{"id":11174,"date":"2026-04-13T07:58:14","date_gmt":"2026-04-13T07:58:14","guid":{"rendered":"https:\/\/www.proefschriftmaken.nl\/portfolio\/thomas-awio\/"},"modified":"2026-04-13T07:58:25","modified_gmt":"2026-04-13T07:58:25","slug":"thomas-awio","status":"publish","type":"us_portfolio","link":"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/thomas-awio\/","title":{"rendered":"Thomas Awio"},"content":{"rendered":"","protected":false},"excerpt":{"rendered":"","protected":false},"author":8,"featured_media":11177,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-11174","us_portfolio","type-us_portfolio","status-publish","has-post-thumbnail","hentry","us_portfolio_category-new-template"],"acf":{"naam_van_het_proefschift":"Increasing smallholder rice production in East Africa: fertilisers or good agronomic practices?","samenvatting":"Er is geen Nederlandse samenvatting beschikbaar. De Engelse samenvatting vind je <a href=\"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/thomas-awio\/\">hier<\/a>.","summary":"Sub-Saharan Africa (SSA) continues to grapple with the challenge of meeting the demand for staple food crops, especially cereals, where self-sufficiency is the lowest compared to the rest of the world. Rice is one of the major cereals in SSA, a main source of calories for households of all income groups, and the second largest source of food energy, next to maize, yet farm yields are very low. The low crop productivity is the reason why SSA is unable to meet the food demand of its population. In order to meet the food demand on available arable land, increasing crop productivity in smallholder farming systems is thus required. This will minimise reliance on large food imports and crop area expansion into marginal lands and forest areas.\n\nLow crop productivity in SSA farm lands is attributed to, among other factors, soil fertility constraints and sub-optimal soil and crop management. In order to address the low soil fertility that limits crop productivity, farmers apply NPK fertilisers. Considering that fertilisers are not easily available to farmers, are costly and their prices are unstable, relying on fertilisers to boost crop productivity in order to address the food demand of SSA becomes a challenge. Yet, fertilisation with only NPK is not always resulting in better yields on farmers\u2019 fields. Crop responses to NPK fertilisation can be influenced by other nutrients, recommended agronomic practices (RAP) and inherent soil fertility. On the basis of the background and research questions presented in Chapter 1, the effect of secondary and micro-nutrients (Chapter 2), RAP under researcher supervision and as applied by farmers (Chapter 3), and inherent fertility on rice yield and NPK use efficiency (Chapter 4), and effect of joint experimentation on farmers\u2019 management practices and rice grain yield (Chapter 5) were quantified for lowland rice.\n\nMicro-nutrients are shown to constrain crop productivity, where their application in combination with NPK has been reported to enhance NPK use efficiency, leading to higher crop yields. In Chapter 2, the contribution of NPK, and combinations of NPK + secondary and micro-nutrients on lowland rice yield was assessed under irrigated and rainfed lowland conditions in Tanzania and Uganda. NPK fertilisation increased grain yields across locations and years under irrigated conditions, compared to yields from good agronomic practices only; but, inconsistent effects were observed under rainfed conditions. Adding secondary nutrients (Mg and S) and micro-nutrients (B, Cu, Mn, and Zn) to NPK further enhanced grain yield in Tanzania but not in Uganda. However, the additional yield gains were lower than the gains made with only NPK application, compared to unfertilised control yields. Effects of applying only NPK, and NPK plus secondary and micro-nutrients were only significant when water supply was adequate, but not under poor water management, where crops suffered from drought, even when good crop management practices were applied. Applying secondary and micro-nutrients only without NPK resulted in yields that were similar to unfertilised control plots, and lower compared to only NPK fertilisation. These findings demonstrated that for good agronomic practices and fertilisation to be effective in improving rice productivity, proper water management is key. Adding other nutrients than NPK would not be required in a first step in enhancing rice productivity thus, the need to first focus on attaining full yield potential from NPK application.