After examining the conditions in the forest, a study should be made of the soil in some cultivated field. It will be found that in the field the soil has lost many of the marked characteristics noticed in the woodland. In walking over the field, the soil will be found to be hard and compact. The surface may be covered with growing plants, for if the seeds which have been put into the soil by the farmer have not germinated and the plants made growth, nature has quickly come to the rescue and filled the soil with other plants which we commonly call weeds. It is nature's plan to keep the soil covered with growing plants, and from nature we should learn a lesson. The field soil, instead of being moist, is dry; instead of being loose and friable, it is hard and compact, and it appears in texture entirely different from the woodland soil. The cause of the difference is not hard to discover. In the woods, nature for years has been building up the soil. The leaves from the trees fall to the ground and form a covering which prevents washing or erosion, and these leaves decay and add to the humus, or vegetable mould, of the soil. Roots are constantly decaying and furnish channels through the soil and permit the circulation of air and water. In the field, nature's lesson has been disregarded and too often the whole aim seems to be to remove everything from the soil and to make no returns. Consequently the organic matter, or humus, has been used up; the tramping of the horses' feet has closed the natural drainage canals; after the crop is removed, the soil is left naked during the winter and the heavy rains wash and erode the surface, and remove some of the best plant-food. After a few years of such treatment, the farmer wonders why the soil will not produce as liberally as it did formerly. _Experiment No. 1._--The fact that there is humus, or vegetable mould, in certain soils can be shown by burning. Weigh a potful of hard soil and a potful of lowland soil, or muck, after each has been thoroughly dried. Then put the pots on the coals in a coal stove. After the soil is thoroughly burned, weigh again. Some of the difference in weight may be due to loss of moisture, but if the samples were well dried in the beginning, most of the loss will be due to the burning of the humus. CONDITIONS WHICH AFFECT FERTILITY. There are certain conditions which affect soil fertility and of these the most important are: Texture; Moisture-content; Plant-food; Temperature. TEXTURE AND ITS RELATION TO FERTILITY. By texture is meant the physical condition of the soil. Upon good texture, more than upon any other one thing, depends the productivity of the soil. When the texture is right the soil is fine, loose, and friable; the roots are able to push through it and the feeding area is enlarged. Each individual particle is free to give up a portion of its plant-food, or its film of moisture. The conditions which are found in the woods' soil are almost ideal.