Impacts of Freezing-Thawing Cycle on Soil Penetration Resistance Under Different Tillage Practices in Black Soil

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(p0.05),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(p0.05).Soil penetration resistance was obviously less after the freezing—thawing cycle than before(p0.05).Soil penetration resistance was greater under continuous corn system than under corn—soybean rotation system.How-ever,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.