Catch crop diversity increases rhizosphere carbon input and soil microbial biomass

Abstract

Catch crops increase plant species richness in crop rotations, but are most often grown as pure stands. Here, we investigate the impacts of increasing plant diversity in catch crop rotations on rhizosphere C input and microbial utilization. Mustard (Sinapis alba L.) planted as a single cultivar was compared to diversified catch crop mixtures of four (Mix4) or 12 species (Mix12). We traced the C transfer from shoots to roots towards the soil microbial community and the soil respiration in a 13C pulse labelling field experiment. Net CO2-C uptake from the atmosphere increased by two times in mix 4 and more than three times in mix 12. Higher net ecosystem C production was linked to increasing catch crop diversity and increased belowground transfer rates of recently fixed photoassimilates. The higher rhizosphere C input stimulated the growth and activity of the soil microbiome, which was investigated by phospholipid fatty acid (PLFA) analyses. Total microbial biomass increased from 14 to 22 g m−2 as compared to the fallow and was 18 and 8% higher for mix 12 and mix 4 as compared to mustard. In particular, the fungal and actinobacterial communities profited the most from the higher belowground C input and their biomass increased by 3.4 and 1.3 times as compared to the fallow. The residence time of the 13C pulse, traced in the CO2 flux from the soil environment, increased with plant diversity by up to 1.8 times. The results of this study suggest positive impacts of plant diversity on C cycling by higher atmospheric C uptake, higher transport rates towards the rhizosphere, higher microbial incorporation and prolonged residence time in the soil environment. We conclude that diversified catch crop mixtures improve the efficiency of C cycling in cropping systems and provide a promising tool for sustainable soil management.

Flower strips as a carbon sequestration measure in temperate croplands

“…Further, we found that flower strips with many different plant species and evenly distributed and more diverse plant populations had lower C sequestration rates. Thus, in contrast to a previous study showing that cover crop diversity may have a positive effect on C inputs (Gentsch et al 2020), the present study suggests a potential trade-off between C sequestration and plant species diversity in the flower strips.…”

Using fall‐seeded cover crop mixtures to enhance agroecosystem services: A review

“…Rhizodeposition during CC growth (root-derived C) is another important way that CC can add C to agroecosystems (Kuzyakov & Schneckenberger, 2004). In a pulse labeling experiment using fall-seeded CC, Gentsch et al (2020) concluded that diversified CC mixtures improve the efficiency of C cycling in cropping systems through greater atmospheric C uptake, transport rates towards the rhizosphere, microbial incorporation, and a prolonged residence time in the soil environment. Austin et al (2017) found that CC rhizodeposition accounted for 33% of total belowground C inputs of cereal rye.…”

Soil nitrogen and water management by winter-killed catch crops

“…Catch crop mixtures were shown to overyield the root biomass of pure stands and show higher potential for efficient soil exploration by roots (Heuermann et al, 2019). Increasing CC diversity also stimulates soil microbial diversity and biomass (Gentsch et al, 2020;Vukicevich et al, 2016), which represent a considerable reservoir for N during winter (Paul, 2007) and may contribute to N immobilization.…”