Effect of tillage system and straw management on organic matter dynamics

Abstract

-The choice of cultivation system in arable agriculture exerts a strong influence not only on soil health and crop productivity but also on the wider environment. Conservation tillage using non-inversion methods conserves soil carbon, reduces erosion risk and enhances soil quality. In addition, conservation tillage has been shown to sequester more carbon within the soil than inversion tillage, reducing carbon dioxide losses to the atmosphere. Stable, well structured topsoils that develop following long-term conservation tillage lead to more energy efficient systems due to the reduced power requirements for cultivation. Long-term experiments, e.g. more than 20 years, that confirm the impact of conservation tillage over an extended period are not common. Here we evaluate the impact of different tillage methods and winter wheat straw management, either incorporated or removed, on organic matter turnover and soil quality indicators. No-till, chisel and mouldboard ploughing was carried out for 23 years on a silty clay loam soil in South West England that was not considered suitable for non-inversion tillage due to weak soil structure. In order to assess the effect of contrasting cultivation and straw disposal method on soil carbon dynamics, a range of assays were conducted, including water extractable organic carbon, hot water extractable carbohydrate, microbial biomass carbon, activity of β-glucosidase and acid phosphatase enzymes, C sequestration and the natural abundance of 13 C. Our results show that the soil organic carbon concentration in the topsoil was greater under no-till than mouldboard ploughing, while a reverse trend was observed in the lower depths. A 14-17% increase in soil organic carbon was observed in the topsoil for chisel plough and no-till treatments compared to mouldboard ploughing. Water extractable organic carbon was found to constitute only 1-7% of the microbial biomass carbon. Hot water extractable carbohydrate was one of the most sensitive indicators of soil quality and had a significant a negative correlation with bulk density and positive correlation with soil organic carbon microbial biomass carbon β-glucosidase and acid phosphatase. The choice of cultivation method exerted a major control on microbial and carbon dynamics. No-till and chisel ploughing maintained carbon in the soil surface horizons, which will benefit the stability of this weakly structured soil, but mouldboard ploughing distributed carbon more uniformly throughout the soil profile, particularly when straw was incorporated, hence leading to the retention of more carbon in the soil profile. soil quality / carbon sequestration / tillage / straw management / winter wheat

Influence of tillage practices on soil biologically active organic matter content over a growing season under semiarid Mediterranean climate

“…Under CT, the C-MB values were similar in both soil layers, a consequence of the soil being turned. These results are consistent with those reported in the literature (Hazarika et al, 2009;Madejón et al, 2009;López-Garrido et al, 2011). The contribution of C-MB to the bulk SOC (on average 1.5%) was rather low; agricultural land values commonly range between 1 and 5%.…”

Response of Organic Matter Decomposition to No-Tillage Adoption Evaluated by the Tea Bag Technique

“…As the decomposition of both high and low quality OM (green tea and rooibos tea, respectively) was positively related to NT age, our results provide indirect evidence that the activity of both opportunistic bacteria and fungi increased with the time span since the conversion from CT to NT. Although our findings should be substantiated by further microbiological analyses, including microbial biomass and microbial community profiling, they are consistent with previous investigations and likely result from the lack of disruption of the hyphal network under NT [30,31] and the regular supply of C by cover crop, as well as the increase of soil aggregation over time under NT [32], which provides a variety of new habitats and micro-environments for soil microbial communities involved in the short-term processing of readily-decomposable organic C [12,33,34].…”

Variability of soil physical quality in uneroded, eroded, and depositional cropland sites

“…As reported in earlier studies, these processes are attributed to the exposure of the surface from its natural vegetative cover (Fahnestock et al, 1995;Pimentel et al, 1995), resulting in increased raindrop impact and surface sealing, and therefore, higher rates of runoff and soil erosion (Assouline, 2004;Assouline and Mualem, 2006). Yet, the conservation practices followed in the studied agroecosystem, including no-till, residue management, and manure application, are assumed to increase the physical quality of the soil (Herencia et al, 2007;Hazarika et al, 2009), and thus, mitigate the magnitude of these processes.…”