FIKLD EXPERniENTS. 27 



the yield in 19 10 about four-tentlis of a ton per acre and in 

 191 1 there was a small increase in yield over the plot to which 

 Thomas phosphate powder was applied. In top dressing ex- 

 periments* on the College farm no appreciable benefit was 

 found from the use of phosphoric acid. 



The fertilizer for plots A and C would cost in these amounts 

 about $8.50 for each of the three yearly applications or about 

 $25 for the three years for each fertilized plot. It would seem 

 doubtful that on this particular land any advantage was de- 

 rived from the addition of the Thomas phosphate powder 

 other than maintaining the fertility of the soil. On this plot 

 there was for the three years 1.85 tons of hay cut more than on 

 the unfertilized plot. As the cost of applying the fertilizer was 

 small and the extra labor in harvesting the crop not much 

 increased because of this increased yield the extra hay was 

 obtained on plot C at a cost of about $13.50 per ton. On plot 

 A the increased yield of 2.8 tons was obtained at a cost for 

 fertilizer alone at the rate of a little less than $9 per ton. 



The Station practices top dressing its mowing lands at High- 

 moor Farm each year with a mixture of 100 pounds of nitrate 

 of soda, 100 pounds of muriate of potash and 150 pounds of 

 acid phosphate. This costs for the materials applied to the 

 land about $6 per acre. Such a mixture supplies more phos- 

 phoric acid than the crop of hay removes from the soil, about 

 the same amount of potash as the crop of hay removes and 

 about one-third to one-half of the nitrogen. It is doubtful if in 

 average years more than 100 pounds of nitrate of soda can 

 be applied without danger of loss from leaching. 



Top dressing of mowing lands is profitable if the resulting 

 increase in the hay crop is to be used and fed on the farm. 

 At the price fixed in 1913 for the valuation of fertilizers at 

 tide water in ton lots the fertilizing constituents of a ton of 

 mixed hay are worth over $7. To sell hay is to sell oft" from 

 the farm fertilizing materials that will cost, including the cart- 

 ing of the hay to a shipping point, the purchase and applica- 

 tion of fertilizers to make good those sold in the hay at least 

 $9 for every ton sold. Not to plan to replace the fertilizing 

 constituents is to rob the farm of that amount of plant food. 



*Bulletin 94, Maine Station. 



