N and K requirements of lowland cabbage (Brassica oleracea L. var. capitata) on peat, grown under netted structure

A.C. Leong, H. Salbiah and A. Izham

Abstract

In the year 2000 Malaysia’s net import of cabbage was 22.5 million tonnes worth RM11.6 million. The loss in foreign exchange can be reduced by planting heat tolerant cabbage varieties in the lowlands under netted structures. The netted structure can prevent the entry of most of the common lepidopteran pests of cabbage, thus reducing the frequency of insecticide application. The current recommended fertilizer rate is meant for cabbage in open field planting. This rate may not be applicable for cabbage under netted structure. Therefore different rates of N and K were evaluated, to further improve the nutrient uptake efficiency of cabbage grown under netted structure. Four rates of N and K were investigated, using the cabbage variety KK Cross. The 4 x 4 factorial experiment was laid out in a RCB design replicated four times and repeated over three crop cycles.
N and K can be reduced from 240 kg/ha to 120 kg/ha with no detrimentaleffect on cabbage yield. Doubling the N rate had increased the average yield by only 9%. The foliar analysis of %K in the composite samples of the cabbage heads reconfirmed the yield results obtained. %N was higher in the highest N rate compared to the lowest N rate. This was reflected in the yield obtained. The rates of 120 kg N/ha and 120 kg K/ha can be recommended for cabbage on peat under netted structure. However more split application of N fertilizer should be advocated during the rainy season, to minimize leaching of the highly soluble N fertilizer.

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