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In Ethiopia, scattered trees in crop fields have been practiced for centuries. (Photo: Tesfaye Shiferaw /CIMMYT)

Matching nutrients to agroforestry systems for greater maize and wheat yields

Written by Marta Millere on September 11, 2020. Posted in Features.

Globally, the COVID-19 pandemic and associated lockdowns have created bottlenecks across the agricultural value chain, including disrupting the supply of fertilizer. This could negatively impact the already low yields in smallholders’ fields in the Global South. Livelihoods of these resource-poor farmers and food security of those they feed call for innovations or smarter application of existing knowledge to avoid increasing food insecurity.

In a recent study, a team of scientists from the International Maize and Wheat Improvement Center (CIMMYT) and Plant Production Systems, Wageningen University, found that there are clever ways to mix and match maize and wheat varieties with mineral fertilizers in tree-crop systems for greater nutrient use efficiency. The study explored the impact of different combinations of nitrogen (N) and phosphorus (P) fertilizers on crop yield in tree crop systems. It also identified mineral fertilizer-tree combinations that maximize agronomic nutrient use efficiencies under different contexts.

Tree-crop-fertilizer interactions for wheat growing under Faidherbia albida and maize growing under Acacia tortilis and Grevillea robusta through omission trials of N and P were explored in open fields and fields under tree canopy, using a split plot design. The experiments were conducted under different agroecologies in Ethiopia (Meki and Mojo) and Rwanda, where retaining scattered trees in fields has been practiced for centuries. The trials were replicated four times and over two seasons. Trees with approximately similar ages, crown structures and pruning history were used for a researcher-led and farmer-managed on-farm experiment.

The results demonstrated that different on-farm tree species interact uniquely with crops, resulting in different responses to N and P fertilization. Except for F. albida, perhaps the most ‘ideal’ agroforestry species, the other two tree species under the current study raised the question of tree-crop compatibility for optimum productivity. F. albida significantly improved N and P use efficiencies, leading to significantly higher grain yields in wheat. The P use efficiency of wheat under F.albida was double that of wheat grown in an open field. By contrast, G. robusta and A. tortilis trees lowered nutrient use efficiencies in maize, leading to significantly less maize grain yields compared with open fields receiving the same fertilization. The case study also identified probabilities of critically low crop yields and crop failure to be significantly greater for maize growing under the canopy of these species.

A tree-crop system in Ethiopia. (Photo: Tesfaye Shiferaw /CIMMYT)

In conclusion, the study demonstrated that tree-crop interactions are mediated by the application of N and P fertilizers in tree-crop systems. In F. albida-wheat agroforestry systems, N fertilizers could be saved, with localized application of P fertilizers close to tree crowns. Such adaptable application may help smallholder farmers cope with COVID-19-imposed fertilizer limitations. In G.robusta-maize and A.tortilis-maize agroforestry systems, maize did not respond to N and P fertilizers applied at recommended rates, although the application of these nutrients compensated for competition. This implies mineral fertilizers can offset the effect of competition, while they fail to provide the yield advantages like mono-cropping situations.

The researchers underlined the fact that fertilizer recommendations need to be adapted to agroforestry systems. However, in order to quantify the exact magnitude and nature of fertilizer-tree interaction in agroforestry systems accurately, factorial application of higher and lower rates of mineral fertilizer is needed. They also called for further research to identify fertilization rates that minimize tree-crop competition for G. robusta-maize and A. tortilis-maize systems, while additional studies are needed to identify the rates and timing of application that optimize F. albida-wheat facilitation.

This work was carried out by the International Maize and Wheat Improvement Center (CIMMYT) and Plant Production Systems, Wageningen University

Download your copy of the publication: Should fertilizer recommendations be adapted to parkland agroforestry systems? Case studies from Ethiopia and Rwanda

CIMMYT and CGIAR staff members put their tree seedlings in the ground. (Photo: CIMMYT)

CIMMYT and CGIAR staff join Ethiopia’s record-breaking tree-planting campaign

Written by Rodrigo Ordóñez on August 1, 2019. Posted in News.

Staff members of CIMMYT and other CGIAR centers in Ethiopia participated in the country's nationwide campaign that resulted in the planting of more than 350 million trees in one single day. (Photo: CIMMYT) — Staff members of CIMMYT and other CGIAR centers in Ethiopia participated in the country’s nationwide campaign that resulted in the planting of more than 350 million trees in one single day. (Photo: CIMMYT)

July 29, 2019, was a remarkable day for Ethiopia. People across the country planted 353,633,660 tree seedlings in just 12 hours, according to the official count, in what is believed to be a world record. This figure also exceeded the target of a nationwide campaign calling citizens to plant 200 million trees in one day. This initiative was part of the Ethiopian government’s “Green Legacy” initiative, which aims to plant 4 billion trees by October.

The International Maize and Wheat Improvement Center (CIMMYT) and other CGIAR centers working in Ethiopia joined the tree-planting campaign. In the morning of July 29, staff members turned out at Adwa park, near Addis Ababa’s Bole International Airport, to plant tree seedlings. This activity was coordinated by the International Livestock Research Institute (ILRI) after receiving an invitation from the Bole subcity administration.

Ethiopia’s tree-planting day received worldwide attention. Al Jazeera reported that, “in addition to ordinary Ethiopians, various international organizations and the business community have joined the tree planting spree which aims to overtake India’s 66 million planting record set in 2017.”

A greener future for CGIAR

Ethiopia’s reforestation efforts align with CGIAR’s sustainability strategy.

In its current business plan, CGIAR has five global challenges including planetary boundaries. Food systems are driving the unsustainable use of the planet’s increasingly fragile ecosystem. A stable climate, water, land, forests and the biodiversity they contain are a precious, yet finite, natural resource. Food systems account for about one-third of greenhouse gas emissions and will be profoundly affected by its impacts. Agriculture is driving the loss of the world’s forests and productive land, with 5 million hectares of forests lost every year and a third of the world’s land already classified as degraded. Agriculture accounts for about 70% of water withdrawals globally, is a major cause of water stress in countries where more than 2 billion people live, and water pollution from agricultural systems poses a serious threat to the world’s water systems.

With Ethiopia’s increasing population, there is a high pressure on farmland, unsustainable use of natural resources and deforestation.

At the Agriculture Research for Development Knowledge Share Fair organized in Addis Ababa on May 15, 2019, CGIAR centers demonstrated how they are working together to improve agriculture production and environmental sustainability, tackling local challenges and generating global impact in partnership with other organizations, communities and governments.

At the fair’s opening ceremony, Seleshi Bekele, Ethiopia’s Minister of Water, Irrigation and Electricity, noted that the country has policies, institutional arrangements as well as human and financial resources to work towards sustainability. As a result, Ethiopia has made remarkable achievements towards meeting the Sustainable Development Goals with the continued support and contributions from partners like CGIAR. He also called CGIAR centers to support the efforts to plant 4 billion tree seedlings in 2019, as part of Ethiopia’s climate change adaptation and mitigation goals.