CLOVER AS A PREPARATORY CROP FOR WHEAT. 485 



Summary. 

 The following are some of the chief points of interest which I 

 have endeavored fully to develop in the preceding pages : 



1. A good crop of clover removes from the soil more potash, 

 phosphoric acid, lime, and other mineral matters, which enter into 

 the composition of the ashes of our cultivated crops, than any other 

 crop usually grown in this country. 



2. There is fully three times as much nitrogen in a crop of clover 

 as in the average produce of the grain and straw of wheat per 

 acre. 



3. Notwithstanding the large amount of nitrogenous matter and 

 of ash-constitueilts of plants in the produce of an acre, clover is 

 an excellent preparatory crop for wheat. 



4. During the growth of clover a large amount of nitrogenous 

 matter accumulates in the soil. 



5. This accumulation, which is greatest in the surface-soil, is 

 due to decaying leaves dropped during the growth of clover, and 

 to an abundance of roots, containing when dry from If to 2 per 

 cent, of nitrogen. 



6. The clover roots are stronger and more numerous, and more 

 leaves fall on the ground when clover is grown for seed, than 

 when it is mown for hay ; in consequence more nitrogen is left 

 after clover seed than after hay, which accounts for wheat yield- 

 ing a better crop after clover seed than after hay. 



1. The development of roots being checked when the produce, 

 in a green condition, is fed off by sheep, in all probability leaves 

 still less nitrogenous matter in the soil than when clover is allowed 

 to get riper and is mown for hay ; thus, no doubt, accounting for 

 the observation made by practical men that, notwithstanding the 

 return of the produce in the sheep excrements, wheat is generally 

 stronger and yields better after clover mown for hay than when 

 the clover is fed off green by sheep. 



8. The nitrogenous matters iil the clover-remains on their 

 gradual decay are finally transformed into nitrates, thus affording 

 a continuous source of food, on which cereal crops specially 

 delight to grow. 



9. There is strong presumptive evidence that the nitrogen which 

 exists in the air in the shape of ammonia and nitric acid, and that 

 which descends in these combinations with the rain which falls on 

 the ground, satisfies, under ordinary circumstances, the require- 



