Page 330 produced by the decorticators, the tendency of the planter to clog when work- ing in wet ground and to harm the seed when operated at too high a speed, and the incidence of Aspergillus rot in certain areas, were in fact resulting in the establishment of a population far below expectation. The survey showed an actual average establishment of 13,000 plants per acre only. The spacing was accordingly reduced to 3 in. (theoretical population 64,000 per acre), and a population of 24,000 was produced.
Overall, a mean establishment of 18,000 plants per acre, corresponding to about one-third of the seed used, was found. The establishment turned in part on variety, Spanish Bunch (from Texas) giving an establishment percentage of 27, while Natal Common and Valencia (known in South Africa as Virginia Bunch), gave respectively 36 per cent. and 39 per cent.
At harvest time yields were recorded field by field, and it was then possible to correlate the yields with the plant population. In addition, similar data were provided by the results of fertility trials carried out by the Scientific De- partment in the production areas. These data are plotted in Fig. 1 for fields and experiments planted with the varieties Valencia and Spanish Bunch (Texas); Natal Common showed a much greater variability and there was no obvious relationship between yield and plant number. The diagram shows clearly that for Spanish Bunch and Valencia a considerable increase in yield can be ex- pected with an increase in plant population. With further data a similar result may well be obtained for Natal Common.
This increase appears to be more marked on the experimental plots than on the units, which would imply that the Department's staff, who were able to give more systematic care to the plots, were able to secure a higher yield per plant. Some of the difference may also be due, at least in part, to more efficient harvesting and picking, which was done by hand on the experimental plots (owing to their small size) and by machine on the units. It should be noted that in this diagram the yields on the units have been adjusted for the estimated weight of nuts left in the ground.
1,150
MEAN YIELD,
Ib. KERNELS
PER ACRE
1050
850
650
450
EXPERIMENTS: UNITS:
оо
PLANT NUMBER,
THOUSANDS PER ACRE
250
5
10
15
20
25
30
FIG.1.-RELATION BETWEEN PLANT NUMBER AND YIELD, GROUNDNUTS, KONGWA,
35
1947-48 SEASON
Page 330.
112
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