Soil temperature is a property that directly affects crop growth and is influenced by the energy balance on the soil surface. Thus, soil management systems influence soil temperature because they change soil surface conditions. The objective of this study was to determine the effect of three soil management systems on soil temperature throughout the snapbean cycle. A field experiment was arranged in a randomized block (split plot) design with four replicates, on a soil classified as Hapludalf. The treatments were continuous no-tillage for 7 years (PD); no-tillage revolved by disc moldboard ploughing (PDar); and no-tillage revolved by chiseling (PDesc). The soil temperature was monitored throughout the snapbean cycle. An automated data collection system collected information every 10 minutes with thermopar (copper-constantan) sensors installed at depths of 0.025 m and 0.10 m. Soil bulk density and snapbean yield were determined. The lowest maximum temperature and the lowest daily amplitude were observed for PD. The PDar system showed a maximum temperature of 42.2 °C, the PDesc system of 43.7 °C, and the PD of 36.1 °C at 0.025 m depth. The daily soil temperature variation during a day with 12 hours of sunlight at the beginning of the snapbean development (02/12/2002) indicated that the peak temperature was reached at about 15 o'clock, with values of 40 ºC in PDar and 30 ºC in PD, at the 0.025 m depth. When the plants shaded the soil, there were no differences in soil temperature among management systems. The differences in soil temperature were not reflected in the snapbean yields since the effects of high soil temperature are observed at seed germination.
no tillage; minimum tillage; thermopar
