Carbon and nitrogen stocks in relation to organic matter fractions, aggregation and pore size distribution in no‐tillage and conventional tillage in northern France

Abstract

The magnitude of and mechanisms for long-term differences in soil organic matter stocks under no-tillage and conventional tillage are still relatively poorly known. We quantified differences in total C and N stocks after 32 years of no-tillage (NT) and conventional tillage (CT) in plots with a long-term cultivation history before differentiation and the same annual C and N returns to the soil. The role of physical protection of organic matter (OM) in these stock differences was further investigated by examining the changes at different levels of structural complexity, i.e. organic matter fractions, aggregation and pore-size distribution. Four structural zones were sampled: loose and dense soil zones under CT and the 0-5 cm (rich in OM) and 5-20 cm (massive structure) soil layers under NT. The C and N stocks, calculated for an equivalent mass of dry soil, were only 10-15% larger under NT than under CT. Mineral-associated N and particulate organic matter accounted for about 50% of the difference in N stocks. However, 66% of the total difference in C stocks was due to differences in the particulate organic matter (58%) and free residues (8%) fractions. The additional C and N under NT were almost exclusively situated in aggregates larger than 250 mm in diameter. Our results suggest that physical protection of OM under NT contributes significantly to the differences in C and N stocks between NT and CT by (i) enhanced macroaggregate formation in the 0-5 cm layer due to greater microbial activity and OM content and (ii) a better protection of soil organic matter in the 5-20 cm layer due to the presence of small pores and lack of soil disruption by tillage or climate.

No-till in northern, western and south-western Europe: A review of problems and opportunities for crop production and the environment

“…Data from long-term trials summarised by of sampling not given). Similarly in France, measurements made on the Boigneville long-term field trial (32 years) have shown that the difference between C stocks in ploughed and no-till treatments within the 0-28 cm depth during a 32-year period was +5.2 Mg C ha -1 in favour of no-till (Oorts at al., 2007a) which is equivalent to 162 kg C ha -1 yr -1 . In a semi-arid area in northern central Spain the soil carbon accumulation to a depth of 30 cm after 10 years of no-till was 25% higher than after mouldboard ploughing (Sombrero and De Benito, 2010).…”

Effets des techniques culturales sans labour sur le stockage de carbone dans le sol en contexte climatique tempéré

“…Ces re´sultats sont comple´te´s par les observations de Oorts et al (2006aOorts et al ( , b, 2007 sur ce meˆme dispositif concernant l'analyse des me´canismes susceptibles d'expliquer les diffe´rences d'e´volution des compartiments de la matie`re organique sous l'influence des traitements applique´s. Ils montrent ainsi que l'horizon de surface du sol sous semis direct pre´sente des stocks de carbone et d'azote respectivement supe´rieurs de 5 a`15% et de 3 a1 0% a`ceux mesure´s dans l'horizon laboure´correspon-dant, avec des diffe´rences entre traitements qui ne sont pas toujours statistiquement significatives.…”

“…La pre´sentation a trois objectifs. (Balesdent et al 1990;Wylleman et al 2001 ;The´venet et al 2002 ;Oorts et al 2006aOorts et al , b, 2007. Le sol est un sol brun calcique sur loess (Haplic Luvisol): les principales caracte´ristiques de l'horizon laboure´au de´but de l'expe´rimentation e´taient les suivantes : argile : 22% ; limon (2Á50 mm) 70% ; sable : 8% ; carbone organique : 10 mg g (1 ; N total Kjeldhal : 1,2 mg g (1 ; CEC : 0,125 mmol c g (1 ; pH 6,1.…”

Soil conservation in the 21st century: why we need smart agricultural intensification

“…Often, carbon storage and biodiversity protection under conservation systems are mentioned as important ecosystem services for which farmers could be paid. Research in the last decade has consistently shown that carbon storage gains in conservation systems are lower than was anticipated two decades ago and are generally well below 1 t C ha −1 yr −1 (Oorts et al, 2007;Angers and EriksenHamel, 2008;Christopher et al, 2009;Eagle et al, 2012;Govers et al, 2013). Furthermore, paying farmers to store carbon would only be viable at much higher carbon prices than the current market prices, which are around USD 10-15 t −1 (Grace et al, 2012;Govers et al, 2013).…”