The decomposition of standardised organic materials in loam and clay loam arable soils during a non-vegetation period

The decomposition of plant organic materials in the soil during the non-vegetation period in a cool temperate climate is associated with nutrient loss and asynchrony in nutrient supply for subsequent crops. Therefore, it is important to select sustainable management tools to regulate the decomposition rate of organic material during the non-vegetation period. The aim of the present study was to assess the influence of soil type (loam vs. clay loam), green manuring (wheat straw vs. wheat straw + red clover), and incorporation depth of organic materials (4–7 vs. 14–17 cm) on mass loss, decomposition rate and stabilization of standardised organic material in the organically managed arable soils. A Tea Bag Index method was used in the field experiments with standardised organic plant materials of green and rooibos tea. In addition, litter-bags of locally grown red clover were investigated. The findings of this study suggested that of the three management factors investigated soil type had a significant and longest effect. The mass loss and decomposition rate of the standardised organic materials were significantly (P < 0.5) higher and stabilization significantly lower in the loam soil than in the clay loam soil. During the non-vegetation period, green tea lost 46.3% of its initial mass, rooibos tea lost 19.7% and red clover lost 66%. The study showed that decomposition of fast-decomposing materials could be slowed down during the non-vegetation period by choosing soils with a higher clay content, shallow organic material incorporation depth and manuring soil with N-rich plant residues.