MULCH, any material kept in a loose con dition at the surface of the soil for the purpose of checking evaporation, conserving moisture, protecting plant-roots or low-growing plants from frost or heat, preventing puddling and washing of the soil, retarding growth in spring, keeping the surface soil open, supplying plant food, protecting fruit or flowers from dirt, and keeping down weeds. The materials most fre quently applied are straw, marsh-hay, leaves, litter and brush; hut the most widely important mulch is the surface soil itself, kept powdery by frequent tillage, given especially after rains when it is desirable to break the crust formed upon the surface. Since mulches keep the soil beneath them moist by breaking the capillary, they are of particular advantage in dry cli mates; but since the vegetable mulches, such as straw and leaves, cannot be used in summer where the land must be cultivated and since they supply hiding places for insects, they can rarely be used advantageously in fruit planta tions, in which they are often also a positive detriment because they encourage the growth of roots near the surface. In climates liable to
extremes of temperature this position of the feeding roots is often disastrous to the crop if not to the plants themselves. Except, there fore, for winter protection, when such seems to be necessary, the soil itself is generally best. But the depth of the powdery layer will depend largely upon the climate, character of the soil, and kind of crop; in arid regions, with light soils, and with deep-rooted plants, the soil mulches are usually deeper than with the re verse conditions.