Orchard Soil Health Indicators and Yield Efficiency Show Similar Trends In Apple Replant Disease, Groundcover Management Systems, and Integrated Versus Organic Fruit Production Studies

We are developing a protocol for evaluating soil health in apple (Malus X domestica Borkh.) orchards of New York State. Soil health may be described as soil functionality, in terms of agricultural productivity, environmental prudence and resource conservation, but soil health research has focused mostly on annual crop systems. Our objective is to determine the optimal set of chemical, physical, and biological soil indicators for testing soil health in orchards, and then to relate soil management practices to soil health and orchard productivity. We have used three research sites with different long-term management histories, including pre-plant compost or fumigation in an Apple Replant Disease (ARD) site; in-row pre-emergence herbicide, post-emergence herbicide, sod, or mulch in a Groundcover Management Systems (GMS) study; and a comparative study of integrated and organic fruit production (I/OFP) systems. Based on ANOVA and means separation procedures (P<0.05), soil microbial respiration (MR), percent organic matter (%OM), percent nitrogen (%N), and percent carbon (%C) were significantly higher in the compost plots than in fumigated plots at the ARD site. These aforementioned indicators plus Potentially Mineralizable Nitrogen (PMN) were higher in GMS mulch plots than in sod and herbicide plots, and MR and %OM were higher in IFP plots than in OFP plots. Previous reports suggest that higher MR, %OM, %N, %C, and PMN are indicative of healthier soils. Trends in yield efficiency (kg fruit/cm² trunk cross-sectional area, TCSA) followed those of soil health indicators. Trees in the ARD compost plots had significantly higher yield efficiency than those in fumigated plots, and trees under IFP had higher yield efficiency than those under OFP. In the GMS experiment, yield efficiency was statistically similar across treatments. However, TCSA was higher for trees in mulch than those in sod and herbicide plots, which were statistically similar in size. While large apple trees are often inefficient fruit producers, this was not true in the GMS experiment. The similar yield efficiency for trees of substantially different TCSAs suggests that large tree size and high yield efficiency are not mutually exclusive.