\n\nRecommended or good agronomic practices (RAP), considered as an integrated, coherent set of crop, soil, water, weed, disease, and pest management practices is crucial in enhancing yields along with fertiliser use as they are shown to improve rice yields, compared to farmers\u2019 practices (FP). In Chapter 3, the contribution of RAP with or without NPK fertilisation on rice yield and yield gaps was assessed. RAP with or without fertilisation significantly increased grain yield by 12 and 33%, respectively, compared to FP. RAP without fertilisation gave the highest mean net income (ca. USD 220 ha-1), while fertiliser costs made RAP + NPK to give the lowest mean net income (ca. USD 50 ha-1). Exploitable yield gaps of 720 \u2013 2730 kg ha-1 were observed among farmers. Timing of weeding was the main factor that contributed to yield variation among fields, with average grain loss of 62 kg day-1 of delayed weeding. The findings of this chapter demonstrated that application of RAP when water supply is adequate, followed by NPK fertilisation, can substantially boost rice productivity and farmers have considerable potential to increase rice yields, although fertilisation at current rice and fertiliser prices poses a risk to farmer\u2019s profit. Realising yield gains requires that farmers with good water management should combine timely weeding (i.e., weeding within 2 \u2013 3 weeks after transplanting) with other crop management practices.\n\nFertilisers remain an expensive crop production input for most rice farmers in SSA. Improving fertiliser nutrient use efficiency is important for increasing both fertiliser use and rice yield, thus increasing farmers\u2019 returns on fertiliser investment. Chapter 4 investigated on-farm, under irrigated lowland rice conditions, how indigenous nutrient supply and management practices affected N, P, and K uptake, agronomic efficiency and recovery efficiency of fertiliser, and physiological efficiency of nutrients taken up.\n\nA large variation in indigenous N, P, and K supply was observed among farmers\u2019 fields. Indigenous N supply reduced apparent N recovery, and agronomic and physiological N efficiencies independent of treatment. Similarly, physiological efficiencies of P and K decreased with increasing indigenous supply. Delaying weeding and fertilisation, and interaction between indigenous nutrient supply and delayed weeding, reduced fertiliser nutrient use efficiencies. The Chapter findings demonstrated that appropriate weeding time is necessary to allow plants to efficiently utilise nutrients from indigenous sources, and from fertilisers when farmers decide to apply. There is a need for site-specific fertilisation strategies based on soil available nutrient levels and proper weeding, and fertilisation needs to be synchronised with the correct crop stage for optimal uptake and utilisation by crops.\n\nIn Chapter 5, after one year of a joint experimentation with farmers where different RAP components for rice were tested, change in management practices and grain yield of participating farmers (participated in the joint experimentation) and non-participating farmers (did not participate) within the same production system was assessed. Participating farmers who had lower yields during joint experimentation subsequently improved their management practices and grain yields, compared with farmers that had middle- and top-yields during the joint experimentation. Similarly, farmers that participated in the joint experimentation improved their management practices and had higher grain yield compared with those that did not participate. Different farm types were identified, which differed in their application of RAP, but not in their household characteristics. These findings demonstrated the potential benefit of exposing farmers to RAP, through participatory learning, on boosting rice yields. Household wealth was not crucial in innovation adoption in the current production and farming systems.\n\nChapter 6 presents the implications of the results in Chapters 2 \u2013 5 in relation to enhancing smallholder lowland rice productivity and nutrient use efficiency in SSA. In conclusion, proper water management is the first step towards lowland rice intensification, followed by good crop management practices, especially timely weeding. Proper water management and good agronomic practices should form the foundation for all other steps aimed at lowland rice intensification. NPK fertilisers can then be used to further enhance yield, however, appropriate rates based on inherent soil fertility levels need to be used, which would also help enhance use efficiencies of fertiliser nutrients. Secondary and micro-nutrients may be applied in addition to NPK to further improve grain yield but to a limited extent.","auteur":"Thomas Awio","auteur_slug":"thomas-awio","publicatiedatum":"12 juni 2023","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/thomasawio?iframe=true","url_download_pdf":"","url_epub":"","ordernummer":"FTP-202604130755","isbn":"978-94-6447-655-2","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":11178,"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\/11174","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\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=11174"}],"version-history":[{"count":1,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/11174\/revisions"}],"predecessor-version":[{"id":11175,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/11174\/revisions\/11175"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/11177"}],"wp:attachment":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=11174"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=11174"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}