60 Report of the Department of Agronomy of the 



ample worked out, for instance, the N would be 15 -r- 450 = 3| per ct., 

 the P 4.4 per ct., and the K 4.4 per ct. Having these percentages 

 given it is very easy to calculate the amount of the mixture required 

 to give a certain amount of any one element per acre. 



Sometimes the farmer desires to use N, P and K in a certain 

 proportion as 1-2-1, 2-4-3, 3-5-2, etc. In this case the simplest 

 method of procedure is to decide, also, how much of one of the ele- 

 ments will be used per acre, and with this as a basis to reduce the 

 proportion chosen to a formula of pounds per acre and compute as 

 above. If the proportion 2-4-3 be selected and 20 lbs. of nitrogen 

 to an acre be taken as a basis, the formula will become 20-40-30, by 

 dividing 20 by 2 and multiplying each term of the proportion 

 by the quotent, 10. If 3-5-2 be selected as the proportion and 

 GO lbs. of P per acre as the basis the formula will become 36-60-24. 

 If a different basis per acre is decided upon after such a mixture has 

 been made, the amount to be used can be found from the percent- 

 ages, computed as above. 



It will often happen that only two elements are desired in a mixture. 

 This would simplify still further the above calculations. 



In the above calculations, nitrate of soda, acid phosphate and sul- 

 phate of potassium have been used only for example and not because 

 of preference for those particular forms of the three elements. 



It is never advisable to decide first upon definite percentages of 

 N, P and K, as for instance 2 per ct. N, 4 per ct. P, and 3 per ct. K, 

 and then attempt to make the mixture conform to this arbitrary 

 formula. Such will usually require the addition of some make 

 weight or " filler," or it may be the materials are too low in com- 

 position for the formula. There is no good sense in going to the 

 expense of mixing sand or dry earth with a fertilizer simply to increase 

 its weight and make it conform to a certain formula. Fertilizer 

 companies do this and let the farmer pay all the extra expense 

 involved. The only good reason for ever using a filler is to act as 

 a drier or absorbent in connection with certain moist salts: as 

 calcium nitrate, potassium chloride, or even sodium nitrate. A 

 certain amount of dry absorbent material may be added in such 

 cases to insure good mechanical condition and prevent the formation 

 of lumps. For this purpose nothing is better than fine dry peat 

 or muck. But unless the fertilizer is to stand several weeks or 

 months after mixing there is no need of this precaution. 



If we leave out of consideration all forms of caustic lime (and 

 there is never any need of using such in a mixed fertilizer) there are 

 very few other materials used in fertilizers but can be mixed together 

 freely without unfavorable results. Basic slag is the one to be 

 especially mentioned. It contains a small amount of caustic lime 

 and should not be mixed with ammonium compounds, nor acid 

 phosphate. In any mixture it should not stand long after mixing 

 because of its tendency to cause caking. Wood ashes have some- 



