250 Bukeau of Farmers' Institutes. 



ence in the quantity of plant food present in the acre of soil. 

 However delicate may be the methods of chemical analysis, the 

 methods of plants are still more delicate, and plants are able to 

 show differences in soil where chemical analysis distinguishes none. 

 Indications of Needs of Soil Afforded by Appearance of 

 Crops. — • It is impossible to give any fixed rules which will cover 

 all cases and enable a farmer to tell without any experiment on his 

 pa it what food constituents his soil lacks. In a general way, the 

 crops themselves may give some valuable suggestions. 



(a) As a rule, lack of nitrogen is indicated, when plants are 

 pale green in color, or when there is a small growth of leaf or 

 stalk, other conditions being favorable. 



(b) A bright, deep green color, with a vigorous growth of leaf 

 or stalk, is, in case of most crops, a sign that nitrogen is not lacking 

 but does not necessarily indicate that more nitrogen could not be 

 used to advantage. 



(c) An excessive growth of leaf or stalk, accompanied by an im- 

 perfect bud, flower, and fruit development, indicates too much 

 nitrogen for the potash and phosphoric acid present. 



(d) When such crops as corn, cabbage, grass, potatoes, etc., have 

 a luxuriant, healthful growth, an abundance of potash in the soil 

 is indicated; also, when fleshy fruits of fine flavor and texture 

 can be successfully grown. 



(e) When a soil produces good, early maturing crops of grain, 

 with plump and heavy kernels, phosphoric acid will not generally 

 be found deficient in the soil. 



Such general indications may often be most helpful, and the 

 condition of crops should be studied carefully with these facts in 

 mind. 



Plant-Food Needs in Relation to Kind of Soil.- — -The kind 

 of soil may furnish information as to what kind of plant food is apt 

 to be lacking. While soils of the same class differ widely in com- 

 position, there are certain general suggestions which they may 

 afford. In sandy soils potash is commonly deficient and hence 

 this element must be a prominent ingredient of a fertilizer for 

 such a soil. Sandy and gravelly soils usually require liberal 

 amounts of phosphoric acid also, owing to the fact that in such 

 soils phosphate compounds are liable to leach beyond reach of 

 plants. On the other hand, clay soils are usually well supplied 

 with potash and are ;i[>t to be deficient in phosphoric acid and 

 lime. In lime soils there may be a lack of nitrogen. 



