AVERAGE PEODUCE PER ACRE. 115 



It may be added parenthetically, that these figures represent 

 very fairly the average composition of the ash of wheat and oats 

 as grown in this country. It is more difficult to give an average 

 of the ash of turnip bulbs, as the proportions of the constituents 

 vary within certain limits according to the crop, its state of 

 maturity, soil, manure, &c. The potash is sometimes less and 

 sometimes greater than that above given ; but when that is so, 

 there is generally a corresponding increase or decrease of the 

 soda or chloride of sodium. There is more uniformity when 

 analyses are made both of the bulb and top of the individual 

 plant, the composition of the one appearing to be, in some 

 measure, the complement of the other. 



But to return : the comparison above instituted between 

 wheat and turnips with respect to phosphoric acid, might be 

 carried out in the same way with respect to amount of potash 

 w^hich these crops respectively require. Suffice it to say that, 

 though the percentages of potash are respectively 31 and 40 of 

 the ash, yet an average crop of, say 20 tons of turnip bulbs 

 requires from the soil 150 lbs. of potash, while 4 quarters 

 of wheat, grain and straw, require only 35 lbs. In fact 

 turnips req^uire more potash than any crop that we cultivate — 

 exceeding even potatoes in that respect, and exceeding beans 

 and pease nearly as much as they exceed wheat. And yet we 

 find the French agricultural chemist, M. Ville, led away 

 apparently in the same manner as the American writer referred 

 to, classing potatoes, pease, and beans as " potash plants " while 

 he does not include turnips in the same category {Artifical 

 Manures, pp. 225 and 402). The case of potash — or of any 

 other mineral — is not like that of nitrogen, supplies of which, in 

 comljined form, may be carried to the plant in rain or dew ; the 

 needful potash must exist in the soil or in the manure ; and 

 happily, it generally exists in considerable abundance in the 

 former. We have been here considering two plants of ditierent 

 orders — as widely different as can well be in their characters 

 and haljits of growth. But if we now look at the above state- 

 ments of the analyses of two cereal plants, wlieat and oats, we 

 shall find that the same considerations and similar allowances 

 are necessary before we take the analysis of lUO parts of ash as 

 indicating in any definite degree either the amount or the 

 relative ])roportions of mineral substances which the respective 

 crops draw from a given extent of land. The weight of a good 

 average croji — say (juarters of oats — is 1U20 lbs. as compared 

 with 201 G lbs. of wheat. The dillerence, therefore, is not 

 very great. Neither hav(^ we any extra quantity of water to be 

 allowed for on either side. But if, on glancing at the above 

 columns of figures, a person were to conclude that a crop of 

 wheat requires from an acre of land twice as much potash, and 



