More Sustainable Crop Production by Using Better Fertilisers

"Increased food production will critically depend on application of inorganic fertiliser. However, fertilisers greatly vary in their composition, their efficacy to promote crop yield and their impact on crop nutritional value. A prime example where different fertiliser efficacies manifest themselves is the form in which K+ is offered: Preliminary studies suggest that polyhalite forms of K (e.g. K2SO4.MgSO4.2CaSO4.2H2O) are more effective in augmenting plant growth than their traditionally used counterparts (i.e. potash in the form of KCl (MOP), K2SO4 (SOP) or KNO3). This may be due to improved 'balanced fertilisation' the benefits of which have long been known in agronomy. Furthermore, at the plant soil boundary, multiple interactions between uptake of minerals have been described (e.g. the stimulating action of K+ on uptake of NO3- or the inhibitory effect of Fe on Zn nutrition) which can be explained by competition and mutual effects on mineral bioavailability.

To evaluate the physiological impact of Polyhalite, we will use rice cultivars to answer the following questions:

-(1) How does K fertiliser type affect net K and N uptake?
Different forms of K+ salt (constant total K+ molarity) will be applied in varying concentrations to rice roots. Net K+ and nitrogen (as NO3- and NH4+) uptake will be measured via depletion assays, using flame photometry for K+ and HPLC for NO3- and colorimetry for NH4+. Rice ecotypes with high and low KUE (K+ use efficiency) will be used to assess how K+ salt composition affects KUE.

-(2)Does K fertiliser type affect plant nutrient distribution?
Plant tissues derived from rice grown on different forms of K+ salt will be analysed using ICP-OES to obtain complete nutrient profiles. Sampling of root, young leaf, old leaf, flag leaf, stem and grain will occur at varying developmental stages to cover the entire growth cycle. Plants will be grown in hydroponics and pots (sand) with defined fertilisation regimes.

-(3) How do different forms of K fertiliser affect microbial communities in the rhizosphere?
Rice will be grown in the presence of different K fertiliser both in hydroponics (to mimic closed hydroponic cropping systems) and in pots (to mimic field cultivation), and growth parameters will be scored. To assess general microbe development, number of colony forming units of bacteria and fungi will be determined using 16S rRNA gene fingerprinting and Biolog Ecoplate kits respectively.
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