134 CHAPTER VIII 



might have formed. This may be repeated while the plants 

 are still small and unlikely to be injured. Cultivation to keep 

 the ground loose and to destroy weeds should start soon after- 

 wards, getting shallower as the roots spread, and must be 

 continued until after flowering. 



Under irrigation, and to a less marked extent on dry 

 lands, the crop should now be ridged (earthed up) to check 

 tubermoth injury, and to prevent the soil cracking, which is 

 undesirable, for when exposed to light the tubers assume a 

 greenish colour. 



Potatoes respond to heavy irrigation, provided this is well 

 distributed, better than any field crop. Experience has shown 

 that where possible water should not be applied during the 

 extreme heat of the day, as this practice seems to predispose 

 the plants to disease. Wide fluctuations in the soil moisture 

 should be avoided, as malformed tubers are common if the 

 growth is interrupted. Heavy irrigation should be avoided 

 also during the early growth of the crop. 



Harvesting. — The main crop should be dug when 

 thoroughly mature, i.e., when the skin is firm, the tops have 

 dried and the tubers separate easily from the rhizomes. Tuber 

 development and starch storage are most rapid during the last 

 month of growth, and continue as long as the tops are green. 



In areas of dry winters, having relatively low tempera- 

 tures, the potatoes are often left in the soil and are lifted 

 only when required. On the High Veld they may be left in 

 the soil until August. 



The early crop is often harvested before maturity, as the 

 loss in yield is counter-balanced by the hisfh price obtained for 

 new potatoes. The early crop seldom yields as heavily as the 

 main crop. 



If the vines are frosted before maturity the tubers should 

 be left in the ground for some time to enable the skin tb 

 harden. 



The crop is usually lifted by hand, double mouldboard 

 plough, or potato digger. The latter implement is coming into 

 more general usage, although some difficulty has been found 

 in South Africa in hard, dry ground to get the digger to dig 

 deeply enough. 



In the Union, potatoes are sold in bags 153 pounds gross. 

 Unfortunately, £frading is little practised. Medium-sized 

 potatoes are preferred to those very large, and no discrimina- 

 tion with regard to colour is shown. Prices fluctuate from a 



