The effect of certain mineral elements on peanut fruit filling

In controlled experiments Jumbo Runner type peanuts were grown in soil which was known to produce good vine growth but poor quality fruit. By using the technique of separating the zone of fruit formation from that in which root growth occurred, a study was made of certain fruit characteristics as affected by supplying various salt solutions to the fruiting zone. The treatments were made to quartz sand which constituted the fruiting medium and the solutions were added in such a way that a continuous supply of the elements desired was available. By using proper treatments the specific effect of each of the anions and cations used was determined. Particular attention was given to the effect of calcium. The comparative effects of applying potassium to the rooting and fruiting zones, with and without calcium in the fruiting zones, were also determined. Fruit filling was evaluated by determining the total number of ovarian cavities in the fruit from a given treatment and by calculating the percentage of this number which contained well-developed kernels. Other fruit characteristics, such as disease, maturity, and percentage of 2-cavity size were also determined. In 1946 the effects of various treatments on gynophore development and disease incidence and stem composition were obtained. The results from these experiments may be summarized as follows: 1. Of the ions Ca, K, Mg, Cl, S04, KH2, and P04, calcium was found to be the only one which consistently increased fruit filling when applied to the fruiting zone. This was true regardless of the combination in which it was supplied. 2. In general, the addition of magnesium salts to the fruiting zone proved to be slightly beneficial to fruit filling. 3. The addition of potassium to the fruiting zone or rooting medium slightly depressed fruit filling in some instances in the absence of calcium in the fruiting zone. However, if a solution of calcium sulfate containing as little as 20 ppm calcium were supplied, no detrimental effect resulted from potash additions. This was true even when potassium was added at the rate of 320 ppm potassium. 4. The application of chloride, sulfate, and phosphate ions to the fruiting medium did not significantly affect fruit filling, although in 1943 phosphate tended to reduce the quality of fruit. 5. Chemical analyses of stems showed that calcium sulfate additions resulted in an increase in calcium and potassium and a decrease in nitrogen content.