Influence of mineral nutrition on seed development of two groundnut cultivars

Two groundnut cultivars, the small‐seeded and “pops”; slightly susceptible Natal Common (NC) and the medium‐seeded, pops susceptible Makulu Red (MR) were grown in two different soils and in nutrient solution in the green house during summertime in Germany. The objectives were to work out optimum growth conditions in order to define the role of Ca in seed development. In both experiments the medium‐seed MR produced more vegetative matter and less seeds in comparison with NC, although plant and soil analysis revealed adequate Ca supply. This was also found in a nutrient solution experiment, where application of 6 meq Ca/l to the fruit medium increased seed formation of NC, but was without effect in MR. Attempts to stimulate pod formation by varying the nitrogen supply showed that fruit set was poorer at 2 meq N/l and 0.5 g N/pot than in the treatments offered 4 meq N/l nutrient solution or inoculated with rhizobium. Also lowering the K concentration from 3.6 to 0.6 meq/l and thereby changing the K/Ca ratio from 0.6 to 0.1 had no influence on seed formation. Application of 45Ca to bunches of detached pegs in the laboratory indicated improved translocation of Ca from the pericarp to the seed in NC. This might partly explain the lower pops‐susceptibility of this cultivar.