Traditional agriculture relies on periods of fallow to rest and replenish the soil naturally. This has often lead to the notion that soils, especially fertile ones, do not require artificial fertiliser input to maintain soil nutrient levels. But with increasing population and commercial pressure, fallow periods in the Pacific have clearly been reducing. This results in reduced yields that are often reported by growers, but because the effect has occurred slowly over many years, the cause is not always properly appreciated.
To combat falling productivity nutrient budgeting is essential for improving farm productivity and agricultural resilience and sustainability. Understanding nutrient budgets 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, costs are minimised, and environmental impacts avoided.
