SOILS AND MANURES 355 



is equal to that obtained by cropping each year over the same CHAP, 

 period, the cost of production is reduced and the profit con- VIIIi 

 sequently increased. Unless the cost of fallowing and rent of 

 the land (or its equivalent in interest) are heavier than the 

 cost of production of a crop without fallow, fallowing will 

 thus pay for itself while at the same time it cleans the land. 



Not only so, but the cost of cultivation is lessened by plough- 

 ing under two or more crops of weeds on the fallowed land 

 before they have had a chance to seed. Where farms are large 

 and land is cheap, there need be no loss of revenue, if each 

 year only one-third or one-quarter of the land is kept in fallow 

 and the rest under crop. For example, if 1,000 acres of arable 

 land is all that a South African farmer can maintain each year, 

 owing to lack of either capital or labour, or both, he might 

 have 200 or 300 acres of it under fallow each year. During 

 the comparatively slack season, from the end of December to 

 the end of March, he could usually employ his draught animals 

 and " boys " to cultivate these fallow land's. By this means 

 he would save much of the time and expense which would 

 otherwise have to be devoted to cleaning the crop during the 

 following growing season. 



3(1. Rotation of Crops for Fertility Conservation. — One of 

 the cheapest and most profitable methods of resting the land 

 after it has once reached good cropping condition (f 306) is 'to 

 adopt a system of change or " rotation " in which some other 

 crop than maize is grown every third or, even, second year. 

 Some farmers grow potatoes the third year with the aid of 

 commercial fertilizers, but for unmanured land the best kind 

 of rotation for maize is a leguminose crop, such as cowpeas, 

 kaffir beans, velvet beans, soybeans, peas, or peanuts (If 313;. 

 This rotation crop may be cut for hay or silage, or, better 

 still, ploughed into the ground at the beginning of winter. 



Practising rotation of crops is one of the best methods of 

 checking the wearing-out of the land {Burtt-Davy, 15). The 

 principal advantages of rotation are: — 



(i) That as some crops require more of one kind of plant- 

 food than others, an intermediate crop can be grown between 

 two crops of a kind without interfering with the general fertility 

 of the soil, and still allow time for the chemical changes which 

 replace a certain proportion of the available salts required for 



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