Figure 3

Soil temperatures in different soil layers and production systems (RFFM, seedbed was prepared as alternating ridge-furrow units mulched with transparent polyethylene film; RFFSM, alternating ridge-furrow units mulched with transparent polyethylene film and wheat straw; FFM, non-contoured seedbed mulched with polyethylene film; CK, non-contoured seedbed without mulch) during two growing seasons in the Loess Plateau. *,** and *** denote significance at the P < 0.05, 0.01, and 0.001 levels, respectively; ns, not significant.