86 MASS. EXPERIMENT STATION BULLETIN 204. 



Yields on No-nitrogen Plots. 

 The yields of the plots without nitrogen, 4, 7 and 9, have been closely 

 studied to ascertain whether there were any consistent differences in their 

 production which might be due to variations in soil; but no uniform 

 relations have been found. During the thirty years, 1889-1918, there 

 was but one season, 1892, when the yields of the three were closely alike. 

 Sometimes one plot has been the best and at other times the poorest. 

 Plot 7 has been the highest in twelve years and the lowest in seven, while 

 plot 4 was highest in eleven and lowest in fifteen years; therefore 7 may 

 be a httle the best, while 4 has been possibly a bit poorer than 9. But the 

 differences are slight and cannot be used to explain the variations in 

 yields on the plots receiving sulfate of ammonia. Previous to 1910 the 

 divergences between the highest and the lowest yields on these plots 

 without nitrogen were often from 25 to 30 per cent, and even more, while 

 after the somewhat heavy liming in 1909 — though it covered only one- 

 half the area — the divergences were nearly always less than 10 per cent. 



Yields on Sulfate op Ammonia Plots. 



The yields on the plots which receive sulfate of ammonia have been 

 somewhat erratic, with first one plot and then the other showing marked 

 inferiority to the other two, and also to the adjacent plots which receive 

 no 'nitrogen. There is an indication from the flow of drainage water 

 that plot 8 may have soil slightly more open in texture than the soil of 

 5 and 6; otherwise there is no apparent reason for the variations that 

 have occurred in the yields of these plots in different seasons, by which 

 8 has oftenest been the lowest producer. 



Tables of rainfall and crop yields are given on pages 88 and 89. The 

 gross weights of crops for the individual plots are used without division 

 into grain and straw when the cereals are listed. Nitrogen is definitely 

 known to be a promoter of plant growth rather than maturit}^, hence 

 the total weight per plot is a proper measure of the crop-producing power 

 of a nitrogenous fertilizer. 



Crops Grown. 



Eight different kinds of crops have been grown in the period of thirty 

 years covered by the tables. Each kind of crop is taken up separately 

 in discussing the comparative yields from the plots with sulfate of am- 

 monia and from those without it. 



Corn. — Corn has been grown in five of the seasons included in this 

 summary. The first crop was in the first year of the experiment. Corn 

 had been grown continuously since 1883, and soil conditions had become 

 such that the yield was smaller than in any of the subsequent years; 

 therefore this year will not be considered in the discussion. The four 

 crops to be compared were grown under somewhat varied conditions of 

 soil and previous cropping. 



