24 MASS. EXPERIMENT STATION BULLETIN 281 



Tlie toxic olTec-t was first observed in 1929 soon iifter the nitrate was applied. 

 At first the effect was thought to be a temporary foHage burn caused by contact 

 with the salt, but later it was found to be permanent. 



The disappearance of the moss is not due to crowding l)y grasses aiul clovers 

 as happens with some plants and treatments. The moss is actually killed. The 

 toxic effect increases with an increase in the amount of nitrate applied. The 

 effect is somewhat cumulative from year to year, so that small applications made 

 annually may in time produce the same effect as large ones, it seems. Since the 

 first observation of the toxicity of sodium nitrate for this moss was made on ex- 

 periment C, the effect has been observed at several other places, and experiments 

 have been started for studying the problem further. 



Discussion of Results 



All experiments reviewed in this bulletin have shown that chemical fertilizers 

 were generally beneficial on depleted pastures. There have been definite and 

 measurable beneficial changes in the character of the vegetation. In all cases 

 where records of yields were secured these were generally increased by the 

 fertilizers. 



In the Dickinson pasture experiment a rather generous annual application of 

 basic slag and low-grade sulfate of potash practically displaced bluets with white 

 clover. No nitrogen was used in this experiment. The soil on which the experi- 

 ment was located is not typical of any large proportion of permanent pastures in 

 Massachusetts. 



Experiments A, B, and C were located on soils which are typical of a large 

 proportion of permanent pastures in the state — on soils notaljly deficient in plant 

 nutrients. These experiments, likewise, have sho\vn beneficial changes in vege- 

 tation from the application of lime, phosphorus, and potassium. Of all single 

 materials used in these experiments, lime was most effective in producing desir- 

 able changes in the character of the vegetation. Lime and potash were the most 

 effective combination of two elements in producing such changes; but lime, pot- 

 ash, and phosphate were the most effective of all. Since gypsum alone induced 

 a fair percentage of white clover in the stand on experiment B, there is some 

 evidence that it was the calcium in the lime which produced the principal benefit 

 rather than the effect of lime on the soil reaction. 



With the exception of the elimination of haircap moss, nitrogen applied as 

 nitrate of soda has not produced any profound changes in the character of the 

 vegetation, such as were caused by the minerals. On the other hand, nitrogen 

 added seems not to have interfered with the action of the minerals in encourag- 

 ing white clover. Experiment B has given definite results on this point. Data 

 from experiment C are inadequate for a conclusion. 



While nitrogen has not been an important positive factor in imi)roving the 

 quality of the pasture fiora, its effect on the quantity has been marked. It has 

 produced the greatest relative increase in yield when used alone, but the great- 

 est absolute increase when usetl in connection with minerals. In table 17 figures 

 are given which show average increases in grass and clover due to added nitrogen 

 in experiment C of 48 to 214 per cent with minerals, and 3U per cent without 

 minerals. Other data from the same experiment show tliat in individual cases 

 added nitrogen caused yields several times those from minerals alone. 



The observations and records of ex{)eriment li have brought out the im- 

 portance of white-clover years in the measuring and interpretation of results. 

 Due to causes not fully understood, white clover comes and goes by seasons. In 



