摘要:

A point‐based technique was used to determine the effects of grazing, due to stocking rate and cattle‐to‐sheep ratio, on the defoliation pattern of three grass species. At each of 100 systematically located points per grazing treatment the nearest plant of each of three target species was recorded as being in one of five defoliation categories which ranged from ungrazed to severely, but uniformly, grazed. Each treatment was sampled at the end of each of three consecutive grazing seasons. The data for each species were subjected to log‐linear and canonical correspondence analyses. In these analyses the proportional composition of defoliation categories was the dependent variable and stocking rate, cattle‐to‐sheep ratio and year were the independent variables. The results indicated that (1) stocking rate had an overriding effect on defoliation pattern; (2) ratio had a lesser but significant influence on the defoliation pattern of all three species; (3) similar defoliation patterns may be achieved at different cattle:sheep ratios provided that the stocking rate is adjusted; (4) the grazing capacity concept must be reconsidered to account for the differing impacts of grazing by cattle and by sheep on individual grass plants; and (5) the sampling technique applied in the study provided meaningful information on the defoliation pattern of the target species.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638353

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Nitrogen was applied as ammonium nitrate in solution to kikuyu pasture at 225 kg N ha‐1, split into three equal dressings and applied in October, December and February. The first, at 75 kg N ha‐1was labelled in the ammonium ion and the latter two dressings were not labelled. Herbage, soil and roots were sampled monthly to determine the proportions of the labelled N in the herbage, root and soil over the season. Total15N recovered over the season, as a percentage of that applied as15NH4NO3, was 99.0%. A total of 52.1% of the labelled N was recovered in the herbage over the season, the highest recovery being in November. Recovery rates declined from November through to March. However, the accumulated recovery of15N was curvilinear over the season. The recovery rate of15N in the roots was lower than in the herbage, and the highest percentage recovered was in December. The15N recovered, as a percentage of that applied, in the soil depth classes showed similar trends. The highest percentage ofI5N was recovered in the 0–300 mm depth class and the lowest in the 600–1000 mm depth class. Leaching of15N, although minimal, did occur over the season.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638354

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Studies were carried out to determine the effect of time of inter‐planting centro (Centrosema pubescens) with cassava (Manihot esculentaCrantz), at various spacings, on the seed yield components of centro. Apart from the seed yield itself, time of planting centro did not have any significant effect on the number of flowers per inflorescence, pods per seedhead, seeds per pod and weight of 100 g seeds of centro. There was a negative correlation between seed yield and time of planting centro at all cassava interrow spacings. A similar correlation was found for cassava interrow spacing at the various times of planting the legume, due to a reduction in the population of centro. Seed yield was maximized (982 kg ha‐1) when centro was planted at the same time with cassava and at a spacing of 1 m × 1 m.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638355

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An analysis is presented of data from a stocking rate trial carried out in 1962–1963 at Chobela Livestock Station in southern Mozambique. The data set had limitations but an attempt was made to draw any conclusions possible for management. Data from the trial showed optimum gains per hectare at 0.64 head ha‐1(approximately 1.8 ha LSU‐1) in years of below‐average rainfall, and an annual livemass gain of 146 kg head‐1at a stocking rate of 0.33 head ha‐1(approximately 4.2 ha LSLT‐1). Potential livestock carrying capacity was determined using a model developed in Mozambique, and the calculated value of 4.3 ha LSLT‐1for a similar livemass gain was close to that determined from the trial data.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638356

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Seeds of four indigenous plant species were sown in 1990 in small‐scale field trials in an arid, non‐seasonal rainfall region of the southern Karoo, South Africa. Seeds of a winter annualTetragonia echinata(Aizoaceae) showed innate dormancy but those of three perennial shrubsPteronia empetrifolia, P. pollensandOsteospermum sinuatum(all Asteraceae) emerged only after the first substantial autumn rain. In good rangeland, seedling growth and survival was better in clearings than in undisturbed vegetation. In poor, continuously‐grazed rangeland, sheep had more influence on growth and survival ofO. sinuatumseedlings than did vegetation clearing. These findings should be tested by means of large‐scale trials replicated in time and space.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638357

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An experiment, using the micrometeorological mass balance method, was conducted to determine the effect of pasture sward height on volatilized nitrogen (N) losses. An altered sward structure (cut to a height of 30 mm) demonstrated higher volatilized N losses after fertilizer application than a sward retaining approximately 1.00 mm of residual herbage. The mean difference between treatments was estimated at 765 ± 109 g N ha‐1(P<0.05) for 33 h after the application of urea at 50 kg N ha‐1. This implies that residual herbage remaining on a pasture at the time of N fertilizer application may reduce volatilized N from the pasture.

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638358

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1022-0119    

DOI:10.1080/10220119.1994.9638352

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor