Resumo

RODRIGUES, M. A. et al. Tall cabbage (Brassica oleracea var. costata) response to the application of nitrogen, boron and an organic amendment permitted in organic farming. Rev. de Ciências Agrárias [online]. 2009, vol.32, n.1, pp.93-100. ISSN 0871-018X.

The Portuguese are one of the greatest brassica consumers in the entire world. Tall cabbage is grown in Portugal over an area greater than 1000 ha. Tall cabbage consumption is very popular at Christmas time. In this work, results from nitrogen and boron application, as conventional fertilisers, and from the use of Dix10, an organic amendment (˜ 10 % total N) permitted in organic farming, are reported. Young cabbage plants were prepared in a greenhouse in micro-pots and transplanted with protected roots on August 29, 2005, spaced at 0.8x0.5 m between and within rows. The soil was loamy textured with 0.83 % organic matter, pH(H2O) 5.2, and with median P and high K content levels. Six treatments were established: SAd treatment, without any fertilization; Dix10, applied in a rate equivalent to 80 kg N/ha; NB and N⁺, with 80 and 160 kg N/ha as urea, respectively; and B^-and B⁺ treatments, without B and with 4.4 kg B/ha as borax. Boron treatments were fertilised with 80 kg N/ha and N treatments with 2.2 kg B/ha. Thus, NB is a median treatment with 80 kg N/ha and 2.2 kg B/ha. SAd plants yielded 13.7 Mg biomass/ha and took up 33.9 kg N/ha and 40.9 g B/ha, which are values significantly lower than that obtained on fertilised plots. In Dix10 treatment, cabbage yielded 18 Mg biomass/ha and took up 45.1 and 51.3 g B/ha. NB treatment produced higher biomass (38.6 Mg/ha) and N uptake (107.9 kg/ha) than SAd and Dix10 treatments. N⁺ treatment did not increase the yield, neither N uptake if compared with NB. B⁺ treatment has not any influence in biomass yield but increased tissue B content and B uptake. In N⁺ treatment there was a significant decrease in tissue B concentration and B uptake, which suggests antagonism of N over the uptake of B. The biomass yields and the apparent N and B recoveries showed that the lower biomass yielded in SAd and Dix10 treatments were due to a shortage of soil N availability in these treatments during the growing season.

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