Inoculação e reinoculação via folia com Bradyrhizobium japonicum, Bacillus subtilis e Aschophyllum nodosum na cultura da soja

Abstract

Innovations in soybean cultivation have been constant over the years, and currently, biological management is gaining more and more visibility, aiming to meet the nutritional demand of soybeans, especially the need for nitrogen, the nutrient most required by the crop, in addition to generating a more sustainable activity with lower financial cost. This study aims to evaluate the efficiency of seed inoculation and reinoculation of soybeans with B. japonicum associated with co-inoculation with B. subtilis and/or seaweed extract based on A. nodosum. An experiment was conducted in the 2024/2025 season, using a randomized block design, with four replications. The tested treatments were: Treatment 1 (T1): B. japonicum inoculated on the seed; Treatment 2 (T2): Co-inoculation of B. japonicum + B. subtilis on the seed; Treatment 3 (T3): Inoculation of B. japonicum + A. nodosum seaweed extract on the seed; Treatment 4 (T4): Co-inoculation of B. japonicum + B. subtilis + A. nodosum on the seed; Treatment 5 (T5): B. japonicum inoculated on the seed and reinoculated as a topdressing; Treatment 6 (T6): Co-inoculation of B. japonicum + B. subtilis on the seed and reinoculated as a topdressing; Treatment 7 (T7): Inoculation of B. japonicum + A. nodosum seaweed extract on the seed and reinoculated as a topdressing; Treatment 8 (T8): Co-inoculation of B. japonicum + B. subtilis + A. nodosum on the seed and reinoculation as a topdressing; Treatment 9 (T9): Control without any inoculation and reinoculation; Treatment 10 (T10): Application of mineral nitrogen fertilizer. It is concluded that the synergy between the microorganisms B. japonicum and B. subtilis constituted the most efficient strategies to maximize soybean productivity under the evaluated conditions, promoting greater accumulations of dry mass, both in the aerial part and the root, high nodulation and photosynthetic capacity, and the addition of the seaweed extract based on A. nodosum to these treatments did not promote visible gains in the crop. The co-inoculation of B. japonicum and B. subtilis with foliar reinoculation (T6) was the most outstanding treatment, as it promoted the greatest accumulation of nodule dry mass (1.35 g/plant) and root dry mass (7.45 g/plant). Treatment T6 also achieved the highest average of pods per plant (106.25) and weight of 100 grains (20.5 g), resulting in a maximum yield of 4,280.25 kg ha-1, surpassing nitrogen fertilization by 51% and the control by 111%. The economic analysis demonstrated that management based on bioinputs showed greater financial efficiency compared to mineral nitrogen fertilization.