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Jul
15

Growing Salad in Coir

Article taken from The Commercial Greenhouse Grower, written by Robert Harris

Environmentally friendly, cost effective and easy to manage - three key reasons why Wight Salads, the UK's biggest independent tomato grower, has switched all its conventional production into coir over the past five years.

The move reflects a national trend. After a slow start - coir first appeared in the early 1990s in salad crops under glass - the substrate is becoming a more common sight under tomato, pepper and cucumber crops.

Wight Salads uses coir on 20ha of specialist tomatoes grown under glass on the Isle of Wight. Cherry, baby plum, beef and on-vine tomatoes are aimed at top-end outlets such as Waitrose, M&S and Sainsbury's.

"We were growing these crops on rockwool until five to six years ago," says Paul I Howlett, the company's head of agronomy. "The main reason for switching was that we had invested a lot of money in a complex composting facility for our organic tomato production, which makes up about a quarter of our UK business.

"Coir comes from a renewable source and is fully biodegradable. We can now reuse it in our organic system. We had previously been sending rockwool to landfill, knowing it would never break down. That was very costly. Rockwool also takes a lot of energy to manufacture - none of this sat comfortably with our company ethos. Supermarket customers are putting more pressure on suppliers to be more environmentally friendly. Mr Howlett believes coir's environmental benefits fit perfectly with that philosophy, especially as those benefits extend back through the manufacturing process too.

"I visited Sri Lanka in February and was immediately impressed by the way the coconut sector was managed. Everyone involved in the industry pays a levy to raise research and development funds, which has resulted in effective pest disease control programmes and the introduction of new varieties. I visited several plantations and came away convinced of the sector's sustainability."

The ethics of the process also stacked up. "Workers are treated fairly, there is a no child labour policy and pay is above average and growing. I could see the whole process was sustainable and that people were treated in the right way," says Mr Howlett.

The visit also confirmed his earlier trials work that he was getting a top-quality product. "Our initial concern was that yields would fall as we'd been told coir was more difficult to manage for optimum growth. We've not optimum growth. We've not seen any problems."

Botanicoir has been working closely with Wight Salads to develop different blends. The product has excellent water and nutrient retention properties and provides plenty of oxygen to roots. It also drains well and has good structural integrity, he adds. "We wanted a company supplying best company supplying best quality material, and we have that."

Independent consultant Wim van Wingerden of ClimateAnalysis.nl agrees there is no difference between the yield and quality of a crop grown in rockwool and one grown in coir.

About 40% of his pepper and Cucumber growers in the Lea Valley in Essex have already switched, and he expects that percentage to climb.

"Coir can compete on price. And there is more environmental pressure to switch to coir, which also gives growers an advantage over the competition. Coir is well proven in North America, Canada and in other countries of Europe for these reasons."

Some subtle differences in nutrition are required during the first few weeks of growth, Mr van Wingerden explains. "With coir it is important to adjust the recipe. Potassium is already available in the slabs, so you need to reduce that and increase calcium in the recipe at the beginning of the season.

"You also need some extra trace elements, such as I manganese, boron and iron, as you can get a little fixation to the coir. I use slightly higher levels anyway regardless of substrate as it is easy for plants to become deficient."

Irrigation management is easy, if not easier, than with rockwool, he maintains. "I prefer a drier slab as this gives more flexibility when it comes to manipulating plant development and growth.

"Unlike rockwool, which is almost impossible to rehydrate if it dries, coir can be rewetted easily, which helps the irrigation management. And, if it is overwatered, a drier slab will still readily drain so you can get back on track quickly."

Kalum Balasuriya, managing director of Botanicoir, says coir is becoming the substrate of choice. "It is easy to manage, and by blending different particle sizes we now have crop-specific coir blends to suit varying needs with regards to rooting, moisture levels, nutrient requirements and climate."

Up to 40% of the UK's glasshouse salad crop growers are now using coir, he maintains. "As environmental pressure builds and more growers become aware of the benefits, I believe that figure could rise to 70-80% within, five years."

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