Soil Fertility 87 



in the muriate form ; alunite, which furnishes it in the sulfate 

 form ; and Nebraska potash, beet-root molasses potash, manure 

 ash, cement dust, and blast furnace dust, which contain the 

 potash as a mixture of carbonate and sulfate. Most of the 

 product is in an available form and in the various materials 

 ranges from about 6 to 45 per cent pure. 



38. Effects of the different plant-foods on vegetation. 

 The effects of foods on the resulting vegetation has been ex- 

 haustively studied by scientists and some very significant 

 facts have been established. Some of the most important of 

 these are given in the ensuing paragraphs. 



Effects of nitrogen. Vegetative growth of that part of the 

 plant above ground is encouraged by nitrogen. It also imparts 

 a deep green to the leaves. Absence of this color often indi- 

 cates a lack of nitrogen. In the cereals nitrogen has the tendency 

 to increase the plumpness of grains. With all plants nitrogen 

 is a regulator that governs to a certain extent the utilization 

 of phosphorus and potassium. It also produces succulence 

 in crops. This is especially desired in many vegetables, and, 

 therefore, growers supply the soil plentifully with nitrogen, 

 especially for such crops as lettuce, radishes, and cabbage. 

 In the case of many general farm crops, however, an excessive 

 use should be discouraged. In this connection it must be 

 remembered that nitrogen is the most expensive plant-food 

 and that, unless the crop actually requires it, an excess is an 

 extravagance. Moreover, too much nitrogen has some unfavor- 

 able effects on crops. It delays maturity by encouraging 

 growth; it weakens the stalks of cereals and hay crops and 

 causes the plants to lodge, or bend over; it may lower the 

 quality of certain grains and fruits, as is the case with barley 

 and peaches; and it may decrease the resistance of plants to 

 disease. However, nitrogen should be used when needed. 



Effects of phosphorus. Phosphorus hastens the maturity 

 of plants, increases root development, decreases the ratio of 

 straw to grain by hastening the filling out of the latter and pro- 



