8Houlbrooke D J, Thom E R, Chapman R C, et al. A study of the effects of soil bulk density on root and shootgrowth of different rygegrass line[J]. New Zealand Journal of Agricultural Research, 1997, 40(4): 429-435.
9McGarry D, Bridge B J, Radford B J. Contrasting soil physical properties after zero and traditional tillage of an alluvial soil in the semi- arid subtropics[J]. Soil and Tillage Research, 2000, 53(2): 105- 115.
10Lpez-Fando C, Pardo M T. Changes in soil chemical characteristics with different tillage practices in a semi-arid environment[J]. Soil & Tillage Research, 2009, 104(2): 278-284.