132 CHAPTER VITI 



stubby sprouts and turn a slight greenish colour. Very few 

 sprouts are broken off during planting. 



Immature tubers produce more vigorous plants than those 

 fully matured, hence it is the custom in some countries to 

 dig tubers before maturity, or to allow the crop to ripen pre- 

 maturely by withholding water ; or to plant late and to allow 

 the crop to be frosted before maturity. Tubers not fully 

 matured are easily bruised in handling, and the germination 

 is apt to be slow and irregular. However, with careful hand- 

 ling, storage, and if sprouted as described, excellent crops 

 are obtained, as will be seen from the following experiment 

 conducted at the Ontario Agricultural College : — 



Seed obtained from planting of: Average of six varieties. 



May 31st 192-37 bushels per acre*.^ 



June 14th 194-80 ,, 



June 28th 201-84 



July 12th 2i9-46 ,, 



The farmer, under irrigation growing both early and main 

 crops, experiences difficulty in getting the seed lifted in 

 November and December to sprout in time for January plant- 

 ing. While germination may be hastened by placing the 

 tubers in a warm, moist situation (a covering of moistened 

 stable manure is often of assistance), this method is not always 

 successful. Potatoes are grown in the Low Veld — e.g., Koe- 

 does Eiver and Barberton — in time to be lifted in October and 

 ready for the main crop planting in December and January, 

 and these could be used for seed by the farmers on the High 

 Veld. 



Rotations. — As previously stated, potatoes follow green 

 manure better than most crops, as the comparatively loose soil 

 produced is suited to their growth. 



Below are some suggested rotations : — 

 (1) Without Irrigation — dry lands. 

 1st year — Maize. 



2nd year — Maize, with an application of phosphates. 

 3rd year — Cowpeas (kaffir beans), ploughed under. 

 4th year — Potatoes, manured as previously recom- 

 mended. 



If an excess of nitrogen is indicated by too much top 

 growth at the expense of tuber formation, then the potatoes 



