Finger Millet Growth and Nutrient Uptake Is Improved in Intercropping With Pigeon Pea Through “Biofertilization” and “Bioirrigation” Mediated by Arbuscular Mycorrhizal Fungi and Plant Growth Promoting Rhizobacteria

Krishna Saharan,Thomas Boller,Ansgar Kahmen,Lukas Schütz,Andres Wiemken,Natarajan Mathimaran

doi:10.3389/fenvs.2018.00046

Abstract

Legume-cereal intercropping is well known in traditional dry land agriculture. Here, we tested whether finger millet, a shallow-rooted cereal, can profit from neighboring pigeon pea, a deep-rooted legume, in the presence of “biofertilization” with arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR), under drought conditions. We conducted a greenhouse experiment using compartmented microcosms. Pigeon pea was grown in a deep compartment with access to a moist substrate layer at the bottom, whereas finger millet was grown in a neighboring shallow compartment, separated by 25-µm nylon mesh, without access to the moist substrate layer. In the presence of a common mycorrhizal network (CMN), with or without PGPR, a drought condition had little negative effect on the biomass production of the finger millet plant whereas in absence of biofertilization, finger millet biomass production was less than half compared to well-watered condition. Biofertilization strongly increased nitrogen and phosphorus uptake by both plants, both under well-watered and drought conditions. In the presence of AMF, both plants also acquired 15N and 33P, offered in a labeling compartment accessible to fungal hyphae but not to roots. Our results show that “biofertilization” with AMF alleviates the negative effects of drought condition on finger millet, indicating that the CMN connecting pigeon pea and finger millet exert clearly a positive influence in this simulated intercropping system.

Highlights

Soil microorganisms play a major role in plant productivity and plant health, both in natural (van der Heijden et al, 2008) and agricultural (Artursson et al, 2006) ecosystems
When arbuscular mycorrhizal fungi (AMF) were present as biofertilizer, pigeon pea produced more than twice as much biomass under wellwatered conditions and about 1.6 times more under drought conditions; the plant-growthpromoting rhizobacteria (PGPR) treatment “Pseudomonas fluorescens alone (Pf) ” alone stimulated growth only marginally (Figure 2A)
Under drought conditions, the more than 2-fold reduction of growth was nullified in the presence of AMF, and finger millet accumulated as much biomass as under well-watered conditions (Figure 2B, Figures S2C,D)

Summary

Introduction

Soil microorganisms play a major role in plant productivity and plant health, both in natural (van der Heijden et al, 2008) and agricultural (Artursson et al, 2006) ecosystems. Particular, arbuscular mycorrhizal fungi (AMF; Gianinazzi et al, 2010; Smith and Smith, 2011) and plant-growthpromoting rhizobacteria (PGPR; Lugtenberg and Kamilova, 2009) may serve as “biofertilizers” (Vessey, 2003) to improve performance and sustainability of crop production, under stress conditions (Dimkpa et al, 2009; Smith et al, 2010). Another important element of integrated soil fertility management is plant intercropping, the technique of cultivating two or more crops simultaneously in the same field (Brooker et al, 2015). Intercropping offers farmers the opportunity to achieve yield advantages and increased yield stability by exploiting nature’s principle of diversity, even on marginal land (Brooker et al, 2015)

Methods

Results

Discussion

Conclusion