IMPACT OF CLIMATE CHANGE ON CROP NUTRIENT AND WATER USE EFFICIENCIES

摘要

Implicit in many discussions of plant nutrition and climate change is the assumption that we know what to do relative to nutrient management here and now, but that these strategies might not apply under some as-yet experienced array of changed climate factors. Here we review existing knowledge on interactive influences of atmospheric carbon dioxide (CO2) concentration, temperature and soil moisture on plant growth, development and yield, as well as on plant water use efficiency and physiological and uptake efficiencies of soil-immobile nutrients. Increases in atmospheric CO2 will increase both leaf and canopy photosynthesis, especially in C3 plants, with minor changes in dark respiration. This additional carbon supply will increase biomass of these plants without marked alteration in partitioning of dry matter among roots, stems and leaves. Elevated CO2 also is expected to reduce transpiration of most plants, and improve water use efficiency. However, spatial and temporal variation in these attributes will impact agronomic performance and water use of crops in a site-specific manner. Nutrient acquisition is closely associated with overall plant biomass and is strongly influenced by root surface area. When climate change variables alter soil factors to the extent that root exploration of the soil is restricted, nutrient stress will reduce growth. Our analysis suggests that with climate change plant size may also change but nutrient concentration will remain relatively unchanged; therefore, nutrient removal will scale with growth. In pursuing a nutrient replacement philosophy for sustainable production, changes in regional input requirements will be most remarkable where we alter the cropping system to accommodate shifts in crop eco-zones or we alter the farming system to capture new uses from existing systems. For regions and systems where we currently do an adequate job managing nutrients, we stand a good chance of continuing to optimise nutrient use under a changed climate. If we can and should do better, climate change will not help us.