426 
Journal of Agricultural Research 
Vol. XXX, No 5. 
EFFECT OF VARIOUS QUANTITIES OF 
SODIUM NITRATE WITH AND WITHOUT 
DICYANODIAMIDE ON COWPEAS 
The data given in Table VI for the 
Norfolk sandy loam further emphasize 
the results reported in Table V. 
Applications of sodium nitrate had 
little effect on the growth of cowpeas 
either when used alone or with dicyano- 
diamide. In the latter case the nitrate 
usually increased the injury slightly 
instead of counteracting it. 
The relative abundance of nodules 
on the roots of the cowpeas was not 
appreciably affected by the treatments, 
except that quantities of dieyanodiam- 
ide large enough to injure plant growth 
usually inhibited nodule formation. 
The untreated pots were usually the 
best inoculated. 
SUMMARY 
In pot experiments using Norfolk 
sandy loam and Chester loam, the 
&.A/. 40 40 40 40 40 40 
CPAAETC'AXS A/O A//77PC?<9^yV /=>OT~&. 
Fig. 2.—Diagram showing the yield of cowpeas from pots receiving various amounts of dicyanodiam- 
ide and sodium nitrate 
The results with the Chester loam 
agree very closely with those in Table 
V in showing a fair increase in growth 
with sodium nitrate. Furthermore, 
the dicyanodiamide injury was slightly 
less in the presence of nitrate nitrogen, 
10 pounds of the ammonia equivalent 
being sufficient to more than counteract 
40 pounds of ammonia as dicyanodia¬ 
mide. The leaf yellowing and other 
visible signs of the dicyanodiamide 
poisoning were not lessened in the 
presence of nitrate nitrogen. 
marked difference between the toxicity 
of dicyanodiamide for wheat and for 
cowpeas was especially noticeable. 
The injury to wheat was only slight, 
even at the high concentration of 40 
pounds of the ammonia equivalent per 
acre. For cowpeas, 5 pounds of 
ammonia as dicyanodiamide was de¬ 
cidedly toxic. 
Where used on wheat, dicyanodiam¬ 
ide at the rate of 40 pounds of ammonia 
per acre produced some tip burning 
and decreased the green weights of the 
