Graduate Thesis Or Dissertation
 

Influence of grazing and nitrogen fertilization on winter growth, seed and straw production of Lolium multiflorum Lam

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  • The influence of grazing closing dates and form and amount of nitrogen fertilizer on Gulf annual and Oregon annual ryegrass was studied at locations in the Willamette Valley of Oregon. Closing dates were established as mid-April, and May 1 together with ungrazed plots for comparison. Fertility consisted of a single 207.2 kgN/ha application February 1 of sulfur coated urea (SCU-30, a recent development of TVA); 207.2 kgN/ha in the form of ammonium sulfate applied in split applications during the trial; and a single application May 1 of 140 kgN/ha in the form of ammonium sulfate. Considerable total seed yield and seed size reductions were caused by late grazing of both varieties but little effect was induced by fertility variables. Crop residue in the form of straw was considerably reduced by later closing dates in both varieties. Later applications of nitrogen regardless of form tended to increase amounts of straw, The number of fertile tillers per unit area was significantly increased by later closing dates on Oregon annual ryegrass but significantly decreased in the Gulf annual variety. Another factor affected by later closing dates was the number of spikelets per spike which was significantly decreased in both varieties. The number of spikelets per spike was significantly increased by application of sulfur-coated urea. The largest amount of forage produced for grazing was achieved from treatments of SCU-30 applied at beginning of grazing February 1. The least amount of vegetative growth was harvested from plots that received no nitrogen during grazing. Intermittent clipping in the same quadrats gave more yield than a final single clipping. It was evident from this research that the loss of seed yield due to grazing would be justified by the production of high quality forage. Also the addition of nitrogen fertilizer in late winter would increase available forage in quantities to offset the fertilizer cost.
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