Response of two peanut (Arachis hypogaea L.) cultivars to boron and calcium

The response of two peanut cultivars (Tainan 9 and SK 38) to applications of six boron (B) rates (H₃BO₃ at 0, 0.12, 0.25, 0.5, 1 and 2 kg B ha^–1) at two calcium levels nil (-Ca) or CaSO₄ at 100 kg Ca ha^–1 (+Ca)] to a B-deficient Oxic Paleustult was studied in a pot experiment. Without added Ca, both cultivars had low seed yields and gave only small responses to B. Similarly, without added B, both cultivars had low seed yields and did not respond to Ca. But, with added Ca or B, they responded strongly to B and Ca, respectively. In both cultivars, deficiencies of Ca or B depressed seed dry weight by depressing seed size by over 75%. Boron deficiency further depressed seed dry weight by decreasing the number of seeds per plant by decreasing the number of seeds per pod in Tainan 9, and the number of pods per plant in SK 38. Seed dry weight was depressed more than pod dry weight, so that both Ca and B deficiencies severely depressed the shelling %. With added Ca, tainan 9 responded to lower levels of B than SK 38, reaching maximum seed dry weight at 0.12 kg B ha^–1. At this low level of B. SK 38 yielded only half the seed dry weight of Tainan 9. But SK 38 continued to respond to increasing levels of B to 2 kg ha^–1, producing a maximum seed yield 40% higher than Tainan 9. The results indicate that where all other nutrients are adequate, SK 38 will yield better than Tainan 9 on soils with high B, but worse on soils with low B. The implications of these findings for the selection of peanut cultivars are discussed.