Technical Yearbook 2023

Recompaction due to cultivation after soil preparation The levelling of soil after soil preparation to ease the planting process, remove rocks, drive in material, or establish a cover crop, is common practice. While no heavy traffic is preferred in the first two years after establishment of the vineyard, such wheel and implement traffic will lead to severe recompaction in the topsoil (photo 11). These cultivation actions are sometimes unavoidable however, thus the following guidelines can be applied: • Avoid wheel traffic on the vine row after soil preparation. The vine rows must be clearly marked out to ensure that no wheel traffic occurs across or on the vine row. • If there is a possibility of traffic on the vine row, soil loosening with a toe implement to a depth of 50 - 60 cm should take place on the row before planting. For this action, the moisture status of the soil is very important. If the soil is too dry, clods can form (photo 12), while soil that is too wet can cause a smearing action which can severely restrict root growth. • Make the planting holes slightly deeper to ensure that the vine roots can grow into the loose soil beneath the compacted layer.

PHOTO 7. The paraplough and the result of the cultivation between the vine row and the tractor wheel. Note the large volume of loose soil that can now be colonised by the roots.

Planting hole compaction causes stress conditions for young vines and gives rise to secondary problems which will further impact negatively on the vines. Photos 8, 9 and 10 below compare planting hole compaction at adjacent vines. For this study, chemical and biological soil analyses in the root zones were requested. The analyses did not show any chemical differences between the two samples, but the plant-parasitic nematode analyses differed drastically. At the vigorously growing vine where the roots were not confined, parasitic nematodes only constituted 30% of the population. However at the weak growing vine where roots were confined in the planting hole, 70% of the population was parasitic nematodes and a chemical treatment was subsequently recommended. The secondary negative effects and costs of performing corrections should never be ignored.

PHOTO 10. Side view of the vigorously growing vine on the right, with minimal planting hole compaction and good root distribution. Only 30% of the population is parasitic nematodes.

PHOTO 8. Two adjacent planting holes with weak growing (left) and vigorously growing (right) vines next to each other (top view).

PHOTO 9. Side view of the weak growing vine on the left, with planting hole compaction and parasitic nematodes comprising 70% of the population.

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TECHNICAL YEARBOOK 2023