| Summary: | Phosphorus (P) is an essential nutrient but is commonly limiting for food production in tropical
and subtropical maize cropping. The efficiency of P fertiliser uptake is often low (5–30%) for various
site-specific reasons and so identifying the drivers of P efficiency for different systems is important. We
conducted a sensitivity analysis on the parameters of a well-established cropping systems model
(APSIM) for a wide range of soil, crop and management factors to understand their influence on yield.
The analysis was conducted for two contrasting maize cropping systems: (a) a high-input, large-scale
commercial system in subtropical Queensland, Australia and (b) a low-input, small-holder system in
tropical, western Kenya. In Queensland, yield was most sensitive to available P and mineral N supply,
and the sensitivity of both increased with in-crop rainfall. Available P was also the most important
parameter in Western Kenya, but N supply had much weaker influence due to higher levels of organic
matter. Parameters controlling P sorption were more important than other soil parameters at both sites
irrespective of seasonal conditions. In conclusion, these results suggest that efforts to improve efficiency
of P use by plants need to account for interactions between water and N supply in environments where
these are limiting. They also highlight a potential constraint to modelling of these systems as some of
the most influential parameters are difficult to measure directly.
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