308 MASSACHUSETTS AGRICULTURE. 



post, a grand object is accomplished when snch materials are 

 added as will, by chemical change, produce ammonia. For 

 this purpose such substances must be procured as contain 

 nitrogen. 



Decayed flesh, horn shavings, and glue, contain nitrogen, but 

 no ammonia. Mow, if you add them to the compost, chemical 

 transformation speedily begins, the nitrogen is set free and goes 

 over to the. hydrogen, which is always at hand, and ammonia is 

 formed. If this change did not take place either in the com- 

 post heap or in the earth after applying it to the soil, they 

 would have no more effect upon crops than bits of lead or iron. 

 The stalk and seeds of plants require nitrogen. To obtain it, 

 substances in which it is an ingredient must first pass through 

 two chemical changes. Tliey must first be decomposed and 

 ammonia formed ; then the ammonia itself must be decom- 

 posed, and thus, through this circuitous path, the plant secures 

 its nitrogen. Substances containing nitric acid are proper in- 

 gredients for compost, such as saltpetre, nitrate of soda, rubbish 

 of old clay walls, earth taken from under old buildings, &c. 

 Substances rich in carbon are easily procured, such as straw, 

 foliage, litter, weeds, turf, charcoal dust, &c. To form the seed 

 of grain, substances containing phosphoric acid must not be 

 omitted, — burnt bones, wood ashes, animal excrement, oil cake, 

 stable manure, &c. 



It would be easy to give recipes ; but they are in most cases 

 very unsafe sources of information. The farmer does not want 

 recipes ; he must understand principles, and then his guidance 

 .will be of that kind which will seldom lead him astray. Some 

 farmers have complained that in their experiments with guano, 

 its application produced the most luxuriant leaves and stalks, 

 but did but little to produce grain. Chemistry teaches that 

 guano is what may be called a quickly-forcing manure, being 

 so rich in ammonia that it at once aflbrds a copious supply of 

 nitrogen to the plant, and thus aids prodigiously at the outset 

 in its growth, but is deficient in that which produces some 

 kinds of grain. If the ground does not contain that principle, 

 the application of this manure may aid you but little in pro- 

 ducing seed. 



Suppose you sow wheat upon a field which contains none of 

 the phosphates. You apply guano of a variety which does not 



