Complementary Haney Soil Health Tool Outputs Reveal Selective Responses to Organic Amendments in Apple Orchard Soils

Organic amendments can influence different dimensions of soil functioning, which may not respond in parallel. This study evaluated complementary outputs of the Haney Soil Health Tool (HSHT) after four years of amendment application in two apple orchards under organic and conventional management in northern Italy. Digestate, green compost, and mushroom compost were compared with orchard-specific controls in randomized complete block designs, with orchards analyzed independently. Treatment effects were selective across HSHT outputs. Estimated plant-available N and H3A-extractable Fe were unaffected by treatment in either orchard. Estimated plant-available P differed among treatments only in the conventional orchard (p < 0.001), with the highest values under digestate and higher values under green compost than under the control. H3A-extractable K showed significant overall treatment effects in both orchards (organic, p = 0.046; conventional, p = 0.002), with approximately 49% higher values under digestate than under the control in the organic orchard, although no pairwise differences remained significant after Tukey adjustment in the conventional orchard. No treatment effects were detected for 1-day CO2-C, water-extractable organic C or N, microbially active C, or the Soil Health Score. These findings show that joint interpretation of individual and integrated HSHT outputs provides a more differentiated assessment of treatment responses than reliance on the Soil Health Score alone.