152 



DRY FARMING 



that increases the water-holding capacity of the soil and 

 at the same time makes it easier to work. The amount of 

 this constituent in decayed form in a soil is the greatest 

 single index to its "fertility". 



But the stubble lessens the efficiently of tillage and 

 seeding operations, and long stubble if plowed under 

 may seriously interfere with the upward movement of 

 soil moisture from the subsoil and with the downward 

 penetration of the roots, thus lessening the yield. Ex- 

 cept on drifting soils or on heavy, tight clay, stubble is 



Fig. 61. — Effect of Disking Before Plowing. 



Diagram showing on the left, land plowed and then harrowed ; on the 



right, land disked, then plowed and then harrowed. Note the air spaces 



in the former which result in the drying out of the furrow slice, unless 



the land is firmly packed. 



a nuisance until it decays. It decays rapidly in humid 

 but very slowly in dry climates. In the West we need 

 to maintain the organic matter content of our soil, but 

 we hesitate to fill it with too much undecayed stubble, 

 except in the fallow year. 



125. Subsoil Moisture Must be kept Available to Plant 

 Boots. — Moisture and "plant food" are both necessary for 

 crop growth. The former is often found in relatively 



