56 CHAPTER IV 



fibrous condition, decay will be slow. If possible, therefore, 

 plough these crops down before maturation is too far 

 advanced, i.e., at flowering or soon after, and when moisture 

 conditions are favourable, i.e., before the last rains. 



Under irrigation the soil moisture can be regulated, con- 

 sequently the time of the year when green manures should 

 be ploughed under is not so critical. 



After ploughing the land should be worked down, pre- 

 ferably by discing, to ensure thorough incorporation of the 

 organic matter into the soil, and more or less even distribu- 

 tion. 



When Inadvisable to Practise Green-Manuring. — It 

 is a questionable procedure under arid, and sometimes semi- 

 arid conditions, because, firstly, the crop may leave the soil in 

 a very desiccated state, and, secondly, the nitrogen added in 

 this way may stunulate too succulent a growth of the succeed- 

 ing crop, thus causing the latter to suffer prematurely from 

 drought. 



In general, excessive green-manuring may furnish a super- 

 abundance of nitrogen, which acts detrimentally towards many 

 crops. Crops often show a tendency to mature late on land 

 heavily green-manured, and where rust is prevalent this fact 

 should be taken into consideration. In some, the growth of 

 straw will be excessive, lodging will take place, and the yield 

 of grain will be disappointing. 



Crops to Follow Green Manures. — Where practicable 

 cultivated crops, e.g., potatoes and maize, are the best to grow 

 after green-manuring, as their cultivation assists in changing 

 the organic matter into available plant food. Of the winter 

 cereals, wheat and rye give the best results after green- 

 manuring. Oats is apt to lodge badly and to be coarse 

 strawed, and the quality of barley for malting purposes is 

 usually poor if grown immediately after a green manure. As 

 the winter cereals require a compact seed-bed, the green 

 manure should be ploughed under as early as possible, so that 

 decay may be well advanced before the cereals are sown. 

 Nitrification during the South African winter is slow, so that 

 on the whole the use of leguminous green manures on land 

 where winter crops are grown is particularly good practice. 



In grain farming, green-manuring is a much more urgent 

 and necessary operation than, for example, in dairy farming, 

 where large quantities of manure are available for application 

 to the land. 



