Importance of Experimental Technique in Fertilizer, Dusting, and Calcium Experiments With Florida Runner Peanuts

THE peanut produces a flower above the ground which, when fertilized, forms a gynaphore or peg that pushes into the soil where the fruit develops. The flowering of this plant in Florida is more or less continuous during about three of the summer months, and for this reason a plant will have nuts of different degrees of ripeness at anytime during this period. In that respect it is similar to a tomato plant. Tomatoes can be harvested as they ripen, but this is not possible with the peanut. The peanut plant has to be removed from the soil on harvesting which can be done only once. For that reason, one must use judgment as -to when it is the best time to harvest. If peanuts are harvested early, there are likely to be many green nuts or shrivels, and if they are harvested late, many of the mature nuts 'will shed and be left in the 'soil. In either case, some nuts are left in the soil. This makes it most difficult to obtain a reliable measure of the total yield resulting from any treatmerit. In the past, little attention has been given to the nuts left in the soil in comparing fertilizer or other treatments, presumably because' it was considered that the peanuts would shed proportionally for the various treatments. However, there may be differential shedding of nuts due to such causes as differences in fertilization, maturity, inoculation, disease and insects, or other pests. Of course, peanuts in experimental tests should be harvested at the same stage of maturity, as pointed out by Albrecht (i) 3 and others, but there is no standard measure of maturity and small differences in maturity cannot be detected by observation. Bledsoe, et al. (2) have pointed out that some of the inconsistencies of fertilizer results on peanuts might be due in part to the fact that the nuts that were shed and left in the soil were not taken into consideration. They gave results which suggest that sulfur, dustings may cause the plants to retain the nuts on the vines much better and thus leave fewer nuts in the soil. The object of this paper is to summarize results of some fertilizer, dusting, and calcium experiments and show that other treatments may affect the amount of nuts shed and left in the soil. These studies revolve around sulfur treatments. The general recommendation for the control of leafspot of runner peanuts in Florida is 15 to 20 pounds of sulfur dust per acre per dusting, at about 2-weeks intervals, beginning about 65 days after planting and applied three or four times (10). These infrequent dustings which are applied during the rainy season in Florida lead one to raise the question as to whether some of the beneficial effects of the sulfur might npt be due in part to some other effect, such as the nutrition of the plant, especially since Harris, et al. (5) found that sulfur had a beneficial effect on cotton. Bledsoe, et al. (2) thought they could detect some effect of sulfur in reducing the damage of peanuts by the velvetbean caterpillar, Anticarsia gemmatills (Hbn.). Calcium sulfate is sometimes very beneficial on peanuts (3, 4, 7) presumably • because the gypsum is a readily available source of calcium. Could it be that in some cases it also supplies needed sulfur? Fertilizers contain sulfates. Thus, the sulfur problem is entangled with fertilizer, dusting, and calcium treatments. METHODS