Humus Improves the Land. 221 
or applications of muck or some other organic dress- 
ings. It is not necessary that the chemical fertil- 
izers should be mixed before application; in fact, 
upon lands of varying soil and conformation, it is 
ordinarily better to apply the different ingredients 
separately, because different parts of the plantation 
may need different amounts of the various materials. 
The low lands will ordinarily need less of the nitro- 
gen and perhaps more of the potash and phosphoric 
acid. In general, it is advisable to buy the plant- 
foods separately, as advised in the preceding pages. 
Farmers do not appreciate the importance of 
humus as an ameliorator of land. In farm lands, it 
is usually supplied in form of green crops, stubble 
or sward, and barn manures. When humus is ab- 
sent, sandy soils become too loose and leachy and 
hot, and clay soils bake and become lumpy. The 
different physical characteristics of clay lumps and 
mellow soils are largely due to the greater amount 
of humus in the good soil, and yet we have seen 
that the chemist may pronounce the cloddy soil 
richer in native plant-food. If the farmer has 
much of this hard, unproductive land, what is to 
be done with it? To cover it with commercial fer- 
tilizer would be of little benefit. It must first be 
put in fit condition for the growing of crops. A 
crop of clover plowed under would quickly improve 
it, but if the land is planted to orchard he does 
not care to seed it down. The next recourse is 
stable manure. Of this, perhaps enough can be 
had to cover the hardest spots. For the rest, 
