May, 1912.] 



433 



Scientific Agriculture. 



that reducing the profits, but unless 

 there is actual need for it the tendency- 

 is to reduce the yields given when com- 

 pared to fish manure alone. Thus the 

 use of 560 lbs. of fish manure and 56 lbs. 

 of sulphate of potash resulted in a net 

 profit of only Rs. 82 as against a profit 

 of Rs. 114 with fish manure alone. On 

 the other hand, with one experiment in 

 the Kistna delta, potash gave an actual 

 increase in the profit obtained. 

 _2. Manures obtained from Bones, the 

 chief of which are bone-meal and bone 

 superphosphate, can under certain cir- 

 cumstances be used with advantage in 

 manuring paddy. Bone meal is ex- 

 ceedingly rich in phosphoric acid, and 

 as a rule contains a fair proportion of 

 nitrogen, and at the same time it under- 

 goes rapid decomposition in paddy soil, 

 and its manurial ingredients are thus 

 quickly made available for plant food. 

 To a certain extent, therefore, it con- 

 forms to the principles laid down on the 

 first part of this article, but the amount 

 of humus it can yield is exceedingly small , 

 and the best effects are produced when 

 it is used in conjunction with a manure 

 containing large quantities of organic 

 matter, particularly with green-manures. 

 In this ease, the substances produced by 

 the decomposition of the green manure 

 assist the solution of the phosphoric 

 acid of the bones, and thus make the 

 latter much more available for the plant 

 than would otherwise be the case. The 

 same strictures which apply to the use 

 of potash manures with fish manures 

 apply also in this case. Unless the soil 

 is very deficient in potash, recourse 

 should not be had to this ingredient 

 owing to its tendency to reduce the 

 yields and profits. Thus at Coimbatore 

 5C0 lbs. of bone-meal yielded a net profit 

 of Rs. 112 per acre, whereas the same 

 quantity to which 56 lbs. of potassium 

 sulphate were added only gave Rs. 79. 



Bone superphosphate is obtained by 

 treating bones with sulphuric acid, by 

 which the phosphoric acid is made solu- 

 ble, and when added to a soil is at once 

 available as a plant food. This manure 

 is therefore a "quick-acting manure," 

 and its effect is best seen when given in 

 55 



the form of dressing to crops already in 

 the ground. Usually it contains some 

 nitrogen in addition to the phosphoric 

 acid, but its value is mainly dependent 

 upon the amount of the latter ingredient 

 present, and consequently with soils poor 

 in humus, such as are general in Southern 

 India, it is best used in conjuction with 

 the bulky organic manures. Thus at 

 Coimbatore, land manured solely with 

 a green-manure crop grown on the land 

 itself gave 2,814 lbs. of paddy and 2,691 

 lbs. of straw, whereas similar lands 

 manured with the same green-manure 

 crop plus 112 lbs. of superphosphate 

 gave 3,733 lbs. of paddy and 4,043 lbs. of 

 straw. The conclusion in the case is 

 obvious, especially when it is noted that 

 the large increase was due to an amount 

 of super, valued at less than Rs. 3. 



It must also be pointed out that the 

 use of comparatively large dressings of 

 super does not yield a commensurable 

 increase in the crop obtained, so that, 

 except under exceptionable circum- 

 stances, a dressing of 112 lbs. of super 

 to the acre is the maximum necessary. 



3. The Mineral and Artificial Man- 

 ures. — These manures which include 

 superphosphate, ammonium sulphate 

 and saltpetre are with the exception 

 of the last not of great importance to 

 the ryot owing to their comparative 

 scarcity and high price. Saltpetre is 

 produced locally in large quantities, and 

 as it contains both potash and nitrogen, 

 it is under certain conditions of cultiv- 

 ation a good manure, but the nitrogen 

 being present in the form of nitrate, it 

 is as was shown at an earlier stage not 

 suited for paddy manuring. 



Ammonium sulphate is only produced 

 in India to a very limited extent, and 

 is mainly imported from Europe, so that 

 although it is a quick-acting manure and 

 quite suited to paddy cultivation, the 

 cost of the nitrogen is so great that at 

 present it may be left out of account by 

 the ryot. 



Superphosphate is prepared from 

 mineral phosphates in exactly the same 

 way that bone superphosphate is pre- 

 pared from bones, and consequently 



