Can no-tillage and crop diversification sustain nutrient stocks in acidic and poorly-fertilized soils? Evidence from 32 years of real-world agricultural management in Paraguay

Intensification under technical and economic constraints has driven widespread soil fertility decline in Paraguay. In this context, whether no till with crop diversification alone can maintain fertility under low-input conditions remains uncertain. Our objective was to evaluate how contrasting agricultural systems defined by types of soil tillage and crop sequence affect soil nutrient stocks under long-term low-input management. We measured stocks of macro and micronutrients to 30 cm and assessed associations between pH and nutrients. Diversified no till helped maintain higher stocks of total N (+15%) and of available P (+40%), exchangeable K (+27%), Ca (+72%) and Mg (+43%) relative to conventional tillage. In contrast, extractable concentrations of redox sensitive micronutrients (Cu, Fe, Mn) were higher under conventional tillage, consistent with disturbance induced transient mobilization. Depth resolved analyses (0-10, 10-20, 20-30 cm) indicated that most between system differences in total stocks were concentrated in the surface layer. Although this study focused on nutrient stocks, consistent relationships between pH and nutrients were observed while pH remained below the minimum threshold recommended for the regional commercial crops (pH 5.5). Thus, diversified no till farming conserves fertility in low input contexts, but the benefits are limited due to soil acidity. Finally, integrating periodic soil diagnosis with amendments, particularly liming, offers a practical pathway to sustaining production in Paraguay. • No-tillage (NT) and crop diversification improved nutrient cycling in Paraguay • Diversifying crops and cover crops under NT sustains higher soil N, P, K, Ca, and Mg • Diversified NT systems alleviate soil acidification compared to conventional tillage • Cationic micronutrients are mobilized by tillage and stabilized by SOM under NT • Liming and proper fertilization could amplify the NT systems' benefits in Paraguay