178 AgricidUiral Gazette of S.S.W. \_Mar. 2, 1920. 



treatment of them (that is, their removal instead of plougliing in or feeding' 

 off), especially in the ease of short season annual leguminous crops, will 

 increase the nitrogen in the soil. Better results may be seen in a crop like 

 maize following annual legumes like peas or vetches which have been cut 

 for fodder or hay as compared with maize following no legume, but this 

 merely serves to emphasise how fast the land is being depleted of nitrogen 

 without a leguminous crop. As a rule, the nitrogen in the roots and stubble 

 of leguminous plants about equals the amount of this element taken from the 

 soil ; and when the tops are removed the nitrogen is just barely maintained in 

 the soil, but not increased. There seems to be an impression amongst some 

 farmers that the nitrogen obtained from the air by the bacteria is all present 

 in the nodules or tubercles on the roots. Usually only about one-third or 

 less of the total nitrogen in leguminous plants is contained in the roots and 

 stubble, and this is reckoned to be also about the same as that taken by such 

 plants from the soil, the other two-thirds being taken from the air. It will 

 be seen, therefore, that when the top growth of legumes is entirely removed 

 from the soil (instead of being ploughed under or fed off) there is no actual 

 gain in nitrogen — no more than theie would be if any non-leguminous crop 

 were grown and ploughed under entirely as green manure. As regards feeding 

 off in comparison with ploughing under the whole crop as green manure, 

 it may be reckoned that a quarter of the nitrogen in the feed consumed is 

 retained by the animal, the remaining three-quarters being voided in the 

 manure. Thus, if the nitrogen is just barely maintained in the soil by 

 ploughing in only the roots and stubble of a leguminous crop — ^and even this 

 method has been observed by farmers to be beneficial to the following crop — 

 how much more so will be the system of feeding off or ploughing in the whole 

 cr.)p 1 In the case of lucerne and clo^ er ci'ops which are cut for hay sevei'al 

 times in a season, there is at each haying an appreciable loss of leaves which 

 •are rich in nitrogen, which with the roots and stubble adds to the soil more 

 than sufticient for maintenance of this element, so that tlie net result is an 

 increase in nitrogen for the subsequent crop. If it were not for the 

 continual loss of the leaves and the deep rooting, the lucerne crop would do 

 no more than maintain the nitrogen in the soil, and would therefore not have 

 such an excellent reputation for rebuilding the fertility of the soil. 



The question is often raised as to whether the nitrogen of the soil can be 

 maintained by green manuring with non-leguminous crops which are suitable 

 for the producticm of organic matter (such as rye, rape, barley, &c.) as catch 

 crops or cover crops. It is true that nitiogen is part of the organic matter, 

 and it might be thought that if the organic matter of the soil is increased by 

 green manuring with non-legumes that the nitrogen will be correspondingly 

 increased. This cannot be possible, as all the nitrogen of non-legumes comers 

 from the soil and not mostly from the air as in the case of legumes. The 

 practice of green manuring with Jion-legumes, therefore, may save nitrates 

 from being leached from the soil as would happen on fallow land during 

 heavy rainfall, and would in many casps be better than no cro[) at all 

 (except in dry districts), but it would not actually increase the nitrogen in 



