Foliar versus soil phosphorus (P) application for improving P use efficiency in wheat and maize in calcareous soils

Phosphorus (P) is the most deficient nutrient in agricultural soils after nitrogen. Additionally, exogenously applied P quickly transforms into less soluble compounds through various chemo-sorption reactions resulting in poor fertilizer use efficiency (15-25%). Therefore, this pot experiment was conducted to investigate the impact of foliar P (0, 45, 90 and 135 mM KH2PO4) in conjunction with soil applied P (0, 10 and 20 mg P kg(-1)) for enhanced growth and P use efficiency of maize and wheat in calcareous soils. There was a linear increase in plant height and biomass both with the increasing application of soil and foliar P in both wheat and maize crop. However, the effect of foliar P was more pronounced in P deficient condition compared to 10 or 20 mg P kg(-1). Soil applied P at 10 and 20 mg P kg(-1) increased plant dry biomass by 10.8 and 16.8% in maize and by 29.9 and 35.5% in wheat over control, respectively. Foliar P application didn't improve soil phosphorus. The interaction between soil and foliar P was significant (p <= .05) showing that increase of either foliar or soil P application, tissue P content of both maize and wheat increased. In both season the higher foliar P solution resulted in higher P uptake though the increase in wheat were lower than maize. Therefore, the low recovery of soil P associated with poor soil characteristics could be corrected through its foliar application if administered at proper growth stage with suitable concentration strength and appropriate source.

Automated summary

The study showed that applying foliar and soil phosphorus in alkaline soils can enhance growth and phosphorus use efficiency of maize and wheat. Foliar phosphorus had a more significant effect on plants under phosphorus deficiency conditions, while soil applied phosphorus at 10 and 20 mg P kg(-1) significantly increased plant biomass. The interaction between soil and foliar phosphorus was significant in increasing tissue phosphorus content in both crops.