did you survey Agricultural Water Management or any horticulture journal? the papers published by ASCE or ASAE, CSSA, SSSA and ASA would be helpful. keep me updated please.

Marcus, infact  very little work is available with regard to leaching of micronutrients in apple orchards . one of the prime reasons could be the surplus availability of micronutrients in soils growing apple , especially in the context of temperate conditions under which apple is grown . As much as 53-78% of applied nitrate , 5-11% of applied phosphate and 69-112% of applied K have  been reported leached beyond plough layer of the soil . 

Let me put up another response . Nitrogen leaching followed the similar pattern during the times of fertigation ( April -June) ..Here is PDF enclosed for further reading ..