Agrochemicals and Shade Complexity Affect Soil Quality in Coffee Home Gardens

Soil quality can directly influence the health, yield, and quality of a particular crop species, and agrochemicals are often used to boost soil micro- and macro-nutrients. The excessive application of agrochemicals, however, is often the cause of imbalances in acidity and nutrient concentration and can cause soil to deteriorate. The presence of multiple shade trees in farmland can positively influence soil quality. Here, we evaluate the effect of agrochemical use (i.e., organic, mixed, and intensive) and shade tree complexity (i.e., sun, low, and high) on soil quality (i.e., pH, macronutrients, and micronutrients) in 56 coffee home gardens in Indonesia. We found that Al, Fe, K, and Mn were significantly higher in farms that used agrochemicals, and pH was more acidic in fields with intensive use of agrochemicals. C:N ratio and Mn were higher in soils with high shade complexity than in sun-exposed soils. The use of agrochemicals, however, is not sustainable as it increases the Al concentration and decreases pH, both of which are associated with poor coffee growth and reduced soil quality. Shade tree removal and the use of invasive, non-native species, such as eucalyptus, can also negatively influence soil quality, and thus the maintenance of complex shade cover with native trees should be prioritised.