Precision application of water and nitrogen for bell pepper under subsurface drip irrigation

A 2-year field experiment was conducted in 2007, 2008 to investigate the effects of subsurface drip fertigation strategies on bell pepper yield and root distribution. Two irrigation cycles of 4 days and 8 days (C₄,C₈) and four nitrogen application levels of 0,75,150,300 kg N·ha^-1 (N₀,N₇₅,N₁₅₀,N₃₀₀) comprised the irrigation and fertigation treatments. The experimental results showed that the total root length, surface area, volume, weight, density of roots significantly increased with the application amount of nitrogen among 0-150 kg N·ha^-1. The characteristic parameter of roots declined at nitrogen level of 300 kg N·ha^-1 contrarily. 4 days irrigation cycle promoted the growth of root system and obtained higher yield under the same nitrogen application level. The conics relationship between yield and nitrogen application amount was found. Maximum yield were obtained by treatment N₁₅₀C₄ in both years. The experiment also found that the remarkable linear relation existed between yield and total root length of less than 2 mm.