May, 1912.] 



431 



Scientific Agriculture. 



Dadaps cut in Dadaps not cut in 

 1907. 1907. 



19 acres 



8 acres 



Unman- 



manured. 



unmauured. 



ured. 



1903 2,330 



3,880 



1,327 



1904 5,245 



5,173 



2,426 



1905-1906 9,582 



8,644 



4,130 



1906-1907 4,742 



6,344 



3,410 



1907-1908 5,933 



7,655 



4,199 



1908-1909 7,991 



10,259 



3,238 



1909-1910 7,081 



7,645 



1,803 



1910-1911 5,622 



6,729 



1,405 



THE PRINCIPLES OP PADDY 

 MANURING. 



By W. H. Harrison, 

 Agricultural Chemist. 



(Continued from page 3^3.) 



Part II. 



(From the Department of Agriculture, 

 Madras, Vol. HI., Bulletin No. 63.) 



Having now briefly summarized the 

 conditions peculiar to paddy cultivation, 

 and their effect on the question of 

 manuring that crop, it becomes neces- 

 sary to review the manures available in 

 Southern India for this purpose, and to 

 discuss briefly their utility. For this 

 purpose the manures may be classed as 

 follows :— 



h Bulky Organic Manures. — This class 

 includes most of the popular manures 

 for paddy, e.g., green manures, poonacs, 

 farmyard manures, fish manures, etc., 

 and all of them are characterized by the 

 large proportion of organic matter they 

 contain, and, as decomposition must take 

 place before either humus is formed, or 

 the manurial ingredients become avail- 

 able as plant food, it is necessary 

 to apply them before transplanting. 

 The rate of decomposition of these 

 manures is, however, very rapid under 

 the conditions mostly obtaining under 

 paddy cultivation, and within less than 

 one month it has proceeded far enough 

 to be of benefit to the young plants, and 

 consequently there is usually no neces- 

 sity to apply these manures more than 

 one month previous to the time of trans- 

 planting. On the other hand, if applied 

 only very shortly before transplanting, 



the manure is not sufficiently decom- 

 posed to be of much value to the plants, 

 and in addition actual harm may occur 

 owing to the products of decomposition 

 seriously affecting the growth of the crop. 



Wherever the local conditions render 

 it possible to grow a crop previous to a 

 paddy crop, manuring by means of a 

 green-manure crop may be carried out. 

 Such crops as Sesbania aculeata (daincha), 

 C 'rotalaria juncea (sunn-hemp), Tephrosia 

 purpurea (wild indigo), Phaseolusmungo 

 (green gram), etc., through the agency 

 of peculiar bacteria which live on their 

 roots possess the power of assimilating 

 the free nitrogen of the atmosphere and 

 storing it up in their tissues. On plough- 

 ing these crops into the soil decomposi- 

 tion takes place, and the nitrogen they 

 have absorbed becomes available for the 

 ndxt crop. In other words, through 

 their use the cultivator has the power 

 of obtaining the usually expensive nitro- 

 gen at a very low cost, and consequently 

 green-manuring must not be despised. 

 The nitrogen supplied to a crop by 

 means of poonacs costs from As. 8 to Sh 

 per lb., that supplied by means of arti- 

 ficial manures costs about As. 10 per lb., 

 whereas the nitrogen supplied by a 

 green-manure crop is obtained merely at 

 the cost of ordinary cultivation charges, 

 and may be put down as a maximum of 

 one anna per lb., and usually the actual 

 figure is much less than this. 



Under favourable conditions, daincha 

 will grow to a height of over 8 feet, and 

 enough can be grown on one acre to 

 supply sufficient nitrogen to manure 

 about four acres of paddy. Sunn-hemp 

 being a smaller growing plant will not 

 yield so much green-manure, but even 

 in this case the produce of one acre will 

 answer for over two acres of paddy, 

 Wild indigo and the grams are in com- 

 parison to the above only dwarf plants, 

 the amount obtained from an acre should, 

 unless the crop is very heavy, be applied 

 to the land on which it is grown. 



With regard to green-manures, it must 

 be borne in mind that the potash and 

 phosphoric acid they contain is obtained 

 from the soil on which they are grown, 



