Long-term organic no-tillage onion system enhances soil enzyme activity and fertility attributes in southern Brazil

Onion (Allium cepa L.) production under conventional agricultural standards often leads to soil degradation and low sustainability. Conservation systems are thus relevant for recovering and improving soil attributes. This study evaluated the impact of a long-term (14 years) organic No-tillage Vegetable System (NTVS), with onion crop, on soil quality. The experiment in southern Brazil compared eight crop succession treatments, including winter cover crops black oats (BO), oilseed radish (OR), BO+OR), and fallow (weeds), followed by onions in spring and grains (velvet bean, soybean, millet, common beans) in summer. Soil chemical attributes (pH, P, K, Ca, Mg, cation exchange capacity - CEC, organic matter - OM) and enzyme activity ((fluorescein diacetate hydrolysis (FDA), arylsulfatase, and β-glucosidase)) were analyzed. The organic NTVS maintained or increased soil fertility. The winter cover crop consortium (BO+OR) and common beans in summer were linked to the highest enzyme activity and optimized nutrient cycling. The organic NTVS is a viable and sustainable cultivation system for onion production, contributing to soil conservation.