Nutrient inputs and outputs in a commercial orchard and their practical implications

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Abstract
Fertiliser requirements of a 14-year-old grassed-down commercial apple orchard in Canterbury were determined by direct measurements in the field of major inputs and outputs of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), and chloride (Cl) over a 2-year period. Each of the nutrients studied was affected differently by the various sources and sinks of nutrient cycles in the orchard ecosystem. Fertiliser additions provided the main sources of N, P, K, and S whereas precipitation and irrigation constituted the major inputs of Na, Cl, Ca, and Mg. Ca, Mg, S, Na, and Cl were mainly lost through leaching. Most of the P and K were removed by the harvested fruit crop and N was lost equally between leaching and fruit harvests. Total outputs exceeded total inputs for K, Ca, Mg, Na, and Cl, the reverse being true for N, P, and S. Practical implications of these results with respect to fertiliser recommendations for apple orchards are discussed.