For most smallholders working with low-power tractors, if the soil to be worked is heavy, after the first rains is a good time to plough.
Many smallholders make the mistake of attempting to use their ploughs as subsoilers (eg rippers), ie, ploughing too deep. This results in the plough digging in, with the tractor straining and digging in itself. At best all this achieves is a lumpy, uneven result. At worst it will result in tractor strain, broken linkages, etc, or even injury and death as the tractor flips over backwards upon itself.
So let’s first make the distinction between subsoiling, or ripping, and ploughing.
Subsoiling takes place with a long, thin tine, and should, if done properly, break up the soil at a depth of 30cm or more. The ideal effect is achieved in a very slightly damp soil which “shatters” around the tine as it passes through. The “rip” in the earth left by the tine enables air, moisture and nutrients to reach deep into the soil, and the loosened shattered soil allows easier penetration of plant roots.
In normal conditions subsoiling need not be done every season. It is almost a “once-off” to prepare virgin (ie, unworked) ground for crops. The exception is very heavy, clay soils which easily become compacted. In such a case a seasonal rip may be beneficial for root and nutrient penetration.
Having decided whether the soil needs subsoiling or not, let’s turn to ploughing, which requires some skill and which, when you get it right, will give you a deep sense of pride and achievement. Many things on a smallholding afford one great pleasure, and one of them is seeing a perfect “throw” off the shares of one’s plough as one thunders up and down one’s field on one’s tractor. So, if good ploughing takes skill, it also takes preparation.
In most cases one’s small tractor (that’s small in power, not small in size) will be able to handle no more than a two-share plough, with the choice between whether to use a disc plough or a mouldboard plough being made on the basis of one’s soil type. Many believe discs are better suited to soft, sandy soils. If used in harder, heavier soils the discs tend to ride up to the surface and the plough merely bumps along the crust of the earth, rather than digging in. Digging in to heavier soils is better achieved, therefore, by the toe of a mouldboard plough. If using a two (or more) disc implement it is important to ensure that both shares descend into the soil to the same depth. Otherwise one will finish up with furrows of different depths and an uneven result.
To ensure the plough is horizontal, hitch it to the tractor and allow the implement to descend slowly to the ground on a flat surface, noting which disc or share touches first. Turning the centre bottle screw of the three-point lift will raise or lower the rear of the implement until you have both discs touching simultaneously.
The object of ploughing, as stated above, is not to work the soil to any great depth but merely to turn over the top layer of soil and vegetation, ie, to flip it upside-down. In this way the leaves and stems of anything growing are upended and buried, while the roots are exposed. Thus, with exposed roots and buried leaves and stems the plant dies, later adding nutrient and fibre to the soil as it decomposes.
The layer of soil turned over should also be sufficiently deep and soft to allow penetration by whatever seed planting method one uses after ploughing. Thus, ploughing with a small tractor should result in a layer of not more than 10 or 15 cm of soil being flipped. Any deeper and the plough will dig in.
And, the direction of travel of the tractor and plough should ensure that the ploughed material is thrown over the previously ploughed furrow.
Thus most fixed ploughs throw to the right. So with a conventional fixed plough one will always be running to the left of the most recently worked soil, with the right hand wheels of the tractor running in the leftmost furrow. In this way the front share will make its throw into the previously ploughed furrow and the rear share into the furrow made immediately before by the front share. (On bigger ploughs a third share would make its throw into the furrow of the second, and so on).
The efficiency of the throw is affected by the state of the soil, the angle of the share and the speed of the tractor, particularly the latter two.
If the share is too upright or the speed too slow the soil will merely be cut away from the ground, will lift up on the share and flop back into the furrow like a long piece of soft pasta. So plough angle and speed are the key. But be warned: Speed kills. Ground engaging implements should never be used in anything other than first gear on a small tractor.
The angle of a plough is set adjusting the levelling box (the screw device on one arm of one’s three-point lift) and experience will show you at what angle to set the plough for your soil not to achieve a pasta result.
But there’s another component one can sometimes adjust. Some ploughs have their hitching pins mounted eccentrically on a bolt-on bar (see image below), held in place by two u-bolts. By loosening the u-bolts and rotating the bar one can raise and lower the hitching pins, and also swing the angle of the plough to the left and right.
Swinging the back of the plough to the left, ie rotating the bar so that the right hand hitching pin is further forward than the left hand one, will increase the width of the material ploughed with each pass, but will open up a space between the two shares. It may also increase the possibility of the pasta effect because the angle of the plough share will be flatter, thus exerting less throwing force on the material being turned. So while this may cause less strain on a small tractor it may in reality be counterproductive.
Swinging the back of the plough to the right will reduce the width of the ploughed material, will result in the efforts of the two shares overlapping and will make a more forceful throwing angle.
After ploughing, and especially in heavy soils, it is usually necessary before planting to run a disc harrow over the ground. This has the effect of leveling the soil, breaking up clods of earth and cutting up the ploughed plant material, which aids in quicker decomposition and helps to prevent regrowth.
Be aware, however, that apart from taking time and using fuel, each pass of the heavy wheels of the tractor compacts the soil particularly at depth, negating any efforts one has made in subsoiling.
This is part two in a six-part series on Cultivation. For more, click here.