Positive legacy effect of previous legume proportion in a ley on the performance of a following crop of Lolium multiflorum

Abstract

Aims We investigated the legacy effects of a previous ley's legume proportion on the performance of a following grass crop in a rotation. Methods In April 2015, a pure Lolium multiflorum L. crop was sown after the removal of legume containing swards (0-100% legumes), and was harvested four times over the following one-year period (3 times in 2015 and once the following April 2016). Labeled 15 N fertilizer (50 kg N ha −1) was applied during the 2nd and 3rd re-growth periods to determine N fluxes. Results Across the one-year period, a significant legume-legacy induced increase in biomass yield of L. multiflorum was observed over the entire range of previous legume proportions when compared against the non-legume ley, the effect being 2.15 and 1.73 t ha −1 (P ≤ 0.001 each) in swards with 50% and 100% previous legume proportion, respectively, or up to +31%. The legume-legacy effect on biomass yield was most pronounced at the 1st harvest (June) and persisted into the 2nd harvest in August (P ≤ 0.05 both, over the entire range of previous legume proportion), though was no longer evident at the 3rd harvest (September). Importantly, the legume-legacy effect returned in the 4th harvest in April (P ≤ 0.05). Examining the source of N contributing to N yield confirmed that more N was derived from the soil at harvest 1 and 2 for previous legume containing leys (P ≤ 0.001) compared to those which contained no legumes, with a significant increase still seen for legume mixtures at harvest 3 (P ≤ 0.01). Conclusions The results demonstrate a sustained soiltransferred performance-enhancing legacy effect on a following crop in a rotation, with previous legume proportions of 50% having a comparable effect compared with that of a previous legume monoculture.

Plant species identity drives soil microbial community structures that persist under a following crop

“…The aboveground biomass yield was harvested as part of the study outlined in Fox et al. (2020). For the purposes of the present study, the phosphorus (P) content of L. multiflorum from the June legacy harvest was determined via ICP‐OES.…”

“…Moreover, because the response of fOTU richness, the relative abundance of the fungal phylum Glomeromycota in March, and P yield in June, were related to Tp abundance, the effect of Tp proportion and its associated legacy effect on these responses was analyzed via linear regression (for the end of the conditioning phase) or linear mixed effects regression (for the legacy samplings, as this was a repeated measure, Pinheiro & Bates, 2000). Both types of models included a quadratic legume proportion term to allow for flexibility in the response curves (Fox et al., 2020), and the marginal and conditional R 2 values for the linear mixed models were calculated as described in Nakagawa and Schielzeth (2013). The range of realized Tp proportions for which any of the response variables were significantly different from the value at 0% Tp proportion was calculated using the Johnson–Neyman technique (Potthoff, 2006).…”

“…Beneficial legacy effects, associated with a preceding legume crop (such as the annual pea plant Pisum sativum ), have been documented on following cereal crop performance in arable systems (Evans et al., 1991; Stevenson & van Kessel, 1996). Positive legume‐associated legacy effects have also recently been demonstrated for a following grass crop ( Lolium multiflorum ) after a three year ley (Fox et al., 2020). As these preceding crops were removed from the system, these legacy effects must be soil transferred.…”

“…(a) A conceptualization of the expected response of the yield of bi‐component mixtures based exclusively on the identity effects of the two components (IE, green line) and, if in addition to that, the two components show (positive) interactions, the so called diversity effect (DE, blue line). For the purposes of this example, the biomass yield of the following crop ( Lolium multiflorum ) at the legacy harvest in June is displayed (Fox et al., 2020, i.e., the same experimental system and sampling times as discussed in this study), at varying proportions of the two components legumes (Leg) and nonlegumes (non‐Leg) of the previous sward. For further conceptual details on identity and diversity effects in mixtures and their analyses based on a simplex design, consult Kirwan et al., 2009.…”

“…Physiological differences between plant species, particularly in litter quality, has been suggested as the reason why plant functional group identity (particularly legumes) was the stronger driver of soil microbial community composition, compared to plant species richness, in the Jena biodiversity experiment (Dassen et al., 2017). Nevertheless, strong diversity effects deriving from plant species interactions, in intensively managed fertile grasslands, on aboveground plant performance, such as biomass yield (Finn et al., 2013; Nyfeler et al., 2009), N uptake from symbiotic and soil sources (Nyfeler et al., 2009; Suter et al., 2015) and soil‐transferred legacy effects (Fox, Suter, Widmer, & Lüscher, 2020), would suggest that besides plant species identity effects on soil microorganisms, significant plant diversity effects could also be expected (Figure 1a). A greater understanding, however, as to how and to what extent plant identity and diversity (determined by species richness and evenness) influence the structure of the soil microbiome is still required, particularly under field conditions.…”