Undervine soil management in vineyards

Many Australian grape growers are evaluating
the use of traditional under-vine soil management techniques in order to improve soil conditions
and vineyard performance. Traditionally, most Australian vineyards are
managed to maintain a bare under-vine strip. There are many advantages to using a system
like this. The major benefit of maintaining a weed free under-vine area is that there
is no competition with the vines for water and nutrition. Bare soil under-vine also provides
a high level of solar reflection and heat. In some situations, this may protect vines
against spring frost. A clear herbicided under-vine strip is relatively easy to manage and cost
effective to maintain. A bare soil under-vine also comes with disadvantages.
Long term reliance on synthetic herbicides can lead to herbicide resistance in weeds.
It is important to follow a herbicide resistance management strategy to avoid this occurring. Plant roots provide many important functions
in soil. Plant roots provide an important food source for soil organisms including bacteria,
fungi, protozoa, insects and earthworms. Without plant roots, soils are limited in the diversity
of soil biology they can support and this reduces the potential for the natural cycling
of nutrients in the soil. Without plants and with limited soil biological
activity, some soils are prone to surface water pooling especially under drip irrigation.
These soils tend to have poor water infiltration and uneven distribution of soil moisture through
the soil profile. The higher solar radiation and reflection
caused by bare under-vine soils can significantly increase the vine canopy temperature. At very
high temperature this can be detrimental to the fruit and vines. Two alternatives to bare under-vine soils
include: allowing plants to grow under the vines and the use of compost and mulch. Plant roots can penetrate compact soils and
provide a pathway for water to infiltrate. Improved soil structure, moisture and the
addition of a food source make soils more conductive to soil biological activity. However, under-vine plants compete with the
vines for soil moisture and nutrients. If the completion is great, vines may have decreased
shoot growth and yield. This is exacerbated when water supplies are limited. This figure shows the drying pattern of an
under-vine soil with weeds growing in it (the red line) and a neighboring soil without weeds
(the blue line). It is clear that the soil with the weeds growing in it is drier than
the weed-free soil. In this vineyard, despite early season increases in soil biological
activity which was beneficial in the vineyard, the vines growing with under-vine weeds for
four years has a 30% decrease in yield with no improvement in fruit or wine composition. In some cases where vine growth is excessively
vigorous or yield is very high, reductions in canopy growth and yield may have a positive
effect on overall vine balance and improved fruit and wine composition. Changes to under-vine soil management requires
evaluation of the risks and benefits to soil condition and vine performance. Additional
resources to assist your decision making can be accessed at the following websites

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