{"id":15239,"date":"2026-05-19T10:13:51","date_gmt":"2026-05-19T10:13:51","guid":{"rendered":"https:\/\/www.proefschriftmaken.nl\/portfolio\/omotola-obasoro\/"},"modified":"2026-05-19T10:14:11","modified_gmt":"2026-05-19T10:14:11","slug":"omotola-obasoro","status":"publish","type":"us_portfolio","link":"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/omotola-obasoro\/","title":{"rendered":"Omotola Obasoro"},"content":{"rendered":"","protected":true},"excerpt":{"rendered":"","protected":true},"author":7,"featured_media":15240,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-15239","us_portfolio","type-us_portfolio","status-publish","post-password-required","hentry","us_portfolio_category-new-template"],"acf":{"naam_van_het_proefschift":"Multispecies swards and multiple soil functions","samenvatting":"De groeiende wereldbevolking, stijgende inkomens en veranderingen in dieetvoorkeuren in de richting van dierlijk voedsel hebben de veehouderij ge\u00efntensiveerd, wat leidt tot een groter gebruik van hulpbronnen en een grotere ecologische voetafdruk. De overgang naar een duurzamer systeem voor dierlijke productie is daarom een prioriteit in veel landen van de Europese Unie. Agrarische graslanden zijn in dit opzicht relevant, vooral wanneer op grasland gebaseerde productiesystemen voor herkauwers worden opgezet op marginale gronden die ongeschikt zijn voor akkerbouw. Conventionele agrarische graslanden worden echter doorgaans gedomineerd door monoculturen van Engels raaigras (Lolium perenne), die hoge giften van minerale stikstofmest (N) vereisen met bijbehorende milieueffecten. In semi-natuurlijke experimentele graslanden is aangetoond dat het verhogen van de plantensoortendiversiteit door de toevoeging van vlinderbloemigen en kruiden de levering van ecosysteemdiensten in de bodem kan verbeteren. Verschillen in beheer, soortkeuze en productiedoelstellingen tussen deze experimentele en agrarische graslanden beperken echter de directe vertaling van bevindingen. Hoewel sommige studies in agrarische graslanden het effect van diversificatie op individuele bodemfuncties hebben onderzocht, is er weinig bekend over de gelijktijdige levering van meerdere functies. Daarom is het hoofddoel van dit proefschrift om te onderzoeken hoe verschillende typen zodes en stikstofmeststoffen meerdere ecosysteemdiensten in de bodem be\u00efnvloeden. Dit onderzoek werd uitgevoerd binnen het multidisciplinaire HEARTLAND-project.\n\nDe drie geteste hoofdhypothesen waren:\nHypothese 1: Multispecies zodes beheerd met een combinatie van minerale en organische mest produceren de hoogste stikstofopbrengst en hebben een constant hoge stikstofgebruikseffici\u00ebntie (Hoofdstuk 2).\nHypothese 2: Er is een verhoogde opname van zink (Zn) en selenium (Se) in soortenrijke graslanden door een selectie-effect en facilitatie door grassen (Hoofdstuk 3).\nHypothese 3: Multispecies zodes ondersteunen een lagere abundantie van plantparasitaire nematoden, terwijl organische mest de abundantie van opportunistische microbenetende nematoden verhoogt (Hoofdstuk 4).\n\nDe resultaten toonden aan dat multispecies zodes beter presteerden dan monoculturen van Engels raaigras wat betreft biomassaproductie, stikstofopbrengst en stikstofgebruikseffici\u00ebntie (NUE), ondanks lagere mestgiften. De aanwezigheid van vlinderbloemigen was een cruciale factor voor deze verhoogde productiviteit via biologische stikstofbinding. De hoge NUE ging echter gepaard met een negatievere stikstofbalans, wat duidt op een mogelijke uitputting van de bodemstikstof op de lange termijn. Een combinatie van minerale en organische mest leverde niet consequent de beste resultaten; de prestatie hing af van de specifieke NUE-index.\n\nWat betreft de opname van micronutri\u00ebnten (Zn en Se) presteerden de multispecies zodes eveneens beter dan de monoculturen. Dit werd voornamelijk gedreven door de hogere biomassaproductie en de aanwezigheid van soorten met inherent hogere concentraties aan selenium. Er was bewijs dat vlinderbloemigen de opname van deze elementen voor naburige soorten faciliteerden, soms ten koste van hun eigen opname.\n\nTenslotte bleek dat multispecies zodes minder plantparasitaire nematoden bevatten dan monoculturen. Dit wijst op een 'verwateringseffect', waarbij de diverse samenstelling minder gunstig is voor deze plaagorganismen. De toevoeging van vlinderbloemigen en kruiden kan dus dienen als een ecologisch duurzame strategie om de druk van plantparasitaire nematoden te verminderen zonder de stabiliteit van het bodemvoedselweb aan te tasten. De abundantie van bacterie-etende nematoden was niet hoger onder organische bemesting maar vergelijkbaar met minerale bemesting.