30G Agricultural Chemistry. 



the conclusion, that nitrogenised manures are altogether tuifit for 

 grain, because, by their use, the produce of grain was diminished, 

 and because the deficiency increased with the amount of the 

 ammoniacal sahs employed as manure. 



Yet this conclusion, which is, in this form, a direct contradic- 

 tion to those of Mr. Lawes, is no better founded than those latter 

 conclusions, according to which nitrogenised manures are pecu- 

 liarly appropriate for grain, because the increase or diminution 

 of the produce is proportional to the presence or the deficiency in 

 the soil of those mineral constituents which the soil must supply 

 to grain for its development simultaneously with the ammonia. 

 If these mineral constituents are deficient or absent, while others, 

 required for the straw, are rendered soluble and available in 

 greater proportion by the action of the ammoniacal salts, then 

 the produce of grain diminishes, while that of straw increases ; 

 in spite of the excess of ammonia no more nitrogen is assimilated 

 than is supplied by the natural sources of that element. 



A single indispensable mineral constituent, no matter which, 

 determines and regulates the produce. If all the others be pre- 

 sent in excess, while this one is deficient, the plant does not 

 thrive. If this one constituent be present, in an available form, 

 and exactly in the proportion required for the growth of a full 

 crop of wheat, and if the soil receives no ammonia artificially, 

 the plant obtains its supply of nitrogen from natural sources ; an 

 excess of ammonia is not assimilated. If all the mineral con- 

 stituents are present on the soil and in excess, then, by the addi- 

 tion of ammoniacal salts, the produce is increased, for in that 

 case the conditions of the assimilation of the ammonia are 

 secured.* 



From these very facts it follows, indisputably, that if the 

 farmer wishes to preserve the fertility of his fields, or if he 

 wishes to increase their produce, he must, before all other con- 

 siderations, attend to the importance of rendering available and . 

 efficient the constituents present in the soil. He must enrich the 

 soil with mineral constituents supplied from without, and supply 

 such as are wanting, if he would increase his produce in a given 

 time ; and if he would render durable the increased produce, he 

 must restore to the soil all the mineral constituents removed in 

 his crops, and in the same proportions. The whole art of agri- 

 culture must be directed to these objects, and when the farmer 

 has, in this way, given to his soil the necessary quality, then the 

 use of nitrogenised manures will give the most satisfactory 

 results. 



* Schattermann observes, that with lucerne and clover, ammoniacal salts had 

 no perceptible effect. 



