Summary

In the years to come, sustainable land use is one of the big challenges for plant science. One promising low-input strategy is to make use of the potential of intercropping. In dryland agriculture, deep-rooting plants,  intercropped within shallow-rooting ones, may act as "bioirrigators" that can transfer water from deep soil layers to the topsoil for the benefit of the system. Our recent experiments have shown that bioirrigation is  facilitated by the presence of a common mycorrhizal network (CMN) shared by the intercropped plants. The ambition of the research that we propose in this project is to identify the morphological, physiological and competitive traits that make plants ideal bioirrigaors in CMN facilitated intercropping systems. With this research we seek to establish the basic knowledge that will allow installing effective CMN facilitated bioirrigation in intercropping systems as a measure to stabilize and increase the yield of small holder or subsistence farmers in dryland agriculture. To achieve this goal, we will perform a series of experiments at different levels of complexity with finger millet as target plant for bioirrigation and different legume species (cow pea, pigeon pea, lab lab) as potential bioirrigators.

We seek to achieve our overall goal by addressing six specific research questions:

• Do the three selected legume species perform hydraulic lift and thus meet the basic requirement to act as bioirrigator?
• What is the competitive strength of different legume species on finger millet and how are these competitive interactions ameliorated or enhanced by a CMN?
• What is the return in terms of water, nutrients and yield for finger millet when investigating carbon into a CMN with different legume species?
• Does CMN facilitated bioirrigation of different legume species improve the water relations, the nutritional status, andyields of finger millet when connected to intercropped legumes via a CMN during drought?
• What are the optimal population densities and ideal spatial arrangement of FM and its intercropping partners in order allow the establishment of a CMN, maximize the beneficial effects of bioirrigation, and minimize intraspecific competition?
• What is the acceptance of CMN facilitated bioirrigation in intercropping systems of a potential end user?

To address these questions, we have arranged a highly-qualified consortium of Indian and Swiss Scientists that will address these questions at different scales:

(i) controlled greenhouse experiments to assess the ecological basics of CMN facilitated bioirrigation,
(ii) controlled lysimeter studies to determine the effects of CMN facilitated bioirrigation on the water relations and total water use of the intercropping systems,
(iii) replicated field trials to assess the optimal planting
density of the intercropping partners to minimize competitive effects yet maximize beneficial yield effects, and
(iv) on-farm trials to test the applicability of bioirrigation in a real world farming scenarios and to test the acceptance of this new technology by the farmer.

In order to successfully complete these experiments, the consortium will employ a set of highly complementary methods that range from basic ecophysiological approaches to state of the art compound-specific stable isotope analyses, modern molecular tools and a world class large-scale lysimeter system. With the combination of esteemed Indo-Swiss expertise in crop physiology and agronomy together with the availability of world class infrastructure at the different institutions, we feel that our consortium is ideally suited to successfully conduct the work we propose here and to make with this a significant impact on science and the development of new biotechnology.