Integrated application of biofertilizers and poultry manure enhances rhizosphere biological functioning and buckwheat (Fagopyrum esculentum Moench) grain yield in a cold-climate agroecosystem.

Abstract

This study examined the effects of integrated organic and biofertilizer application on soil biological properties and buckwheat (Fagopyrum esculentum Moench) productivity under local cold-climate agroecosystem conditions in southwestern Iran. Field experiments were conducted during the 2022 and 2023 growing seasons at the research farm of Yasouj University using a factorial randomized complete block design with three replications. The first factor consisted of poultry manure applied at four rates (0, 4, 8, and 12 t ha⁻¹), while the second factor included seven biofertilizer treatments: control, mycorrhiza, Azotobacter, plant growth-promoting rhizobacteria (Pseudomonas putida), mycorrhiza + Azotobacter, mycorrhiza + Pseudomonas putida, and mycorrhiza + Azotobacter + Pseudomonas putida. Poultry manure application significantly increased root colonization, with the highest values, 27.96% and 18.85% in the first and second years, respectively, observed at the highest application rate. Soil microbial activity, assessed through basal and substrate-induced respiration, was markedly enhanced under integrated organic and biofertilizer treatments, particularly when poultry manure was combined with multiple biofertilizers. These treatments also stimulated acid and alkaline phosphatase activities, indicating enhanced phosphorus mineralization potential, nutrient cycling, and biological functioning of the soil. Yield components, including spikes per plant and seeds per plant, responded positively to integrated treatments. Grain yield was maximized under higher poultry manure rates combined with multi-strain biofertilizer applications, although the most effective biofertilizer combinations differed between the two growing seasons. Overall, the co-application of poultry manure and biofertilizers improved soil biological functioning, enhanced nutrient cycling as reflected by increased microbial respiration and phosphatase activity, and significantly increased grain yield and yield components of buckwheat. These findings suggest that integrated organic and biofertilizer-based nutrient management can be an effective strategy for optimizing organic buckwheat production and improving soil biological quality under local cold-climate agroecosystem conditions.