Response of cabbage (Brassica oleracea var. capitata) transplants to nitrogen, phosphorus and potassium nutrition

by More, Ketseemang.

Poor root development is a problem in transplants that are produced in cavity trays, as transplants tend to break when being pulled out of the cavity trays during transplanting. Cabbage transplants were propagated at different levels of nitrogen, phosphorus and potassium in separate experiments to determine the amount of nitrogen, phosphorus and potassium that could optimise shoot and root development. The transplants from the nitrogen experiments were then planted into the field to determine the effect of pretransplant nitrogen on the yield and head quality of cabbage. To determine the amount of nitrogen that could optimise shoot and root development, cabbage ‘Drumhead’ transplants were propagated at 0, 30, 60, 90 and 120 mg·ÖL-1 N. Nitrogen application enhanced shoot and root growth regardless of season. Leaf nitrogen and pulling success also improved as nitrogen increased during the two seasons. Leaf nitrogen content in transplants that were propagated during autumn increased from 10.3 to 28.3 g·kg-1 while during spring, leaf nitrogen increased from 13.0 to 43.7 g·|kg-1 as applied nitrogen increased from 0 to 120 mg·çL-1. x In autumn, quality transplants were obtained from transplants that were propagated at 90 mg·L-1 N, as a result the transplants gave the highest cabbage yield. In spring, quality transplants were obtained from transplants that received 60 mg·vL-1 N, which in turn gave the highest cabbage yield. Pretransplant nitrogen increased head diameter and head height but did not affect core diameter and core height during autumn. During spring pretransplant nitrogen increased head diameter but did not affect head height. Core diameter was increased by pretransplant nitrogen while core height was not affected. Pretransplant nitrogen applied at 90 mg·:L-1 in autumn and 60 mg·:L-1 in spring is enough to give quality transplant that would give high yield. Potassium was applied at 0, 15, 30, 45 and 60 mg·IL-1 during cabbage transplant production to evaluate the effect of potassium nutrition on cabbage transplant shoot and root development. Applied potassium improved fresh shoot and root mass, plant height, leaf potassium content, pulling success and net assimilation rate. Dry shoot and root mass, leaf number, leaf area, root: shoot ratio, root mass, leaf mass ratio, specific leaf area, relative growth rate and leaf area ratio were not affected by applied potassium. Applying at least 15 mg·L-1 K during cabbage transplant production gave quality transplants. Cabbage transplants were propagated at 0, 15, 30, 45 and 60 mg·9L-1 P, to determine the impact of phosphorus nutrition on shoot and root growth of cabbage transplants. Applied phosphorus improved leaf area, fresh and dry shoot mass, fresh and dry root mass, pulling success and leaf phosphorus content. Most of the increases in growth were achieved with 15 mg·L-1 P. Therefore, application of at least 15 mg·L-1 P during cabbage transplant production was enough to give quality transplants.