CHAPTER X. 



THEORIES UNDERLYING CULTIVATION OF SOILS. 



'"PHE objects of cultivation are : (i) to allow roots to 

 penetrate easily into the soil ; (2) to allow air and water 

 to find easy access into roots and the soil ; (3) to allow absorp- 

 tion of moisture and of gases by soil to take place easily ; 14) to 

 allow the microbes which help in the formation of nitrates to 

 thrive more freely with free access of CO 2 , O and N; (5) to 

 facilitate weathering of particles of soil chiefly by the action of 

 O,CO 2 and H 2 O. (6) Nests of parasites are also broken up 

 and disturbed by cultivation. In one word, cultivation 

 helps to bring about a mechanical, chemical and biological 

 change in the character of soil. 



119. The advantages of protracted cultivation are : (a) 

 better aerification, (b) better tilth and (c) exposure of insect 

 and fungus pests to the action of birds, ants, sun-light 

 &c. Cold weather preparation for kharif crops is actually 

 practised by the best cultivators who know it improves the 

 soil and gives them a better return. In the rabi season 

 protracted cultivation is not always desirable as there is loss 

 of moisture, the retention of which is needed for proper 

 germination and growth. 



1 20. The advantages of deep cultivation are : (i) Roots 

 can penetrate deeper and find food from the subsoil. Young 

 plants have a great tendency towards root development. 

 Hellriegel found that barley plants 10 days old and only in 

 their third leaf had 42 Ibs. of dry matter in their roots for 

 every 58 Ibs. of dry matter in the leaves and stem, while 

 these relations were 29 : 71 when a month old, and 8 : 92 when 

 ripe. He also found that barley plants with only one leaf having 

 roots 9 or 10" long, and when they had their second leaf, 

 the roots were 20" long, and barley plants a month old had 



