446 



If a field is unproductive on account of poor drainage or because 

 of a lack of humus, it would not be made more productive by add- 

 ing commercial fertilizer. On the other hand, if a field is unproduc- 

 tive, due to a lack of available plant-food, then the addition of 

 fertilizers will increase its productivity. The essential conditions of 

 a field which are the poorest or at the lowest ebb must be sought out 

 and improved before the fertility of the field is increased. It hap- 

 pens many times that poor yields are not due at all to a lack of plant- 

 food, but are due to essential conditions other than those of plant- 

 food. 



THE ELEMENTS NEEDED BY DIFFERENT SOILS. 



Soils whose fertility has been greatly reduced through long- 

 continued cropping and which respond readily to applications of 

 stable manure, should receive a general fertilizer containing all three 

 valuable fertilizer ingredients, nitrogen, phosphoric acid, and potash. 



Sandy and light soils are especially benefited by applications of 

 potash and will not, in general, be benefited by phosphoric-acid fer- 

 tilization. The clay and loam soils, on the other hand, do not often 

 need potash, but are apt to be improved by applications of phosphoric 

 acid. Experiments have shown that acid soils (indicated by the 

 litmus paper test) will respond to applications of lime (carbonate) 

 and available phosphates. 



Marshy soils, like all low-lying moist soils, are rich in organic 

 matter and in nitrogen and require as a rule, potash and phosphoric 

 acid, and sometimes lime. Potash or, still better, potash and phos- 

 phoric acid, have been found very effective in improving the produc- 

 tive capacity of black marshy soils. 



It may be stated, as a general proposition, that soils of different 

 types are likely to be especially benefited by the following special 

 systems of fertilization: sandy soils by nitrogen, prairie soils by 

 phosphoric acid, peaty soils by potash and phosphoric acid, and all 

 acid soils by carbonate of lime. 



Phosphorus alone will not produce a maximum yield on lands 

 that have been subjected for a long time to exhaustive cropping. 

 Such lands must have nitrogen always, potassium often, and lime 

 sometimes, before they will yield a full return. The need of lime 

 may be determined by the growth of clover. So long as clover 

 grows luxuriantly lime is not required, but when clover fails to grow 

 on well manured land, dying out the second season and being re- 

 placed by sorrel, then lime should be added. Lime should always be 

 preceded and followed by liberal fertilizing or manuring, for lime 

 used alone, while it may stimulate the land to extra production for 

 a year or two, will in the end produce greater exhaustion; but by 

 alternating lime with manure and fertilizers the land will be kept 

 in a healthy condition and will steadily increase in fertility. This 

 is why limestone soils are celebrated for their productiveness* 



Potassium is likely to be needed in soils which have been ex- 

 haustively cropped, especially if hay and straw have been sold from 

 the -land as well as grain. It is also sometimes the chief element 

 needed on muck soils. 



