Soil fertility response to pruning, fungicide, and fertilization in lowbush blueberry

Management improves the growth and fruit yield of cultivated lowbush blueberries, but it remains to be seen how the pruning method, fertilizers, and fungicide applications affect soil fertility. This study investigates the impact of pruning, fungicide, and fertilization management practices on key soil parameters related to soil fertility, namely: soil organic matter (SOM) content, soil pH, nitrogen and phosphorus mineralization, nitrification, and phosphorus saturation index (PSI). A split–split–plot experiment was established, including two pruning methods (mechanical and thermal), two fungicide regimes (with or without), and three types of fertilizer applications (mineral, organic, or none). Mineral fertilizer applications significantly and strongly affected most soil fertility indicators, with increased nitrogen (+77 kg ha −1 ) and phosphorus (+117 kg ha −1 ) mineralization and SOM (+34 g kg −1 ), while reducing soil pH (−0.18) and nitrification (−46 kg ha −1 ). Thermal pruning decreased nitrification (−26 kg ha −1 ), soil pH (−0.12), and SOM concentration (−29 g kg −1 ). Fungicide applications showed no significant impact on soil fertility. While mineral fertilizer improves soil fertility, repeated application of organic fertilizer increases soil pH (+0.34), nitrification (+53 kg ha −1 ), phosphorus mineralization (+161 kg ha −1 ), and the soil phosphorus saturation index at undesirable levels (PSI > 2.8%) in lowbush blueberry production systems. The loss of SOM with thermal pruning is noteworthy and highlights the management impact and need for regular monitoring to maintain soil fertility in such fields.