Soil quality indicators for intensive vegetable production systems in Java, Indonesia

We explored the value of ergosterol, phospholipid fatty acid (PLFA) profiles and neutral lipid fatty acid (NLFA) 16:1ω5c as soil quality indicators for the intensive systems of vegetable production in the humid tropical climate of West Java, by comparing organic and conventional management. Additionally, we measured dehydrogenase and β-glucosidase activity. A secondary forest was included to obtain reference values under undisturbed conditions. Organic and conventional agriculture, and secondary forest each differed in the composition of the microbial community measured by PLFA profiles. Ergosterol appeared not to be universally applicable as a fungal biomarker and in this respect seemed to be inferior compared to PLFA fungal markers. NLFA 16:1ω5c may provide additional information as an indicator of arbuscular mycorrhizal fungi, but its high variability complicated the interpretation of data. The ratio of cy17:0 to 16:1ω7c was effectively applied as an indicator of physiological stress experienced by the bacterial community. Conventional vegetable production resulted in higher cy17:0/16:1ω7c ratios. Finally, a soil quality index, developed by stepwise canonical discriminant analysis and based on the absolute amount of PLFA 16:0, the relative amount of PLFAs 10Me16:0 and 10Me18:0, and dehydrogenase activity, was successfully validated.