SOIL PREPARATION

tillage and planting density instead of the genetic traits of the rootstock. In a comprehensive analysis and review of grapevine rooting systems, Smart et al . (2006a) confirmed this conclusion. Their studies, that included more than 200 trench wall root profiles and approximately 40 different species and hybrids of Vitis and Muscadinia, suggested that soil layers impeding root penetration, the presence of stoniness and gravel lenses and depth to the water table have a greater effect on depth of root penetration than genotype. This applies even in deep fertile soils. Assessment of grapevine root distribution in existing vineyards can, therefore, give an excellent indication of which type of soil preparation would be necessary when vineyards have to be replanted. Similarly, root distribution will clearly show how effective soil preparation was before planting (Figure 4.1).

FIGURE 4.1: Good root distribution in a vineyard after effective deep soil preparation. Root ends were painted white for better visibility (Photo: ARC Infruitec-Nietvoorbij).

48 | ROOT RESPONSE TO SOIL CONDITIONS