92 THE APPLE 



5 . The tillage and cultivation of clay soils is also made easier 

 by the plowing under of cover crops. This is because the humus 

 which has been incorporated in the soil lessens the puddling and 

 cementing of these soils. 



6. Light soils are also benefited by the addition of humus- 

 making material, in so far as they are rendered more retentive of 

 moisture, and therefore suffer less from drought. The action of 

 the humus on these looser, light soils is seemingly that of making 

 them more compact, while the tendency with the clay soils, as has 

 just been pointed out, is to loosen or lighten them. 



7. The decay of vegetable matter in the soil helps to break 

 down the plant food that is already in the soil but not available to 

 the plant. By the action of this decay and the consequent action 

 of organisms in the soil, plant food is set free. 



8. Where legumes, such as the clovers, vetches, etc. are used 

 for the cover crop, not only is the food which the plants took up 

 from the soil returned to it by the decay of the plants, but the 

 nitrogen which the plants assimilated from the air is also given 

 up to the soil. This is an addition of a costly plant food. 



9. Where windfalls are of value a heavy mulch on the soil 

 will serve as a cushion, thereby preventing the soiling or bruising 

 of the fallen fruit. 



10. Cover crops make young, late-growing trees better able to 

 stand severe winters, by causing them to mature their wood properly 

 in the fall. 



Other advantages are frequently claimed by orchardists, but 

 those just given will serve to illustrate the principal recognized 

 benefits. 



Bad effects of cover crops. The effects of cover crops are not all 

 good. It has been found that such crops reduce the soil moisture 

 during the fall and in some cases keep the soil dry until winter sets 

 in. They also retard the growth of trees somewhat, and in certain 

 instances, for example, the rye crop may cause great injury to 

 the orchard in times of drought. From a hasty survey of the sub- 

 ject it would seem that the good effects of cover crops are often 

 counterbalanced by their ill effects, and that if we are to avail 

 ourselves of the advantages, we must be prepared to put up with 

 the disadvantages. 



