Technical Yearbook 2023

Tractor wheel compaction Trying to alleviate tractor wheel compaction is a futile exercise because the soil will just recompact again with the first wheel traffic on the loosened soil. The intensity and depth of the compaction can vary greatly and factors like soil water content and stone percentage play an important role. Soils with a higher stone percentage are not prone to compaction. Contrary to general belief, sandy soils compact just as easily as soils with a high clay or silt content (photo 15). Recompaction occurs varyingly in zones where the most wheel traffic takes place and can stretch between 15 - 50 cm deep. It is a function of the type of implement used. Tractor wheel traffic is therefore a given. Correct soil preparation and establishment practices allow roots to utilise the soil volume optimally so that tractor wheel traffic does not impact negatively on the vine.

can coincide with a root flush. Untimely root pruning is detrimental for shoot growth and can affect yields as the carbohydrate reserves which are stored in the roots can possibly be cut off. The degree of loss brought about by the action will thus determine whether the roots have to be pruned on both sides of the vine, or only on one side. In most cases, it is recommended to spread out the action over at least two seasons. Wheel traffic in the cultivated rows also has to be limited to a minimum for a season in order to allow the new roots to colonise the loosened soil. This has implications for the management of cover crops and the vineyard’s chemical programme. Summary Recompaction is unavoidable over the lifetime of a vineyard due to the mechanised nature of grapevine cultivation. The causes of compaction are not always obvious however, and deep tillage is not always the answer to all problems. It is important to do a thorough investigation into the cause of the problem prior to performing any cultivation. To this end the advice of an expert is required, who can perform and evaluate the following actions: • Profile pits to determine where the compaction is located, as well as the intensity thereof. • Determine where the roots are concentrated and what the effect of the cultivation action will be on the roots. • Take soil samples to investigate the possibility of chemical and biological causes. • Plan corrective actions in order to perform these actions at the optimal time and with the correct implements. • Adapt your management practices to ensure the long term success of the correction and avoid reoccurence of the problem. Optimal deep soil preparation and controlled wheel traffic before establishment, the correct approach to making planting holes during establishment, and the establishment and management of cover crops are non-negotiable basic practices which serve as a basis for long-term soil health and vine production. If these actions are performed correctly from the outset, it will significantly contribute to the maintenance of well aerated soil profiles, good water infiltration, healthy soil biology, optimal conditions for root development and satisfactory yields.  Reference https://www.wineland.co.za/recompaction-of-soil-in existing-vineyards/

PHOTO 15. Recompaction (30 cm deep) on sandy soil after a single movement of a tractor wheel.

Root pruning Although root pruning is not necessarily involved in the alleviation of compaction, the two actions are mostly unavoidably linked. The appropriate timing for both actions is therefore of utmost importance. Timing is determined by the soil water content around autumn so pruning

Contact Johan de Jager (Vinpro) at johan@vinpro.co.za or Bennie Diedericks (Soilution) at bennie@resalt.co.za if you want to find out more about practical approaches to uplift recompacted soils and improve root growth, as discussed in this article.

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WINETECH TECHNICAL YEARBOOK 2022