Paspalum plicatulum was grown at Brisbane in boxes of sand receiving basal nutrients and frequent irrigation; weekly levels of ammonium nitrate application were varied according to growth and development stage.The rate of tiller appearance increased to a maximum 40-50 days after sowing and almost ceased thereafter. Tiller leaf number, survival, fertility, inflorescence branching, seeds per raceme and seed size were positively related to tiller age. Young tillers were more sensitive to variations in nitrogen supply than old tillers.Adequate nitrogen nutrition during the vegetative phase from sowing to floral initiation (93 days) increased tiller and hence inflorescence density; increased inflorescence branching was compensated by fewer seeds per raceme. Good nitrogen nutrition during the phase from floral initiation to inflorescence exsertion (142 days) increased survival of late-formed tillers and hence inflorescence density; inflorescence branching, seeds per raceme and seed size were also increased. Nitrogen stress during the final maturation phase did not affect seed yield.

Five levels of urea were applied as single or split dressings in early summer, at floral initiation (about Febraury 14), or at inflorescence exsertion to Paspalum plicatulum cv. Rodds Bay grown in rows on a red-yellow podzolic soil. All components of seed yield-tiller density, tiller fertility, raceme number and seed number, and seed size-were influenced by external nitrogen supply. The effects of adequate nitrogen supply during one development phase usually persisted subsequently when differences in plant nitrogen concentration had disappeared. Nitrogen applications during the vegetative and floral initiation stages were most influential. The efficiency of response varied from 5.6 kg additional crude seed produced per kg N at the 50 kg N ha-1 level to 1.2 at the 400 kg N ha -1 level. High levels of urea (200 or 400 kg N ha-1) induced lodging and poor recovery of seed at harvest during a wet year, accentuated moisture stress during a dry year, but improved seed viability.

Weeds are a serious problem in this region during both the establishment of pastures and their productive period, causing serious reduction in growth, vigour, productivity and persistence. Factors responsible for weed infestation and possible methods of prevention and control are outlined in this paper. The biology and weed Ecology of Cassia alata, Digitaria insularis, Jatropha gossypifolia, Mimosa spp, Sida spp, Solanurn rnauritianurn and Solanum torvum are briefly described and detailed recommendations are given for the control of these weeds.

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