42 



MASS. EXPERIMENT STATION BULLETIN 262 



usual pasture season is about 160 days and extends from early May to the 

 middle of October. The rainfall for the six months period, May 1 — October 

 31, as averaged over the last forty years at the college meteorological station 

 is 22.9 inches. In 1928 the total rainfall for that period amounted to 28.8 

 inches. It was reasonable to assume that the experiment had probably been 

 unduly favored by this liberal moisture supply. In 1929 the total precipitation 

 for the same period vv^as only 15.8 inches, with 0.7 of an inch in July and 1.-5 

 inches in August. In spite of this prolonged drouth, all plots showed a greater 

 carrying capacity than in 1928, and all plots except the check and plot VI 

 which received no nitrogen in 1929, showed an increased return per acre. This 

 fact is so contrary to the natural expectation under normal untreated pasture 

 conditions that it deserves special attention. 



Chart B. — Monthly Rainfall in Inches During the Pasture Season. 

 1928 and 1929. 



April May June July August September October 



Carrying Capacity of the Plots 



The carrying capacity in animal units for each plot during 1928 and 1929 is 

 presented in Chart C. An animal unit was taken as the equivalent of one 

 mature cow, one and one-half heifers, eight ewes or ten lambs. The pasture 

 season was taken as 163 days, and the carrying capacity equals the total pas- 

 ture days for the plot divided by the days in the pasture season. For ex- 

 ample, on this basis Plot I with a carrying capacity of 15.2 would have fur- 

 nished pasturage for 15 cows during the entire season. It is evident that, with 

 the exception of Plot I which had been in pasture for a longer period and 

 thus had a better pasture turf at the beginning of the experiment, there was 

 but slight variation between the plots (I, II, III, V) which received the com- 

 plete fertilizer and were grazed the entire season. In order to put all plots on 

 a directly comparable basis, that portion of the grass which was harvested as 

 hay was converted to animal units by taking 25 pounds of hay per day as the 

 equivalent of one animal unit. On this basis Plots VII, VIII and IX ranked 



