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SYED OMAR S.R.. M.H. AHMAD HUSNI. A R. ANUAR AND M A. ROZ1LAN

bilitiesofP. Mn, Band Zn (Lucasand Davis 1961). Peat soil limed with morę than 7 t ha"¹ has been shown to reduce the yield of tapioca and ground-nut (Joseph etal. 1974).

Fertilizadon ofpeat soil with copperatalllevels of limę increased copper uptake by corn quad-ratically,afterwhich the uptake declined with morę than 16 kg Cu applied ha’¹ (Fig. 2). The highest uptake of copper was observed when peat was treated with 11.8 and 15.9 kg Cu ha” (values deduced from regression equation) at liming rates of 4 and 10 t limę ha’¹, re$pectively. However, Kanapathy (1976) showed that application of copper between 5.6 and 11.2 kg Cu ha’¹ was sufficient to overcome copper deficiency in peat soil. The highest uptake of Cu by corn as was observed between 11.8 to 15.9 kg Cu ha”¹ does not necessa-rily mean that it would give the highest dry matter yield, sińce it could be at excessive levels in plant. Thiswas indicated in l abie 2. where application of 5.0 kg Cu ha"¹ gave a non significant dry matter yield increase over treatmentsof 10.0,15.0 and 20.0 kg Cu ha”¹. I lence, this study suggests that fertili-zation with 5 to 10 kg Cu ha” is sufficient to offset copper deficiency in corn grown on peat soil. This is within the rangę recommended by Kanapathy (1976).

Application of copper and limeat all rates on peat soil significantly increased extractable copper and soil pH compared tocontrol (Tables 2 and 8);

Peat treated with copper at 20 kg ha” ¹ gave the

highest value of extractable copper. 41.5 /ig g”¹ (Table2). Itwaspreviouslydemonstrated that the optimum production of dry matter yield of corn occurred when the application of copper to a peat

soil at 5 kg Cu ha"¹, and this ratę corresponded to

the extractable copper of 8.7 /igg” ^!. Earlierwork bylocalresearchers(Josephetal. 1974; Kanapathy 1976) did not show the critical levelofextractablc copper for corn grown on peat. The results ob-tained from this study could be used asaguideline fot* growing corn on peat/organic soils. Organie

soils with less than 8.7 //g g”¹ of DTPAextractable copper should be considered for*copper fertiliza* tion.

Liming peat soil increased soil pH significanth compared tocontrol (Table3). Applicationoflime

at 10 i ha"¹ gave the highest soil pH (5.03) compared to all other treatinents. Using boundary linę approach (Webb 1972; Walworth et <il. 1986). minimum pH of the peat required to bring maxi-mum growth of sweet corn was 4.40 (Fig. 3). This pl 1 wasslightly higher than the pH rangę ofpeat

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