Farmers on film

Responsible for feeding hundreds of millions of people in Europe and several billion worldwide, farmers are pragmatic by necessity. They get straight to the root of an issue and choose methods they feel best benefit their crops. This is part of the reason why they have relied on agricultural inputs for decades. These products protect crops against harmful insects and diseases, improving their yield. As a consequence, for a good fifty years, farmers (and consumers) were under the impression that the optimum solution had already been found. At the dawn of the 21st century, the warnings given by environmental movements caused the public to question this type of agriculture.

Agricultural inputs were suspected of polluting the water table, damaging biodiversity and, in the medium term, killing the soil. The term “sustainable agriculture” was coined, and authorities began to tighten up the use of crop protection products. As for farmers, they quickly became aware of what was at stake and started looking for alternative solutions to maintain their yield. One of these solutions was agricultural plastics.

Polymeric mulch film captures moisture and protects plants from weeds. Less water, fewer agricultural inputs… the perfect recipe for sustainable agriculture.

Polymers: an alternative crop protection product

Before we go any further, it’s useful to know exactly what agricultural plastics are. They mainly refer to plastics used for mulch, silage and haystack films, greenhouse coverings, protective nets for tree crops (fruits) and horticultural crops (vegetables), various twines and, to a lesser extent, irrigation hoses. The entire market represents 720,000 tonnes per year in Europe, or 1.5% of the overall demand for plastics. Films alone represent over 75% of agricultural plastics.

Different forms of agricultural plastics serve many purposes for farmers, in particular by improving yields while eliminating the need for certain crop protection products.

Polypropylene and high and low-density polythenes together constitute nearly 99% of agricultural plastics. These are sturdy, well-established polymers that we know how to recycle. Biobased or biodegradable polymers such as PLA or PBAT (polybutylene adipate terephthalate) also make up part of the overall agri-plastic demand. Although they only represent a small proportion of production (around 1%), they’re gaining ground year-on-year. (see our interview)

Sustainable agriculture: agri-plastics could give farming another bite of the cherry

First, let’s take a look at some of the functions of these plastics, especially those used in mulch films. Every gardener is familiar with the technique of spreading a layer of natural or synthetic material on the ground around their plants to mitigate the effects of weather – by limiting evapotranspiration, for example – and prevent the spread of weeds. In the past, farmers used straw or wood chips, though this practice isn’t so common today, primarily for reasons of productivity. Using this technique on vegetable crops spanning several hectares requires a considerable workforce. Today, they tend to use plastic films that can be laid mechanically. Mulching helps increase the temperature of the soil and retain moisture, promoting root development and plant growth. This simple polymer layer means that crops require less water, helping conserve this resource, which is so valuable, especially in the horticultural regions of southern Europe. From an ecological standpoint, this is a real benefit! It’s not the only one either: these films naturally protect crops from weeds and other pests, such as certain strains of disease-carrying fungi. This results in fewer crop protection products contaminating the soil. Plus, in instances when the weather suddenly changes, these agricultural films make it possible to reduce thermal shocks that can be detrimental to crops. 

Mulch films and mini tunnel films can be laid and deposited mechanically. Some are designed to biodegrade after a few months in the soil.

Mulch films are not just enhanced tarpaulins. To make them easy to lay, they need to be lightweight and strong enough not to tear. They’re usually made from polythene and are extremely thin – less than 100 μm thick, or 1/10th of a millimetre. Though polythene could be made even thinner, this seems to be the optimum thickness for mulch films. Any thinner, and they would become more fragile and much more delicate to handle during recovery.

 Wrapping crops in cotton wool

When it comes to protecting crops, agricultural polymer films are becoming essential. By using plastics, farmers can better control the ever-changing nature of the weather. In addition to mulch films, tunnels are often used. These are films suspended a few centimetres from the ground to protect crops from bad weather. Thunderstorms, hail, wind, downpours… farmers can rest easy knowing that the weather won’t compromise their production. Twice as thick as mulch films, tunnel films are much more hard-wearing. White or transparent, they amplify the heat and light required for proper crop development. Since they’re suspended, these polythene tunnels also allow rainwater to directly support the crops beneath them via a system of channels, avoiding any risk of mildew. Polythene has long since proved its worth, and film manufacturers are now beginning to offer EVA (ethylene vinyl acetate), a polymer with increased elasticity that makes it easier to tension during installation. 

Polythene protective nets are the ideal solution for protecting tree crops, such as apples, from hail and other violent storms.

 Lesser known but equally impressive, tree nets are also used to protect fruit trees from hail, insects and birds. Made of high-density polythene, they’re UV resistant and have a lifespan of a good ten years. Anti-insect nets have finer meshes and are made from polyamide or PLA yarn (an industrially compostable polymer). Depending on their composition, they will vary in weight, mesh hole size, lifespan and breathability. On top of protecting crops, farmers have also seen that the nets aid the formation of a microclimate favourable to crop growth.

Polythene: giving nature’s larder a shelter

It’s not unusual to come across mounds covered in huge plastic tarpaulins whilst walking in the countryside. This might be a bit of a visual eyesore, but there’s a reason why a polythene tarpaulin is there.

It serves a key function for livestock farmers since it allows them to store fodder and grain for their animals. Stored this way, protected from water and light, the fodder stays fresh and retains its protein content, so livestock can continue feeding on natural produce in winter. This means farmers don’t need to enhance their livestock’s diet with food supplements that aren’t always popular amongst consumers. Simple to manufacture, these tarpaulins can be made of polythene (PE), whether recycled or otherwise.

Silage tarpaulins, usually made from polythene, might not look the best. However, they do perfectly conserve the grain that will be used to feed cattle in winter.

  If they’re recycled, they’ll be a little thicker and consequently a little more complicated to handle, though their efficiency will remain the same. Until recently, farmers used to use old tyres to weigh down these tarpaulins to prevent them from blowing away in strong winds, though this technique is gradually being abandoned. On top of its obvious lack of visual appeal, tyre degradation presents a food risk for livestock. When old tyres break down, they can release iron filings. Instead, high-density PE bags filled with sand or gravel are now placed around the tarpaulin to keep it in place.
The same types of films are used to wrap bales for exactly the same reasons. An added benefit is that once wrapped, the bales are much easier to handle and don’t break down during transportation.

Greenhouses and polyfilms: two peas in a pod

For a long time, agricultural greenhouses were made of glass. However, this fragile, expensive and heavy material requires a substantial framework to support it. Though glass is still used for small, privately owned greenhouses, polycarbonate is now systematically replacing it. Equally transparent and aesthetically appealing, this polymer is also shatterproof, lightweight and very easy to handle when it comes to assembling the greenhouse.
Agricultural professionals now use polythene covers to protect their crops. Lightweight and easy to assemble, they come with various advantages! Different additives can be added to the polythene depending on the required function. Consequently, some of these films have anti-UV properties, notably absorbing UVB, which is responsible for the germination of certain fungi that can devastate crops. They can also come with an anti-dust coating so as not to block the transmission of light or absorb the infrared radiation emitted by the plants under the greenhouse, limiting temperature increases. Conversely, they can be enriched with a mineral filler or an EVA copolymer (ethylene-vinyl acetate) to limit heat loss at night by capturing the infrared radiation reflected by the ground. Depending on the region they’re intended for, they can also be made more or less opaque in order to obtain ideal light levels for horticultural crops.

Depending on the additives used, polythene greenhouse films adapt to the climatic conditions of a given region