•2!.") 



as little as possible with the normal cropping. This rules out 

 the possibility of giving the whole, or a large part of the growing 

 season to a green manure crop, and it becomes necessary to take 

 advantage of the intervals in the normal rotation. Now in 

 ordinary farming on a standard four-course rotation, the only 

 intervals usually available will be : (a) From the wheat harvest 

 until the roots are sown the following spring, and similarly after 

 oats or barley when seeds have not been sown with them in the 

 spring, (b) From the time the roots are lifted until the spring 

 corn is sown. As regards (b) mangolds or swedes and main crop 

 potatoes are lifted too late for a catch crop to be put in. so that 

 it is only when these crops have failed or after early potatoes 

 or white turnips that this interval can be utilised. 



Where a less rigid rotation is followed, as in market gardening 

 districts, and even in ordinary farming now that the tractor has 

 made possible much greater elasticity in rotations, many more 

 favourable opportunities of catch cropping with green manures 

 present themselves. 



Suitable Crops. — It is thus clear that catch crops must Ije 

 used which are able either to make rapid growth in the late 

 summer and in autumn, or which can withstand the winter. 

 The best crop to use depends very much on the district, but the 

 widespread use of mustard is due to the very rapid growth it 

 makes even on poor soils, so that if sown on the stubble in 

 August, or even early September, it will give a good stand for 

 turning in before winter corn or when the heavy frosts come on 

 in November or December. Other crops which are to be recom- 

 mended in districts where they are known to do well, are rye, 

 oats. Italian rye grass, buckwheat (which does well on poor light 

 soils), rape (giant or ordinary), and thousand-headed kale; all 

 of these in a good season may give a good bulk of green stuff by 

 the end of the autumn. In the case where the crop can be grown 

 on through the winter for turning under in January or February 

 before spring corn, or even later, before roots, other crops to be 

 considered are vetches, crimson clover, red clover, winter beans, 

 late swedes or turnips, and winter oats, rye or barley. 



It is generally the case that a leguminous crop is to be pre- 

 ferred to a non-leguminous one, by virtue of its power of gather- 

 ing nitrogen, but the Woburn results show that this is not always 

 true, and in any case, since it is bulk of organic matter, rather 

 than nitrogen which is primarily to be aimed at, the crop should 

 be chosen which will give the largest growth in the fine, available 

 and then, other things being equal, preference should be given 



