Effect of reduced and no-tillage, straw and green manure management on soil physical properties and earthworms

Abstract

Conventional tillage system is not only high energy and labour consuming process, but it can also have negative impact on soil properties. The objective of this study was to determine the influence of conventional deep ploughing (DP), shallow ploughing (SP), shallow loosening with heavy cultivator and disc harrows (SL), shallow loosening with rotary cultivator (RK) shallow green manure (red clover and timothy catch crop) incorporation with rotary cultivator (GMR) 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 stationary two-factorial field experiment was carried out at the experimental station of Lithuanian University of Agriculture at 54052’50N latitude and 23049’41E longitude over the years 2000-2004. The soil of the trial site was as an Endocalc(ar)i Endohypogleyic Luvisol, clay loam on sandy light loam, pH was 7.6, humus content was 28.6 g kg-1, K2O was 134 mg kg-1, and P2O5 was 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 smallest <0.25mm 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 at the first year of experiment in 3-13 cm depth. Soil penetration resistance increases in undisturbed soil layers. In SP it begins to increase from 12 cm depth, in SL – from 9 cm depth and in SR and GMR from 6 cm depth, while in NT it becomes higher from the very soil surface. SR, GMR and NT increased the number and biomass of earthworms and decreased the amount of smallest <0.25 mm soil aggregates.