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Soil health depletion due to intensive tillage operations is a global issue in the agricultural sector. Conservation tillage (CT) which involves non-inversion tillage and leaving ∼30% of the soil surface covered with crop residues, is a strategy designed to enhance soil health. However, no comprehensive study to investigate the long-term effect of CT on soil biological activity and the soil nutrient supply has yet been widely carried out. Biological and chemical soil properties were assessed at depths 0–5, 10–15, and 20–25 cm depths after 18 years of CT and conventional tillage practice (PT). Various stages in the vegetative growth of maize were investigated in 2021 in Hungary. The findings indicated that tillage intensity, soil depth, and growth stages all significantly influenced soil enzyme activities and the concentration of soil nutrients. Less soil disturbance resulted in a significantly larger concentration of soil carbon parameters (total organic carbon and labile carbon) in CT plots, where the activity of β-glucosidase and dehydrogenase (DHA) in the upper soil layer increased significantly (0.7–2.6 and 2.6–4.7 times, respectively) compared to PT. The high amount of organic matter and the greater resistance to erosion observed in CT also contributed to the higher concentration of available nutrients (NH4, NO3, Ca, K) and total P in the surface soil layer. Phosphatase activity was highest in the mid-stage of vegetative growth and was positively correlated to the total P concentration. The alterations in soil water content were clearly negatively correlated with the change in DHA and phosphatase activity. Overall, due to the more balanced environmental conditions, the decomposition of organic substances was more balanced and slower in CT than in PT. This implied that the mobilization of nutrients in the soil was more balanced as well, and that the nutrients were released gradually. The enhancement of the soil nutrient-supplying capacity achieved by means of long-term conservation tillage provides a promising strategy for sustainable nutrient management.
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