Figure 3

Nitrogen accumulation of pea with (a) N0, (b) N1 and (c) N2 in three cropping systems. S, sole cropping; Int-1, intercropping with strip width ratio of 80:80 cm for maize:pea; Int-2, intercropping with strip width ratio of 120:80 cm for maize:pea. N0, N1, and N2 represent the N fertilizer rate at 0, 90 and 135 kg N ha−1 for the pea crop. 15, 30, 45, 60, and 75 day after sowing are respectively at the VE, V3, V8, V12 and V16 stage of maize. The error bars are standard error of the means (n = 9).