Land use affected nutrient mass with minor impact on stoichiometry ratios in Pampean soils

• Published in: Nutrient cycling in agroecosystems 2018-03, Vol.110 (2), p.257-276
• Main Authors: Alvarez, Roberto, Gimenez, Analía, Caffaro, María M., Pagnanini, Federico, Recondo, Verónica, Molina, Cecilia D., Berhongaray, Gonzalo, Mendoza, María R., Ramil, Denise A., Facio, Facundo, De Paepe, Josefina L., Steinbach, Haydee S., Cantet, Rodolfo J.
• Format: Article
• Language: English
• Subjects: Agricultural ecosystems; Agriculture; Biomedical and Life Sciences; Cultivation; Fertility; Flooded soils; Fluxes; Forest soils; Forests; Human influences; Land use; Life Sciences; Mineralization; Nitrogen; Original Article; Soil fertility; Stoichiometry
• ISSN: 1385-1314; 1573-0867
• DOI: 10.1007/s10705-017-9896-0

The effect of land use on soil nitrogen (N) and phosphorous (P) stocks and the stoichiometry ratios are not fully understood. We determined the impact of land use on total N and P stocks along with some of their fractions and carbon (C), N and P ratios in soils of the Pampas. The effect of human activities on N and P fluxes in agroecosystems was also assessed. We sampled 386 soils under contrasting land uses down to 1 m depth. Well drained uncultivated soils were used as control treatment, paired with forest, cropped and flooded soils. Significant effects of land use on N and P stocks were detected to 1 m depth. Cropping decreased soil total N and P contents, mineralizable N and extractable P by an average of 14, 21 and 63% respectively. Conversely, forest soils had larger total N stocks (17%), mineralization (10%) and extractable P (37%) than uncropped controls. Flooded lands had the lowest fertility. Nitrogen and P pools under cultivation decreased higher as soils had higher initial levels N and P. In some low fertility soils, cropping led to N and P increases. Stoichiometry ratios were minimally impacted by land use. The ratio of the cumulative P surface balance to the N surface balance for the last 140 years was + 0.01 kg P/kg N in uncropped control soils and − 0.08 kg P/kg N in cropped soils. Despite this difference, the soil N/P ratio was unaffected by land use indicating that processes at the profile level regulated it.