160 TALKS ON MANURES. 



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 hi the average produce of the grain and straw of wheat 

 per acre. 



"3. Notwithstanding the large amount of nitrogenous matter 

 and of ash-constituents 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 one and 

 three- fourths to two 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. 



" 7. The development of roots being checked, when the produce, 

 in a green condition, is fed off by sheep, hi 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, account- 

 ing for the observation made by practical men, that, notwithstand- 

 ing the return of the produce hi 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 in 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 shape of ammonia and nitric acid, and 

 descends, in these combinations, with the rain which falls on the 

 ground, satisfies, under ordinary circumstances, the requirements 

 of the clover-crop. This crop causes a large accumulation of 

 nitrogenous matters, which are gradually changed in the soil into 

 nitrates. The atmosphere thus furnishes nitrogenous food to the 

 succeeding wheat indirectly, and, so to say, gratis. 



" 10. Clover not only provides abundance of nitrogenous food, 

 but delivers this food in a readily available form (as nitrates), more 

 gradually and continuously, and, consequently, with more cer- 



