SOIL PREPARATION

SUMMARY PLANT HOLES

• Uneven and/or poor growth of young vineyards is often caused by inadequate plant holes. Sub- tle differences inside and outside the plant holes can result in roots experiencing a potting effect i.e. they cannot grow outside the plant hole. • A potting effect can be created by plant holes with smeared sides, round plant holes and by plant holes in heavy-textured soil filled up with soil of a lighter texture e.g. sand, as well as re-compaction of the loose soil outside the plant hole. • Plant holes should not be dug when the soil is too wet, and they should not be re-filled with mate- rial other than what was removed while digging them. • Roots growing from loose soil in the plant hole to more compact soil outside have to exert pressure to force particles out of the way

through longitudinal growth. If the soil from which the root is growing is not firm enough to support the root section behind the tip, the root will buckle and grow in anoth- er direction. • A disadvantage of round plant holes is the angle of incidence root tips and the side of the hole. The larger the angle of incidence, the easier a root will grow parallel to the soil layer instead of pene- trating it. Square plant holes with uneven sides are the best. • Re-compaction of loosened soil can be overcome by plant holes that are deeper than the compact- ed layer. • Sophisticated grapevine machine planters are available on the mar- ket and will replace the manual planting of grapevines in future. The principles that are involved to prevent root restrictions, however, remain the same.

84 | SPECIAL SOIL PREPARATION STRUCTURES