IV] A MEDIEVAL FARM 51 



Whatever the order, the rotation consisted of two 

 corn crops and a fallow ; each year one of the fields 

 was fallow, the second wheat or rye, and the third 

 Lent corn. 



The dung made by the animals contained elements 

 of fertility derived from the pasture land. The addi- 

 tion of this dung to the arable land thus involved a 

 transfer of fertility from the wide areas of the pasture 

 land to the smaller areas of arable land. The process 

 maintained the fertility of the arable land, but it must 

 in time have impoverished the pasture ; but the im- 

 poverishment of the pasture went on only very slowly 

 for two very interesting reasons. In England the 

 supply of nitrogen compounds in the soil is most 

 frequently the factor limiting the wheat and other 

 grain crops ; so long as the nitrogen supply is kept 

 up a certain level of crop production can be main- 

 tained. In pasture land a considerable amount of 

 nitrogen fixation is continually going on through 

 bacterial activity. Hence the element that played 

 the most serious part in fertility under the conditions 

 of low yields then obtaining was being brought in as 

 quickly as necessary from the atmosphere. 



The next substance to give out and cause the 

 collapse of the system would have been calcium 



hushandrie, 1573: drink corae = barley ; bread come = wheat ; compas 

 = farmyard manure (compost); champion = the unenclosed common 

 field or its farmer. 



4—2 



