5Arvidsson J, Keller T, Gustafsson K. Specific draught for mouldboard plough, chisel plough and disc harrow at different water contents[J]. Soil and Tillage Research, 2004, 79:221 --231.
6Shahgoli G, Fielke J, Desbiolers J. Optimising oscillation frequency in fscillatory tillage[J]. Soil and Tillage Research 2010, 106(2): 202--210.
7Sakai K, Hata S I, Takai M, et al. Design parameters of four-shank vibrating subsoiler[J]. Trans of ASAE, 1993, 36( 1 ): 23-- 26.
8Busscher W J, Bauer P J, Frederick J R. Deep tillage management for high strength southeastern USA CoastalPlain soils[J]. Soil and Tillage Research, 2006, 85: 178-- 185.
9Temesgen M, Hoogmoed W B, Rockstrom J, et al. Conservation tillage implements and systems for smallholder farmers in semi-arid Ethiopia[J]. Soil and Tillage Research, 2009, 104: 185-- 191.
