182 now cuors feed 



that, hold 150 per cent of water. So the humixs of Schul)« 

 ler imhibed 181 per cent ; the peat of Zenger, 377 per cent ; 

 while Wilhehn examined a very porous peat that took up 

 519 per cent. These difFei-ences are dependent mainly on 

 the mechanical texture or porosity of the material. 



The want of capillary retentive power for Avater in the 

 case of coarse sand is undeniably one of the chief reasons 

 of its unfruitfulness. The best soils possess a medium re- 

 tentive power. In tliem, therefore, are best united the 

 conditions for the regu.ar distribution of the soil- water 

 under all circumstances. In them this process is not hin- 

 dered too much either by wet or dry weather. The re- 

 taining power of humus is seen to be more than double 

 that of clay. This result might appear at first sight to 

 be in contradiction to ordinary observations, for we are 

 accustomed to see water standing on the surface of clay 

 but not on humus. It must be borne in mind that clay, 

 from its iraperviousness, holds water like a vessel, the wa- 

 ter remaining apparent ; but humus retains it invisibly, 

 its action being nearly like tliat of a sponge. 



One chief cause of the value of a layer of humus on 

 the surface of the soil doubtless consists in this great re- 

 taining power for water, and the success that has attended 

 the practice of green manuring, as a means of renovating 

 almost wortliless shifting sands, is in a great degree to be 

 attributed to this cause. The advantages of mulching are 

 explained in the same way. 



Soils which are over-rich in humus, especially those of 

 reclaimed peat-bogs, have some detrimental peculiarities 

 deserving notice. Stoeckhardt ( WiJdci's Centralblatt^ 

 1858, 2, 2:2) examined the soil of a cultivated moor in 

 Saxony, which, when moist, had an imbibing power of 

 60-69° 1„. After being thoroughly dried, however, it lost 

 its adhesiveness, and the imbibing power fell to 26-30° j„. 



It is observed in accordance with these data that such 

 joils retain water late in spring ; and when they become 



