114 Bulletin 174. 



decaying vegetable matter. Tliis would probably be the condition 

 in the case assumed in the question, 



11. If humus in soil under cultivation is jperishahle^ ought it not 

 to he the farmer' s first care to keep good the quantity first found in 

 the virgin soil f 



Yes ; and this can be done only by adding humus from time to 

 tiine in the shape of barn-yard, manure and other forms of organic 

 matter. 



12. In addition to the htmnus returned to the soil in mamire, 

 from, forage fed to stocky and Ijy plowing under stubble and roots, 

 do you think it a good plan to sow some cover-crop in corn rows at 

 last cidtivation, and on oat and wheat stubble as soon as the crop is 

 ofi\ for plowing under the following spring f 



Usually a cover-crop is desirable, and especially so if the soil is 

 lacking in humus. 



13. What are good crops for this purpose f 

 Crimson clover, vetch, peas, rye, rape, barley, oats. 



14. Which of these are leguminous plants f Name all the kinds 

 of leguminous plants you know f 



The first three named. All the clovers, alfalfa, vetch, peas, beans, 

 lupines. 



15. Why is it advised to ploio under the green-cropjs as soon as 

 the land can be worked in the spring f 



These crops, if allowed to grow, would give off into the air much 

 moisture needed by tlie permanent crop ; and besides this, if left 

 until they had made a large growth, there might not be enough 

 moisture in the soil to cause them to decay. 



16. Do you think a rotation of crops helps the soil to bear the 

 strain of successive cropping f If so, why f 



Yes : this practice admits of supplying humus by means of cover- 

 crops ; it admits of tillage which sets free plant-food , and as different 

 kinds of plants require different proportions of the various plant-foods 

 a rotation prevents an unequal depletion of plant-food, as might be 

 the case if one kind of crop was grown continuously for a long time. 



17. Are you aware that plantfood exists in the soil in both 

 available and unavailable forms, and that when plants have used 

 up most of the available portion we call the soil worn out f 



