Improving cultivation practices in potatoes to increase window of workability and soil structural stability

The objectives of the trials were:

• To quantify the effects of water content at cultivation and OM content on soil cultivatability, bulk density, structural stability and the consequences for crop performance and quality, energy use and machinery work rates on contrasting soils.
• To determine the effect of different seedbed cultivation depths on SNS on contrasting mineral soils, including the effect on SNS of incorporation of green manures with variable depth seedbed cultivation.
• To quantify the effects of consolidation and profile of ridges on soil properties and crop performance and quality.

Results

On average, data from 16 experiments conducted in 2011-2014 with four to six destoner depths as a factor, showed that a significantly lower yield (50.5 ± 0.70 t/ha) was achieved when destoning 3‑5 cm deeper than the commercial depth (53.4 t/ha).  The yields from destoning at 22-28 cm (55.3 t/ha) were numerically greater than at the commercial depth (typically 30-38 cm), although not significantly different but there was no evidence that destoning shallower than commercial depth resulted in lower yield.

Shallow destoning did not affect planting depth or time from planting to emergence, however there was greater variation in planting depth and emergence in soil destoned deeper than commercial practice, particularly on heavy soils. Shallower destoning gives greater opportunity for soils to be cultivated closer to their optimum soil water content as well as reducing the wear on machinery and lowering labour costs.

Where soils have sufficient clay content to have a plastic limit (PL), growers should be aware that the critical cultivation depth in most springs would be shallow enough to cause issues of compaction, even by cultivating at the standard depths used by the industry.

Whilst most sites showed no effect of destoning depth on tuber bruising following commercial harvesting, on very stony soils or stony areas of fields destoning should be carried out 5 cm deeper than the optimum for yield to reduce the risk of stone impact causing bruising and careful attention paid to harvester share depth. The apparent lack of effect of depth of destoning on SMN and crop N uptake is of interest and may be due to most OM being in the top 25 cm of the soil profile.