meter reading to total dry matter yield.Visual estimation was also compared with actual pasture yield measured by cutting. Even though prior training for yield estimation was inadequate, the relationships between visually estimated and actual yield were as good as those from the pasture meter. It is concluded that the pasture meter will not find a regular use as a sampling tool in most grazed tropical pastures.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01420.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractPerennial ryegrass was sown in a field trial with or without a small‐leaved white clover, S184, in September 1969 and cut five times per year in 2 successive years. Yield of clover was low and very unevenly distributed in time. Clover performance is described in four distinct periods, April‐June 1970, July‐September 1970, April‐June 1971 and July‐September 1971, in which yield of clover was respectively low, moderate, low and fairly high and the indirect contribution, the enhanced yield of other sward components, was respectively nil, moderate, moderate and moderate. The ratio of indirect to direct contributions on an annual basis concealed very large differences both within and between years. The presence of clover increased the N content but did not affect the P or K content of other sward c

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01421.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Book reviewed in this article:Land for AgricultureLand Use Policies and Agriculture

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1977.tb01422.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY