The choice of the white clover population alters overyielding of mixtures with perennial ryegrass and chicory and underlying processes

Abstract

Legume-based forage plant mixtures are known to increase biomass production over the mixture species grown as pure stands (overyielding), which has partly been attributed to enhanced nitrogen availability by legumes. However, the relative importance of underlying processes of these positive diversity effects and their drivers are not fully understood. Here we assessed if outcome and causes of diversity effects depend on the legume-species genetic identity. Over five years, we cultivated different white clover (Trifolium repens) populations, a grass and forb species in pure stands and clover-based mixtures and recorded biomass yield. Complementarity and selection effects of mixtures and relative yields of mixture species were calculated based on both unfertilized and nitrogen-fertilized non-leguminous pure stands. Results showed that the clover population altered the overall strength of diversity effects as well as the direction and magnitude of their temporal trends, at least for the grass component of mixtures. Differences in diversity effects between clover populations diminished when fertilized instead of unfertilized non-leguminous pure stands were considered. Hence, a part of these differences likely results from dissimilar effects of clover populations on nitrogen availability. The findings reveal the possibility to improve overyielding of legume-based forage plant mixtures by decisions on legume-species genetic identity.

White Clover does not Increase Soil N2O Emissions Compared to Ryegrass in Non-Frozen Winter, but Increases CH4 Uptake

“…This study was conducted at the experimental station of the Georg-August-University Göttingen in Deppoldshausen (51°34' N, 9°58' E, 342 m a.s.l), South Lower Saxony, Germany. The mean annual temperature and mean annual precipitation (during 2015-2019) recorded by the nearby weather stations were 9.5 ± 0.2 °C and 593.2 ± 57.8 mm, respectively (Nölke et al 2022). The soil is classified as a calcareous Luvisol according to the World Reference Base for Soil Resources (WRB 2014) with a silty-clay soil texture (55% clay, 2% sand, and 43% silt in the top 30 cm).…”

“…The soil is classified as a calcareous Luvisol according to the World Reference Base for Soil Resources (WRB 2014) with a silty-clay soil texture (55% clay, 2% sand, and 43% silt in the top 30 cm). The general soil characteristics determined by our previous studies at the same site were as follows: pH (7.4), total N (1.6 g kg − 1 ), total phosphorus (P) (38 mg kg − 1 ), and total potassium (K) (133 mg kg − 1 ) (Nölke et al 2022).…”

“…In summer 2014, stands were established in a randomized complete block design with four replicates, each plot had a size of 15 m 2 (5 m × 3 m). A detailed description of our study site is shown in Nölke et al (2022). The selected four treatments were: (1) white clover pure stand, (2) perennial ryegrass with and (3) without fertilization, and (4) bare soil.…”

Plant Species Complementarity in Low-Fertility Degraded Soil

“…There are often added benefits to plant productivity from two or more plant species growing together. Intercropping in agriculture and horticulture provides increased yields, often referred to as transgressive overyielding [ 5 , 6 , 7 , 8 , 9 ], for example when legumes are grown together with other crops [ 10 , 11 ]. In this example, the fortuitous spillover of N fixed by rhizobial symbionts from the legume to neighbouring plants is generally viewed as incidental, even though it seems unlikely that evolution has favoured an adaptation in plants that expends metabolic energy and resources towards obtaining N that is then readily shared with competitors.…”