Influence of soil calcium, potassium, and pH on development of leaf tipburn of cabbage in eastern North Carolina

Three hypotheses that involved manipulation of soil calcium (Ca), potassium (K), and pH in relation to the occurrence of leaf tipburn of cabbage in ea stern North Carolina (NC) were formulated and tested: 1) adding K to soil w ill increase (induce) leaf tipburn; 2) adding Ca and K together to soil wil l block K-related tipburn induction, and 3) raising soil pH to levels of 6. 0 to 6.5 will decrease leaftipburn. Six experiments were conducted in comme rcial cabbage production fields in eastern NC in 1996 and 1997 to test thes e hypotheses. Hypothesis 1 was accepted since higher rates of K significant ly (p<0.05) increased leaf K concentration, soil K content and leaf tipburn incidence compared with the control. Total cabbage yield increased as K ra tes increased, however, significant differences were only observed between the control and the highest rate (365 kg K ha(-1)) in 1996. Hypothesis 2 wa s accepted since adding increased amounts of Ca and K did not significantly increase leaf tipburn incidence. Hypothesis 3 was rejected since a range o f soil pH from 5.3 to 6.6 did not increase or decrease leaf tipburn inciden ce, nutrient uptake or total yield. These data suggest that leaf tipburn of cabbage can be increased (induced) with excessive K fertilization and that this practice may be associated with the disorder observed in NC. Also, th e addition of Ca with K may potentially reduce the risk associated with K-r elated leaf tipburn of cabbage.