Strategic tillage to reduce soil structural degradation and improve productivity : SRDC final project report BSS143
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Focus groups of growers were convened to discuss industry attitude and reasons for non-adoption of reduced tillage planting. It was largely agreed that compared with ten to fifteen years ago the industry had moved to reduced tillage practices. The question the groups focused on was, why was it necessary to cultivate the whole block, why not just cultivate the old row? Opinion was expressed that land preparation was undertaken the way it was, generally because that is how it had always been done. Other reasons recorded were difficult soil types relating to soil moisture at the time of tillage; run-off and erosion; cultivation was one factor that could be controlled; risk of crop failure (poor emergence, but this could also be due to poor planting material); soil-borne diseases and insect pests; and the technique had not been thought about before. Benefits that were perceived included soil structure preservation, and saving of time and energy. During the discussions it was learnt that innovative growers were practising a version of strategic tillage, unknown to neighbouring growers.Interest in the concept of strategic tillage was generated through these groups, to the extent that the strategy is being trialed by several growers.Field trials were conducted at Tully and Bundaberg to compare conventional land preparation, where the whole area was cultivated, with strategic tillage where only the row was disturbed. Results demonstrated that reducing the number of cultivations did not compromise seedbed conditions at either site. This means that fewer tillage operations can be undertaken for the same end result. The inference is that time and energy can be conserved and that soil degradation can be minimised. Yield was not affected by a reduction in tillage for land preparation. With savings in time and energy, the costs of planting can be reduced.Monitoring of the known soil-borne disease, Pachymetra chaunorhiza, showed greater levels under the susceptible variety compared with resistant variety grown at each site. The yield of the susceptible variety was lower than that of the resistant variety. Varietal rotation is suggested to limit or minimise the effect of Pachymetra under strategic tillage. The BSES plant breeding program is providing varieties of greater resistance for the northern areas. Caution in variety selection is required in the central and southern districts to minimise the effect of Pachymetra. New varieties being released have resistance to Pachymetra. Thus varietal rotation by growers (good hygienic practice) will minimise the effect of the soil-borne disease on productivity and allay concerns about planting directly back into the old row.There was a trend for the number of earthworms to recover more rapidly under less soil disturbance. This is seen as a positive benefit in that earthworms create macroporosity which enhances water movement and aeration.It is recommended that, for the sugar industry to derive the maximum benefit of strategic tillage, a system be developed using controlled traffic principles with direct drilling of cane, and a legume crop or green manure be included in the fallow period. Such a system will improve soil health over time, resulting in a more sustainable sugar industry with less dependence on chemicals for soil pest and soil-borne disease control. This will enhance the industry's environmental image.