14 NEW HAMPSHIRE EXPERIMENT STATION [Bulletin 271 



had an annual top-dressing of 250 pounds of superphosphate in addi- 

 tion to nitrate of soda and manure, and those which did not have this 

 substance. The increase for these plots, then, must have been due en- 

 tirely to the beneficial effects of the manure and nitrate of soda. 



Annual top-dressings of 250 pounds of 16 per cent, superphosphate 

 appear to have stimulated timothy yields more when used without 

 manure or nitrogen. The total increase recorded for these superphos- 

 phate plots (P) is 2,279 pounds, although the increase is not significant. 

 When it is understood that 1,617 pounds of this increase came in the 

 1927 season — the first year after a stand was secured on these plots — 

 it can readily be seen that the effect of the superphosphate was ex- 

 hibited largely in the germination of the seed and in securing a some- 

 what earlier stand. 



In this connection it is well to remember that the plots were top- 

 dressed in the spring of 1926 before we were certain whether a stand 

 would be obtained. When it appeared later that the stand was meager 

 on all the unmanured plots, the land was re-worked and reseeded. This 

 reworking undoubtedly stirred that application of superphosphate to 

 greater depths and stimulated the early growth there as well as t)ie 

 1927 yield of hay. 



Though additional superphosphate was top-dressed annually on these 

 plots, the 1927 increase was not maintained. This seems to indicate 

 that the material was absorbed or fixed in the soil before it penetrated 

 to the layer in which most of the grass roots feed or that there was suf- 

 ficient available phosphoric acid through succeeding seasons to supply 

 the needs of the crop. 



The behavior of these plots to superphosphate serves to emphasize 

 the importance of using an ample amount of this substance at the time 

 of seeding when it can be drilled or harrowed into the soil to a lower 

 depth than if it is applied later as a top-dressing. 



Nitrate of soda (N) on unmanured land gave a slightly better account 

 of itself than where used with manure, the total increase for the five 

 years amounting to 4,884 pounds, or an annual increase of 977 pounds 

 for each 100 pounds of nitrate of soda applied. 



Where nitrate of soda and superphosphate were both applied (NP), 

 the increase was slightly larger than for nitrate of soda alone, but here 

 again the increase came largely in the 1927 season as it did on the super- 

 phosphate (P) plots. 



Since lime was applied as a cross treatment, one group of plots that 

 were manured and top-dressed annually were unlimed, an equal number 

 were treated with two tons in 1925, and a third group of the same size 

 received four tons the same year. 



The hay yields for these variables are shown in the following table: 



