Processing tomato response to soil compaction and fumigation

Abstract

Summary. Permanent raised beds coupled with reduced tillage and cover crops are part of the Australian processing tomato industry’s strategy to move towards more sustainable farming practices. As a consequence, crops may be planted into denser soils. Previous work showed that processing tomatoes had considerable tolerance to no-tillage; mild soil compaction reduced vegetative growth but not fruit yield. This field study showed that severe compaction not only reduced vegetative growth, but also extended the duration of the exponential vegetative growth period, so that fruit and vegetative growth were competing for assimilates. Under these conditions, fruit yield was severely reduced. Accurate management of drip irrigation could not compensate for the narrow, non-limiting water range of a compacted soil. Mild water deficits during the late flowering and early fruit growth phase also reduced fruit yield. Pot experiments under controlled conditions revealed an interaction between soil fumigation and tillage management. Soil fumigation improved shoot growth at high and low soil densities with the greatest effects observed below ground; root length was more than doubled when soil cores with a bulk density of 1.79 t/m³ were fumigated. A cover crop of subterranean clover, grown in the off-season winter period, had no effect on fruit yield under non-compacted conditions. The implication is that cover crops, which have been shown to ameliorate adverse soil physical conditions, can only express their potential when soil conditions in a conventionally managed system are suboptimal.