Excerpt from Moisture Content and Physical Condition of Soils One particular water content has been given special consideration. It is perfectly well known to agriculturists generally and greenhouse men especially that there is a particular water content (or perhaps a more or less narrow range of water content) differing with each soil at which plants grow best, other conditions being the same. This is popularly known as the optimum water content, and is supposed to be that content from which plants draw most readily their needed supply; in other words, the Optimum water content is supposed to be determined by the physiological necessities of the plant rather than by the physical properties of the soil. There are difficulties, however, for which this view fails to offer sufficient and satisfactory explana tion. Plants can do quite well in soils containing considerably less than the optimum water content, other conditions being favorable. That is to say, there is no decided or sharp falling off in the plant growth corresponding with a lowering of the water content until the drought limit is approached, a limit generally much below the Optimum; and, on the other hand, there is no especial difficulty in carrying some of our common crops to a satisfactory maturity in water cultures. The investigation described in the following pages Shows conclusively not only that physical condition and the several properties on which it depends have an intimate relation with the water content of the soil, but that there is marked accentuation in these properties at a critical water content; and that this critical con tent is identical with the optimum water content. The moisture penetration curve shows a minimum force required for penetration at the optimum water content; the moisture-apparent Specific gravity curve shows a minimum point at the Optimum water content; the curves for evaporation show a marked difference in the rate of evapo ration above and below the optimum water content. It is apparent, therefore, that the true significance of optimum water content is that particular content at which the soil can be put into the best possible condition for plant growth. The plant can then best draw its needed water from the soil because all the other factors making for good growth are also at their best. Moreover, an increase in water content in excess of the optimum generally produces a greater detrimental effect on the plant than a decrease below the optimum. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.