Straw management and alternative tillage methods for minimizing soil degradation of Fluvisol

This study investigates sustainable soil management strategies for Fluvisol in northwestCroatia, a fertile but degradation-prone soil, by examining how different tillage practices and straw mulch management affect soil health and crop productivity. On the Šašinovec experimental farm (University of Zagreb Faculty of Agriculture), three tillage practices (conventional tillage, minimum tillage, and reduced tillage) with and without straw mulch are compared on the soil physical properties, soil organic matter and crop yields over three growing seasons. The experimental field was set up in a split-plot design with three replicates for each tillage system. Each block (100 m x 10 m) represents a different tillage system, with or without mulch (straw) as a sub-factor (50 m x 10 m). Conventional tillage (CT) is involves plowing (18-20 cm) in autumn and disc harrowing in spring, while minimum tillage (MT) with multitiller (10-15 cm) in spring and reduced tillage (RT) with subsoiling (35-40 cm) in autumn and multitiller in spring were selected for their potential to minimize soil disturbance, while preserving soil structure and fertility. The mulch used in this study was wheat straw (2.75 t/ha), which is known to better retain moisture, prevent erosion and increase organic matter content. Samples were collected immediately after sowing and after harvest at two depths in three replicates for each plot. The study found that RT with mulch consistently reduced bulk density, lowering soil compaction and improved conditions for root development. This treatment significantly improved water retention, an essential factor for plant health, especially under changing climatic conditions. While the MT and CT treatments had limited effect on reducing the soil bulk density, both MT and RT with mulch increased water holding capacity and soil moisture, which is critical for maintaining crops under drought or erratic rainfall patterns. Another focus was on soil structure, particularly the stability of aggregates, which help resist erosion and retain nutrients. MT with mulch (71.41 %) had a positive effect on aggregate stability, more so than the CT (65.61 %) and RT (61.61 %) treatments. In addition, RT and MT with mulch (4.64% and 4.91%, respectively) had supported higher organic matter content than CT (3.86%), indicating better soil fertility and resilience over time. In terms of yield, the MT and RT treatments with mulch achieved higher soybean (+21 %; +15 % and spring wheat (+55 %; +18 %) yields compared to bare plots with same tillage. This indicates that reduced tillage in combination with mulching can not only maintain but possibly even increase productivity in Fluvisols. Throughout the trial, mulching consistently improved soil moisture and organic matter, highlighting its role in supporting long-term soil health. These results suggest that reduced and minimum tillage in combination with straw mulch, is a sustainable alternative to conventional plowing. The continuous use of mulch and non-inverting tillage practices helps to reduce soil degradation and improve resilience, particularly in soils that are susceptible to degradation, such as Fluvisols. Furthermore, these practices are wellsuited to mitigate the challenges of fluctuating climatic conditions and ensure stable crop yields.