Effects of Biofertilizers on Soil Quality and Environmental Response in Kumquat Seedlings

Abstract

This research was conducted at the College of Agricultural Engineering Sciences, University of Baghdad, to investigate the influence of sustainable fertilization strategies on kumquat seedlings. The study evaluated the effects of two types of fertilizers—organic fish fertilizer and traditional chemical fertilizer—in combination with specific bacterial inoculants, namely Azospirillum sp. and Streptomyces sp., focusing on soil properties, greenhouse gas (GHG) emissions, and microbial dynamics. The experimental results revealed a substantial improvement in soil fertility indicators. Organic carbon levels increased significantly from 0.578% in the control (F0) to 0.769% in the F3 treatment. Similarly, soil organic matter reached its peak value of 1.600% in F3, compared to lower values in other treatments, highlighting the role of these fertilizers in enhancing soil structure. In terms of environmental impact, the study observed a dual effect on gas emissions. While CO₂ concentrations rose from 297 ppm to 380 ppm in F1 due to increased biological respiration, other harmful GHGs saw a drastic reduction. Nitrous oxide (N₂O) emissions fell from 21.6 ppm in F0 to 7.9 ppm in F2, and methane (CH₄) decreased from 3.6 ppm to 0.8 ppm. Consequently, the carbon dioxide equivalent (CO₂eq) dropped from 6,797 to 2,299 in F3, marking a significant reduction in the overall carbon footprint. Furthermore, microbial activity was notably enhanced; Azospirillum and Streptomyces populations reached 8.6 log and 8.79 log, respectively, in the B2 treatment. Overall, the integration of fish fertilizer with a bacterial mixture (B3) provided the most balanced approach for improving soil health, boosting microbial populations, and mitigating environmental pollution. These findings provide a strategic pathway for implementing sustainable, eco-friendly agricultural practices for fruit crops in Iraq.

The experimental results revealed a substantial improvement in soil fertility indicators. Organic carbon levels increased significantly from 0.578% in the control (F0) to 0.769% in the F3 treatment. Similarly, soil organic matter reached its peak value of 1.600% in F3, compared to lower values in other treatments, highlighting the role of these fertilizers in enhancing soil structure.

In terms of environmental impact, the study observed a dual effect on gas emissions. While CO2 concentrations rose from 297 ppm to 380 ppm in F1 due to increased biological respiration, other harmful GHGs saw a drastic reduction. Nitrous oxide (N2O) emissions fell from 21.6 ppm in F0 to 7.9 ppm in F2, and methane (CH4) decreased from 3.6 ppm to 0.8 ppm. Consequently, the carbon dioxide equivalent (CO2eq) dropped from 6,797 to 2,299 in F3, marking a significant reduction in the overall carbon footprint.

Furthermore, microbial activity was notably enhanced; Azospirillum and Streptomyces populations reached 8.6 log and 8.79 log, respectively, in the B2 treatment. Overall, the integration of fish fertilizer with a bacterial mixture (B3) provided the most balanced approach for improving soil health, boosting microbial populations, and mitigating environmental pollution. These findings provide a strategic pathway for implementing sustainable, eco-friendly agricultural practices for fruit crops in Iraq.