April, 1912.] 



843 



Scientific Agriculture. 



when in the form of nitrates is parti- 

 cularly liable to be washed away. On 

 the other hand, the dangers of loss by 

 washing away ammonia is very slight, 

 for, although the substance is very 

 soluble in water, the soil has such an 

 attraction for it as to remove it from 

 solution and so prevents any loss by 

 leaching occurring. These considerations 

 lead to the conclusion that nitrates in 

 any form are not suitable manures for 

 paddy, whereas ammonium compounds 

 or substances which yield ammonia 

 under anaerobic conditions are useful, 

 and actual experiment at Ooimbatore 

 has shown that calcium nitrate and 

 saltpetre are of little value when applied 

 to a paddy crop. 



The factors discussed above have, so far 

 as manurial ingredients are concerned, 

 dealt only with the utility of the 

 different forms of nitrogen, whereas all 

 manuring must have reference to the 

 supply of potash and phosphoric acid as 

 well. 



Paddy being a cereal, the general re- 

 quirements of that class apply in so 

 much as those crops respond to the 

 application of nitrogen and phosphoric 

 acid, and these manurial ingredients 

 are therefore the ones most generally 

 used, whereas potash is usually only 

 applied when the soil is known to be 

 deficient in that respect. 



Thus broadly speaking, in manuring 

 these crops attention is primarily paid to 

 supply an adequate amount of nitrogen 

 and phosphoric acid, the supply of potash 

 only receiving a secondary consideration. 

 That this holds good for paddy is shown 

 by the results of the manurial experi- 

 ments carried out in the Godavari and 

 Kistna Deltas and at Ooimbatore, for out 

 of seven experiments the use of nitrogen 



and phosphoric acid gave an increased 

 yield over nitrogen alone, and further in 

 five of the cases the addition of potash 

 actually produced a decreased yield. For 

 instance, at Ooimbatore, nitrogen (in the 

 form of a green-manure crop) and phos- 

 phoric acid gave a yield of 3,733 lbs. of 

 paddy and 4,043 lbs. of straw per acre, 

 whereas nitrogen, phosphoric acid and 

 potash gave only 3,294 lbs. of paddy and 

 3,228 lbs. of straw. Thus the need for 

 supplying potash in paddy manuring is 

 comparatively unimportant and is deter- 

 mined chiefly by the character of the soil 

 on which the crop is grown. This is an 

 exceedingly fortunate result to obtain, 

 for potash is expensive and consequently 

 the fact that its use can usually be dis- 

 pensed with decreases very greatly the 

 cost of manuring. It is true that in these 

 experiments the use of a comparatively 

 large amount of potash has often led to 

 a large increase in yield, but in these 

 cases, the cost of the manure supplied 

 has often been greater than the increased 

 value of the crop obtained, and has in 

 fact resulted in a small loss to the cultiv- 

 ator. 



The position arrived at so far may be 

 summarized as follows : — 



1. Paddy soils need manuring with 

 bulky organic manures which readily 

 decompose under anoerobic conditions, 

 yielding humus. 



2. Nitrates are unsuited for the pur- 

 pose, whereas ammoniacal manures or 

 manures which yield ammonia under 

 anserobic conditions of fermentation are 

 of great value. 



3. Nitrogen and phosphoric acid must 

 be applied to all paddy soils, whereas 

 potash should only be applied when the 

 soil is in particular need of that ingre- 

 dient. 



