Study On The Response Of Crop Species And Varieties To Mollisol Compaction

The Northeast China is a main food production region,and it plays an important role in ensuring the food security for China.However,the extensive use of farm machines at this region results in the risk of soil compaction.This situation is becoming much more serious,and becomes one of the most issue that threatening the food security.This research was conducted in the farm land of Northeast Agricultural University to explore the effects of different tractor and number of passes on the soil compaction degree,the response of soybean and maize to the soil compaction on plant growth and yield,meanwhile the response of up ground biomass and root traits of soybean varieties bred in different ages,also the effect of soybean root on compacted soil amelioration.The results will provide the theoretical foundation for the appropriate use of agricultural machinery,establishing a rational cropping system,selecting soil compaction-resistant varieties,and potential study of crop root ameliorating the compacted soil.The main results were shown as followed:?1?Effects of mechanical operation on the soil compaction and crop growth.Three kinds of tractor type?small tractor with pressure 110.0 kPa and weight 1.3 t,medium sized tractor with pressure 73.9 kPa and weight 3.3 t,large tractor with pressure 64.4 kPa and weight 6.9 t?and five number of tractor passes?0,4,6,8,12 times?both significantly affected the soil penetration resistance.The soil compaction degree had a positive corelation with tractor weight?P<0.05?.The tractor caused the highest increase of penetration resistance at 10-20 cm soil layer.The different number of tractor passes generated the significant difference at 30-40 cm layer.Tractor types affected soybean and maize yield significantly.Soybean yield varied with different tractor types as followed:small tractor(3.7 t ha^-1)>large tractor(3.2t ha^-1)>medium sized tractor(3.1 t ha^-1),and maize yield as followed:medium sized tractor(10.8 t ha^-1)>large tractor(9.8 t ha^-1)>small tractor(9.8 t ha^-1).Compared with the un-compaction treatment,small tractor with 8 passes significantly increased soybean yield by 21.9%,and medium sized tractor with 12passes significantly increased maize yield by 20.4%.?2?The growth and yield of soybean varieties bred in different ages have different response to soil compaction.Soybean biological characters and yield showed a significant difference among different breeding years.Soybean varieties bred at 1970s-2000s had more plant dry weight,nodule root dry weight,nod number of main stem,pod number,yield and higher plant height than varieties bred at 1940s-1960s.This indicated that soybean varieties bred at 1970s-2000s can be more resistant to compacted soil than varieties bred at 1940s-1960s.Jinyuan 2?bred 1941?,Hefeng 22?bred 1974?,Heinong 35?bred 1990?,Hefeng 45?bred 2003?and Beidou 5?bred 2006?could be considered to be the varieties with soil compaction tolerance as their high yield productivity during two years'experiment.Nodule dry weight and hypocotyl diameter are most sensitive to soil compaction and they can be guide parameters for breeding.?3?Porosity amelioration of compacted soil by soybean root.The amelioration of soil compaction by soybean root showed a significant difference between different breeding years.Dye tracing depth and dye tracing area present the macro-porosity distribution at vertical and horizon profile,the results showed that soybean bred at 2003 Hefeng 45 modified the soil pore structure better than other soybean varieties.Hefeng 45 can be a potential varity to amend soil compaction.Medium root width of soybean is a main character that could amend soil macro-porosity,and this amendment in vertical profile is greater than horizontal profile.In summary,mechanical operation generated the soil compaction.Soybean can more tolerance to soil compaction than maize.Soybean varieties bred after 1970s showed a better performance in soil compaction tolerance,and Hefeng 45 bred 2003 had a better performance in crop yield and ameliorating the soil macro-porosity.