Apparatus required.
Plot experiments, hoeing and mulching. Thermometer. Soil sampler (Fig. 42, p. 88). This tool consists of a steel tube 2 in. in diameter and 9 in. long, with a slit cut along its length and all the edges sharpened. The tube is fixed on to a vertical steel rod, bent at the end to a ring 2 in. in diameter, through which a stout wooden handle passes. It is readily made by a blacksmith.
Farmers and gardeners throughout the spring, summer and autumn, are busy ploughing or digging, hoeing or in other ways cultivating the soil. Unless all this is well done the soil fails to produce much; the sluggard's garden has always been a by-word and a reproach. In trying to understand why they do it we must remember that plant roots need water, warmth and air; if the soil is too compact or if there is too much water the plant suffers, as we have seen.
Fig. 40. After harvest the farmer breaks up his land with a plough and then leaves it alone until seed time
One great object of cultivation is, therefore, to prevent the soil being too compact and too wet. After the harvest the farmer breaks up his ground with a plough and then leaves it alone till seed time (Fig. 40). A gardener does the same thing with a fork in his kitchen garden—he cannot very well elsewhere, or the plant roots might become too cold. If there is frost during the winter both farmer and gardener are pleased because they say the frost "mellows" the ground; you can see what they mean if you walk on a frosty morning over a ploughed field. The large clods of earth are no longer sticky, they already show signs of breaking up, and if they are not frozen too hard can easily be shattered by a kick. The change has been brought about in exactly the same way as the bursting of water-pipes by frost. When water freezes it expands with enormous force and bursts open anything that confines it; water freezing in the pores of the soil forces the little fragments apart. This action is so important that further illustrations should be looked for. A piece of wet chalk left out on a frosty night often crumbles to pieces. It is dangerous to climb cliffs in the early spring because pieces of rock that have been split off during the winter frosts by the expanding water may easily give way. Frost plays havoc with walls built of flints and with old bricks that are beginning to wear. If there are several frosts, with falls of rain or snow and thaws coining in between, the soil is moved about a good deal by the freezing and melting water. Bulbs and cuttings are sometimes forced out of the ground, whilst grass and young wheat may be so loosened that they have to be rolled in again as soon as the weather permits. When the ground has been dug in autumn and left in a very rough state all this loosening work of the frost is very much helped, because so much of the soil may become frozen. If in spring you dig a piece of land that has already been dug in autumn, and then try digging a piece that has not, you will find the first much easier work than the second in all but very sandy soils.
A little before the seeds are sown, the soil has to be dug or cultivated again so that it may become more level and broken into smaller pieces. The farmer then harrows and the gardener rakes it, and it becomes still finer. Very great care is bestowed on the preparation of the seed bed, and it will take you longer to learn this than any other part of outdoor gardening. The soil has to be made fine and dry, and no pains must be spared in getting it so.
When at last the soil is fine enough the seed is put in. But it is not enough simply to let the seed tumble into the ground. It has to be pressed in gently with a spade or a roller, not too hard or the soil becomes too sticky. Fig. 41 shows this operation being carried out on the farm. Then the soil should be left alone.