苗床内土温的高低直接影响秧苗根的生长，水分及养分的吸收能力，肥料的分解和利用率等，这一切又导致了地上部生长发育的好坏。土温过低必然降低根部对水分和养分的吸收能力，长时间过低的士温还易发生萎根和锈根，也是造成小老苗、病苗，死苗的重要原因。在北方的早春寒冷季 Soil temperature in the seedbed directly affects the seedling root growth, water and nutrient absorption capacity, decomposition and utilization of fertilizers, etc., all of this led to the growth and development of the ground above and below. Soil temperature is too low will inevitably reduce the root of water and nutrient absorption capacity, too long a taxi temperature is also prone to rooting and rust roots, but also cause small seedlings, disease vaccine, dead seedlings an important reason. Early spring cold season in the north