ASSESSMENT AND POSSIBLE ADAPTION OF THE DOUBLE-DISC OPENER PLANTER TECHNIQUE IN THE WET TROPICS

THE AVAILABILITY of double-disc opener planters has allowed the adoption of minimum and zero tillage planting methods as part of an improved farming system. Comparisons of double-disc opener (DD) and conventional mouldboard furrow (MF) planters in the wet tropics have been confounded by cultivation issues. An experiment was conducted at Tully to evaluate the performance of double-disc opener and mouldboard furrow planters under the same cultivation regime, row tillage (RT). Conventional (CT) and zero (ZT) tillage systems were also included. There was no difference in germination and early growth between the two planters due to a modification to the DD planter giving more consistent soil cover and depth over the setts. Cane planted with the DD planter was almost 100 percent lodged, whereas lodging was negligible with MF planted cane. This difference was due to depth of anchorage being 93– 133 mm less with MF planted cane. Plant cane yields of the DD planted treatments were not reduced by lodging as stool removal at harvest offset any weight loss associated with lodging. This resulted in 21–36% more gaps > 0.5 m in the first ratoon crop than the MF planted cane. Consequently, yields in the first ratoon were 12–25% lower in the DD than the MF planted cane. The CCS of the Q200A was only marginally reduced due to lodging. Nutrient uptake by the plant was not influenced by the amount of soil disturbance. Nutrient distribution down the soil profile was fairly uniform with CT and RT but there was a concentration of calcium and magnesium near the soil surface with ZT. The results are discussed in relation to the viability of a ZT-DD system in the wet tropics and how the RT-DD system may be adapted to minimise lodging.