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An experiment at the Kongwa Experiment Station, testing various plant populations, showed maximum yields in the neighbourhood of 50,000 plants per acre. Populations of this magnitude cannot be realised in single row planting without crowding the plants unduly unless the row width is 18 in. jor less.
Such narrow rows could not with present equipment and staff be cultivated efficiently. The most efficient method of planting may consist of sowing paired rows 6 in. apart, with 36 in. between the midpoints of pairs. These pairs would be treated as single rows in the later cultivations and harvesting. Fertiliser could be placed in a single band at the midpoint of each pair, a procedure which might result in a more efficient utilisation of the fertiliser.
In general, the evidence shows that the achievement of a high plant population is of the first importance. It may prove to be more critical than any other factor affecting yield per acre in the Kongwa Region. This may also apply to the other
areas.
Following the population survey, experiments were set out at the Kongwa Experiment Station to measure the effect on groundnut germination of a number of possible adverse factors. Where planting was followed by a wet period the germination was 46 per cent.; but where conditions after planting were dry, the figure fell to 19 per cent. (In another experiment, which was carried through to harvest, yields of Spanish Bunch were reduced from 1,094 to 845 16. kernels per acre by dry post-planting conditions.) Natal Common withstood dry post-planting conditions better than Valencia, giving 26 per cent. germination as against 13 per cent. for Valencia, although under wet post-planting conditions the two varieties gave similar values of 44 per cent. and 49 per cent. respec- tively. Under dry conditions, depth of planting made little difference to germination, but under wet conditions seed planted at 4 in. gave 40 per cent. germination only as against 53 per cent, at 2 in.
Date of planting
In the 1947-48 season no planting was possible on the Kongwa Experiment Station until December 24, owing to late clearing. Planting had, however, begun on the main fields on December 15, and there were areas in which rain adequate for germination had fallen as early as December 3. Con- sequently, the planting date trial conducted at the Kongwa station does not fully represent the range of planting dates possible. In this experiment, five varieties Spanish, Natal Common, Valencia, Virginia Bunch and a local mixed variety known as Kongwa (equivalent to Mgogo in certain Unit records)—— were sown on four dates, December 24, and January 2, 14 and 28.
The results are overwhelmingly in favour of early planting, particularly for the varieties which tend to the runner type. The three varieties best suited to the Kongwa conditions are Valencia, Natal Common and Spanish. The weak adherence of the mature Valencia pods to the vine makes mechanical harvesting difficult. Virginia Bunch is clearly better adapted to areas of longer season, while the Kongwa variety-which, being mostly a runner, is not readily handled with the present equipment-is probably of most use as a source of breeding or selection material adapted to local conditions. This applies par- ticularly to the more upright component of the mixture, which may be a Valencia strain. The full evaluation of the results of this experiment is presented in section 12. It may be summarised by saying that the runner and semi-runner varieties, Kongwa and Virginia Bunch, yielded about 1,500 and 1,600 lbs. kernels per acre at the earliest planting, 1,200 and 1,000 lbs. at the second, and then fell off sharply; while the more upright varieties, Natal Common and Spanish, which can use a shorter season, yielded 1,200 and 1,300 lbs. kernels per acre at the first planting and were still producing 1,000 and 900 lbs. kernels per acre at the third. Valencia probably behaves similarly, with a slightly greater preference for early planting, but the results in this particular experiment were obscured by large and probably fortuitous variations in plant population. It should be pointed out that the fourth planting took place early in the mid-season gap in the rains, which in the 1947-48 season lasted for five weeks. This is undoubtedly responsible, at least in part for the poor stands, and so for the poor yields at the getale, but is shown in section 12 that theagielding capa97per plant also declined with the late plantings.
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