\n\nConcluderend laat dit proefschrift zien dat het verhogen van de plantendiversiteit in agrarische graslanden kan leiden tot het gelijktijdig verbeteren van meerdere bodemfuncties, hoewel er rekening moet worden gehouden met trade-offs zoals bodemuitputting. Minerale bemesting biedt op korte termijn de hoogste opbrengst, maar op de lange termijn komen voordelen van organische bemesting waarschijnlijk duidelijker naar voren.","summary":"Growing global population, increasing income, and dietary shifts toward animal-based food have intensified livestock production, increasing resource use and environmental footprint. Transitioning to a more sustainable livestock production system is therefore a priority in many countries in the European Union. Agricultural grasslands are relevant in this regard, especially when grassland-based ruminant production systems are established on marginal lands unsuitable for arable cropping. However, conventional agricultural grasslands are typically dominated by perennial ryegrass (Lolium perenne) monoculture, which require high levels of mineral nitrogen (N) fertilizer with associated environmental impact. In semi-natural experimental grasslands, increasing plant species diversity through the inclusion of legumes and forbs has shown to enhance the delivery of soil-based ecosystem services. However, differences in the management practices, choice of species and production objectives between semi-natural experimental grasslands and agricultural grasslands limit the direct extrapolation of the findings from experimental grasslands to agricultural grasslands. While some studies in agricultural grasslands have investigated the effect of increasing species diversity on individual soil-based ecosystem functions, such as biomass productivity, biomass quality, N cycling, and soil biodiversity; there is limited evidence on the effect of sward diversification and management practices on the simultaneous delivery of multiple soil-based ecosystem functions. Therefore, the main aim of this research is to examine how different sward types, managed with different N fertilizer forms, influence multiple soil-based ecosystem functions in agricultural grasslands. To achieve this aim, I conducted this research within the multidisciplinary context of the HEARTLAND (Health, Environment, Agriculture, Rural Transformation and Land Management) project, working alongside four other PhD candidates.\n\nThe three main hypotheses tested were:\nHypothesis 1: Multispecies swards managed with the combination of chemical and organic fertilizer will produce the highest herbage N yield and consistently have high N use efficiency (Chapter 2).\nHypothesis 2: There will be increased Zn and Se uptake in species-rich grasslands, due to a selection effect and facilitation by grass species (Chapter 3).\nHypothesis 3: Multispecies swards will support lower abundances of plant parasitic nematodes while organic N fertilizer application will increase microbial-feeding nematodes (Chapter 4).\n\nTo test the first hypothesis, I conducted a two-factorial field experiment using four sward types: perennial ryegrass monoculture, permanent pasture and two multispecies swards and three N fertilizer treatments: mineral N fertilizer (protected urea), organic fertilizer (cattle slurry), and a combination of both mineral and organic fertilizers. The experiment was laid out in a complete randomized block design with four replicates. A N fertilizer rate of 70 kg N\/ha\/yr was applied to the permanent pasture and the two multispecies swards while 170 kg N\/ha\/yr was applied to perennial ryegrass to compensate for the absence of biological N fixation in the sward.\n\nMultispecies swards outperformed perennial ryegrass monocultures in terms of biomass production, N yield and N use efficiency (NUE) despite receiving lower N fertilizer amount. This highlighted the potential of multispecies swards in efficient utilization of N while reducing reliance on high external N inputs. A key driver underpinning this finding is the presence of legumes, as higher legume proportions were positively associated with increased herbage N yield, emphasizing the central role of biological N fixation in supporting productivity and NUE in agricultural grasslands. However, the high NUE in the multispecies swards was accompanied by a more negative partial N balance \u2013 an indication of soil N depletion, suggesting a trade-off. Swards managed using a combination of mineral and organic N fertilizer did not consistently achieve the highest herbage N yield or NUE. Instead, their performance depended on the specific NUE index considered.\n\nThe second hypothesis was tested using the field experiment and a greenhouse experiment which was designed along a plant species richness gradient. The treatment in the greenhouse experiment included twelve monocultures, six 2-species mixtures, two 3-species mixtures, two 6-species mixtures, and one 12-species mixture. Zn and Se uptake increased with increasing species richness. Specifically, the sown multispecies swards achieved greater Zn and Se uptake than perennial ryegrass monocultures in both experiments. The enhanced Zn and Se uptake was primarily driven by increased aboveground biomass of species and the presence of species that inherently contained higher concentrations Se. The greenhouse experiment further indicated that legumes, rather than grasses facilitated Zn and Se uptake for the neighbouring species. There was also an indication of asymmetric facilitation in which some legumes increased Zn and Se uptake for the neighbouring species at their own expense.\n\nI tested the third hypothesis using the field experiment. Multispecies swards supported lower abundance of plant-parasitic nematodes than perennial ryegrass monoculture. This reduction suggests that diverse swards may be less favourable to plant-parasitic nematodes, potentially due to the inclusion of legumes and forbs that are considered less suitable hosts. This was supported by a negative relationship between plant-parasitic nematode abundance and the proportion of legumes and forbs. While these findings suggested that the inclusion of legumes and forbs in swards can reduce pressure from plant-parasitic nematodes without negatively affecting soil food-web structure, the sustenance of this benefit may be dependent on maintaining the species composition of the multispecies sward, which may require frequent reseeding and the associated costs. The abundance of bacterial feeding nematodes was not greater under organic N fertilization but comparable to mineral N fertilization. The limited effect of organic N fertilizer observed may reflect the relatively short timeframe of this study, as benefits associated with organic N inputs often emerge over longer periods.\n\nIn conclusion, the results in this thesis showed that increasing plant diversity through the inclusion of legumes and forbs can deliver multiple ecosystem functions simultaneously in agricultural grasslands, although trade-offs exist and this require careful consideration. While mineral N fertilization supported greater biomass production and NUE compared to organic or combined fertilizer treatments, this should be interpreted with care as they reflect short-term responses.","auteur":"Omotola Obasoro","auteur_slug":"omotola-obasoro","publicatiedatum":"8 juni 2026","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/omotolaobasoro?iframe=true","url_download_pdf":"https:\/\/ebook.proefschriftmaken.nl\/download\/6b533e78-e0c5-4dfb-b206-fa245fdf1f14\/optimized","url_epub":"","ordernummer":"18866","isbn":"978-94-6534-416-4","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":15241,"naam_student:":"","binnenwerk":"","universiteit":"Wageningen University","cover":"","afwerking":"","cover_afwerking":"","design":""},"_links":{"self":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15239","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio"}],"about":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/types\/us_portfolio"}],"author":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=15239"}],"version-history":[{"count":1,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15239\/revisions"}],"predecessor-version":[{"id":15242,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/15239\/revisions\/15242"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/15240"}],"wp:attachment":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=15239"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=15239"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}