Evaluating the use of permanent beds for growing vegetables in North Queensland

Systems for vegetable production in the dry tropics of North Queensland, Australia, have been dominated by intensive tillage and extensive use of nonrenewable polyethylene inputs. A field trial was established to investigate agronomic practices and soil health changes in capsicum and zucchini crops grown with intensive tillage and permanent bed systems. In 2011, conventional intensive tillage with 'plasticulture' was compared to a permanent bed system with subsurface drip irrigation, no soil disturbance and organic mulch produced from a summer sorghum crop. Soil compaction was a major production constraint in the permanent beds in 2011, along with water and nutrient management. Compared to intensive tillage, marketable yield in permanent beds had reductions of 70 and 30%, respectively in capsicum and zucchini. In 2012, the same intensive tillage system was compared to a permanent bed system where minimal soil disturbance had been produced by zone tillage in 10% of the cropped area. It was also compared to a modified system which had permanent beds and zone till but, in addition, had a polyethylene film mulch over the planting beds. The zone tillage and improved fertigation management in 2012 led to marketable yields that were not significantly different among the three tillage systems. In 2013, crops in permanent beds covered with a biodegradable film instead of polyethylene film, had marketable yields that were comparable to the intensive tillage system. Results from the first three years of this study gave indication that minimum tillage has the potential to provide acceptable marketable yields with less dependence on polyethylene use.