Quantifying the sustainability of grazed pastures on the Northern Tablelands of New South Wales

An experiment was conducted to examine the effect of deep-rooted perennial grasses on the water and nitrogen economy of 3 mature pasture communities w ith different botanical compositions but the same fertiliser history. One p asture was dominated by volunteer naturalised pasture grasses (Eleusine tri stachya and Danthonia spp.) (termed 'degraded'), another was phalaris (Phal aris aquatica) dominant (phalaris), and a third was dominated by phalaris i nto which white clover (Trifolium repens) had been recently sown (phalaris- white clover). Two replicates of each pasture type were grazed continuously over 4 years w ith young weaner sheep changed each year. Measurements of hydrology, nutrie nt cycling, botanical composition and animal production were made in order to quantify the sustainability characteristics of each of the pasture types . Data are summarised as absolute measures at various points in time and also as trends over time. The ranking of standardised treatment measures was th en summed to provide an index of sustainability with or without a weighting assumed to be representative of the relative importance of various layers of sustainability viewed from the perspective of a hypothetical 'typical' g razier. The results show that the phalaris-white clover treatment was subst antially more sustainable, in both ecological and economic terms, than eith er of the other treatments. The unweighted index for the phalaris-white clo ver pasture was 3.61 compared to 2.08 and 1.98 for the phalaris and 'degrad ed' pastures, respectively.