Co-Application of Humic Acid and Bacillus Strains Enhances Seed and Oil Yields by Mediating Nutrient Acquisition of Safflower (Carthamus Tinctorius L.) Plants in a Semi-Arid Region

Abstract

Faced with the deterioration of natural resources, current trends in agriculture are focused on seeking eco-friendly methods to improve plant growth promotion and crop productivity. Plant growth promoting rhizobacteria (PGPR) and humic substances can improve crop production in sustainable farming due to their various features. This study examined how humic acid (HA) and inoculation with PGPR (Bacillus megatorium and Bacillus subtilis) affect the agronomic performance of safflower (Carthamus tinctorius L.) in a semi-arid environment. In the field experiments, PGPR inoculated and non-inoculated safflower seeds were cultivated in soil treated with humic acid (0, 200, 300, and 400 kg ha(-1)), alone or in combination. It was observed that PGPR and HA improved growth, yield parameters and seed mineral contents. Their plant growth responded positively to inoculation with Bacillus sp. strains owing to the N-fixing and P-solubilizing capabilities, whereas greatly positive response in the seed yield and quality was found when applied in combination with humic acids. The combined application of 300 and 400 kg ha(-1) HA with Bacillus subtilis inoculation enhanced seed and oil yields by an average of 162% and 221% relative to the control plants. This study confirms that integrated management strategies can ensure higher crop productivity of safflower in sustainable and semi-arid environments.