43 



CAUSES OF LOSS OF ORGANIC MATTER AND NITROGEN. 

 Such a loss as this, amounting, in the extreme case of a 

 garden worked from the beginning at high pressure, to 150 pounds of 

 nitrogen per annum per acre, or over 2 per cent, of that originally 

 present, cannot be lightly considered. Some part of the loss is due 

 to what is actually removed from the land by the leaf taken from the 

 garden, but as this only amounts, for say ten maunds of tea per acre 

 to about thirty-two pounds of nitrogen per annum, there must be, for 

 the cases in which the greatest loss takes place, an enormous leakage 

 in other directions. Where does this leakage occur? The answer is 

 only too obvious. Wherever very deep constant cultivation has been 

 in vogue for many years, where no weeds are allowed to grow, 

 and where the stock of nitrates formed during the cold weather 

 has not been retained in the spring by green manuring, there the 

 loss is great, and much goes down the drains. As an additional 

 evidence of the connection between a very great amount of cultiva- 

 tion and the greater loss, it will be seen that there is every appear- 

 ance of this leakage having become greater in recent years. 



PREVENTION OF LOSS OF ORGANIC MATTER AND NITROGEN, 



But why should cultivation and the absence of weeds or green 

 manuring cause a loss of nitrogen ? In reply, let us consider the soil 

 for a moment as a vast living mass of bacteria or microbes. They 

 occur in such enormous quantities that in a fertile surface soil they 

 are numbered by hundreds of millions to the cubic inch. And all 

 these organisms feed, and utilise the stores of the soil for food. Some, 

 and more especially in unaerated soils, use the organic matter and 

 nitrogen, destroying the usefulness of the latter and giving it off 

 as gas into the air. These have little importance in a tea-soil so long 

 as the land is not water-logged, and is well aerated throughout. 

 Others utilise equally the nitrogen, but form nitrates from it, 

 useful enough in themselves and absolutely necessary for plant 

 growth, but formed largely at a time when they cannot be 

 absorbed by the plant, and which are hence immediately washed 

 into the drains and so away by the first large downfall of the rainy 

 season. These are most active in a thoroughly aerated soil, and 

 hence are increased by a very large amount of cultivation. What 

 then can be done? the land must be cultivated thoroughly in order 

 to keep the bushes vigorous and flushing regularly, and yet this 

 results in an enormous loss of the most valuable and expensive 



