Crop rotations for increased soil carbon: perenniality as a guiding principle

Abstract

Abstract. More diverse crop rotations have been promoted for their potential to remediate the range of ecosystem services compromised by biologically simplified grain-based agroecosystems, including increasing soil organic carbon (SOC). We hypothesized that functional diversity offers a more predictive means of characterizing the impact of crop rotations on SOC concentrations than species diversity per se. Furthermore, we hypothesized that functional diversity can either increase or decrease SOC depending on its associated carbon (C) input to soil. We compiled a database of 27 cropping system sites and 169 cropping systems, recorded the species and functional diversity of crop rotations, SOC concentrations (g C kg/soil), nitrogen (N) fertilizer applications (kg NÁha ). We categorized crop rotations into three broad categories: grain-only rotations, grain rotations with cover crops, and grain rotations with perennial crops. We divided the grain-only rotations into two sub-categories: cereal-only rotations and those that included both cereals and a legume grain. We compared changes in SOC and C input using mean effect sizes and 95% bootstrapped confidence intervals. Cover cropped and perennial cropped rotations, relative to grain-only rotations, increased C input by 42% and 23% and SOC concentrations by 6.3% and 12.5%, respectively. Within grain-only rotations, cereal + legume grain rotations decreased total C input (À16%), root C input (À12%), and SOC (À5.3%) relative to cereal-only rotations. We found no effect of species diversity on SOC within grain-only rotations. N fertilizer rates mediated the effect of functional diversity on SOC within grain-only crop rotations: at low N fertilizer rates (≤75 kg NÁha ), the decrease in SOC with cereal + legume grain rotations was less than at high N fertilizer rates. Our results show that increasing the functional diversity of crop rotations is more likely to increase SOC concentrations if it is accompanied by an increase in C input. Functionally diverse perennial and cover cropped rotations increased both C input and SOC concentrations, potentially by exploiting niches in time that would otherwise be unproductive, that is, increasing the "perenniality" of crop rotations.

Soil aggregate stability increased with a self-regenerating legume cover crop in low-nitrogen, no-till agroecosystems of Saskatchewan, Canada

“…Cover crops occupy niches within grain systems, providing soil protection from erosion, organic matter and nitrogen additions, and enrich the soil microbiome (Lupwayi et al 2017;King and Blesh 2018). Seed cost is a barrier to cover crop adoption; use of self-regenerating plants such as black medic helps to overcome this (Wilson et al 2017).…”

Feedbacks between nitrogen fixation and soil organic matter increase ecosystem functions in diversified agroecosystems

“…Use of legume cover crops can build soil organic C and N (Drinkwater et al. , King and Blesh ), thereby supplying N to crops while also sequestering atmospheric CO 2 , and reducing NO 3 − leaching to aquatic systems and N 2 O emissions. Given that legume N 2 fixation varies with soil properties and interspecific interactions, predictive understanding of this variation is needed to inform managing legumes as a N source for crop production.…”

“…) and sequester carbon (C) in soil (McDaniel et al. , King and Blesh ). Given the potential for legume N sources to alleviate environmental impacts, there is a critical need to understand patterns of, and ecological controls on, legume N 2 fixation across variable agroecosystem conditions.…”

“…Legume cover crops can sequester atmospheric CO 2 by increasing C inputs to agroecosystems and building stocks of SOM (Poeplau and Don , King and Blesh ). In some long‐term experiments, management systems with legume cover crops do not have greater net C inputs to soil compared to lower diversity rotations such as continuous grains, yet the diversified systems still accumulate more SOM over time (Drinkwater et al.…”

Erosion and Sediment Control Best Management Practices in Agricultural Farms for Effective Reservoir Sedimentation Management at Cameron Highlands

“…Nowadays, a number of modified tillage operations are available with the objective of providing improved soil-water-plant relations, reduce soil erosion and runoff, helping in moisture conservation and reducing the time and cost of tillage operation [15]. The term minimum tillage describes the preparation of the seed-bed with minimum soil disturbance [18]. The tillage practices for BMPs erosion control are strip or zone tillage and Mulch Tillage.…”