SOIL PREPARATION

CHAPTER 9

Root distribution correlated well with depth of soil preparation. Despite serious re-compaction at Nietvoorbij, grapevine root distribution in the soil- volume trial still reflected the positive effect of deep soil preparation 26 years after it had been carried out. An explanation for this long-term benefit of soil preparation is the fact that roots can explore the full potential rooting depth within 2 years after planting thus establishing the root frame very early, i.e. before re-compaction normally takes place. Thereafter rooting depth remains constant, but rooting density increases with time. Although a very reliable indicator of soil conditions, root mapping is tedious and time consuming, but well worth the effort. In fact, root distribution remains the ultimate indicator of soil conditions for grapevine growth. From the above discussion it is concluded that there is inadequate knowledge to predict the rate at which different soils will naturally re-compact and how soon that will happen. In general, red and yellow soils, as well as gravelly soils, will retain their loose structure for a longer time after soil preparation while the beneficial effect of loosening is expected to be short-lived on soils containing a high fine sand silt fraction (Saayman & Van Huyssteen, 1981). At this stage, the recommendation to growers is to redo soil preparation on all soils after the productive life time (20-25 years) of a vineyard has expired.

PHOTO: SHUTTERSTOCK.

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