Effectiveness of different exchangeable cation extractants in predicting nutrient uptake in maize planted in tropical peat of peninsular Malaysia

This study was conducted to determine the effectiveness of different types of exchangeable cation extractants in extracting exchangeable K⁺, Ca²⁺, and Mg²⁺. It also aimed to assess the relationship between the amounts extracted and those taken up by maize (Zea mays subsp. Mays) planted in Sapric and Hemic peat materials. Three different extractants were used to test their effectiveness in extracting basic cations. These are NH4OAc at pH 7 (T1), NH4OAc pH 4 (T2) and Mehlich-1 [0.5 N HCl + 0.025 N H2SO4 (T3)]. Results showed that Mehlich-1 was 96-162 % more effective in extracting calcium and magnesium than NH4OAc pH 4 while ammonium acetate (pH 4) was 34-46 % higher in extracting potassium in both peat materials than NH4OAc at pH 7. All of the available nutrients extracted were significantly higher in Hemic compared to Sapric, yet the uptake of these nutrients by the maize was 32-37 % higher in Sapric than in Hemic. Available Ca2+ was the most abundant nutrient compared to K+ and Mg2+, yet the K uptake by maize was the highest regardless of peat materials. This implies that although extracted nutrient levels were higher in Hemic, maize plants performed better in Sapric, indicating that they are selective in nutrient uptake, absorbing only the nutrients required for growth, rather than those most abundant in the soil. Additionally, each basic cation shows a different preference for the extractants used, affecting the suitability of each extractant.