24 POTASH-PHOSPHATE MANURING, 



be entirely changed, owing to the predominance and rank 

 development of clovers and other legumes. 



This is well illustrated in the pictures on page 23, 

 which have reference to the experiments by Prof. Hell- 

 stroem of Sweden. 



To sum up: It is necessary to supply liberal amounts of 

 potash and phosphoric acid to the soil in order that the costly 

 nitrogen present , or applied in the form of fertilizers , or in the 

 form of green manuring, may exert its full effect upon the 

 growing plants and thus produce a maximum crop. 



PLANT FOOD MUST BE AVAILABLE TO BE USEFUL. 



All farmers should know, by this time, that what is 

 commonly called "plant food," comprises three ingredients: 

 Potash, phosphoric acid and nitrogen. Large quantities of 

 these plant food elements are usually present in agricul- 

 tural soils, most of which, however, is in an insoluble 

 (unavailable) condition, and, therefore, useless to growing 

 plants. Thus soils may contain, as shown by chemical 

 analysis, large supplies of plant food and still fail for the 

 lack of it. Prof. Wagner shows this by an experiment, 

 illustrated in Fig. 9. 



The four pots to the left contain clay soil, the four 

 pots to the right sandy soil. The crop planted was peas 

 The first two pots in each soil received no potash fertilizer, 



