Tillage system and farmyard manure impact on soil physical properties, CO₂ emissions, and crop yield in an organic farm located in a Mediterranean environment (Croatia)

A 2-year study was carried out in a Croatia to assess the impacts of tillage and fertilisation on soil bulk density (BD), penetration resistance (PR), CO₂ emissions and grain yields. The tillage treatments were: conventional tillage (CT), minimum tillage (MT) and reduced tillage (RT). Inside these plots, subplots were fertilised with organic fertiliser, 600 kg ha⁻¹ (CF), 15 t ha⁻¹ (FYM₁₅) and 30 t ha⁻¹ (FYM₃₀) of farmyard manure. In 2017, BD at 10–20 cm was significantly higher in MT than in RT and CT. The same was observed in 2018 at 0–10 cm and 10–20 cm. In 2017, RT had a significantly lower PR than MT and CT. In 2018, PR in RT was significantly lower than MT. In 2017 and 2018 FYM₃₀ and FYM₁₅ application decreased significantly BD in comparison to CF. In 2017, the highest dose of farmyard manure (FYM₃₀ 50, 5 kg ha⁻¹ day⁻¹) increased significantly CO₂ fluxes comparing to CF (40.7 kg ha⁻¹ day⁻¹). Soil CO₂ fluxes under CT (47.9 and 52.3 kg ha⁻¹ day⁻¹ in 2017 and 2018, respectively) were significantly higher than RT (39.1 kg ha⁻¹ day⁻¹) in 2017 and MT (41.7 kg ha⁻¹ day⁻¹) in 2018. Conventional tillage (2.26 t ha⁻¹) had significant lower oat yields than RT (2.72 t ha⁻¹) and MT (2.56 t ha⁻¹). The opposite occurred in barley yields. Farmyard manure significantly increased oat yields in 2017 compared to CF. Overall, reduced tillage with addition of FYM₃₀ can be considered a sustainable management practice, since improved soil physical properties, reduced CO₂ fluxes and increased grain yield.