422 
J oumal of Agricultural Research 
Vol. XXX, No. 5 
as the check, it will be observed that 
sodium nitrate produced an increase 
of growth in about the same proportion 
as would be expected where the only 
source of nitrogen was nitrate. On 
the sandy loam nitrate equivalent to 
5 pounds of ammonia per acre was 
more than sufficient to counteract the 
40 pounds of ammonia as dicyanodia- 
mide. On the Chester loam this 
quantity was not quite sufficient, but 
10 pounds was more than adequate. 
C. Dicyanodiamide and Sodium Ni¬ 
trate in Varying Proportions; 
Nitrogen Constant 
This experiment was planned so 
as to keep the nitrogen content con¬ 
stant throughout while supplying the 
nitrogen as dicyanodiamide and sodium 
nitrate in different proportions. Such 
mixtures would approximate ordinary 
fertilizer practice on the basis of 
nitrogen content, but would contain 
a portion of the nitrogen as unavailable 
dicyanodiamide. The data given in 
Table III and shown in Figure 1 
confirm the results reported in previous 
tables, again demonstrating that di¬ 
cyanodiamide is not markedly toxic 
and that the reduction in green weight 
is overcome by the application of 
very small quantities of sodium nitrate. 
The yields obtained with mixtures of 
the two materials depended almost 
wholly on the nitrate content, particu¬ 
larly on the sandy soil. The yields 
on the Chester loam were somewhat 
irregular and not always in agreement 
with those to be expected from the 
fertilizer treatments. 
RESULTS WITH COWPEAS 
In order to determine the residual 
effects of dicyanodiamide applications, 
a few of the pots which had grown a 
crop of wheat were planted to cowpeas 
without additional treatment. The 
green weights of the plants are given 
in Table IV. 
The results obtained on the Norfolk 
sandy loam show a marked injury by 
dicyanodiamide even to the second 
crop, in fact greater than to the first 
crop. However, there seems to be 
no doubt that the cowpea is much less 
tolerant of dicyanodiamide than is 
wheat. This point is well illustrated 
in subsequent tables. During growth 
the cowpeas showed the same leaf 
yellowing and mosaic appearance as 
where fresh applications of dicyanodi¬ 
amide had been used, but possibly 
to a slighter degree. This is in agree¬ 
ment with the results reported by the 
majority of investigators which show 
that dicyanodiamide is not readily 
decomposed in the soil. Under green¬ 
house conditions, where there was no 
leaching, the dicyanodiamide would 
necessarily have to be broken up 
chemically in order for its injurious 
effects to be eliminated, unless perhaps 
a small amount might be removed from 
the soil solution by absorption. 
On the Chester loam the results 
obtained with cowpeas were somewhat 
indefinite, the mixture of dicyanodia¬ 
mide and sodium nitrate giving slightly 
smaller green weights than the check, 
whereas both dicyanodiamide alone 
and sodium nitrate alone gave increases 
over the no-nitrogen treatment. The 
differences are not very significant. 
Table III.— Green weights of wheat from pots receiving varying quantities of both 
dicyanodiamide and sodium nitrate 
Treatment 
No fertilizer__ 
No nitrogen__ 
Sodium nitrate 40.... 
Sodium nitrate 35, dicyanodiamide 5 
Sodium nitrate 30, dicyanodi¬ 
amide 10 ...... 
Sodium nitrate 20 , dicyanodi¬ 
amide 20 ..... 
Sodium nitrate 10 , dicyanodi¬ 
amide 30..... 
Sodium nitrate 5, dicyanodi¬ 
amide 35... 
Dicyanodiamide 40.. 
Fertilizer ratio Green 
NH 3 -P 2 O 5 -K 2 O weight 
Grams 
0 - 0-0 
0-8-4 
4-8-4 
1 
4-8-4 
4-8-4 
4-8-4 
4-8-4 
4-8-4 
20.3 
19.3 
16.4 
15.5 
12.2 
12.3 
8.3 
10.8 
7.8 
9.2 
4-8-4 
{ 
6.8 
7.9 
Increase 
Increase 
Average 
or de¬ 
crease 
over 
Green 
weight 
Average 
or de¬ 
crease 
over 
check 
check 
Grams 
8.2 
12.7 
8.9 
16. 7 
19.2 
10.3 
22.8 
6.1 
} 19.8 
10.9 
/ 21.4 
\ 18.6 
} 20.0 
3.3 
} 16.0 
7.1 
/ 18.0 
\ 16.0 
} 17.0 
.3 
} 12.3 
3.4 
/ 21.5 
\ 22.1 
}■ 21.8 
5.1 
} 9.6 
.7 
/ 17.6 
\ 20.2 
} 18.9 
2.2 
} 8.5 
-.4 
/ 19.1 
\ 17.1 
J- 18.1 
1.4 
} 74 
-1.5 
f 14.9 
\ 14.3 
| 14.6 
- 2.1 
