Scientific Agriculture. 



432 



[May, 1912. 



and in consequence no enrichment of 

 the land in this respect is obtained. All 

 that happens is that the potash and 

 phosphoric acid present in the soil is 

 taken up by the green manure crops and 

 again returned to the land, but in a 

 condition to be readily absorbed by the 

 main crop which follows. Now as the 

 practice of green-manuring leads to 

 heavier paddy crops, it follows that ulti- 

 mately more potash and phosphoric acid 

 is removed from the soil than would 

 otherwise be the case, and the land in 

 consequence will all the sooner be im- 

 poverished with regard to these two 

 manurial ingredients. Provision must, 

 therefore, be made to supply these ingre- 

 dients to the land in the course of 

 time, and this is done best by occasionally 

 dressing the soil with such manures 

 as super and bone-meal which are very 

 rich in phosphoric acid, and more occa- 

 sionally still with wood-ashes, sulphate 

 of potash, etc., manures which are rich 

 in potash. The point to be remembered 

 is this, that green-manures are not com- 

 plete manures, as they bring only nitro- 

 gen and humus to the soil. 



Green-leaf manures, i. e., leaf and 

 branches cut off from plants growing 

 on waste ground or forests and puddled 

 into the soil have practically the same 

 effect as green-manure crops, but they 

 differ from the latter in so much as they 

 supply potash and phosphoric acid in 

 addition to nitrogen. They are complete 

 manures, and from this point of view are 

 to be preferred to green-manure crops if 

 they can be obtained cheaply in the 

 requisite quantity. Unless, however, 

 they can be obtained locally at a very 

 cheap rate, and in the requisite quantity 

 it will be found more economical to util- 

 ize green manures crops grown on the 

 land itself supplemented by a compar- 

 atively small annual dressing of super- 

 phosphate or bone-meal. 



Comparative tests with green-manure 

 have been carried out at Coimbatore, 

 with the result that green-leaf manure 

 gave a yield of 4,490 lbs. of paddy and 

 5,811 lbs, of straw per acre, whereas the 

 same weight of daincha (grown on the 



ground) gave 4,000 lbs. paddy and 4,400 

 lbs. straw. The difference between the 

 yields of paddy in the two cases is not 

 great, considering the large yields ob- 

 tained, but such as it is it is due to the 

 extra potash and phosphoric acid 

 brought to the soil with the green leaves, 

 for when super is used in conjunc- 

 tion with a green-manure, the yields ob- 

 tained often exceed that obtained when 

 green-leaf manure is used. Compared 

 with the yields from plots receiving no 

 manure which gave only 3,392 lbs. of 

 paddy and 3,124 lbs. of straw, the effi- 

 ciency of green manures and green leaf 

 manures is undoubted. 



Poonacs and fish manures are also 

 bulky organic manures which can be 

 utilized with advantage where they are 

 obtainable at a cheap rate. They con- 

 tain a much larger portion of nitrogen 

 and other manurial ingredients than 

 green manures, and consequently can 

 be used in much less quantity. Thus 

 in an experiment carried out on the 

 Coimbatore Farm to compare the relat- 

 ive values of these bulky organic 

 manures, 4,000 lbs. of green leaves yielded 

 a profit of Rs. 120 per acre, 4,000 lbs. 

 of wild indigo Rs. 98, 400 lbs. of white 

 castor poonac Rs. 109, 500 lbs. of black 

 castor poonac Rs. 104, and 560 lbs, of fish 

 manure gave Rs. 114. 



Poonacs are complete manures, and 

 there is generally little necessity to use 

 any other manure in conjunction with 

 them unless it is -a superior bone-meal 

 to increase the proportion of phosphoric 

 acid put on the land. This mixture is 

 generally very effective in increasing 

 the yield of paddy, and the cost of the 

 super needed for the purpose is com- 

 paratively small. On the other hand, 

 fish manure is not a complete manure, 

 as it i3 practically devoid of potash, and 

 in consequence wherever the soil is 

 deficient in that ingredient, a mixture 

 of sulphate of potash or wood ashes 

 with fish manure can be used with ad- 

 vantage. The use of this mixture, how- 

 ever, should only be attempted after a 

 small trial has given successful results, 

 as not only is the potash expensive s 



