Strip width ratio expansion with lowered N fertilizer rate enhances N complementary use between intercropped pea and maize.

Maize (Zea mays L.)/pea (Pisum sativum L.) strip intercropping is considered a promising cropping system to boost crop productivity. The 3-year (2009-2011) field experiment was conducted at Wuwei, northwest China, with two maize to pea strip width ratios (80:80 cm and 120:80 cm), each under three N fertilizer rates (0, 90 and 135 kg N ha for pea, and 0, 300, and 450 kg N ha for maize). The results showed that expanding maize to pea strip width ratio from 80:80 cm to 120:80 cm coupled with a reduction of N fertilizer rate intensified N competition and improved N compensation. The apparent N recovery and N utilization efficiency of intercropped pea with strip width ratio of 120:80 cm were increased by 8.0% and 8.9% compared to strip width ratio of 80:80 cm. Compared to high N rate, the two indicators of intercropped pea with lowered N rate were increased by 10.0% and 6.0%. For intercropped maize, the two indicators were increased by 6.8% and 5.1%, with strip width ratio of 120:80 cm compared to 80:80 cm. Also, they were improved by 9.7% and 11.5%, with lowered N rate compared to high N rate. Consequently, the grain yield of pea and maize in the 120:80 cm pattern was improved by 11.9% and 7.7% compared to 80:80 cm. We concluded that expanding maize to pea strip ratio coupled with N fertilizer reduction can optimize N complementary use.