Abstract
Translocation of carbon (C) and nitrogen (N) from vegetative tissues to the grain sinks is critical for grain yield (GY). However, it is unclear how these processes respond to crop management practices when two crops are planted in relay-planting system. In this study, we characterized the C and N accumulation and translocation and their effects on yield formation in a pea (Pisum sativum L.)-maize (Zea mays L.) relay-planting system under different levels of source availabilities. Field experiment was conducted at Wuwei, northwest China, in 2012, 2013, and 2014. Two N fertilizer rates (low – N0 and high – N1) and three maize plant densities (low – D1, medium – D2, and high – D3) were designed to create the different levels of source availabilities. During the co-growth period, the rate of C accumulation in intercropped maize was 7.4–10.8%, 13.8–22.9%, and 13.5–32.0% lower than those in monoculture maize, respectively, under the D1, D2, and D3 treatments; however, after pea harvest, these values were 1.1–23.7%, 33.5–78.9%, and 36.8–123.7% greater than those in monoculture maize. At maturity, intercropped maize accumulated 11.4, 11.5, and 19.4% more N than monoculture maize, respectively, under the D1, D2, and D3 treatments. Compared to the monoculture crops, intercropped pea increased C accumulation in stems by 40.3% with N-application and by 19.5% without N application; intercropping maize increased these values by 16 and 11%, respectively. Overall, increasing N fertilization improved the rates of C and N remobilization from the vegetative tissues to the grain sinks across the different density treatments. In intercropped maize, the stems contributed 22, 33, and 44% more photosynthate to the grain sinks than the leaves, respectively, under the D1, D2, and D3 treatments. Quantitative assessments showed that the enhanced C and N remobilization due to high N fertilization and high plant density led to an increase of GY in the intercropping system by 35% compared with monoculture. We conclude that the enhanced productivity in maize-pea intercropping is a function of the source availability which is regulated by plant density and N fertilization.
Highlights
Feeding the world with a growing population is an enormous challenge (Tanton et al, 2003; Fedoroff et al, 2010; Larson, 2013), and the challenge is exacerbated in highly populated countries such as China and India where the small farmable land area per capita is rapidly shrinking due to urban construction and economic expansion in other sectors that compete for land with agriculture (Godfray et al, 2010; Cumming et al, 2014)
During the co-growth period, the growth of one crop influences the performance of the accompanying crop, while some niche differentiation between intercrops usually occurs in the context of space and time
A large compensatory effect on the later-maturing crop may occur (Chen et al, 2018), as the later-maturing crop accelerates its growth with all the available resources after the harvest of the earliermaturing intercrop, leading to a full recovery from the inhibited growth encountered during the co-growth period (Li et al, 2014; Chen et al, 2018)
Summary
Feeding the world with a growing population is an enormous challenge (Tanton et al, 2003; Fedoroff et al, 2010; Larson, 2013), and the challenge is exacerbated in highly populated countries such as China and India where the small farmable land area per capita is rapidly shrinking due to urban construction and economic expansion in other sectors (such as Highways construction) that compete for land with agriculture (Godfray et al, 2010; Cumming et al, 2014). Intercropping has been reported to have significant yield advantages over the corresponding sole cropping (Chai et al, 2014; Hu et al, 2016, 2017) due to more efficient use of available resources (Franco et al, 2018), such as soil water, and nutrients (Mu et al, 2013; Chen et al, 2018). A large compensatory effect on the later-maturing crop may occur (Chen et al, 2018), as the later-maturing crop accelerates its growth with all the available resources after the harvest of the earliermaturing intercrop, leading to a full recovery from the inhibited growth encountered during the co-growth period (Li et al, 2014; Chen et al, 2018)
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