Bioirrigation: a common mycorrhizal network facilitates the water transfer from deep-rooted pigeon pea to shallow-rooted finger millet under drought

Deep-rooted pigeon pea promotes the water relations and survival of shallow-rooted finger millet during drought—Despite strong competitive interactions at ambient water availability

“…Contrary to our expectation, the presence of a CMN between PP and FM and PGPRs did not facilitate higher stomatal conductance of FM during the drought period through the promotion of bioirrigation. This is in contrast to a previous study [20] that involved the same species but an experimental design with smaller pots, where FM in treatments with CMN had significantly higher stomatal conductance than FM without CMN during drought. Also Saharan et al [18] has reported that the presence of a CMN in a PP-FM intercropping system alleviates the negative effect of drought on FM.…”

“…Furthermore, Egerton-Warburton et al [19] showed the AMF facilitated transfer of water (released as HL efflux) from coastal live oak seedlings to water-stressed oak seedlings. Similarly, in a recent study, we [20] report that the presence of a CMN facilitated the transfer of HL water from deep-rooted PP to shallow-rooted FM, and that bioirrigated FM was able to maintain its stomatal conductance under drought. These studies present accumulating evidence that AMF could indeed promote bioirrigation.…”

“…To determine the balance between positive (facilitative) and negative (competitive) effects in an intercropping system, it is however, not only necessary to identify bioirrigation as a process but also to quantify its effect on yield of the involved species. The balance between positive and negative effects in CMN-facilitated intercropping systems has previously not been quantified, possibly because most previous studies have tested the effects of CMN-facilitated bioirrigation utilizing rather smaller pot sizes [18,20,24,25]. However, in small pots reduced plant growth [26] cannot fully inform on the quantitative facilitative and competitive interactions between two plants as they would occur in the field.…”

Spatial arrangement and biofertilizers enhance the performance of legume – millet intercropping system in rainfed areas of southern India

“…Egerton-Warburton et al (2007) have demonstrated that arbuscular mycorrhizal hyphae provide indeed a potential pathway for the transfer of HLW between two plants. Our recent work has shown that a CMN plays a key role in facilitating the transfer of water between the rhizospheres of two intercropped partners in a greenhouse and can in turn improve the water relations of shallow rooted crops during soil drying (Singh et al ., 2019). However, a further experiment with bigger pots (50 L) than in the previous experiment did not show an effect of the CMN on water-relations but treatments with CMN had lower foliar damage than treatments without CMN during drought (Singh et al ., 2020).…”

“…The effects of biofertilizers on stabilizing and improving the yields in intercropping systems by improving water relations via bioirrigation have not yet been tested under field conditions, though recent greenhouse studies have shown evidence of facilitation of bioirrigation by AMF and PGPRs (Saharan et al ., 2018; Singh et al ., 2019). Furthermore, it is unclear to what extent beneficial effects of biofertilizers in intercropping systems depend on an appropriate spacing of the crops and if – given the appropriate spatial arrangement of crops – the establishment of a CMN can indeed facilitate bioirrigation and improve as such the water relations of shallow-rooted crops in intercropping systems in dryland agriculture.…”