Agriculture Reference
In-Depth Information
3
The Vine Root Habitat
Root Growth and Soil Structure
3.1
In the deep gravelly soils of the Bordeaux region, Seguin (1972) found vine roots
at a depth of 6 m. Woody “framework roots” tend to be at least 30-35 cm be-
low the surface and do not increase in number after the third year from planting
(Richards 1983). Nevertheless, smaller diameter “extension roots” continue to
grow horizontally and vertically from the main framework. They may extend lat-
erally several meters from the trunk. These roots and finer lateral roots in the zone
10-60 cm deep provide the main absorbing surfaces for the vine. But in soils with
a subsoil impediment to root growth, such as many of the duplex soils in south-
east Australia (section 1.3.2.1), less than 5% of vine roots may penetrate below
60 cm (Pudney et al. 2001). Nor do vines root deeply in vineyards where irriga-
tion supplies much of the vine's water in summer.
Plant roots and associated mycorrhizae (section 4.7.3.2) help to create soil
structure. A desirable soil structure for vines provides optimal water and oxygen
availability, which are fundamental for the growth of roots and soil organisms.
The structure should be porous and not hard for roots to penetrate, allow ready
exchange of gases and the flow of water, resist erosion, be workable over a range
of soil water contents, allowing the seedlings of cover crops in vineyards to emerge,
and be able to bear the weight of tractors and harvesting machinery with a min-
imum of compaction. The quality of soil structure and its maintenance in vine-
yards are discussed further in chapter 7.
The Creation and Stabilization of Soil Structure
We might expect the soil particles described in chapter 2 simply to pack down,
as happens in a heap of unconsolidated sand at a building site. However, if the
sand is mixed with cement and water, and used with bricks, we can construct a
building—a solid framework of floors, walls, and ceilings. This structure has in-
ternal spaces of different sizes that permit all kinds of human activities. So it is
with soil. Vital forces associated with the growth of plants, animals, and mi-
3.1.1
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