Mineral nutrition of cassava (Manihot esculenta Crantz) grown in replaced soil after bauxite mining at Weipa, Queensland

The yield potential of cassava with optimal mineral nutrition was evaluated in a lateritic red earth that was replaced after bauxite mining at Weipa, Queensland. There were 9 field experiments. In 8 separate experiments, 5 rates each of nitrogen (N), potassium (K), magnesium (Mg), sulfur, copper, zinc (Zn), boron or molybdenum fertilisers were banded into the soil. In the phosphorus (P) experiment, triple superphosphate and rock phosphate were compared, each with 5 rates of P banded, broadcast or spot-placed into the soil. After 2 wet seasons (66 weeks after planting), maximum tuber yields were produced by the banded application of 200 kg P/ha as triple superphosphate, 20 kg Mg/ha and 8 kg Zn/ha. With rock phosphate, only the broadcast placement produced an increase in the yield of cassava, maximum yields being achieved with 400 kg P/ha. In addition, there was evidence that 100 kg N/ha and 300 kg K/ha were needed for maximum yields. Therefore, based on the results of these individual experiments over 2 seasons, 100 kg N/ha, 200 kg P/ha as triple superphosphate or 400 kg P/ha as rock phosphate, 300 kg K/ha, 20 kg Mg/ha and 8 kg Zn/ha are the fertiliser recommendations for cassava grown in replaced soil at Weipa. In addition, early Zn deficiency symptoms (not related to any applied fertilisers) may necessitate a foliar spray of 4 kg Zn/ha as well as the soil-applied Zn fertiliser. However, the use of dolomite at 80 kg Mg/ha may have decreased the tuber yields and/or increased the requirements for certain soil-applied fertilisers. An average yield of 26.0 t/ha of tubers (fresh weight) was obtained with a 51-week growing season, and the recommended rates of fertilisers. This yield was reasonable when compared with 32 t/ha of fresh tubers predicted by a growth model for cassava, grown in North Queensland for 52 weeks without irrigation