Cutting and grazing systems for grass/white clover Trifolium repens L. associations

Gooding, Roderick F (1993) Cutting and grazing systems for grass/white clover Trifolium repens L. associations. PhD thesis, University of Glasgow.

Abstract

The thrust of advice and progressive farming thought over the past three decades has been to encourage systems of grass production based on the optimum response of grass to inorganic fertiliser nitrogen and achievement of maximum economic yields per hectare. Recent public pressure, supported by government and EC initiatives has provoked interest in low input, less intensive systems of sustainable agriculture. The role of white clover within grass / white clover swards which receive no inorganic nitrogen, is seen as pivotal to lower input forage based livestock and mixed farming systems. This is due to white clover's high nutritive value, symbiotic ability to "fix" atmospheric nitrogen and potential to produce yields of forage equivalent to "grass only" swards receiving moderate inputs of fertiliser nitrogen. This move away from traditional high input systems has highlighted the need for detailed prescriptions for the composition and management of grass / white clover swards as a viable and reliable alternative. In this project two experiments were conducted to address the two areas of sward composition and sward management which were considered to be major limiting factors to the attainment of reliability in white clover based animal production systems. In both experiments reported in this thesis the hypotheses being tested were: 1. The white clover component of a continuously sheep stocked grass / white clover sward is enhanced by the imposition of a rest from grazing for a conservation cut. 2. The presence and survival of white clover in a continuously stocked grass white clover sward is determined by the specific / varietal characteristics of the sward components and their combined response to management. Experiment 1 was set up investigate the management of perennial ryegrass / white clover associations over the range of perennial ryegrass maturity and ploidy in association with white clovers of different leaf size. The management system tested was continuous stocking with sheep and the effect and optimum timing of a rest for a conservation cut. Due to the large number of treatments investigated, this was a small plot grazing trial and detailed measurements of sward composition, architecture and white clover development were made using a variety of non destructive techniques including the use of point quadrat, grid quadrats and individual stolon measurements. Experiment 2 was set up to study the effect of similar management options on other important perennial grass species / medium leaved white clover swards and compare the findings with those for both diploid and tetraploid perennial ryegrass associations. This experiment was on a field scale and sward cores were used to measure white stolon parameters and sown and weed grass tiller numbers. Production under grazing was assessed using exclosure cages and "grazing days". In both experiments, conservation yields were assessed and grazing management was based on sward height with stocking rates adjusted using "put and take" ewes and lambs and in the case of experiment 1, buffer grazing. Both experiments demonstrated that continuous sheep stocking of grass / white clover swards does not necessarily have an adverse affect on white clover proportions within the sward. Experiment 1 showed with small leaved white clover, hard grazed to a sward height of 45 mm, high sward white clover proportions can be maintained. Likewise experiment 2 demonstrated that at a sward surface height of 60 mm, satisfactory white clover proportions were achieved using medium leaved white clover in association with each of tetraploid perennial ryegrass, diploid perennial ryegrass, meadow fescue, cocksfoot and timothy. With the exception of the meadow fescue / white clover association, a rest from continuous stocking to take a conservation crop at normal first cut time (April to late May) greatly reduced the proportion of white clover, compared with that in the unrested treatment, within associations of these perennial grasses with medium leaved white clover. (Abstract shortened by ProQuest.).

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Agronomy, range management, plant sciences.
• Colleges/Schools: College of Medical Veterinary and Life Sciences
• Supervisor's Name: Frame, Dr. J. and Thomas, Dr. C.
• Date of Award: 1993
• Depositing User: Enlighten Team
• Unique ID: glathesis:1993-72717
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 11 Jun 2019 11:06
• Last Modified: 22 Jul 2021 11:10
• URI: https://theses.gla.ac.uk/id/eprint/72717