Microbiological indicators of soil quality are related to greater coffee yield in the Brazilian Cerrado region

Abstract One of the main challenges faced by the rapidly growing human population is to increase agricultural sustainability. Soil quality is an essential aspect of agricultural sustainability, but farmers have generally assessed this based on conventional chemical and physical indicators, with little application of indicators of soil functions, such as soil microbiological attributes. These indicators may respond faster to changes in soil conditions and thus they could correlate better with the growth/yield of crops such as coffee. The aim of this study was to investigate the potential of soil microbiological indicators in assessment of soil quality for sustained coffee production, compared to or combined with conventional soil physical and chemical indicators. To accomplish that, two observational studies were performed by measuring soil microbiological, physical, and chemical attributes in coffee field areas with contrasting records of coffee yield but under similar edaphic and climatic conditions in the Cerrado (Brazilian tropical savanna) region of Minas Gerais, Brazil. In the first study, two neighboring field areas with contrasting yield were selected for each of the following three cultivars: Catuai Vermelho IAC 99, Catuai Vermelho IAC 144, and Rubi MG 1192. Samples were taken in two seasons (dry and rainy) of the year. In the second study, four neighboring field areas cropped with the cultivar Catuai Vermelho IAC 144 were chosen based on their contrasting yield records. In both studies, the experimental procedure consisted of collecting four composite soil samples (each composed of four subsamples) taken at a depth of 0–10 cm from each field area within the area of canopy projection of the coffee plant. The microbiological attributes evaluated were microbial biomass carbon; microbial basal respiration; metabolic quotient; urease, β-glucosidase, and arylsulfatase enzyme activities; and fluorescein diacetate hydrolysis. The physical and chemical attributes evaluated were texture, pH, organic matter content, and fertility. Climatic conditions affected the responses and must be considered in evaluation and elaboration of soil quality indexes. The physical and chemical attributes that were most closely related to higher coffee yields were Ca contents, organic matter content, effective cation exchange capacity, and base saturation in both studies in the rainy season. Microbial biomass carbon, metabolic quotient, and β-glucosidase and urease activities were positively related to higher coffee yields, and these attributes exhibited greater ability to discriminate the production potential of the soil than chemical and physical attributes did, in both seasons and studies.