In the Central Rift Valley (CRV) of Ethiopia, low productive cereal systems and a declining resource base call for options to increase crop productivity and improve resource use efficiency to meet the growing demand of food. We compiled and analysed a large amount of data from farmers’ fields (>10,000) and experimental data across the CRV from 2004–2009 to quantify yield gaps (Yg) between actual (average and best performing farmers) and experimental (water-limited potential (Yw)) yields of maize and wheat in homogenous farming zones (HFZs). Resource use efficiencies (nutrients and water) of maize and wheat were also analysed to assess spatial variation and scope for improvements. The average (2004–2009) yield gap of maize and wheat in the CRV ranged between 4.2 t ha−1 and 9.2 t ha−1, and 2.5 t ha−1 and 4.7 t ha−1, respectively, across farming zones. The yield gap was lowest in the Central lowlands, where Yw was also lowest, i.e. 6.5 t ha−1 for maize and 4.4 t ha−1 for wheat, compared with Yw in the Eastern highlands (11 t ha−1 for maize and 6.7 t ha−1 for wheat) and Western highlands (10.8 t ha−1 for maize and 5.7 t ha−1 for wheat). The actual nitrogen (N) and phosphorus (P) application in farmers’ fields was low, as about 46% of maize and 27% of wheat fields did not receive fertilizers, while the average applied mineral fertilizer rates across all farmers (2.6–16.5 kg N ha−1 and 2.2–17.3 kg P ha−1 across HFZs and crops) were far below the recommended rate. On average, the best performing farmers applied 8–20 kg N ha−1 and 5–21 kg P ha−1 ranging across HFZs and crops. Increasing N application to recommended rates had only a small effect on narrowing the yield gap under current farmers’ management. Therefore, the yield gap closure strongly depends on improving other aspects of crop management while paying attention to the interaction with nutrient management. Since rain water use efficiency (seasonal rainfall) of water-limited yields was 12–17.3 kg mm−1 for maize and 7.4–10.6 kg mm−1 for wheat and much higher than that of actual yields (2.7–4.3 kg mm−1 for maize and 2.3–3.5 kg mm−1 for wheat), improving the input use and crop management can increase water use efficiency. A large set of experimental and survey data enabled us to gain insight in the spatial and temporal variation in yield gaps and input rates and in differences between average and the best performing farmers.

The short term nutrient supply of Leucaena leucocephala, Calliandra calothyrsus, Acacia angustissima and Acacia karoo prunings with or without supplemental inorganic nitrogen were tested using rape (Brassica napus L.) in a field trial. Prunings were applied at a rate of 5 t ha−1 to soil, alone or with supplemental N at 37.5 kg N ha−1 (¼ of recommended N). The respective decomposition and N release constants of the prunings were 9.15 and 9.70% for L. leucocephala; 6.15 and 6.40 for A. angustissima; 4.50 and 4.90 for C. calothyrsus; and 2.20 and 2.10 for A. karoo. These constants were best described by the (lignin+polyphenol)-to-nitrogen ratio of the prunings. Total biomass over the two seasons ranged from 1.40 to 17.28 t DM ha−1 and total growth rates ranged from 2.34–26.70 g plant−1 week−1. The cumulative N recovery at week 9 ranged from 21.1–66.1 %. Legume tree leaves can be used as a source of N for vegetable production. Farmers who use high tannin leaf litter are recommended to supplement with mineral N in order to assure adequate N availability during plant growth.

Innovation Platforms (IPs) are seen as a promising vehicle to foster a paradigm shift in agricultural research for development (AR4D). By facilitating interaction, negotiation and collective action between farmers, researchers and other stakeholders, IPs can contribute to more integrated, systemic innovation that is essential for achieving agricultural development impacts. However, successful implementation of IPs requires institutional change within AR4D establishments. The objective of this paper is to reflect on the implementation and institutionalisation of IPs in present AR4D programmes. We use experiences from sub-Saharan Africa to demonstrate how the adoption and adaptation of IPs creates both opportunities and challenges that influence platform performance and impact. Niche-regime theory is used to understand challenges, and anticipate on how to deal with them. A key concern is whether IPs in AR4D challenge or reinforce existing technology-oriented agricultural innovation paradigms. For example, stakeholder representation, facilitation and institutional embedding determine to a large extent whether the IP can strengthen systemic capacity to innovate that can lead to real paradigm change, or are merely ‘old wine in new bottles’ and a continuation of ‘business as usual’. Institutional embedding of IPs and – more broadly – the transition from technology-oriented to system-oriented AR4D approaches requires structural changes in organisational mandates, incentives, procedures and funding, as well as investments in exchange of experiences, learning and capacity development.

