The Effects of Long-Term Organic and Mineral Fertilizer Applications on the Mineral Nutrient Concentration and Carbon-Nitrogen Dynamics of Faba Beans

This study investigates the long-term effects of mineral and various organic fertilizer (animal manure, compost, and mycorrhizae) applications on yield, nutrient uptake, and soil properties of faba bean (Vicia faba L.). A long-term field experiment was established in 1996 at the Cukurova University Research Centre in Adana/Türkiye. Since then, for each cropping season: Control (no fertilizer), Mineral fertilizer (NPK), Animal Manure (25 t ha⁻¹), Compost (25 t ha⁻¹), and Compost (10 t ha⁻¹) + Arbuscular Mycorrhizal Fungi treatments were applied. In the present study, faba beans were grown in winter 2021 and harvested in spring 2022. At harvest, shoot and root dry weight, as well as seed yield, were measured. Plant tissue mineral nutrients were determined, and plant total nitrogen and carbon uptake were calculated. When dry weight data were examined, the highest values for shoot (11.35 t ha-1), grain (9.77 t ha-1), and total dry matter (22.23 t ha-1) were obtained in the compost treatment, while the lowest values were 6.81, 5.32, and 13.09 t ha-1 in the control treatment, respectively. The highest nitrogen (N) concentration in plant tissues was 5.26% in compost+mycorrhiza treatment, while the highest grain nitrogen content was 0.37 t N ha-1 in compost application. In terms of carbon (C) accumulation, compost-treated plants stored 8.65 t C ha-1, equivalent to 31.73 t CO₂ ha-1. In comparison, control plots stored only 5.49 t C ha-1 (20.13 t CO₂ ha-1). Fertilizer application significantly increases shoot K, P, and Zn concentrations, and root P and Zn concentrations. In conclusion, organic fertilizers, such as compost and animal manure, have a positive influence on both plant yield and nutrient quality. These results demonstrate that long-term organic fertilization significantly enhances biomass, seed yield, and mineral nutrient concentration, especially under compost and compost + mycorrhizae treatments. Organic fertilizers fixed significantly more CO2 than control treatments, which is important for combating climate change driven by greenhouse gases.