河北卢龙县是甘薯产区,过去育苗多用零水零火的方法,炕温不高,一般只烧到22℃左右,最高不超过25℃,上水是凭经验,随时零浇。这样,薯坑处于低温多湿的条件下,不利于秧苗生长,而有助于黑斑病的发生与发展。因此,坏坑现象比较普遍而严重,甘薯产量也受到很大影响。 Lulong County, Hebei Province, is a sweet potato producing area. In the past, nursery plants used zero-water zero-fire method. The ken temperature was not high and generally only burned to about 22 ℃. The maximum no more than 25 ℃. In this way, potato pit in the conditions of low temperature and humidity, is not conducive to seedling growth, and contribute to the occurrence and development of black spot. Therefore, the phenomenon of bad pit is more common and serious, sweet potato production has also been greatly affected.