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Conservation cropping on the Atherton tableland krasnozems

J.L. Gunton

Kairi Research Station, Kairi QLD 4872

Our pioneering fathers discovered the Atherton Tablelands in the late 18th Century. The Tableland then was covered in dense tropical and subtropical rainforest or wet sclerophyll forest. Initially cleared for dairying activities and subsequently planted to broadacre maize, Zea mays, and peanuts, Arachis hypogaea.

Fertility decline in maize was halted by using legume -based pasture rotations and better adapted varieties (Martin, pers. comm.). Continuing cultivation using combinations of peanuts, maize (summer) and irrigated potatoes, Solarium tuberosum, (winter) with concomitant exposure of fine seed beds to early storm influences has led to erosion and runoff losses. This soil movement is seriously threatening down-stream structures including the Great Barrier Reef. Research by QDPI officers has shown that stubble management through reduced tillage techniques de- creased soil runoff by 30% compared to conventional tillage, while maintaining or increasing yields (Table 1).

Table 1. Effect of cultivation on yield (t/ha) of maize (M) and peanuts (nut in shell) (P)

Zero tillage did not fare as favourably as reduced tillage under trial conditions. Research continues into assessing quantitative soil and nutrient losses from a wider range of cropping sequences, as well as examining the likely interactions between soil fertility, cropping sequences and cultivation techniques. Small, on-farm projects have been undertaken involving the farming community in the development and adoption of more appropriate and sustainable cropping practices.

Further work in weed control is commencing and a larger adoption program needs then to be implemented, so that a "critical mass" of farmers can carry forward the goal of achievement of "sustainable agriculture".

Funding for research and development approaches are difficult to attract because of the necessary long lead and assessment time involved in adequately sampling the range of climate variables likely to be experienced.

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