Integrated nutrient management with biostimulant decreases drought effect on pasture species depending on soil type

Aims: Integrated nutrient management (INM) combining biostimulants and inorganic fertilizers has potential to reduce fertiliser inputs, facilitate drought resistance, preserve soil health and improve yield in agricultural systems. However, the potential of INM to support nutrient availability under drought needs further investigation, in part as it is soil type dependent. This study investigated biostimulant effect with different fertiliser rates on plant growth and soil nutrient availability in two contrasting pasture soils and watering regimes. Methods: Tall fescue (Festuca arundinacea) was grown for 6 months in light- and heavy-textured soil under glasshouse conditions. Two fertiliser rates (100% and 60% of the recommended rate) were tested with or without biostimulant, under either well-watered or droughted conditions. Shoot and root biomass, soil microbial biomass carbon and extractable nutrients were assessed during and post-drought. Results: Under non-droughted conditions, biostimulant increased plant growth at the high fertiliser rate in heavy-textured soil, but not in light-textured. Under drought, it did not enhance plant growth at any fertiliser rate, though it marginally offset drought effects in light-textured soil at the lower rate, while in heavy-textured soils it increased microbial biomass more strongly at higher fertiliser rates. The negative drought effect on plant growth was stronger in heavy-textured soil, with a legacy post-drought, during which biostimulant improved microbial biomass and extractable phosphorus at higher fertiliser rates, with nitrogen increases restricted to previously droughted soils. Independently, biostimulant enhanced post-drought recovery of plant growth in light-textured soil by stimulating root growth. Conclusion: The use of biostimulants in INM can improve nutrient availability and sustain plant growth to facilitate drought tolerance and post-drought recovery in Tall fescue by stimulating root growth and nutrient availability depending on soil. These findings highlight the need to consider soil type and fertiliser rate in developing INM strategies for plant nutrition and sustainability.