Soil Carbon and Nitrogen Organic Fractions in Degraded vs. Non‐Degraded Mollisols in Argentina

Abstract

The use of no‐tillage has notably increased in the Pampas region of Argentina during the last 10 yr. Two tillage experiments with contrasting previous agricultural use, degraded and non‐degraded soils, were evaluated in the southeast of Buenos Aires province, Argentina. The objectives were to: (i) quantify the effects of tillage and N fertilization on quantity and vertical distribution of C and N in the soil organic matter (SOM) and particulate organic matter (POM) fractions as well as potentially mineralizable N (PMN), and (ii) evaluate these fractions as indicators of soil quality. Tillage systems were conventional tillage (CT), minimum tillage (MT), and no‐tillage (NT) (main plots), and N fertilization rates were 0, 120, and 150 kg ha−1 (subplots). Total organic C (TOC), total N (TN), POM‐C, POM‐N, and PMN were measured at 0‐ to 7.5‐ and 7.5‐ to 15‐cm soil depth. In Exp. I (degraded soil) TOC was greater under NT (27 g kg−1) than under CT (24 g kg−1) in the 0‐N treatments. No differences in TOC and TN were found in Exp. II at 0 to 7.5 cm (non‐degraded soil). Carbon in POM and POM‐N were greater under NT in the fractions of 212 to 2000 and 53 to 212 μm at 0 to 7.5 cm, but they were similar or greater under CT at 7.5‐ to 15‐cm depth in Exp. I. Stratification of TOC, TN, and POM were observed under NT in Exp. I. Potentially mineralizable N was greater under NT (62 mg kg−1) in Exp. I, however, no differences in PMN were observed in Exp. II. Carbon in POM 212 to 2000 μm and PMN were the more sensitive indicators of tillage effects, mainly in Exp. I.

Global impact of biotech crops: Environmental effects 1996-2009

“…Reductions in the level of GHG emissions associated with the adoption of biotech crops is acknowledged in a wide body of literature (CTIC, 2002;Fabrizzi, Morónc, & García, 2003;Jasa, 2002;Johnson et al, 2005;Lazarus & Selley, 2005;Liebig et al, 2005;Reicosky, 1995;Robertson, Paul, & Harwood, 2000;West & Post, 2002). First, biotech crops contribute to a reduction in fuel use due to less frequent herbicide or insecticide applications and a reduction in the energy use in soil cultivation.…”

Organic matter distribution in aggregate sizes of a mollisol under contrasting management

“…Thus, particulate organic matter is very sensitive to the changes produced by soil use and, therefore, its variation throughout time is more indicative of the effect of management practices than total organic matter (Carter, 2002;Fabrizzi et al, 2003). Likewise, its content can indicate the size of the easily mineralizable organic compartment and thus contribute to estimate potential nutrient (e.g.…”

“…Likewise, its content can indicate the size of the easily mineralizable organic compartment and thus contribute to estimate potential nutrient (e.g. N) supply by soil (Álvarez and Álvarez, 2000;Fabrizzi et al, 2003;Oorts et al, 2007). Soil organic matter is present both in inter-aggregate and in intra-aggregate spaces.…”

Long-term effect of tillage systems, straw and green manure combinations on soil organic matter

“…According to Fabrizzi et al (2003), increased carbon storage under no-tillage is mostly attributed to higher particulate organic carbon contents in the upper few cm of the soil profile, which according to Six et al (2002) intervenes in the stabilization of macro aggregates, leading to a slower macro aggregate turnover under notillage compared to conventional ploughing. The study done in a the 4-year crop rotation confirmed that organic and organic-mineral fertilization systems as well as the crop plants in the rotation increased carbon pools (Mikučionienė, Aleinikovienė, 2013).…”