Row covers for quality improvement of Chinese cabbage (Brassica rapa subsp. Pekinensis)

Abstract

Row covers of polypropylene sheeting have been studied in relation to the quality in Chinese cabbage (Brassica rapa subsp. Pekinensis ’Nagaoka 50') for 3 years (1999, 2000, and 2001) in the area of Granada, Spain, under a Mediterranean continental temperate climate, on 55‐day cycles with transplanting in mid March. The mean commercial yield for the 3 years was 11.9 kg m–2 under row covers, but only 2.1 kg m–2 in open air, owing primarily to the important number of non‐commercial cabbages. The cabbages grown in the open air were exposed to lower temperatures than under covers and showed a higher number of plants with bolting and plants lost in the field. The better thermal regime under the covers and the least vapour pressure deficit favoured heading, reducing the number of malformed cabbages. The foliar calcium (Ca) content in the outer leaves was significantly greater in the open air than under the row cover, whereas the reverse was true in the inner leaves. These lower Ca contents in the inner leaves of the open air plants, encouraged tipburn. The use of the row cover constitutes a low‐cost technique to improve open air spring cultivation of this leafy vegetable in this type of Mediterranean continental climate.