74 



SOILS. 



chapt. 9). In so doing it serves indirectly to render the soil 

 ingredients more available, and to impart to the soil the loose 

 condition required in a good seed-bed a " tilth " which can- 

 not be brought about by the operations of tillage alone. 



The only possible substitute for the use of stable manure is 

 found in green-manuring with leguminous crops conjointly 

 with the use of commercial or mineral fertilizers. Unless this 

 is done the use of the latter, alone, ultimately leads to a deple- 

 tion of humus substances, which renders the acquisition of 

 proper tilth by the seed-bed impossible, and causes a com- 

 pacting of the surface soil which no tillage can remedy. 



Proper inctlwd of using stable manure in humid and arid 

 climates. In the humid region it is a common practice to 

 spread the stable manure on the surface of the fields and leave 

 it there without any special operation to put it into the soil; 

 trusting to the rains, earthworms and subsequent tillage for 

 its being brought into adequate contact with the roots ; it is 

 rarely plowed in. In the arid region this mode of using it is 

 impracticable ; it would remain on the surface indefinitely with- 

 out advancing in its decay because of the dryness, and unless 

 plowed in very deep the ordinary, strawy manure would ruin 

 the seed-bed by rendering it too pervious to the dry air, thus 

 preventing germination. Much of this valuable material has 

 therefore been, and to some extent is still being burnt, thus 

 causing a severe depletion of the land, both of humus and of 

 mineral plant-food. The best way to deal with stable manure 

 in the arid regions is to thoroughly rot or cure it before putting 

 it on the land, and then plowing it in. To do this of course it 

 must be put in piles and wetted regularly; a procedure which 

 at the high prices of labor is thought to be too expensive, but 

 which in the end would be found eminently profitable, unless 

 green-manuring is regularly done. The very small proportion 

 of humus generally present in arid soils renders this precaution 

 indispensable, if production and proper tilth is to be main- 

 tained. The saving of stable manure and of all composting 

 material, even if less needful as a means of supplying plant- 

 food in the rich soils of the arid regions, is fully as essential 

 in order to maintain the humus supply. 



