8342937092

SYED OMAR S.R., M.H. AHMAD HUSNI, A R. ANI AR AND M A. ROZILAN

numerous functional groups (carboxyl, carbonyl, phenol, hydroxyl etc.) found in pcat (Stevenson

1982).

Research on Malaysian peat has indicated that

Cucontentisoftenlessthan5/igg'¹ inthesoil (Lee et ai 1988; Kueh 1990), which is Iow enough to cause copper deficiency in crop growth. Work on Cu isso limited that nonę of the published local literaturę have established a critical level of Cu for plant growth both in peat and minerał soils. This is important for interpreting Cu status in soil for plant growth based on soil analysis. Kanapathy (1976) did sonie workon fertilizer requirementon peat soils, but did not ratę the Cu status in this soil.

Through liming, it was possible to grow many annual cropson peat (Kanapathy 1967;JosephW al 1974). Therefore,itis generallyagreed among these researchcrs that liming is essential for crop productionon peat. However, the amountoflimę required to raise the soil pH often varies, probably due to the initial pH and heterogenity of peat. Therefore, itwould be morę meaningful toexpress the critical soil pH rather than amount of limę in reporting crop performance from limę application on peat.

The objectives of this experiment were to de-terminesuitablelevelsofCuand linie applications on peat and the critical levels that promote the optimum growth of sweet corn.

MATERIALS AND METHODS

Undisturbed peat soil (Typie Thopohemists) was taken from Banting, Selangoratadepthoł 0to20 cm. The samples were thoroughly mixed and placed in a plastic pot containing 2.6 kgof moist peat. The potswere treated with 5 levelsof copper sulphate (at equivalent ratesof0,5,10,15and 20 kg

Cu ha^-1) and 4 levelsof linie (at equivalent rates of

0,2,4 and 1 Ot limę ha*"¹) in the form of dolomitic

limestone in a factorial experiment. Each treatment was replicated three limes.

Ali pots were uniformly fertilized. This in-volved an equivalent ratę of390 kg urea (46% N),

195kg triplesuperphosphate (46% P^CL), 150 kg

muriate of potash (60% KgO), 150kgMgS0₄.7H_t>0,

13.7 kg MnS0₄.7H₂0, 20 kg ZnS0₄.5H_t)0, 0.5kg

CoSO₄.7H₂O,0.21 kgNa₂Mo0₄.2H₂0,and 15kg

HjB0₃ ha^-1.

Four sweet corn (Zea maysL.var. Thai Super-sweet) seeds were sown in each pot and watered to field capacity with distilled waterdaily. Aweek after sowing the seedlings were thinned to two uniform plantsper pot.

After 40 days from planting, plant tops were harvested and washed with distilled water before dryingin an oven for 72 h at 65°C. The dried plants were weighed and then ground using a stainless Steel grinder. The plant tissue was digested in a mixtureofconceniratednitricandperchloric acids following a wet ashing melhod (John 1972) and analysed for copper eon tent using atomie absorp-tion spectroscopy.

After harvest, 20 ml. of diethylenetriamine-pentaacetic acid (DTPA) extracting solution was added to moist peat samples weighing 15g (58% of moisture content) from each pot in a 125 mL conical fiask toextract available copper following the method of Baker and Amachei* (1982). DTPA waschosen because it offered the most favourable combination ofstability constants for the simulta-neouscomplexingof Fe, Cu, Mn and Zn (Lindsay andNorvell 1978). The fiask was then covered with stretchable pa rafii m and shaken for 2 h at 120 rpm. After shaking, the mixture was filtered through Whatman No. 42 filter paper. Thefiltrate was then analysed for copper content using atomie absorp-tion spectroscopy. The analysis for Chemical content of untreated peat and limę materiał used for the experiment are shown in Table 1.

RESULTS AND DISCUSSION

Data in Tables 2 and 3 show the effects of copper and limę, respectively, on the dry matter yield of sweet corn. Application of copper at all levels, significantly (P<0.05) inereased corn dry matter yield cómpared tocontrol. However nosignificant difference was observed with the application of morę than 5 kg Cu ha^-1 (Table 2). Liming the peat soil significantly inereased the corn dry matter yield cómpared to control (Table 3). The highest accumulation of dry matter yield was found in soil treated with 41 limę ha^-1 and this was alsosigificantly higher than 2 t limę ha“^l and control. Analysis of variance indicated that there was an interaction (P<0.05) between copper and limę treatments. The surface response curve showed the effects of interaction of copper and limę on the dry matter yield (Fig. 7). Applications at 10 kg.Cu ha"¹ and 4 t limę ha ¹ gave the highest dr)' matter yield of sweet corn (34.6gpot""¹), which isabouta 10-fold inerease in yield cómpared to control (3.56g pot”¹). This indicates the synergistic effeetsof copper and limę applications on peat soil.

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PERTANIKA VOL. 14 NO.l, 1991