Soil Cultivation Techniques
Digging. Technically this means turning soil over to the full depth of an ordinary spade, approximately 10 inches. First a trench should be opened across one end of the plot, 10 inches deep and about the same in width. The soil removed is wheeled to the other end. Then a further narrow strip is turned over into the trench, the process being repeated backwards across the plot until the far end is reached, when the barrowed soil is used to fill in the last trench. Care must be taken to turn each sod right over so that weeds or grass are completely covered.
To save barrowing soil over the length of long plots, these are divided longitudinally into any number of convenient sections of even number. The gardener works down one, back up another, and so on, finishing at the same end as that at which he started.
If grassland is to be dug, the turves should be well chopped as they are turned over, otherwise decay will be slow. A dusting of sulphate of ammonia or Nitro-chalk, 2 ounces per square yard, will hasten decay, as will a dressing of well-rotted dung. If bulky manure is to be incorporated by digging, spread it first on the surface at the required rate and then turn it in in the process of digging.
Trenching. This term is used to describe two distinct operations. Full trenching involves digging the soil 3 feet deep and bringing the lowest spit to the top. This is seldom practised, as subsoil is relatively infertile and it is best to keep the richer surface soil on top. This may be done by a special method of trenching as follows: The plot, if large, is divided into strips as for plain digging, but the preliminary trench is at least 2 feet wide. Some gardeners prefer to work with a 3-foot trench, as this gives more room for movement. The soil from this trench is wheeled to the far end of the plot. The bottom of the trench is divided in half and a further depth of 10 inches is dug out of the front portion and carted back. The subsoil so exposed is broken up with a fork. The step of soil left at the back of the trench is turned over with a spade on top of this subsoil, thus exposing a further strip of subsoil to be forked. Now another trench, half the width of the first, is marked out and the top soil is turned right over on top of the step formed by the second-spit soil in trench No. 1. The second-spit soil in trench No. 2 is turned on top of the subsoil exposed in trench No. 1 and the subsoil in trench No. 2 is broken with a fork. Another half-measure trench is marked off and turned over in the same way. This sequence is continued until the. ground is all dug, the last trench being filled with two heaps of soil from the first.
BASTARD OR HALF TRENCHING is midway between trenching and digging and consists in turning over the soil one spade deep and forking the spit immediately below, without actually altering its position.
If manure is to be incorporated with the soil, either by trenching or by bastard trenching, fork it into the second spit as thoroughly as possible and turn a little in with the top spit as described under ‘Digging’, but do not get any quite close to the surface, where it would impede planting or sowing.
Ridging. This is most serviceable in autumn or early winter. The soil is thrown or drawn into steep ridges, the object being to expose a large surface to the beneficial action of wind, rain, frost, and thaw. Two methods are employed. One is to pull the soil into ridges with a draw hoe as described under ‘Earthing Up’. The other is to mark the plot into 3-foot wide strips, each of which is dug separately lengthwise, i.e. starting at one end and working backwards down the length of the strip with narrow trenches. In digging, the centre spadeful is always turned forward, but the left- and right-hand spadefuls are turned inwards to lie on top of the centre one and so form a ridge.
Stripping Turf. If turf on new land is reasonably free from deep-rooting perenial weeds such as convolvulus (bindweed), coltsfoot, dock, perennial thistle, horsetail (equisetum), and ground elder, it may be turned in by digging or trenching and will in time rot and enrich the soil. Dressing with a nitrogenous fertilizer or manure will hasten the process. Very weedy turf or turf containing pests such as leather-jackets, wireworms, and cockchafer larvae is best stripped and stacked for twelve months to rot. The stack may be of any size but will rot most rapidly if in a sheltered, shady place. Dust alternate layers with sulphate of ammonia or fresh soot and powdered quicklime or fresh hydrated lime. The sulphate of ammonia or soot should not be mixed with lime in the same layer.
Drainage. This may be necessary on heavy or low-lying land if surface water lies for a long time. Land drains are of two types, stone drains and pipe drains.
STONE DRAINS may be prepared with any hard rubble, broken clinker, etc. Trenches are cut about 10 inches wide and 18 inches or more in depth, with a fall of at least 1 foot in 20 feet in one direction. The bottom 9 inches of the trench is filled with the stones, clinkers, or rubble. An inch or so of finer rubble or gravel is placed on top. This is covered with inverted turves and the trench is finally filled with soil. All drains should communicate at their lowest points with a main drain, ditch, or large soakaway.
PIPE DRAINS are laid in trenches cut in the same manner. A little gravel, broken clinker, or small rubble is placed in the bottom of each trench. Special earthenware land-drain pipes are laid end to end but not quite touching on this layer. They are surrounded and just covered with small rubble. Inverted turves are placed on top and the trench is filled with soil. Again, all drains must communicate at their lowest points with a main drain, ditch, or soakaway.
A SOAKAWAY is made by digging a large hole, preferably deep enough to penetrate impervious subsoil such as clay and reach more open or stony soil below. This hole should be filled to within a foot of the surface with clinkers, brick ends, or other hard rubble, the last foot being covered with small rubble, turves, and soil as for land drains.
Drainage can often be improved without making land drains by digging or trenching in plenty of strawy manure, sifted cinders, sharp boiler ashes, or coarse sand. In bad cases faggots of bushy wood may be laid in the bottom of each trench as work proceeds. Household ashes are of no use for improving the drainage of soil, as they are too soft and fine in texture.