Sunlight and water are the two main ingredients for successful farming, without which crops cannot grow.

Photosynthesis, that wonderful chemistry that enables plants to store the energy from the sun as sugars, starch and oils is the foundation of all food chains. Plankton in the sea, and grass, grain and all other crops on land are all created by the marvel of life-sustaining photosynthesis.

The sun is literally the creator of all life and was worshipped by many ancient societies. Sunlight is so essential to life that the bible teaches us that light was the first thing to be created.

It is fair to say that all farmers harvest the sun's energy in the form of grain, roots and fruits, which also produce meat and eggs. Ruminant animals like cattle and sheep can also be fattened by the starch in grass, or produce milk from it.

Daylight is important to farm animals, and cattle don't really thrive until the turn of the year. The main reason for that is that as the amount of daylight increases, so does their appetite. Farmers use artificial light to maximise growth rates in other types of animals like pigs and poultry, as well as to increase milk production from dairy cows.

Free-range poultry, above all else, respond well to longer hours of daylight. Like all birds, they are genetically programmed to lay their eggs in the spring in response to the increasing amount of daylight. That way their chicks will hatch out in warmer weather when there is an abundance of insects to feed on.

One of the techniques poultry farmers use to increase egg production during the winter months is to provide more artificial light to compensate for the shorter hours of daylight.

Farmers, like everyone else, also respond to sunlight. Seasonal affective disorder (SAD), or winter depression, is a well-known medical condition caused by a shortage of light.

We all need sunshine to produce vitamin D. Research has suggested that Scotland's high incidence of multiple sclerosis could be down to a shortage of sunlight in the winter.

In recent decades farmers have turned to harvesting the sun's energy in the form of bio-fuels like oilseed rape that can be crushed to produce oil that is converted into bio-diesel. There are also huge plants around the world that convert grain and the sugar in sugar cane into ethanol for fuel. A recently new technique is to grow crops to be harvested whole for processing in anaerobic digesters to produce methane for heating systems, or more commonly to fuel electricity generators.

I have always argued that it is wrong to use arable land to produce fuel when millions around the world go to bed hungry every night, or die from hunger. That seems to me to be obscene.

A better way of harvesting the sun's energy, that is becoming increasingly popular, is to use solar panels sited on less-productive land to produce electricity to sell into the national grid. There are now some vast solar arrays, as they are called, in sunnier parts of the world like Spain - but there are increasing numbers of more modest ones in the UK. More commonly, farmers are fixing solar panels to the roofs of large farm buildings to provide electricity for their own needs, with the surplus sold into the grid.

Indeed more and more farmers and landowners are turning to the generation of renewable energy as an alternative source of income.

Wind turbines sited on exposed, windy hills are appearing all over Scotland in response to the good returns that can be made. Developers pay an annual income to the landowner of around £25,000 for each large turbine. So a group of 10 should yield the landowner about £250,000. No wonder there are so many applications to construct wind turbines on poor hill land that until recently had little value.

A recent survey by WWF Scotland revealed that electricity generated by wind power has leapt by 15 per cent in the last year, enough to supply the electrical power of nearly 4 in 5 Scottish households. In fact, the survey found that wind turbines generated enough electricity to supply 100 per cent or more of the needs of Scottish homes in 8 out of the 30 days of April.

Despite all these innovations, traditional farming that harvests the power of the sun in the form of crops and livestock products remains the main activity.