Distribution of soil carbon and microbial biomass in arable soils under different tillage regimes

Abstract

We have measured total soil organic carbon (SOC), dissolved organic carbon (DOC), and microbial lipid contents (as indices of microbial biomass and community structure), and their distributions to 60 cm depth in soils from replicated medium-term (2003)(2004)(2005)(2006)(2007)(2008) experimental arable plots subject to different tillage regimes in Scotland. The treatments were zero tillage (ZT), minimum tillage (MT; cultivation to 7 cm), the conventional tillage (CT) practice of ploughing to 20 cm, and deep ploughing (DP) to 40 cm depth. In the 0-30 cm depth range, SOC content (corrected for bulk density differences between tillage treatments) was greatest under ZT and MT, but over 0-60 cm depth the SOC contents of these treatments were similar to the CT and DP treatments. DOC concentrations declined with increasing depth in ZT and MT above 20 cm, but there were no significant differences with depth in the CT and DP treatments. Beneath 20 cm, there was little change in DOC concentration with depth for all treatments, although for the MT treatment, there was less DOC beneath the depth of cultivation. The total microbial biomass decreased with increasing depth over the 0-60 cm range in the ZT and MT treatments, whereas it decreased with depth only below 30-40 cm in the CT and DP treatments. The microbial biomass was significantly different only between 0-5 cm in the ZT, CT and DP treatments, but not for other depths between all treatments. The bacterial biomass was greater in the ZT treatment than in MT, CT and DP near the soil surface, but not significantly different over the whole profile (0-60 cm). The fungal biomass decreased with depth in the ZT and MT treatments over the whole 0-60 cm depth range, whereas it decreased with depth only below 20 cm in the CT and DP treatments.

Soil health: looking for suitable indicators. What should be considered to assess the effects of use and management on soil health?

“…The adoption of no-tillage systems in subtropical southern Brazil for 30 years has increased the concentrations of soil organic C especially at the 0-10 cm top layer, when compared to the conventional tillage . These findings have also been reported from several other geographic regions under temperate and tropical conditions (Melero et al, 2008;Pandey et al, 2010;Sun et al, 2010).…”

“…Under temperate conditions, comparisons between conventional, minimum, and no-tillage soil management showed no differences among the total microbial biomass based on phospholipids profiling (FAME) techniques (Sun et al, 2010). Nevertheless, when fungal and bacterial biomasses were assessed separately, only the fungal biomass had been favored under the more conservationist soil management.…”

“…decrease in organic matter (Grace et al, 1994), loss of structure (Bayer et al, 2001), increased risk of erosion (Volk et al, 2004), in addition to losses of microbial diversity and activity (Gupta et al, 1994). Less aggressive techniques of soil use, like minimum tillage (Sun et al, 2010) and no-tillage (Balota et al, 2003;Babujia et al, 2010) have been identified as less impacting systems of soil management. In general, the no-tillage system, in addition to adequate crop rotation, has shown to improve attributes associated to soil health.…”

“…Enhanced dehydrogenase activity has often been observed at the 0-10 cm layer in soil under no-tillage (Mikanová et al, 2009;Silva et al, 2010;Sun et al, 2010). A stimulation of soil microbial activity is also expected to result in higher general enzyme activities (Nayak et al, 2007), because most of the soil enzymes have microbial origin.…”

Eficiência De Soluções Densas No Fracionamento Físico Da Matéria Orgânica Do Solo

“…Por sua vez, no uso da solução de PTS foi averiguado que a FLO da camada de 0,00-0,05 m do Argissolo em PD apresentou maior estoque de C comparativamente ao solo sob PC, enquanto a FP não variou. Tal resultado é decorrente da maior adição de resíduos em superfície (Vieira et al, 2009;Sun et al, 2011) e melhor agregação das partículas do solo, quando é empregado um sistema conservacionista de manejo (Conceição et al, 2008), enquanto, sob PC, o revolvimento do solo causa o rompimento dos agregados e, consequentemente, exposição da MO aos microrganismos e suas enzimas (Shi et al, 2010).…”