Effects of drip system uniformity on yield and quality of Chinese cabbage heads

Chinese cabbage (Brassica rapa subsp. pekinensis) production experiments with different system uniformities and field scales controlled by driplines were conducted in a solar heated greenhouse in 2009 and 2010. Three Christiansen uniformity coefficients (CU = 62, 81 and 96%) and two nitrogen application rates (150 and 300 kg/ha) were evaluated in 2009. In 2010, three CU values (57, 74, and 95%) and one nitrogen application rate (225 kg/ha) were tested. The uniformity of systems was established by randomly assembling segments of drip tubes with five different nominal emitter discharge rates (1.05, 1.4, 1.65, 2.3 and 2.6 L/h) along a dripline. For all of the system uniformities tested, the plant height, head height to diameter ratio, dry matter above ground and nitrogen uptake displayed high uniformity coefficients throughout the entire growing season. The effects of system uniformity and nitrogen application rate on the mean yield and quality indexes and their uniformities were insignificant. With the increasing of field scale controlled by one dripline, the uniformity of crop growth, yield and quality indexes demonstrated a decreasing tendency. The results of this study showed that uniformity values that are lower than those recommended by the current standards can be used in drip irrigation systems, and their usage should consider the field scale controlled by dripline.