Impact of tillage and residue management on soil heat flux

Abstract

The quantity and percent cover of a crop residue in no-tillage (NT) affects the transmission of radiation through the residue layer and alters soil heat flux compared with conventional moldboard tillage (CT). It has been shown that NT results in cold soil temperature and reduced germination. A residue-free strip over the center of planting row can improve the thermal regime of NT but, limited information has been published on the potential changes in heat flux density in no-tillage soil with different residue management practices. Therefore, we conducted a study on simulated NT plots (with no crop) in 1986 and 1987 to evaluate the impact of tillage and residue-free strips in NT practices on heat flux density of soil-residue systems on Plano silt loam soil. The treatments were NT with a 0.31 kg m −2 residue areal density with 5 (NT 5), 15 (NT 15), and 30 cm (NT 30) wide: residue-free strips. These treatments were compared with 0.61 kg m −2 residue areal density with 15 (NT′ 15) and 30 cm (NT′ 30) wide residue-free strips. A second large field-scale (including crop) experiment was conducted in 1987 and 1988, where: the NT 30 and NT 5 were compared with CT. Heat fluxes for soil and soil residue systems were measured or calculated from 1986 to 1988. In the simulated NT study, soil surface heat flux ( G ss ) in the center of the residue-free strip and conductive ( G mr), and conductive ( G ma) heat flux at 15 cm away from the center of the residue-free strip across the residue layer were significantly greater in the NT 30 than in the other treatments. Increases in G s, G mr and G ma of NT 30 compared with NT 5, NT′ 15 and NT 15 were associated with increased temperature in-the-row and between-the-row at the soil surface and :5 cm depth. In the large field-scale study, the G. was within the range of -123.1 to 313.4 W m-2 in CT, −101.3 to 247.1 W m −2 in NT 30 and −69.8 to 209.1 W m −2 in NT 5 for 0−5 cm soil layer during 8–21 May 1987 and 1988. The G mr values at 15 cm away from the row center were significantly greater in treatments with 0.31 kg m −2 residue areal density than in treatments with 0.62 kg m −2 residue areal density. The G ma in NT 30 and NT′ 30 were significantly greater than in NT 15, NT′n15 and NT 5. The 15 and 30 cm residue-free strips in NT 30, NT′ 30, NT 15 and NT′ 15 displayed greater heat input into the soil surface than the NT 5 system. There was more heat input into the soil surface in no-tillage soil with residue-free strips in the spring which conserves soil and water because of a layer of the residue maintained between-the-rows. These modified residue management systems could prove beneficial for early spring plant germination in cold regions.