COMMERCIAL FERTILIZERS 81 



should also know the requirements of the plants with which he deals. 

 He may secure these facts in a general way from the state experiment 

 station, but the details can best be ascertained by actual field tests by 

 the farmer himself on his own farm. Such tests do not necessitate carefully 

 laid out plats of a definite size. Farmers, as a rule, do not have the time 

 and patience to do much experimenting, neither do they have the train- 

 ing, experience and facilities for such work; but any farmer may make 

 a fair comparison of two or more kinds of fertilizers, or he may test the 

 efficiency of any fertilizer ingredient, such as nitrogen, potash or phos- 

 phorus, on his soil. This can be done by applying a different character 

 of fertilizer through his fertilizer drill, whether it be attached to the corn 

 planter, the potato planter or to the grain drill, to a definite number of 

 rows running clear through the field. This, if marked at one end of the 

 field by stakes, is easily and readily compared at harvest time with the 

 rows on either side treated with the usual fertilizers or in the usual way. 

 Much can often be determined by observation, but more definite results 

 are obtained by measuring the product of a certain number of rows 

 specially treated, as compared with an equal number adjacent treated in 

 the usual way. 



A rapid growth and a dark-green color of foliage indicate the presence 

 of an ample supply of nitrogen in the soil. If the rank growth is accom- 

 panied by a watery appearance it suggests a deficiency of phosphoric 

 acid. If plants make a stunted growth under normal conditions of sun- 

 shine, temperature and water supply, and mature unduly early, it indicates 

 sufficient phosphoric acid in the soil, and suggests that nitrogen or per- 

 haps potash may materially improve the crop. Potash fertilizers are of 

 special benefit in case of tobacco, beets and the legumes. 



The user of commercial fertilizers should place his main dependence 

 upon those that have given him best results. New brands or modified 

 mixtures should be tried on a small scale and in an experimental way 

 until it has been demonstrated that they are better and more economical 

 to use than his old standby. Emphasis should also be placed upon the 

 importance of a systematic use of fertilizers. This can be accomplished 

 through a definite cropping system and a definite scheme of manuring 

 and fertilizing worked out in such a way as best to meet the needs of the 

 soil and crops. It should take into account the fullest possible utilization 

 of the home and local supplies of manure. For example, it is found that 

 the general farm crops in Pennsylvania are most frequently grown in a 

 rotation consisting of corn, oats, wheat and two years of mixed clover 

 and timothy hay. On limestone soils such crops call for a scheme of 

 treatment about as follows: For the corn, 6 to 10 loads of manure per 

 acre should be applied and supplemented with 200 pounds acid phos- 

 phate; to the oats following the corn, no fertilizer except when the soil is 

 poor, in which case 150 to 200 pounds per acre of acid phosphate may be 

 used; to the wheat, 350 pounds per acre of acid phosphate, 100 pounds 



