68 ECONOMY OF FARMING. 



a certain temperature, they retain it considerably longer than most other kinds of 

 soil. The less amount of moisture which they retain is the ground wherefore they- 

 grow cold so little. 



" Humus, next to carbonate of magnesia, has the least power of retaining warmth. 

 A moist soil, rich in humus, gradually warms itself in the sun, because the evapora- 

 ting water is chemically combined with much warmth. Dry soils, very rich in humus, 

 waTm themselves on this account gradually; because, on account of their great 

 porosity, they hold shut up much air, and are the poorest conductors of heat. From 

 Schubler's experiments we obtain the following conclusion : the mote mass the earth 

 possesses in the same volume, or the greater is its absolute weight, so much the 

 greater generally is its retentive power for heat ; so that from the absolute weight of 

 an earth we can judge with tolerable accuracy as to its greater or less power of 

 retaining heat." — Tr.] 



8. All plants draw humus from the soil in proportion to the length of 

 time they remain in the same. 



Winter-wheat, therefore, for an equal quantity of product, requires more humus 

 than barley, and oats more than buckwheat: vetches or tares suck in more humus 

 when they are left to ripen than when they are mowed while green. That the peren- 

 nial increase of the soil be not weakened, the dying portions of the plants must be 

 left to be incorporated in the soil ; otherwise, the increase is arrested. If one, there- 

 fore, takes away the fallen leaves, together with the fruit, from young groves, and 

 applies it in the stalls as litter, the trees sicken, remain crippled, and grow but poorly. 



[Veit, in treating of the exhaustion of the power of the soil according to the 

 properties of plants, considers the subject in reference to the nourishing mass of their 

 products ; the thicker or thinner state of the fruit ; the quality of the leaves and stalks ; 

 the quality of their roots ; the amount of the organic mass remaining in the soil after 

 the harvest ; the duration of vegetation, and the degree of the ripeness of the fruits. 



He remarks ; " the greater the nourishing mass of a plant, so much the greater, 

 other things being equal, is its need of nourishment. ' The exhausting power of 

 different grains, according to their volume,' Thaer says, ' are in the following pro- 

 portion : wheat 13, rye 10, barley 7, oats 5.' The longer a plant takes from the 

 soil, from the time of the sowing the seed till the time of its ripening, so much the 

 more nourishment will it draw to itself, other things being equal. Thus the winter- 

 fruits consume more power of the soil than the summer-fruits of the same species. 

 On the other hand, the exhaustion of powers is so much die smaller, the shorter the 

 period of the vegetation of a plant is, unless other properties produce an exception. 

 The period of the vegetation of different plants cultivated on the farm vary : 



" For buckwheat, summer rape, small maize, flax and white turnips. 12 to 15 weeks. 



" For summer-rye, early-ripe oats, spring barley, millet and hemp, from 16 to 17 

 weeks. 



" For summer-wheat, late-ripe oats, larger barley, lentils, transplanted beets, maize, 

 early-ripe turnips, about 18 weeks. 



" For potatoes, artichokes, late-ripe turnips, beets, &c., 22 to 24 weeks. 



" Winter rape-seed vegetables in the autumn of the seed-year, at least 10 weeks, 

 and in the following year of its fruit about 18 weeks ; together, therefore, 28 weeks. 



" Winter barley, winter speltz, winter wheat and winter rye, ripen indeed 3 weeks 

 later than winter rape, but they are also sowed as much later, and have, therefore, 

 with themselves an equally long period of vegetation." — Tr.] 



9. The greater the organic product which plants produce is, the greater 

 also is the weight of the humus which they employ for this purpose. 



Rich harvests require rich manure. If a person wishes always to raise on the same 

 soil, hemp, maize, or head-cabbage, in equal quantity, it must every year be richly 

 manured. If he omits to do this, the product of^ the second year is very considerably 

 less ; a proof that the great production of the first year has appropriated the greatest 

 part of the humus, and that the small quantity of the same soluble in the second year, 

 IS no longer sufficient for as great production. 



10. Plants that are taken from the fields earlier than their grain or fruit 

 is developed, as well in an absolute as in a relative respect, need less humus 

 than those which not only produce leaves and stalks, but also flowers and 

 fruit. 



