The hollow stem disorder is a common problem in cauliflower, resulting in similar symptoms as those caused by B deficiency. Its occurrence in cauliflower is related to nitrogen and boron levels. There exist little information about this subject in Brazil. The effect of nitrogen rates and boron application periods were evaluated on the cauliflower production and incidence of hollow stem. The experiment was carried out from November 2005 through February 2006 in a Kandiustalf soil (0.54 mg B kg-1, BaCl2 1.25 mg L-1) at Tietê region, São Paulo State, Brazil, in a randomized complete block design with four replicates, four N levels (100; 150; 200 and 250 kg ha-1) and two periods of B application (one and two applications) and a control (without application). Cauliflower curd diameter ranged from 16.45 to 22.03 cm and the commercial yield from 15.71 to 29 t ha-1; these two traits were not influenced by treatments. Nitrogen rates increased linearly in leaves and curds. The hollow stem and curd browning were reduced and commercial yield was increased with B fertilization. The correlation between B concentration on leaves (r= 0.66; p<0.05) and curds (r= 0.76; p<0.05) with hollow stem disorder was negative. Boron fertilization is necessary to reduce the symptoms of hollow stem when cauliflower is grow in soil with medium B level (0.54 mg B dm-3). More studies are needed using other types of soil and other cauliflower cultivars in order to reduce this physiological disorder in tropical conditions and increase the efficiency of boron fertilization.
Brassica oleraceae var. botrytis L.; curd browning; soil
