The nitrogen economy of perennial ryegrass-white clover associations

Bland, Brian Foster (1967) The nitrogen economy of perennial ryegrass-white clover associations. PhD thesis, University of Glasgow.

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An experiment was conducted over the period 1963-65 with New Zeeland cultivars of Lolium porenne (L) and Trifolium repens (L). They were sorn in alternate rows, six inches apart and half the plots in the trial area were established to maintain root segregation between the species using a double layer of 500 gauge black polytheno. Liberal quantities of phosphate and potash fertilizers were applied each year but the grass-legumo associations relied upon soil mineralization, fixation by free-living organisms, rainfall and symbiotic fixation for its nitrogen supply. Variations in defoliation frequency of two, four and six cuts per annum had little effect on the overall dry matter yield which amounted to 5300, 6100 and 6000 pounds per core per annum respectively. However, the average yearly production of nitrogen during the experimental period was 112,166 and 217 pounds of nitrogen per core which suggested a 48% increase by doubling the outting frequency and 98% increase when three times the number of defoliations were employed. Root segregations of perennial ryograss and white clever when grown in close asscociation reduced the dry matter yield by 18% in the establishment year and by 6% in 1964 and it is suggested that root check and root restriction, particularly in respect of the grass component, were mainly responsible. In 1965 the dry matter yield was 26% lower where root barriers had been introduced and from above ground appearance of the grass and from the yield data this was clearly the direct effect of eliminating underground nitrogen transference from the clover. The nitrogen economy of this grass-legume association has been studied over a three year period and only in the final year was it possible to demonstrate above ground the results of underground nitrogen transfer. Clover contributed 30.79 pounds of nitrogen to its grass partner in 1965 and this figure is compared with predicted values using the theory of Walker, Orchiston and Adams and also data computed from supplementary grassland observation plots. Micro-climatic temperature recorded at ground level partially corroborate the findings of Johnstone-Wallace who showed lower diurnal fluctuations of temperature with a grass and clover sward compared with grass alone. Seed of the same New Zealand cultivar of Trifolium repens (L) was inoculated with an effective strain of rhizobium (R.157 originating from Sydney, Australia) and compared with a non-inoculated control. From the limited results of this trial and from field observations it would appear that the indigenous strain of rhisobium at Auchineruive was an effective one. The physical effects of the black polythene used for root segregation were examined through yield data in a special trial and laboratory and field tests were carried out on the permeability of this material as used in the experiments. Dry matter production, nitrogen yields and herbage quality from the perennial ryegrass-white clover association are reported, discussed and compared with data from New Zealand and Holland.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Donald S Hendrie
Keywords: Soil sciences, Biogeochemistry, Agronomy
Date of Award: 1967
Depositing User: Enlighten Team
Unique ID: glathesis:1967-72216
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:11
Last Modified: 24 May 2019 15:11

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