SOIL PREPARATION

CHAPTER 4

SUMMARY ROOT PRUNING

• The partial cutting of roots deprives the grapevine of access to water and nutrients. Root pruning, how- ever, stimulates formation of new roots close to the severed ends. As a consequence, root pruning can either curb excessive vegetative growth or increase performance of declining vineyards when such a decline is due to compaction. The loosening of the inter-row area and the inevitable pruning of roots, to improve performance, should only be done when poor performance is due to soil compaction. • Grapevine response to root prun- ing depends particularly on timing and severity of pruning. In South Africa root pruning is recommend- ed after harvest in autumn to im- prove grapevine shoot growth and yield of vineyards that decline as a result of soil compaction. Optimum irrigation and fertili- sation programmes should be maintained after root pruning in order to enhance root regenera- tion and growth into the loosened soil. Root pruning should be done on one side of the vine row in the first year, followed by ripping the other side of the row in the fol- lowing year. This process should not be repeated more regularly than once in five years, and only if re-compaction dictates it.

• The presence or absence of roots in the inter-row area will also af- fect grapevine response to root cutting. A decrease in canopy size and yield can be expected follow- ing ripping of the inter-row when a significant number of roots were already present prior to root prun- ing. The longevity of root pruning benefits is still uncertain. • New results showed a large ben- eficial effect on grapevine perfor- mance when root pruning was combined with the incorporation of compost. Loosening of com- pacted soil between vine rows should be done to a depth of 50-60 cm. An excavator is the ideal implement, especially when com- post is to be incorporated into the soil. Rippers will also accomplish the task, but cannot incorporate any ameliorant into the soil. • Australian results point to root pruning at bud burst to reduce ex- cessive shoot growth. Root pruning on both sides of vine rows at bud burst will achieve the desired re- duction in excessive shoot growth, but yield will also decline simulta- neously. It is therefore doubtful whether root pruning can be rec- ommended as a general commer- cial practice to control vegetative growth on deep fertile soils.

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