Abstract: In the farmaland system along Yellow River banks of Baiyin city,which consists of wheat,wheat-soybean, maize,maize-broad bean,wheat-maize,pea-soybean or hyacinth bean-millet,high-lift irrigation gives a high ecological efficiency. The biological, equivalent,crude protein and grain yields are 1.78 ?10⁴,1529 and 7077 kg. ha^-1,respectively. 85.7% of dry matters are harvested,and only 14.2% of them are returned back to soil system. The total average input of energy is 1.17?10¹¹J. ha^-1, of which, 81.2% comes from in organic. The output-input ratio of energy is respectively 1.53 and 0.66 and average solar energy efficiency is 0.81% and 0.35% for biomass and grain. As for the economic benefits, the output-input ratio is 2.72 and 1.23 yuan. yuan^-1 for net output and net income, respectively.

Key words: excess sludge, thermophiles, sludge degradation, extracellular enzyme.