Nitrogen mineralization from eucalyptus yardwaste mulch applied to young avocado trees

Consistent use of mulches over several years can provide significant N to avocado. Study of a 3-year-old Ventura, California, avocado orchard mulched annually for 3 years with 12–14 Mg ha−1 chipped eucalyptus showed that total N in the mulched soil was double that of the control. Mulched intact soil cores released 53 kg ha−1 more N annually than control treatments. A litterbag study showed that net mineralization of the applied mulch commenced approximately 8.5 months following application. Mulched soils tended to be warmer and moister than control soils and temperatures varied less. Laboratory incubations of mulch and soil layers showed that net mineralization rates (mg kg−1 day−1) were greatest in the lowest decomposed mulch layer, but that more N mineralized overall (g m2) in the soil due to its greater density.