218 THE CULTURE OF FARM CROPS. 



the crops during a dry season, when the supply in the soil 

 may be inadequate. 



That it is a stimulant to plant growth and thus tends to 

 exhaust the soil. 



These errors are very evident when the character of this 

 substance is understood. 



First. While gypsum in solution enters into a combina- 

 tion with carbonate of ammonia and is decomposed by it, 

 with the result of the formation of sulphate of ammonia and 

 carbonate of lime, it has no more affinity for ammonia than 

 the water of the atmosphere has, and whatever ammonia is- 

 derived from the atmosphere by plants through the rain 

 water, is carried into the soil and from thence by the water 

 into the roots of the plants. Hence there is no necessity for 

 the use of gypsum in the performance of this nutritive func- 

 tion of plants. 



Second. That gypsum does not absorb water, having 

 already in combination as much as it can take up. 



Third. That plants cannot be stimulated into excessive 

 grow r th by any one substance; but when any necessary nu- 

 tritive element is deficient, the crop suffers and only gains 

 its natural luxuriance when the absent element is supplied. 



Fourth. The peculiar effect of gypsum upon the growth 

 of crops containing a large proportion of nitrogen, is due to 

 the contribution of sulphuric acid by it; the sulphur being 

 required to form the nitrogenous compounds known as al- 

 buminoids; all of which contain a notable proportion of 

 sulphur. 



Thus the albumen, gluten, and legumin, of plants, are 

 made up of nearly the same proportions of carbon, hydro- 

 gen, oxygen, nitrogen, and sulphur; and without the sul- 

 phur these nitrogenous compounds could not be formed. 

 And it is a fact, that the plants which contain most abun- 

 dantly these nitrogenous compounds, are largely benefited in 

 their growth 'by the use of gypsum. 



Gypsum is easily dissolved in 400 times its weight of wa- 

 ter, and hence the small quantity rarely exceeding 100 Ibs. 

 per acre usually applied is very quickly carried into the 



