Manuring And Fertilizing

Cover crops may be said to be supplementary to tillage. In the previous chapter this function has been discussed. It now remains to point out another important function--that of a green manure crop adding humus and plant food to the soil. Not only



do some cover crops add plant food and all humus to the soil, but they tend to conserve these by preventing leaching, especially of nitrates, and they help to render plant food more available by reworking it and leaving it in a form more available for the tree. They sometimes act as a protection against winter injury by holding snow and by their own bulk. They also help to dry out the soil in spring, thus making the land tillable earlier. There are two great classes of cover or green manure crops, leguminous and non-leguminous. A non-leguminous crop merely adds humus and improves the physical condition of the soil. In itself it adds no plant food, although it may take up, utilize, and leave behind plant food in a more available form for the tree's use. But in addition to these benefits, leguminous crops actually add to the soil plant food in the form of nitrogen which they have the ability to assimilate from the air by means of bacterial organisms on their roots.

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Next: Non-leguminous Crops

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