SOIL NITROGEN 15 



inferiority in both nitrogen and organic matter of the west legume subplots 

 and equally definite superiority of the east nonlegume subplots, but the adja- 

 cent west nonlegume and east legume subplots run closely alike. Long-time 

 observation of the field causes the belief that the differences between the two 

 outer tiers of subplots are due to soil texture and moisture and not to crops 

 or fertilizers. Like the nitrogen fertilizers, legumes and nonlegumes have left 

 no permanent effects on these soils. 



F. Loehnis in Soil Science has pointed out that the effects of legumes on 

 succeeding crops soon pass off. 



Ratios between nitrogen and organic matter were calculated and averaged 

 for legume subplots and nonlegume subplots on each plot and are tabulated 

 for each year. When nitrogen was added in 1924 to Plots 5, 8, and 10, the 

 ratios of the two series of subplots were practically alike on these plots. For 

 Plots 6, 7, and 9 which were without nitrogen, the ratios were narrower on 

 the legume subplots. In 1931, when nitrogen was withheld from all plots, the 

 legume subplots with oats and peas showed slightly narrower ratios on all 

 plots than the nonlegume subplots with oats. Corn on all plots in 1927, with 

 no nitrogen on all plots, appeared to give a fairly uniform lot of ratios. 



The nitrogen in the subsoils varied within such narrow limits around .05 

 percent that results were averaged by plots and tabulated. In 1924, the plots 

 which had received nitrogen were definitely higher in subsoil nitrogen than the 

 plots which had been without nitrogen. In 1927, the variations were not 

 important. Organic matter in the subsoil ranged from 1.16 to 1.61 with no 

 positive trend. 



The subsoil 20 to 32 inches depth did not exceed .027 nitrogen and averaged 

 .012 on Plot 6, .015 on Plot 7, and .018 on Plot 9. Organic matter in Plot 7 

 was .63 percent and .69 percent in Plot 9. Such small proportions of organic 

 matter and nitrogen at this depth bear out Latimer's statement that Massa- 

 chusetts soils are seldom weathered beyond 30 to 36 inches in depth, as shown 

 in the Soil Surveys. 



Table 10. — Percentages of Nitrogen and Organic 

 Matter in Subsoil 



Nitrogen Organic Matter 

 Plot 



1924 1927 1924 1927 



Subsoil, depth 8 to 20 inches 



5 05 .05 



6 03 .055 



7 02 .06 



8 05 .055 



9 035 .06 



10 06 .07 



Subsoil, depth 20 to 32 inches 



6 012 



7 ' 015 .63 



9 018 .69 



