Interspecific root interactions increase maize yields in intercropping with different companion crops

Abstract

Background Intercropping is assumed to increase food production while reducing fertilizer needs and environmental impacts of crop production. Aims We aimed to (1) investigate the effects of intercropping on yields and nutrient uptake of maize, and (2) determine the relative contributions of above‐ and belowground interspecific interactions (RCabove/below) to these effects. Methods We conducted a 2‐year, small‐scale field experiment with maize grown either in monocropping or intercropped with faba bean, soy, blue lupin, or white mustard as companion crop. We included a treatment in which interspecific root interactions were restricted due to barriers in the soil. Maize and companion crops were analyzed for yields, and maize additionally for nutrient uptake. Maize partial land equivalent ratios (pLER), partial nitrogen and phosphorus equivalent ratios (pNER, pPER), and RCabove/below were calculated. Results Intercropping resulted in a similar productivity of maize as in monocropping on an area basis. Maize pLER, pNER, and pPER were larger than 1.0 in several species combinations, indicating a positive effect of intercropping on maize yields and N and P uptake. Interspecific root interactions accounted for 62–85% of the maize yield increase in legume/maize intercropping, but for only 22% in mustard/maize intercropping. Conclusion Our results indicate that intercropping is beneficial for crop production since it increases maize yields and N and P uptake of maize plants, and it also provides yields of a companion crop. A substantial part of these positive effects can be attributed to interspecific root interactions.

Soy and mustard effectively mobilize phosphorus from inorganic and organic sources

“…Thus, maize plants could potentially benefit from intercropping with one of the other plant species if the different plant species have a joint rhizosphere in which complementary and facilitative interactions can occur. Such positive intercropping effects on maize have been proposed earlier in various studies on intercropping (Homulle et al 2022;Li et al 2020a;Schwerdtner and Spohn 2021;Tang et al 2021). Moreover, plant species that effectively mobilize P from different soil P pools (such as soy and mustard) could potentially be used in crop rotations and/or as cover crops with likely positive effects on the P uptake of subsequent crops (Hallama et al 2019).…”

“…In the field, soy and lupin seeds had been inoculated with commercial Bradyrhizobium sp. inoculants, which are assumed to be also part of the microbial community introduced here (for details, see Schwerdtner and Spohn 2021). The soil was sieved (< 2 mm), mixed with tap water (1:2), and shaken on an overhead shaker for 1 h before being filtered through cellulose filters (Rotilabo®,type 113P,Carl Roth GmbH & Co. KG,Karlsruhe,Germany).…”

The potential of durum wheat–chickpea intercropping to improve the soil available phosphorus status and biomass production in a subtropical climate

“…The acidification of the rhizosphere by exudates from the Cp likely benefited the intercropped Dw by increasing P availability through the dissolution of P minerals [ 26 ]. In addition, Schwerdtner et al [ 20 ] reported that Cp species secrete higher levels of phosphatase in P-deficient soil conditions through their root systems. These results support the idea that cluster-root formation plays a significant role in acquiring P from alluvial soils under semi-arid climates.…”

Lupin causes maize to increase organic acid exudation and phosphorus concentration in intercropping

“…An inoculum was applied to the mineral substrate at the beginning of the experiment to introduce a soil microbial community. For this purpose, fresh soil (with a loamy sandy texture) was sampled from an agricultural field (for details see Schwerdtner & Spohn, 2021). The soil was sieved (<2 mm), mixed with tap water (1:2) and shaken on an overhead shaker for 1 h before being filtered through cellulose filters (Rotilabo®, type 113P; Carl Roth GmbH & Co. KG).…”

“…For this purpose, fresh soil (with a loamy sandy texture) was sampled from an agricultural field (for details see Schwerdtner & Spohn, 2021).…”