Benefits of good shelter

Press, 20 April 1982, Page 25

Benefits of good shelter

The productivity. of many horticultural crops can increase with the provisions of effective shelter.

Sensitive crops, such as pip fruit, stone fruit and berry fruit, need good shelter, but all horticultural crops would benefit by protection from the wind.

To be of maximum value, however, an effective shelter belt must more than compensate for both the production lost from the space occupied by the trees, and the cost of the establishment and maintenance. The warmer conditions created by adequate shelter prolong the growing season and crops are often earlier. There are potential fuel savings with heated glasshouses if they are suitably sheltered because cool winds remove much of the, heat produced. Without shelter, wind can damage stems, leaves, flowers and fruit, reducing growth and subsequently the yield. Wind also increases the loss of water from the

soil, placing plants under moisture stress.

The cooling effect of the wind can also slow the growth rate. Low temperatures during blossoming can retard bud growth and restrict the growth of the pollen tube, preventing fertilisation. Although the benefits of shelter on crop productivity far outweigh any disadvantages, there are certain drawbacks to be considered.

Insect pests may be harboured in the trees, and the shelter may be an alternate host for many of the crop diseases. The shelter will compete with the crop for water and nutrients, and crop growth may be checked by the retention of excessive moisture, and. the shading effect of the shelter.

The height of a shelter belt determines its wind reduction. The trees deflect the wind upwards causing a reduction in windspeed on the leeward side. The original windspeed develops again at a distance from the belt of

about 40 times the height. Good wind shelter is provided to a distance of 10 to 15 times the height of the shelter belt.

The shelter belt should not be too dense, with about 40 to 50 per cent permeability. A solid barrier may cause wind turbulence on the leeward side, resulting in crop damage. Another important feature in the design of shelter is that it must be continuous. If

spaces exist at either the base or along the length of the shelter the, wind will funnel through with increased speed, so there is the likelihood of greater damage. The efficiency of a shelter belt depends on the uniformity of the trees. When establishing a shelter belt, care must be taken to replace anyfailed trees, and about 80 per cent weed control is desirable up to the first two years after planting.