Abstract:
Objectives Interspecific competition and compensation are important mechanisms to showcase the advantage of intercropping systems. The objective of the present study was to explore the N competitive ability of maize relative to legumes during intercropping. We also examined the maize N uptake recovery effect under sole cropping and when intercropped with different legumes.
Methods A field experiment was conducted at the experimental site of the Gansu Academy of Agricultural Sciences in Zhangye, Gansu Province, China, from 2018 to 2019. The experiment included three intercropping systems: maize and pea (M/P), maize and faba bean (M/F), maize and soybean (M/S), and four sole cropping systems, including sole pea (SP), faba bean (SF), soybean (SS), and maize (SM). The crop dry matter weight and N concentration at the maturity stage were investigated, the N uptake equivalent ratio (NER) of the intercropping system and partial N uptake equivalent ratio (pNER) of the crops were calculate. Maize competitive ratio relative to legume (CRml), the relationship between CRml and NER, the partial nitrogen uptake equivalent ratio of legume (pNERl), the partial N uptake equivalent ratio of maize (pNERm), and the N uptake of intercropped maize were assessed.
Results Over the two years average, NER values of M/P, M/F, and M/S were 1.33, 1.26, and 1.38, respectively. The pNERl value among intercropping systems was not (P>0.05) different. The pNERm value in M/S was (P<0.05) greater than that in M/P and M/F; N uptake of intercropped legumes was (P<0.05) lower than sole legumes, but legume N concentration was not (P>0.05) different between intercrop and sole legumes. Maize N concentration among the intercropping systems was not (P>0.05) different. Maize N uptake in M/P, M/F, and M/S was 62.2%, 51.0%, and 79.9% of the value recorded for sole maize. Maize N uptake in M/S was 33.4% and 62.6% higher than in M/P and M/F, respectively. CRml value in M/S was higher than 1 and (P<0.05) higher than in M/P and M/F, but the CRml value in M/P and M/F were lower than 1. The recorded values for the maize recovery effect in intercropping systems were less than 1. A significant positive correlation was found between CRml and NER, pNERm, and a significant negative correlation between CRml and pNERl.
Conclusions Based on the two years of study, the maize/pea, maize/faba bean, and maize/soybean intercropping system showed higher N uptake equivalent ratio than the sole maize system in Hexi Corridor. Maize and legumes compete for N during intercropping, with pea and faba bean stronger than soybean in competing for N during the intercropping. After harvesting the legumes, maize did not show any apparent N uptake recovery effect.
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