Plant nutrition: Its role in sustainability of simple and complex agro-ecosystems

Abstract

Agro-ecosystem sustainability depends on the ability of farmers to maintain soil productivity, avoid angry neighbours, keep customers happy and deal with the regulatory bureaucrats that try to control their activity. As plant nutrition issues are redefined by society, new applications emerge for a basic understanding of nutrient use-efficiency in soil-plant processes to avoid excess on rich soils as commonly found in the temperate zone and make the best of it on depleted soils common in the tropics. Current understanding of plant nutrition, largely focussed on monocultural situations, needs to be augmented by the interactions that occur in more complex systems, including agroforestry and intercropping as these may form part of the answer in both the excess and shortage type of situation. Simulations with the WaNuLCAS model to explore the concepts of a ‘safety-net’ for mobile nutrients suggested a limited but real opportunity to intercept nutrients on their way out of the system and thus increase nutrient use-efficiency at the system level. The impacts of rhizosphere modification in mixed-species systems depend on the degree of synlocation of roots of the various plant components, as well as on the long term replenishment of the nutrient resources accessed.