Soil physical properties and earthworms as affected by soil tillage systems, straw and green manure management

Conventional tillage is not only high energy and labour consuming process, but it can also have a negative impact on soil properties. The objective of this study was to determine the influence of different tillage systems: deep conventional ploughing (CP) at 23–25 cm depth, shallow ploughing (SP) at 10– 12 cm depth, shallow loosening with a chisel cultivator and disc harrows (SL) at 8–10 cm depth, shallow loosening with a rotary cultivator (SR) at 5–6 cm depth, shallow green manure (red clover and timothy catch crop) incorporation with a rotary cultivator (GMR) at 5–6 cm depth and no-tillage (NT) on soil bulk density, penetration resistance, aggregate size distribution and earthworms. The experiment was carried out in two backgrounds: straw removed (N) or straw chopped and spread at harvesting (S). A long-term two-factorial field experiment was carried out at the experimental station of the Lithuanian University of Agriculture at 54o52′50 N latitude and 23o49′41 E longitude. The soil of the trial site was an Calc(ar)i-Endohypogleyic Luvisol (LVg-n-w-cc), clay loam on sandy light loam, with a pHKCl of 7.6, humus content of 28.6 g kg-1, K2O – 134 mg kg -1, and P2O5 – 266 mg kg -1. Straw incorporation had no significant influence on bulk density, penetration resistance and quantity of earthworms, but significantly reduced the amount of the smallest <0.25 mm aggregates. No significant differences of bulk density vs. CP were obtained in reduced autumn tillage – SP, and SL, while in reduced spring tillage systems – SR, GMR and NT significant changes were observed only in the first year of experiment at 3–13 cm depth. Soil penetration resistance increased in undisturbed soil layers. In SP it increased from 12 cm depth, in SL from 9 cm depth and in SR and GMR from 6 cm depth, while in NT it became higher from the very soil surface. SR, GMR and NT increased the number and biomass of earthworms and decreased the amount of the smallest <0.25 mm soil aggregates. Significant differences in soil aggregate size distribution and stability were found already in the first year. Reduced and no-tillage significantly increased the amount of water stable aggregates in both 0–15 cm and 15–25 cm soil layers compared to deep ploughing. Collapse