Effects of nitrogen application and irrigation cycle on bell pepper root distribution and yield under subsurface drip irrigation

Subsurface drip irrigation is a water-saving technology. A 2-year field experiment was conducted in 2007 and 2008 to investigate the effects of subsurface drip fertigation strategies on bell pepper yield and root distribution. Two irrigation cycles of four days and eight days (C4, C8) and four nitrogen application levels of 0,75,150,300 kg/hm2 (N0, N75, N150, N300) comprised the irrigation and fertigation treatments. The experimental results showed that the length, surface area, volume, weight, density of the roots significantly increased with the application rate of nitrogen less than 150 kg/hm2. The characteristic parameter of roots decreased with the nitrogen application rate increased to 300 kg/hm2. Four days irrigation cycle promoted the growth of root system and obtained higher yield than eight days irrigation cycle. The conics relationship between yield and nitrogen application rate was found. Maximum yield were obtained by treatment of 150 kg/hm2 nitrogen application rate and four days irrigation cycle. The results show that there is remarkable linear relation between yield and total root length which is less than 2 mm.