EXERCISE 26 



PLANT FOOD REMOVED BY CROPS 



Statement. The rate at which a farmer exhausts his soil will depend in large part upon what he 

 takes off the soil and what he returns. The wise farmer keeps books with the f ertility in his soil just 

 as he does with the money he has in the bank. 



Materials. Pencil ; paper ; tables in Appendix. 



Directions. Assume that the element nitrogen is worth 20 cents a pound, phosphorus 8 cents a 

 pound, and potassium 8 cents a pound. 



1. If an acre of corn yields 30 bushels, assuming that it is removed from the farm, compute the 

 amount and value of the plant food removed. How does the value of the plant food removed by the 

 grain and the value of the grain itself compare at the present market price ? Compute and record in a 



Fig. 31. In which form should the farm products be sold? 



0, in a load of 50 bushels of wheat sold from the farm how much plant food is removed and what is it worth as compared with the wheat ? b, in 

 a load of 6 fat hogs weighing 250 pounds each how much plant food is removed and what is its value compared with that of the hogs at 

 present market prices? c, in a load of cream of 1500 pounds, how much plant food is there and what is it worth compared with the cream, 



assuming the cream to contain 38 per cent butter fat ? 



table on the following page the amount and value of plant food removed from an acre by each of the 

 following crops : wheat, 1 6 bushels; oats, 26 bushels; red clover, 1 ton; timothy, 1 ton; alfalfa, 3 

 tons ; apples, 70 bushels. Compute the market value of each of these crops and compare it with the 

 value of the plant food removed from the soil. 



2. A ton of alfalfa hay removes $11.45 worth of nitrogen, phosphorus, and potassium. A ton of 

 hogs remove $7.71 worth, and a ton of cream removes $1.85 worth of these materials. Is the plant 

 food contained in these products counted when the buyer fixes the price which the farmer is to receive 

 for them, or does the farmer sell his products and " throw in " the plant food ? What does the farmer 

 receive for a ton of each of the products named at present market prices ? 



3. American farmers produce about 3,000,000,000 bushels of corn, 700,000,000 bushels of wheat, 

 1,000,000,000 bushels of oats a year. Compute the value of the plant foods taken from the soil each 

 year by each of these crops. Considering only these three crops, compare the value of the mining 

 operations of the farmers in value of mineral removed with that of the gold mined, the silver 

 mined, and the coal mined in the United States in a year. 



Questions. What is the most exhaustive crop grown in your community considered alone from 

 the standpoint of the plant food taken from the soil ? The least exhaustive crop ? What types of 

 farming are most exhaustive of soil fertility? What types are least exhaustive? Make a plan of 

 farming which you think would be profitable and maintain the land. 



References. Waters, H. J. Essentials of Agriculture, pp. 83-84. Ginn and Company. Burkett, C. W. 

 Soils, pp. 266-274. Orange Judd Company. Roberts, I. P. The Fertility of the Soil, pp. 20-29. The Mac- 

 millan Company. Lyon, Fippin, Buckman. Soils, their Properties and Management, p. 418. The Macmillan 

 Company. 



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