Maine wild blueberry systems analysis

We conducted a multi-disciplinary large-scale study covering three production cycles from 2010 to 2015 on four cropping input systems (organic, low input, medium input and high input) that fit along gradients of capital inputs and potential environmental effects to identify and quantify system effects on yield from pollination, weeds, insect pests and diseases. Structural equation modeling was used to produce a “path analysis” of the dynamics, and relationships are described by standardized Beta or correlation coefficients. Key positive factors identified were that the number of flower buds per stem and fruit set were consistently correlated with higher yield. Greater numbers of flower buds were associated with higher magnesium (Mg) in the leaves, lower organic matter, and lower soil pH from the addition of sulfur and fertilizer. Higher input of pollinators was a major factor in improving yield. Protecting against losses from weeds, insects and diseases improved yield. Interesting findings included that burning for pruning was associated with reduced plant stand, and frost was a major limiting factor to yield. Burning and insecticides decreased beneficial insects, but insecticides also reduced yield losses. Mummy berry and leaf spot diseases reduced yield, and bees increased mummy berry. Leaf aluminum (Al) was positively related to stem density and mummy berry disease. Higher levels of management were associated with higher levels of stem and leaf spot diseases and higher use of fungicides to control all diseases. System management accounted for the greatest variation in yield followed by the field site and then year. Yield among the high versus medium and low versus organic systems were not significantly different but the two groupings were significantly different.