SHORT-TERM EFFECTS OF CROP ROTATIONS AND WOOD-RESIDUE AMENDMENTS ON POTATO YIELDS AND SOIL PROPERTIES OF A SANDY LOAM SOIL

A 3-yr study (1988-1990) was conducted on a Beaurivage sandy loam soil located in St-Lambert, Quebec, Canada, to evaluate the shea-term effe cts of crop rotations and organic amendments on soil properties and po tato yields (Solanum tuberosum, L.). Treatments consisted of yearly fa ll rye (Secale cereale, L.) as a green-manure cover crop, barley (Hord eum vulgare, L.) grown every 3-yr in potato crop rotation, partially h umified bark residues and fresh tree clippings applied once at 100 m(3 ) ha(-1) in the beginning of the experiment, and continuous potato in monoculture used as check. Fertilizer rates were applied at 150, 100, 160 and 40 kg ha(-1) rates for N, P2O5, K2O5 and Mg, respectively. Res ults indicated that more rapid changes of soil C content were observed with Ligneous material incorporation than with fall rye and barley re sidue additions. Compared with fresh tree cuttings, partially humified bark induced rapid changes in soil organic C and cationic exchange ca pacity (CEC). A temporary soil structural stability improvement was ob served in 1989 under fall rye cover crop. However soil bulk density in creased significantly (P < 0.05) in these plots in 1990, and this was also related to low potato yields. Barley residues and ligneous amendm ents significantly improved soil water content during the critical flo wering stage, and this increased potato yields and specific gravity (P < 0.05). In general, soil amendment would improve potato yields and q uality through improved soil water content on a short-term.