Scientific Agriculture. 



62 



January, 1909. 



known as leguminous ( Pulse order ) has 

 the power of utilising the free nitrogen 

 of the atmosphere into its own consti- 

 tuents. This it does either directly by 

 making the free nitrogen unite with its 

 own substances or indirectly by making 

 it unite with other substances in the 

 air and then utilising it for its own 

 purpose." 



Green manuring is not a new system 

 of manuring for India. It appears to 

 have existed in various parts of India 

 from very early times, though its 

 rationalistic explanation in the light 

 of agricultural chemistry was not 

 known. It is the same as what is known 

 as the " Pachaithol valam " in Malabar, 

 Travancore and other places on the 

 West Coast. Leaves of certain kinds of 

 trees, such as Portia or Silanti (Thes- 

 phesa populnea), Erukku {Calopropis 

 gigantea) Mango (Nanagifera mdica) 

 Avarum ( Cassia agriculata ) are in 

 these places commonly used as manure 

 for field crops. A few months prior to 

 the cultivation of the staple crop, horse 

 gram is usually grown in the fields 

 with a purpose to produce leaves to 

 get them ploughed into the soil. In the 

 case of the trees mentioned above, their 

 leaves are chopped and applied to the 

 soil soon after ploughing, in order that 

 they might mix with the earth and 

 decay. In some cases a few of the 

 staple plants are taken en masse from 

 the ground and in that spot cropped 

 leaves with mud are put in and over 

 this the plants are placed so that they 

 might strike root below in the manured 

 ground. Even leaves of ordinary jungle 

 trees are largely used as manure. Thus 

 it will be seen that our old farmers had 

 some idea about the utility of the appli- 

 cation of green leaves to the soil. They 

 knew that when some plants were 

 plouged into the soil or are simply raised 

 on it, the soil becomes exceedingly pro- 

 ductive. But it was only at the end of 

 the last century that the German 

 chemist made some investigations on 

 the subject and discovered that these 

 leguminous plants develop certain nodu- 

 les at their roots which serve to accumu- 

 late millions of nitrifying bacteria. 

 This genus of plants known as legumi- 

 nose ( Pulse order) were found to enrich 

 the soil in which they grew. They 

 have the peculiar power to absorb from 

 the atmosphere more nitrogen than 

 they require. They take just what they 

 want for their growth and leave the 

 surplus in the soil, In the above, we 

 have shown what " Green manuring " is. 



One of the important properties 

 of green manure is nitrification. 

 Besides ^nitrification it has also other 



properties. When the various parts 

 of these leguminous plants get de- 

 composed and get mixed with the 

 soil the particles of the soil are made 

 to recede from one another, and as a 

 result the soil gets loosened. Thus these 

 green manures serve to assist in the 

 physical growth of the staple crop. 

 Again, the decomposition of vegetable 

 substances causes the evolution of car- 

 bonic acid. Plants, we know, are unable 

 to assimilate any substance except in 

 solution. It is for this reason that water 

 is so necessary to plant life. The pre- 

 sence in the soil of carbonic acid or its 

 source in the form of decomposing plants 

 is highly useful for the healthy growth 

 of plants ; for carbonic acid has the 

 property of dissolving various com- 

 pounds which are insoluble in water. 

 Side by side with these advantages, there 

 is, perhaps, one minor disadvantage- 

 The decomposition of organic substances 

 also causes the evolution of sulphurated 

 hydrogen, which is extremely injurious 

 to plant life. But the evil effects of 

 this gas might be considerably minimised 

 by turning up the earth more frequently 

 than when other manurial agents are 

 used. 



Various plants are used as green 

 manure. Which of them is best cannot 

 be definitely said. It largely depends 

 upon the nature of the soil and the 

 variety of the staple crop. For instance, 

 horse gram, which is known to be a good 

 green manure, proves a failure when 

 tried on a crop of black gram. In a 

 lecture delivered by Mr. Herbert Wright 

 some time ago he mentioned the use of 

 Grotaralia striata, ground-nut, dadaps 

 and albizzia as green manures best suited 

 for tea plantation. They are found 

 equally useful in the case of coffee, 

 cocoa and rubber. There are other green 

 manures, such as mimsoa pudica, certain 

 varieties of cassias, tephrosia purpuera 

 and Sesbania grandiflora, which might 

 be used with great advantage in coconut 

 and tobacco plantations. Mr. Wright 

 is a staunch advocate of " Green manur- 

 ing." He believes " that the growing of 

 leguminous crops, besides enriching the 

 soil when dug in, keeps the temperature 

 of the soil more uniform in both the 

 damp and dry seasons, breaks the force 

 of rain and reduces the amount of wash, 

 prevents the loss of plant food by the 

 percolation of water and drainage, and 

 helps to keep the weeds in check." Of 

 the green manures 'mentioned above, 

 Crotalaria striata is not very commonly 

 used as green manure. The seed of 

 Crotalaria striata is sown broadcast and 

 the plants may be uprooted within six 

 or eight months after sowing. It yields 

 a large amount of a green organic 



