Glomalin as biochemical indicator of soil quality and its relationship with different physical, chemical, biochemical and biological parameters.

REYNA D; COFRÉ NM.; DUVAL M; FERRARI A; GABBARINI L; KRAEMER F; WALL LG

Rosario

Congreso; 7th World Congress on Conservation Agriculture; 2017

CAAPAS-AAPRESID

Glomalin is a protein produced by arbuscular mycorrhizal fungi (AMF). It is a hydrophobic gycoprotein very abundant in the soil, where it functions as a structuring biochemical component. Glomalin-Related Soil Proteins (GRSP) concentration in soils (mg BCA-reactive GRSP per g dry soil) is positively correlated with soil quality and is associated with different land uses. Analysis of easily extractable (EE) and total (T) GRSP fractions was used to characterize no-till productive agricultural soils associated with different treatments, replicated across a 400 km transect in the Argentinean pampas, during two sampling seasons, summer and winter. Treatment categories were grouped according to the sustainability of the soil management, in terms of crop rotation, fertilization, agrochemicals use and pest control, as good agricultural practices (GAP) and poor agricultural practices (PAP). Non-cultivated soils from nearby natural environments (NE) to the treatments in each geographic location were used as references. In silt soils environments the GRSP concentration showed strong potential to discriminate between different land uses, shown a significant trend NE>PAP>GAP. On the other hand, in sand or clay soils the GRSP concentration did not show this significant trend and thus did not discriminate between different land uses. This was observed both with EE-GRSP and T-GRSP and either in summer or winter. Thus the glomalin as indicator of soil quality was affected by edaphic?climatic differences between sites. Afterwards we analyzed the relationship of GRSP fractions with different physical, chemical, biochemical and biological parameters in order to better understand the applicability of the glomalin value as an indicator of soil quality. Correlation analysis showed high interdependence between GRSP and the arbuscular mycorrhiza community (spore numbers in 100 g dry soil), and also in relation to the available phosphorus. The hydrophobicity characteristic attributed to glomalin was also corroborated through its correlation with soil neutral lipid fatty acids - NLFA (nanomoles per g of dry soil) and the glycoprotein characteristic suggested by its correlation with total soil carbohydrates - CHt (kg per ha). Glomalin is consider an important component of soil organic matter, with a high correlation with total organic carbon - TOC (percentage of dry weight) and with total nitrogen ? N (percentage of dry weight), possibly showing a differential and characteristic relationship with the different organic fractions of the soil: coarse particulate organic carbon - POCc, fine particulate organic carbon - POCf and mineral organic carbon -MOC (percentage of dry weight). The relationship of the glomalin with the structural stability of the aggregates (weighted average diameter per mm) was also verified. Thus, in silt soils, in which the glomalin discriminate between different land uses, its value was related to other chemical and biochemical characteristics, while it was not like that in soils were glomalin did not worked as a quality indicator. These observations suggest a more complex meaning of glomalin a soil value.