Soil acidification reduces land productivity across agricultural systems worldwide. The standard remedy is to periodically apply lime to the soil surface which, over a number of years, is assimilated into the soil profile and raises soil pH. Lime applications can be viewed as an investment in soil productivity. This paper presents a dynamic model to determine an optimal lime application for a cereal crop. The results for the Western Australian Wheatbelt using wheat as an indicator of soil productivity, show that optimal application rate and frequency vary with rainfall and initial soil pH. Incorporating lime through the soil profile increases net present value by up to 6% compared to traditional surface lime applications and reduces lime application rates and required time for soil acidity amendment.