The rubber tree book . o activity. Plant-roots cannot possibly growwithout oxygen from the air. Hence, in a water-logged soil,the roots are confined to shallow surface layers. Only afterdrainage can the roots go down so far as the circulation of airextends. When the air penetrates down, the bacteria startactively upon their work of supplying nitrogen to the roots ofthe trees. The constant presence of an over-supply of water in thesoil means death to the beneficial bacteria on which the rootsof the trees depend for their nitrogen nourishment. It alsomeans that the roots of the trees cannot brea
The rubber tree book . o activity. Plant-roots cannot possibly growwithout oxygen from the air. Hence, in a water-logged soil,the roots are confined to shallow surface layers. Only afterdrainage can the roots go down so far as the circulation of airextends. When the air penetrates down, the bacteria startactively upon their work of supplying nitrogen to the roots ofthe trees. The constant presence of an over-supply of water in thesoil means death to the beneficial bacteria on which the rootsof the trees depend for their nitrogen nourishment. It alsomeans that the roots of the trees cannot breathe. With poorly-developed, badly-nourished roots, trees cannot maintain ahealthy condition. Not only is this the case, but water-logging encouragesthe activity of certain detrimental bacteria known as de- 6o THE RUBBER TREE BOOK nitrifiers. Denitrification implies the reversal of the processof nitrification which brings fertility to the soil and involvesthe reduction of the nitrates even to nitrogen gas, which escapes. Fig. 12.—View of a Twenty-four-nionths Tree on EasternSumatra Rubber Estates, showing Fine Development ofvarious series of Lateral Roots in a well-aerated Soil. into the atmosphere. Hence, a serious loss of fertility to thesoil not readily replaced. Drains are not meant to be receptaclesfor water, but means of getting rid of it. They can scarcelybe too numerous. It is common for a planter to find that ROADS, BRIDGES AND DRAINS 6i cutting an additional drain is one of the very best ways of gettingrid of the disease of Fomes. It is, therefore, absolutely essential at all costs to ensurethat land is well drained. Many estates, more especially inSumatra and the Straits Settlements, leave very much to bedesired in this respect. The water-level in the drains is muchtoo high. If the managers and the visiting agents of suchestates realized how much the root-systems of the treeswere restricted from this cause, and the constant loss of thefertility of the soil which was
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