2-16 



Green Man uein g . 



[June, 



to a deep-rooted, nitrogen-gathering crop. The system of green 

 manuring already mentioned as finding application in the 

 Biggleswade district, and elsewhere, in which the green crop is 

 sown with the spring corn, and turned under in the autumn or 

 early in the following year, merits a more extended trial, and 

 has the advantage that less rapidly growing legumes such as 

 serradella, sainfoin, lucerne, and white, alsike, hop or Bokhara 

 clover can be used. There is much scope for the trial of new 

 crops not previously grown to any extent in this country. Among 

 such may be mentioned an annual sweet white clover, Melilotus 

 alba, var. annua, which has lately come into prominence as a 

 fodder and green manure crop in the United States. Some seed 

 of this crop has recently been obtained at Bothamsted, and is to 

 be tried during the coming season. Soy beans also are used as 

 green manure in America and could profitably be tried in this 

 country. One of the chief difficulties liable to be met with in 

 green manuring is that the catch crop has often to be sown in 

 very dry soil, with somewhat uncertain prospects of good ger- 

 mination. Here again, there is much scope for the introduction 

 of new T varieties specially adapted to give good germination and 

 growth under dry conditions. 



■ When to Plough in. — A point needing careful consideration 

 is whether green manures preceding a spring-sown crop should 

 be turned under at the beginning or the end of the winter. This 

 depends to a large extent on the district. On a light soil, where 

 decomposition is rapid and leaching considerable, it is probably 

 best to leave the crop above ground as long as possible. Such a 

 soil does not suffer appreciably by being protected from the 

 action of frost, while if the crop is turned under at the beginning 

 of the winter, decomposition may have proceeded so far by the 

 spring that a large part of the nitrogen will have been lost in 

 the drainage water. The results of the Wisley experiments 

 quoted above illustrate this point. On a stiff soil, however, 

 rotting is slower, and leaching much less, while the mechanical 

 action of the unrotted plant material in facilitating drainage 

 during the wet season will be beneficial, so that on such soils it 

 may be better to turn the crop under earlier, say in early 

 December, so that the heavy soil may be exposed to the bene- 

 ficial action of the hard frosts. 



Another practical point to be borne in mind is the minimum 

 time which should elapse between the turning under of the green 

 crop and the sowing of the succeeding main crop. In some 

 cases failure of the main crop has been found to occur if the in- 



