The effects of freezing-thawing cycle on soil penetration resistance were studied on a black soil in Northeast China.The tillage experiment was established in Dehui City

Jilin Province since 2001.We compared soil penetration resistance before and after the freezing-thawing cycle under both no tillage(NT) and mouldboard plow(MP) treatments.Furthermore

we analyzed the relationship between soil penetration resistance and soil moisture content.The results showed that there was a significantly negative logarithmical correlation between soil penetration resistance and soil moisture content(R2=0.838 8).Compared with MP treatment

NT led to a significant increase of soil penetration resistance before the freezing-thawing cycle

especially in the layer of 2.5-17.5 cm(p<0.05)

while resulted in reduction of soil penetration resistance of 2.5-17.5 cm after the freezing-thawing cycle

especially in the layer of 2.5-10 cm(p<0.05).Soil penetration resistance was obviously less after the freezing-thawing cycle than before(p<0.05).Soil penetration resistance was greater under continuous corn system than under corn-soybean rotation system.However

even with the maximum soil penetration resistance

no restriction was found on the crop growth before and after freezing-thawing cycle of both NT and MP.