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. 2017 Sep 14;12(9):e0184503.
doi: 10.1371/journal.pone.0184503. eCollection 2017.

Effects of reduced nitrogen inputs on crop yield and nitrogen use efficiency in a long-term maize-soybean relay strip intercropping system

Ping Chen  1   2 , Qing Du  1   2 , Xiaoming Liu  1   2 , Li Zhou  1   2 , Sajad Hussain  1   2 , Lu Lei  3 , Chun Song  2 , Xiaochun Wang  1   2 , Weiguo Liu  1   2 , Feng Yang  1   2 , Kai Shu  1   2 , Jiang Liu  1   2 , Junbo Du  1   2 , Wenyu Yang  1   2 , Taiwen Yong  1   2
Affiliations

Effects of reduced nitrogen inputs on crop yield and nitrogen use efficiency in a long-term maize-soybean relay strip intercropping system

Ping Chen et al. PLoS One. .

Abstract

The blind pursuit of high yields via increased fertilizer inputs increases the environmental costs. Relay intercropping has advantages for yield, but a strategy for N management is urgently required to decrease N inputs without yield loss in maize-soybean relay intercropping systems (IMS). Experiments were conducted with three levels of N and three planting patterns, and dry matter accumulation, nitrogen uptake, nitrogen use efficiency (NUE), competition ratio (CR), system productivity index (SPI), land equivalent ratio (LER), and crop root distribution were investigated. Our results showed that the CR of soybean was greater than 1, and that the change in root distribution in space and time resulted in an interspecific facilitation in IMS. The maximum yield of maize under monoculture maize (MM) occurred with conventional nitrogen (CN), whereas under IMS, the maximum yield occurred with reduced nitrogen (RN). The yield of monoculture soybean (MS) and of soybean in IMS both reached a maximum under RN. The LER of IMS varied from 1.85 to 2.36, and the SPI peaked under RN. Additionally, the NUE of IMS increased by 103.7% under RN compared with that under CN. In conclusion, the separation of the root ecological niche contributed to a positive interspecific facilitation, which increased the land productivity. Thus, maize-soybean relay intercropping with reduced N input provides a very useful approach to increase land productivity and avert environmental pollution.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. The temperature, daylight hour, precipitation and evapotranspiration during the cropping seasons from 2012 to 2014.
Fig 2
Fig 2. Maize-soybean relay intercropping system in August.
Left side is RN treatment plot, right side is NN treatment, and the yellow line is the plot boundary.
Fig 3
Fig 3. Effect of N application rates on competition ratio and system productivity index of the maize-soybean intercropping systems from 2012 to 2014.
CRSM: yield competition ratio, SPI: system productivity index; Different lower case letters in the same column indicate significant differences (LSD, P < 0.05).
Fig 4
Fig 4. Effect of different below-ground interactions and N application rates on maize root distribution at the early grain-filling stage.
MM with different N application rates (A), IM with different N application rates (B); the X-axis indicates depth (20 cm per layer) and the Y-axis indicates sampling interval (10 cm per interval); N application rates are 0, 180 kg N ha-1 (shared by soybean and maize), and 240 kg N ha-1 (180 kg N ha-1 for maize and 60 kg N ha-1 for soybean), respectively, the same as below.
Fig 5
Fig 5. Effect of different below-ground interactions and N application rates on soybean root distribution at the R2 stage of development in 2014.
MS with different N application rates (A), IS with different N application rates (B), the coordinate axis and N application rates were same as Fig 4.
See this image and copyright information in PMC

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