Net surplus

Sheltering the world from hunger with shade net farming

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Between now and 2050 it is estimated that the world’s population is likely to rise from 7.3 to 9.7 billion. In order to feed everyone, agricultural role players will need to solve problems such as poor and seasonal crop production and damage caused by sunburn, hail, insects and drought.

Shade net is an option that can be implemented fairly quickly to not only overcome many of these impediments, but to also increase production, yield and income. Many farmers have already made the choice to erect large-scale shade net structures and are reaping the benefits from it.

In hot climates vegetables and cut flowers are grown under shade cloth to reduce heat and light intensity. With the help of science, innovative light manipulation and UV management, photo-selective colour netting create an environment that can be manipulated into optimal growing conditions for crops to flourish in

In the short-term, shade net structures boost farmers’ profits, by cutting costs and increasing their quantity and quality of yields. Over the longer term, it may even contribute to the solution of feeding the world’s growing population.

Protect and enhance

A well-constructed shade house can provide the grower with a protected microclimate, ideal for seedlings, vegetables, cut flowers and pot plants. In hot climates, vegetables and cut flowers are grown under shade cloth to reduce heat and light intensity. With the help of science, innovative light manipulation and UV management, photo-selective colour netting creates an environment that can be manipulated into optimal growing conditions for crops to flourish in. Shade netting can also help benefit water efficiency as it reduces the amount of evaporation from free water surfaces.

By using the correct mesh size to manipulate air movement through the shade house the user can control the humidity and therefore also the transpiration rate.

Shade net can be used to manipulate plant growth, for example to get stem length, use a net that allows far-red wavelengths through. This will force the plant to stretch to the light. White shade net or a combination of black and white has been used very successfully on various vegetables, especially when grown hydroponically. Light spectrums can help determine the right colour and percentage for your crops.

It is very important to note that there is no universal shade net to manipulate light. Each plant has its own unique requirement, and each region and crop has its own challenges.

A well-constructed shade net structure will provide protection against adverse weather conditions. It is imperative that some components relating to the structural elements be taken into consideration when planning its design.

Tensioning the net

The net should always be tensioned in the length first, then the width. It must be neatly and tightly stretched, but not too rigidly. If the net is not tensioned tight enough, abrasion may occur on the cross cables and the net could be torn by wind. However, if the net is too rigid it may be mechanically damaged and even possibly tear.

It is recommended that nets be tensioned mechanically with a chain and block and tackle. As this is a complex procedure, they suggest that customers contact their sales staff for an in-depth explanation. It is important to remember that the bigger the surface area between the poles, the riskier the ratio becomes between the surface area in relation to the circumference around each pole. The poles should therefore not be planted too far apart.

The most appropriate time to erect nets is at the coolest time of day. Net not tied securely may shrink up to 10% when exposed to heat for a short period.

Anchors

The anchors are the most important component of the structure. Anchor failure will cause the structure to collapse. In 95% of structures with storm damage, it is the anchors that break, pull out or move.

The anchors should preferably be installed at an angle of 45° or less with the horizon. At 45° a force of 3.5 ton is exerted on the anchor when the tension on the top stay wire is 2.5 ton. Should the anchor be planted at 60°, the force on the anchor increases to 5 ton with the same 2.5 ton tension on the top stay wire.

Anchors should be planted at least 1.5 m deep. It must be able to handle a force of ± 7 tons in order to carry the weight of the structure and withstand the strength of the wind against the sides of the structure.

The wind force against the sides is determined by the density of the net and height of the structure.

The soil around the anchor must be compacted layer for layer using rock or stone for optimal compaction. Where necessary, the anchor should be buried under the wall (undisturbed ground) so as to prevent it lifting against the wall in wet conditions. ¢

Article supplied by Knittex.

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