152 PKACTICAL FARM CHEMISTRY. 



measure on the earliness of his crops, as well as on 

 the succulency of his products. Nitrogen in nitrate 

 form is just the element of plant food of which a 

 generous sujjply is needed for the production of 

 thrifty, vigorous, succulent growth. When he 

 wants to sow his seed, or set his plants, early in 

 spring, he knows his soil to be already filled with 

 mineral plant foods from previous manuring. The 

 nitrogen alone is not in the available (nitrate) form, 

 and its conversion into nitrate during the cool days 

 of early spring is extremely slow — too slow for the 

 needs of the crop. 



The average gardener, in this emergency, again 



applies his fifty tons of compost, and uselessly 



adds several hundred pounds each of potash and 



phosphoric acid to the over- supply 



?i*the Garden* ^^ *^^ ^^^1' I^^^'ely ^^r the purpose 

 of furnishing to his crops a meagre 

 amount of nitrate, which is gradually derived, by 

 the process of natural conversion, from the 500 

 pounds of unavailable nitrogen in the manure ap- 

 plication. In some cases, bone flour, or perhaps 

 complete concentrated manures, are used with simi- 

 lar results and similar waste of mineral plant foods. 

 The few per cent of nitrogen in these fertilizing ma- 

 terials are the only effective agent, while the phos- 

 phoric acid in the bone flour, or the potash and 

 phosphoric acid in the complete fertilizer, are added 

 to the stores in the soil, because not needed for the 

 crop in their full quantities. These are — to say the 

 least— -round-about ways. The only direct method 

 of supplying the deficiency, and by far the cheapest, 

 is by the use of nitrate of soda, or, in some cases, 

 sulphate of ammonia. Nitrate of soda will answer 

 our purpose admirably. It can usually be bought 



