Mill by-product impact on soil nutrients

Mill by-products such as Mud, Ash and Mud/Ash mixtures are known to increase cane yield and sugar yield. Australian farmers broadcast and band these by-products in the fallow at rates greater than 150 wet t/ha and less than 100 wet t/ha, respectively. Eight commercial-size replicated, randomised strip trials were established in bare fallows between Ingham and Proserpine to investigate the impact of by-products banded between 35-100 wet t/ha and broadcast between 140-200 wet t/ha on soil nutrients compared to standard grower fallow practices. The trials were harvested each year over the crop cycle and soil samples collected after each harvest and analysed for nutrient content. The application of Mud, Mud/Ash and Ash resulted in an increase in organic carbon (C), BSES and Colwell phosphorus (PBSES or PCol), exchangeable potassium (Kex), calcium (Caex) and magnesium (Mgex) in the soil and the greater the application rate the larger the increase in these soil attributes. The application of Mud, Mud/Ash and Ash increased organic C, PBSES or PCol and Caex in the soil with Mud?Mud/Ash=Ash, while soil Mgex and Kex increased in soil with Ash>Mud/Ash>>Mud. Data from this study should be used to revise guidelines in the SIX EASY STEPS® nutrient management program for reducing macronutrient fertiliser rates after the application of mill by-products.