Page:The Olive Its Culture in Theory and Practice.djvu/61

Rh olive, and so promote its growth; but for this very reason require that the trees should be frequently manured in order to obtain an annual product. It is the want of nourishment in the ground, that causes the olive to fruit only every other year, or every third year.

An irrigated soil loses its fertility quicker than one that is not watered; so, where irrigation is practiced, it is necessary to frequently manure. In general, it may be said that the olive requires the same kind of soil as the vine, and in proof of that we often see them grown together. Excessive moisture is prejudicial, and also in a dry, hard soil the tree contracts, splits, and leaves the roots gorged with sap. The most favorable soil is an open, loose and fairly fertile one, and should be of at least a yard in depth to give the roots opportunity to extend themselves.

The olive is fond of a chalky soil, that is, one largely made up of lime carbonates. The carbonate of lime is indispensable to vegetable life; and it is noticed, that the oil from olives grown on a calcareous soil, is better than that from a soil lacking in this element. Chalky soils are cold, because they do not easily absorb the heat of the sun. For the same reason red soils are warm, absorbing and retaining a great degree of heat. The best soil for the olive is that in which lime predominates; and where silica exists, and there is no lack of clay. Such a soil would give passage to moisture, and offers no obstacle to the extension of the roots, and at the same time has consistency enough to sustain the tree and preserve the elements of nutrition. The oxide of iron exists in all soils, but where it abounds, the red color declares it. It is favorable to the growth of the olive, particularly in cold regions.

Suppose two adjacent pieces of ground in such a locality; on the red soil the olives will ripen, whereas on a light colored one they will not.

Liebig says, that when at the time of flowering of any vegetable, the soil abounds in phosphates, the fruit sets well, and is started on its road with every advantage; and on the contrary, if these are