EFFECT OF FERTILIZERS ON MOWINGS 5 



Analyses of the crop from these experiments show a weighted average of 

 0.54 percent of phosphoric acid in the dry matter, or 0.47 percent on the basis 

 of cured hay with 14 percent moisture. This is about 30 percent higher than the 

 figures given by Henry and Morrison 3 for phosphoric acid in mixed grass hay, 

 main crop and rowen. Readily available phosphoric acid in the untreated soil 

 of these experiments was 318 pounds per acre 4 (2,000,000 pounds of soil) accord- 

 ing to the Truog method, 5 and that soluble in N/5 sulfuric acid was much higher. 

 Using the figure of 0.47 percent for the phosphoric acid content of cured hay 

 grown on this soil, a 2-ton crop of cured hay would remove only 18.8 pounds of 

 phosphoric acid per acre per year. It would appear, then, that there was during 

 the course of the experiment an ample supply of available phosphoric acid for 

 the hay crop, and that the potential supply is good. 



The question arises as to whether the content of available and potentially 

 available forms of phosphoric acid is high in this soil. The field on which this 

 experiment was conducted had been farmed for many years, and during the 

 fifty-odd years the Experiment Station has had charge of it, more or less phospha- 

 tic fertilizer has been applied. In respect to previous fertilizer treatment it was 

 probably in slightly more favorable condition than the average hay land of 

 Massachusetts. No soil without previous fertilization was obtainable in this 

 experiment for determination of available phosphoric acid. Therefore, in an 

 attempt to get some idea of the content of this nutrient in unfertilized soil, a 

 sample was drawn from a slightly different soil type in a nearby wood, and 

 available phosphoric acid determined by the Truog method. This was found to 

 be 218 pounds per acre (2,000,000 pounds of soil); a figure not as high as that 

 for the untreated soil of the experiment, but still fairly high. There is no positive 

 assurance that the soil in the wood had not been fertilized at some time in the past ; 

 nevertheless the evidence points strongly to the conclusion that the native supply 

 of phosphorus in the soil on which the experiment was conducted was not very low. 



Botanical and Chemical Composition of the Hay. — The effect of the fertilizer 

 treatments on the character of the flora grown in these experiments was deter- 

 mined by botanical analysis of samples taken from Experiment 1A in 1931, and 

 by estimates of the composition of the growth on the plots of Experiment IB 

 in 1933. The results show a slightly superior type of vegetation, particularly 

 with respect to clovers, on the plots which received high potash. On those which 

 received high nitrogen there was a slightly higher percentage of the better grasses. 

 However, the differences were not great in any case. From these experiments it 

 would seem to be impracticable to make any considerable improvement in the 

 quality of the vegetation of an old mowing by the use of fertilizer alone. De- 

 terioration in quality can be deferred by fertilizers, but it appears best to plow 

 and reseed at intervals of 6 to 8 years at most. 



The effect of fertilizer treatments on the chemical composition of the hay crop 

 is shown by the analytical data on samples drawn from Experiment IB and 

 presented in Table 4. The results show only a slight effect of increments of nitro- 

 gen on the percentage of this element in the plant. The principal effect of the 

 nitrogen was to alter the size of the mature plant without materially changing 



•Henry, W. A., and Morrison, F. B. Feeds and feeding. The Henry-Morrison Co., Ithaca, 

 N. Y. 1925. 



*Determination made by John N. Everson. 



•Truog, Erail. The determination of readily available phosphorus in soils. Jour. Amer. Soc. 

 Agron. 23:788-799. 1931. 



