Several frosty mornings about a week ago dealt a deathblow to the blooms on an early flowering rhododendron and four azaleas in my garden.
Despite that disappointing setback, Jack Frost is usually a farmer's friend as he kills off crop pests like slugs and fungal diseases during the winter. He also helps to make a fine seedbed in the spring, by breaking down clods in ploughed land.
Frost is also a chef's friend as it improves the taste of neeps and Brussels sprouts. According to old farming lore, a touch of frost on those two vegetables stops them giving you wind after you have eaten them.
Mind you, while late frosts really only affect potato and fruit growers in Scotland, they can be a real problem for arable farmers in northern Europe and parts of Canada.
Many early potato growers overcome the problems caused by late frosts by covering the potato drills with plastic sheets that create a greenhouse effect for their crop. The sheets increase the temperature of the soil by reducing the loss of radiant and convective heat. Plastic sheets also help to control weeds and pests as well as reducing water loss. All those effects help to increase yields and get the crop to market earlier in the season when prices are higher.
Ancient farmers in Peru developed an ingenious system of raised beds called waru-warus in the high plains of the Andes about 3,000 years ago to produce bumper crops of potatoes in the face of floods, droughts and the killing frosts common at altitudes of almost 4,000 metres.
The system consists of platforms of soil, rather like Scottish run-rigs or "lazy beds", surrounded by ditches filled with water. That water absorbs the sun's heat by day and radiates it back at night, helping to protect crops against frosts.
The combination of raised beds and canals has remarkably sophisticated environmental effects. On the raised beds, night-time temperatures may be several degrees higher than the surrounding region. During droughts, moisture from the canals slowly ascends the roots by capillary action, and when there is a flood any excess runoff is quickly drained away.
The waru-waru system also maintains its own fertility. In the canals, silt, sediment, algae and plant and animal residues decay into nutrient-rich muck which can be dug out seasonally and added to the raised beds. Yields of potatoes from waru-warus regularly outstrip those from chemically fertilised fields.
Scottish farmers have also developed an ingenious method to overcome our colder climate and grow good crops of maize for silage. It involves plastic sheets to warm up the soil, but unlike the ones potato growers use, that have to be removed from the crop, maize growers mostly use a bio-degradable plastic that stays on the ground with up to 90 per cent of the film breaking down in the first season and 100 per cent degraded within two years.
Film systems optimise growing conditions for the maize plants, which thrive in ambient temperatures of 20 degrees C.
The technology used to make film for maize growing is advancing rapidly and the latest products are starch-based. They are designed to be strong enough to create a protective layer, while also allowing the plant to break through the material.
Some films incorporate pinholes, in order to release trapped air and keep the material in close contact with the soil after sowing. These holes also help to prevent excess heat build-up later in the season.
While a maize crop can grow well above your head, the really nutritional part of the crop is not the impressive stems and leaves but the energy-rich, corn-on-the-cob. Farm-scale trials have shown that in a bad growing season, maize under film can be worth considerably more than maize grown conventionally, when both are compared in relation to the energy each crop produces, showing a good return on the additional £120/acre it costs to grow maize under plastic.
The later-maturing varieties grown under film will normally produce a better quality cob, but to achieve this they will need a relatively long grain-fill period between cob set and harvest. Plastic film can facilitate a 90-day grain-fill period, nearly double that for a typical 50-day period for maize grown conventionally.
Conventionally-grown crops will often reach greater heights than maize under film. This can be deceptive because in reality, the crop grown in the open has deposited most of its energy into stem and leaf production, rather than grain.
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