EFFECT OF SOIL FACTORS OX WATER REQUIREMENT. 
51 
These determinations include the variation in water requirement 
arising from seasonal differences, kind and amount of soil used, and 
the kind of fertilizer employed. The magnitude of the probable 
errors shows that there were also in many cases other disturbing fac- 
tors of a serious character which were not under control. Although 
the water requirement for a given crop varies widely according to 
season, soil, and fertilizer, the results show conclusively a marked 
reduction in the water requirement accompanying the use of phos- 
phate as a fertilizer for these soils. Representing the water require- 
ment of the unmanured soil in each case by 100, the mean value when 
nitrogen alone was used was 97; nitrogen and phosphorus, 75; nitro- 
gen, potassium, and phosphorus, 73. These results indicate, there- 
fore, the necessity of an adequate supply of plant food in order to 
secure the most economical use of a given water supply. 
Table XXXIX. — Influence of fertilizers on the water requirement of vhcat and corn at 
Pusa, India, 1 according to Leather (1910). 
Jar capacity. 
M 
Water requirement, using— 
Crop and year. 
"ater in 
soil. 
Xo fer- 
tilizer. 
N 
N+P 
X+P + K 
Mean. 
Mean, 
omit- 
ting 
X+P 
+ K. 
Wheat ( Triticvm sativum i: 
1906-7 
Kilograms. 
f 15 
1 22 
/ 
1 
I 
cr cent. 
10 
15 
20 
10 
15 
20 
900 
6.53 
829 
941 
1,060 
955 
1,050 
944 
1,000 
806 
837 
865 
543 
540 
574 
593 
504 
515 
527 
515 
614 
604 
755 
663 
747 
7:;o 
751 
2 726 
Means for 1906-7 . 
890±37 
91 7 ±30 
545 ±10 
569±14 
1 ! 
1 »{ 
10 
20 
10 
20 
634 
1,133 
696 
821 
3 523 
3 725 
3 500 
3 575 
<571 
4 725 
« 446 
4 505 
576 
861 
547 
634 
1907-8 

Means for 1907-8 
821 ±75 
5S1±35 562 ±43 
1 1 
1 . 
10 
15 
20 
10 
15 
20 
10 
15 
20 
Corn (Zea mays) grown in 
Pusa soil: 6 
459 
368 
604 
500 
589 
381 
450 
421 
429 
404 
377 
529 
645 
'""527' 
412 
505 
480 
2S7 
323 
382 
309 
281 
295 
262 
286 
295 
344 
322 
336 

383 
356 
505 
48.5 
1907 
M52 
401 
375 
404 
401 
Means for 1907 
467±19 
485 ±21 
302 ±7 
334 ±7 
1 A single open pot was used for each treatment. 
2 The mean value 569 was used for the absent term of the X±P+K series in calculating this mean. 
3 In these determinations rape cake was used, equivalent to 5 milligrams X per 100 grains of soil. 
4 In these determinations superphosphate plus phosphoric acid in rape cake was used, equivalent to 10 
milligrams soluble P2O5 per 100 grams soil. 
5 X=Ca(X0 3 )2=5 milligrams X per 100 grams soil: P=superphosphate = 10 milligrams soluble P2O5 per 
1C0 '.{rams soil. 
6 The mean of the X ratios was used in place of the absent term in calculating this average value. 
285 
