No-Till Mitigates SOC Losses after Grassland Renovation and Conversion to Silage Maize

Abstract

Many studies recommend no-till (NT) to increase soil organic carbon (SOC) in the topsoil (<30 cm) of arable land to counterbalance greenhouse gas emissions. Its potential use to mitigate SOC losses during conversion and renovation of grassland ecosystems in the top meter soil is yet to be determined. The SOC dynamics of a 10-year-old grassland converted to silage maize (CM) and renovated and seeded (GR) using either conventional tillage (CT) or NT were compared to an undisturbed grassland control (GC) for 7 years, across three fixed soil depth increments (0–30, 30–60, 60–90 cm). The annual C inputs (Cinput) from crop residues were further analyzed. The systems were either non-fertilized (N0) or fertilized with mineral N (N1) according to a demand of 180 and 380 kg N ha−1 year−1 in the silage maize and grassland systems, respectively. For the 7-year period, the renovated grassland using NT ensured maintenance of the initial SOC in the topsoil, while a conversion toward arable cropping resulted in SOC losses, regardless of the tillage method. The use of NT during conversion significantly reduced these losses from 2.5 Mg ha−1 year−1 to 1.8 Mg ha−1 year−1, for a 28% reduction compared to CT. In the subsoil (30–90 cm), SOC remained stable and was not affected by the cropping systems nor by the tillage method. Reduced annual Cinput was found as the main factor affecting SOC losses after grassland removal, regardless of the tillage method. Our findings highlight the potential of NT to mitigate annual SOC losses after grassland conversion if annual Cinput remains high.

Perennial Crops Can Compensate for Low Soil Carbon Inputs from Maize in Ley-Arable Systems

“…Digestate fertilization might also potentially increased the decomposition of SOC (positive priming effect), counteracting most of the additional carbon inputs [ 43 ]. Very low carbon retention from organic fertilizers (liquid dairy manure) was reported in other studies in mono-cropped cereals [ 44 ] and silage maize [ 30 ]. The fertilizer-induced carbon retention was at least 20% in cropping systems including perennials in these studies.…”

“…The increase in SOC content between 2009 and 2017 was 500–600 kg ha −1 yr −1 higher in CR10 (0% maize, 75% leys) compared to CR6 (50% maize, 25% leys), providing strong evidence in support of hypothesis i. In a comparable field experiment on a sandy loam soil in northern Germany [ 30 ], stable SOC contents were found for crop rotations including both grass-clover leys and silage maize in one out of three years and with cattle slurry application. Since SOC content decreased under continuous maize and increased under permanent grassland, the authors concluded that the ley proportion needed to be higher than 33% to significantly enhance SOC stocks, as was the case in our study.…”

Incorporating leys in arable systems as a mitigation strategy to reduce soil organic carbon losses during land-use change

“…This finding is consistent with previous research showing low retention of digestate carbon and its negligible influence on isotopic composition in crop rotations (Poyda et al, 2022). Likewise, studies have reported low carbon retention from organic fertilizers like liquid dairy manure in monocropped cereals and silage maize (Maillard et al, 2016;De Los Rios et al, 2022b). Legume-grass mixtures and silage maize showed low sensitivity to fertilization, likely due to high biological nitrogen fixation in unfertilized treatments and limited impact of fertilization on root carbon inputs in crop rotations (Poyda et al, 2022).…”

“…Previous research has determined that increasing the time of photosynthetic activity or plant cover throughout the year to increase net primary productivity (NPP), leaving crop residues on the field, as well as reducing the use of tillage can all have a positive impact on SOC, either by promoting its accumulation or by reducing its losses (Weil, 2000;De Los Rios et al, 2022a;2022b). A comprehensive review (King and Blesh, 2018) reported the benefits of using perennial crops and cover crops to increase the SCS of arable lands over cereal and grain-only rotations.…”

Improvement of Active Organic Carbon Distribution and Soil Quality with the Combination of Deep Tillage and No-Tillage Straw Returning Mode

“…While similar to the distribution patterns of soil organic carbon (SOC), the changes in MBC and DOC content are more influenced by different treatments, resulting in two distinct profile distribution patterns with changes in tillage methods (NPT and RT). Under the NPT mode, the straw cover and no-tillage methods contribute to the accumulation of soil organic carbon [40]. After three years of deep loosening, the organic matter accumulated during the previous two years of no-tillage is incorporated into the 10-30 cm soil layer.…”