l8 THE COW PEA. 



phosphoric acid and potash there is supplied to the grow- 

 ing crop, the larger will be the amount of nitrogen drawn 

 from the air." This condition is well described as making 

 the crop "nitrogen hungry," or, to state the proposition in 

 other words, if liberal quantities of phosphoric acid and 

 potash are supplied and nitrogen not given, the plant 

 absorbs sufficient nitrogen from the air to balance the sup- 

 ply of phosphoric acid and potash already used, and not a 

 particle more. Nitrogen is more expensive than any other 

 element in a complete fertilizer, hence it is economy to 

 assist the cow pea crop to secure, free of cost, the largest 

 possible quantity of nitrogen from the air. The larger the 

 amount of phosphoric acid and potash supplied to the crop, 

 to the limit of its healthy feeding, the greater is the assimil- 

 ation of the free nitrogen of the air ; and so, financially, the 

 larger the investment in phosphoric acid and potash, within 

 the above limits, the greater the repayment or dividend in 

 the form of the more expensive nitrogen. The limit of 

 plant growth is determined largely by the mechanical con- 

 ditions of the soil and a suitable supply of moisture to make 

 the plant food available. Plants grown on soils in "good 

 condition" can use a larger amount of fertilizer than those 

 on soils too hard and dry for the full development of roots. 

 Phosphate and potash fertilizers should always be ap- 

 plied before the seed is planted, whether the planting is 

 done broadcast or in drills. In the former case, the fertilizer 

 should be sown broadcast and covered by the plowing or 

 the same harrowing which covers the peas. In the latter 



