Effect of different tillage systems and straw management on some physical properties of soil and on the yield of winter rye in monoculture

Abstract

Field experiments were conducted on Orthic Luvisol derived from loamy sand in 1999-2002. The tillage sy- stems applied were: conventional tillage (CT) including pre- plough (10 cm) + harrowing, mouldboard ploughing (25 cm) + harrowing; reduced or conservation tillage (RT) using tillage ag- gregate consisting of a grubber (10 cm) + heavy harrow and string roller; and no-tillage (NT) where the only soil disturbance was from the direct sowing machine. Two straw management systems for the winter rye monoculture were applied on each tillage system: removed straw after harvest and retained straw. The straw was furrowed under CT, shallowly incorporated (7 cm) under RT and remained as chaff under NT. The physical behaviour of the soil was characterised by soil wetness, bulk density and penetration re- sistance. Under RT and NT with greater soil bulk density compared to CT, the water content of the soil was greater shortly after rainfall only; later, the reverse was true due to enhanced evaporation. The lower water content in the soil and the higher bulk density resulted in increased mechanical impedance for root growth. Retaining the straw did not counteract the negative response in the soil's physical conditions. The effects of the soil tillage and straw management systems on the yields of winter rye in monoculture were con- siderably affected by rainfall distribution during the growing sea- sons. In growing seasons with dry periods, the crop yield was more reduced under RT and NT than CT and on 'straw-retained' than 'straw-removed' plots. However, in growing seasons with fa- vourable rainfall distribution, the crop yield was not negatively af- fected by the RT and NT systems.