No-till technology and legume rotation for sustainable crop production in the Douglas Daly region of the Northern Territory, Australia

The adoption of no till/legume rotation practices combined with low levels of fertiliser, herbicide and insecticide appear to be key elements in the development of an ecologically stable and sustainable crop production system in the Douglas Daly Region of the Northern Territory. Tillage studies involving a maize-soybean rotation system over a 4-year period have shown a 41% average increase in maize yield under no till compared with conventional till. The difference between no till and conventional till was generally highest during the drier years. In a 1-year study of a sorghum-peanut rotation, the yields of sorghum and peanut under no till were similar to those under conventional till. Application of nitrogen fertilizer increased sorghum flag leaf area by an average of 12% for no till compared with conventional till. Total nitrogen concentration in peanut leaves under no till was significantly higher than under conventional till indicating better nodulation and nitrogen fixation under no till.

Sorghum grown following a 2-year-old Centrosema pascuorum cultivar ‘Cavalcade’ ley showed no significant response to applied nitrogen. In the top 60 cm of the soil average soil nitrate nitrogen at sowing and at 8 weeks after sowing was 30 ppm, indicating a reasonable rate of mineralisation in the soil. This was further supported by the fact that the nitrogen content of sorghum stover plus grain was 112 kg ha⁻¹ at the zero level of applied nitrogen.