Effects of drip fertigation uniformity and nitrogen application level on growth, yield and quality of Chinese cabbage

The effects of drip fertigation uniformity and nitrogen application level on crop growth, nitrogen uptake, chlorophyll meter reading (SPAD), yield and quality of Chinese cabbage were investigated in a solar greenhouse to determine the design and evaluation standard of drip irrigation uniformity. Three Christiansen uniformity coefficients of 0.62, 0.80 and 0.96 and two levels of nitrogen applied at 150 and 300 kg/hm2 were used. The continuous measurements using TDR sensors of Hydra Probe demonstrated an approximately similar variation pattern of soil water content and temperature during the growing season of Chinese cabbage for all the treatments tested. The observed difference of soil bulk electrical conductivity (ECb) for different treatments could mainly attribute to the difference of the initial ECb values. Plant height, dry matter above ground, nitrogen uptake and yield with the drip irrigation system demonstrated a more uniform distribution than those with water and fertilizers applied at fertigation uniformity coefficient equal to or less than 0.80. It was found that the influence of fertigation uniformity on plant height, dry matter above ground, nitrogen uptake and yield was insignificant at a significance level of 0.05. The quality indexes of Chinese cabbage, including vitamin C, total sugar, nitrate and cellulose were also insignificantly affected by fertigation uniformity at the same significance level. Increasing fertigation uniformity might not necessarily result in an increased yield and an improved quality of Chinese cabbage. As no negative influence of fertigation uniformity on crop growth, nitrogen uptake and yield was observed, it is suggested that lower uniformity values of drip irrigation system below those recommended by the current standards can be considered.