Huddersfield Soils
By John Grainger

THE CONSTITUENTS OF SOIL

ORGANIC MATTER
Organic matter, the remains of earlier generations of plants and animals, makes the greatest contribution to soil fertility of any single factor. This is somewhat strange, for it is possible to grow plants very successfully in a solution entirely free from organic matter. Indeed, the new cult of hydroponics or water culture can make the non-organic desert bloom, and sometimes even bloom commercially. So long as the relatively cheap stores of fertility in soil are used for the growth of plants, however, the presence of organic matter will play a major part in the continuance of such fertility.

It is useful to distinguish between ‘raw humus’ where pieces of relatively undecayed organic matter occur free among the mineral particles, and ‘humus’ where the clay is well advanced and the organic matter is closely incorporated. When a soil containing raw humus is burned, there is a diminution in volume, but no great shrinkage of volume occurs when soil with only humus is ignited.

ORGANIC MATTER AND WATER
Organic matter affects the water-holding power of soils, and this action is conspicuous on sandy soils:

The relative water holding effect of organic matter is not so marked on clay soil:

Continuous pasturage and natural grassland allow the accumulation of organic matter as raw humus in the uppermost layers; cultivation distributes it through a greater depth.

Accumulation at the surface may be a bad thing on grassland, for the ‘mat’ of organic matter thus created holds a large amount of water after rain and does not allow it to penetrate to the deeper layers, where it would be stored for the use of plants. The water held in the surface mat evaporates quickly, and the roots of plants do not grow into the lower layers as they would if more water were available there. There is also an effect upon the vegetation, for only those plants with somewhat aggressive rhizomes or root systems tend to survive, and these are not always agriculturally desirable.

The system of lea farming takes full advantage of this accumulation of organic matter. Short-term rotations of arable land are interspersed with periods of grassland husbandry, so that the stores of organic matter are used for the arable crops and then replenished by the grassland.

ORGANIC MATTER AND CROPPING
The state of decomposition of organic matter is of importance in the successful growth of crops. Carrots, parsnips and the cabbage family do not take kindly to raw humus, and the Finger-and-Toe disease of the cabbage family is aggravated by organic matter. Potatoes are very tolerant of it, but even with this crop the disease Common Scab appears if the organic matter is in the form of raw humus, though not when it is decomposing.

ORGANIC MATTER AND THE PHYSICAL IMPROVEMENT OF SOIL
Organic matter is of considerable importance in the improvement of soil texture, for it causes the fine particles of a heavy soil to form larger masses, which tend to behave like larger particles, and it also provides a colloidal or jelly-like coating for the finer particles of a sandy soil, making them more retentive of plant food and soil water. Organic matter thus lightens the labour of working heavy soils, and improve the cropping power of light land.

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