Long-term fertilization does not affect soil C:N:S or the proportion between labile/non-labile fractions in Mollisols

VEGA JARA L; GUTIERREZ B F; GARCIA FO; RUBIO G

SOIL SCIENCE SOCIETY OF AMERICA JOURNAL

SOIL SCI SOC AMER

Año: 2020 vol. 84 p. 798 - 810

0361-5995

Agricultural management practices such as fertilization may affect the overall soil quality and nutrient supply capacity. Here, we hypothesized that long-term fertilization promotes: i) an increase in the proportion of easily degradable soil organic C, N and S fractions; and ii) changes in the soil C, N and S stoichiometric ratios in the direction of favoring the specific nutrient added to the soil. We included S in our study due to the increasing importance of S fertilization in many agricultural soils. A long-term experiment involving six fertilization treatments and maize, soybean and wheat as cash crops was conducted for 14 yr in an on-farm network located at the Pampean Region (Argentina). Long-term fertilization did not have a central role at defining the C, N and S distribution between soil organic fractions or their stoichiometric ratios since the particulate organic matter (POM)-C:total C, POM-S:total S; C:N, C:N, and N:S ratios were not affected by fertilization treatments and the mineralizable N:total N ratio varied in a very short range. Instead, long-term fertilization increased residue C inputs to the soil (8.7 - 19 Mg ha-1 over the non-fertilized control) and, in turn, increases in soil total C, N and S followed a linear relationship with residue inputs. This relationship was not affected by fertilization or site factors. Obtained data contributes to understand the effects of continued fertilization on soil properties such as the distribution of fast- and slow-cycling organic matter and nutrient concentration, which are essential for effectively managing soils for sustainable agriculture.