To combat falling productivity comprehensive nutrient budgeting is essential for improving farm productivity and agricultural resilience. Understanding nutrient budget requires careful measurement of the difference between what is being exported within crops or being lost from the land (e.g., as soil adhering to roots, through erosion, leaching or loss to the atmosphere), as well as, what nutrients may be being imported through natural processes (weathering of parent material, nitrogen fixation, decay of plants, rainfall, bird or animal droppings).
Knowing what natural or artificial fertiliser inputs are required to balance this nutrient budget enables farmers to reach an optimal outcome where production is sustained, while costs are minimised, and environmental impacts avoided.
The Gilbert Islands soils tend to exhibit extremely low Potassium levels, high pH values (8.2 to 8.9) and high CaC03 levels make scarce trace elements, particularly iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn), unavailable to plants. Fertility is, therefore, dependent on organic matter for the concentration and recycling of plant nutrients, lowering soil pH, and for soil water retention in the excessively well-drained soils. Although levels of organic matter can be relatively high in undisturbed soils under natural vegetation, they can decrease dramatically as a result of clearance by fire or replacement by coconuts and other introduced plants