A wise gardener gives his land a rest.

In a large garden a good plan is to rest one seventh of the area devoted to vegetables and cut flowers every year, and to sow this seventh with a green manure or cover crop which can be dug or ploughed in at the end of the season. A more intensive programme of green manuring, consisting of turning under two, three or more successive cover crops, may be employed to condition poor soil or to rehabilitate an area in preparation for lawn making or landscaping.

But green manuring must be done to a proper pattern or unfortunate results will follow. Because, when crops are sown and are dug into the land in a fresh condition, the soil organisms begin to work on the green plants and break them down. In doing so they exhaust the land of nitrogen, for they have to make use of a good deal of this nutrient to build their own bodies and those of their rapidly increasing progeny. Fresh green manure, therefore, normally causes a reduction for the time being of the available nitrogen content of the soil.
Notable exceptions are when leguminous plants, such as the quick-growing cowpeas, tick beans and annual lupins, are used for green manuring. These legumes have nitrogenous nodules on their roots, so that when they are dug in, the soil suffers no nitrogen starvation. But, even with leguminous plants, undigested organic substances may remain to damage the roots of the next crop.

Because green-manure crops
do not give as quick results as good composted vegetable refuse, they are less frequently used in home gardens than by commercial growers. It takes considerable time to grow a green-manure crop. Then, after it has been dug or ploughed under, six weeks or more elapse before it is properly rotted down and is ready for plant roots. During this period it is better not to plant or sow.

The best results with green manure come when the following conditions are fulfilled:

1. The land is properly drained so that sufficient air is present.
2. The soil is adequately limed so that it is not acid.
3. An activator is applied at the time the green crop is turned under in order to provide additional nitrogen with which the organisms can start work.
4. The soil is warm.
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