Recent studies have reported the benefits of fertilizer microdosing in increasing crop yields in low input cropping systems. Little information is however available on the mechanisms underlying this effect. The objective of this study was therefore to explore the root-based mechanisms governing the growth enhancing phenomena of the fertilizer microdosing technology. A two-year experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Research Station in Niger. Four treatments comprising (i) 2 g hill−1 of diammonuim phosphate (DAP), (ii) 6 g hill−1 of compound fertilizer NPK, (iii) broadcasting of 200 kg ha−1 of compound fertilizer NPK (recommended rate) and (iv) unfertilized control was arranged in a randomized complete block design with four replications. On average, fertilizer microdosing treatments (2-g DAP hill−1 and 6-g NPK hill−1) achieved 86% and 79% of the grain yields recorded from broadcasting of 200-kg NPK ha−1, respectively, in 2013 and 2014. The leaf area index and leaf chlorophyll content significantly increased with fertilizer microdosing at the early stage of millet growth. At the same stage, fertilizer microdosing enhanced the lateral root length density in the topsoil (0–20 cm) by 72% and 40% at respective lateral distances of 25 cm and 50 cm from the centre of the hill compared with broadcast of 200-kg NPK ha−1. Fertilizer microdosing did not significantly change soil pH in the root zone. It is concluded that the positive effect of fertilizer microdosing in increasing millet yield results from the better exploitation of soil nutrients due to early lateral roots proliferation within the topsoil.

Conservation agriculture (CA) was introduced to farmers in Malawi to address soil degradation, declining crop productivity and the need to adapt to climate variability and change. This research from 2005 to 2014 aimed at analysing the effects of CA on longer-term productivity and profitability compared with conventional systems as practiced in two communities of Central Malawi. CA treatments outyielded conventional ridge tilled control plots in Mwansambo and Zidyana on average by between 22 and 31%, respectively. An economic analysis from 2011 to 2014 found that, on average, income was 50 and 83% greater in CA systems than in conventional systems. The crops were produced with 28 -39 less labour days ha−1 compared with the conventional practice, leading to greater net benefits. Despite the higher returns with CA, there are still challenges with residue retention, weed control, adequate rotations, management of pests and diseases as well as other socio-economic constraints. At the same time, there are opportunities to address these challenges through site-specific and adaptive research using innovation systems approaches.

Wheat grown under zero tillage (ZT) and raised-bed following a legume crop may have a variable N requirement compared with conventionally-tilled flat-sown crop. A field experiment was conducted for two years during 2005–07 to study the effect of varying tillage (conventional and zero), crop establishment (flat and raised-bed sowing) and N fertilization (0–160 kg N ha−1) on wheat grown after greengram at New Delhi, India. Rainy-season greengram performed equally well under flat and raised-bed planting, but the seed yield was 25.9% lower under ZT than conventional tillage (CT) conditions. Wheat following greengram during winter season also showed better growth and yield under CT than ZT, as well as under flat sowing than furrow-irrigated raised-bed (FIRB) system. The grain yield was highest under CT-flat, and decreased by 5.4–9.4% under FIRB system. Nitrogen fertilization up to 120 kg N ha−1 under CT and 160 kg N ha−1 under ZT increased grain yield, and the optimum doses were worked out to be 147.1 and 154.2 kg ha−1, respectively. Nitrogen-use efficiency decreased with N levels but remained more or less similar under tillage and crop establishment practices. Maximum returns and B:C ratio were obtained under CT-flat, followed closely by ZT-flat.

Continuous rice–wheat (RW) cropping in an area of 13.5 million ha with intensive tillage has resulted in over exploitation of resources, decline of the factor productivity, loss of soil fertility and biodiversity and decline of resource use efficiency in the Indo-Gangetic plains (IGPs) of South Asia. This has led to unsustainability of agriculture in the region. Replacement of a cereal-cereal system with a legume–cereal system may prove beneficial for long-term sustainability of the system. A field experiment was conducted with soybean–wheat (SW) rotation in the IGP of India during 2009–10 and 2010–11 to assess the suitability of conservation tillage versus conventional tillage (CT) and crop-establishment techniques, namely bed (B) planting versus flat (F) planting. The study revealed that the zero tillage (ZT) for soybean during rainy and for wheat during winter season either in flat or in bed system performed equally good with CT. The maximum system productivity (7.06 t ha−1 in 2009–10 and 8.48 t ha−1 in 2010–11) was obtained with combined application of wheat + soybean residue. The maximum net returns of ₹46.98 and ₹65.08 thousands and B:C ratio of 2.35 and 3.08 were recorded in the SW system with zero tillage-flat (ZT─F) during 2009–10 and 2010–11, respectively. The minimum energy of 64.67 and 63.01 ×103 MJ ha−1 was utilized as input energy with zero tillage-bed (ZT─B) while the maximum energy use efficiency of 4.10 and 5.14 was obtained with ZT─F and ZT─B for the SW system during 2009–10 and 2010–11 respectively. The gross output energy was maximum with wheat + soybean residue (241.6 and 265.7 ×103 MJ ha−1) contrary to this the net energy (194.4 and 213.4 ×103 MJ ha−1) and energy use efficiency (9.03 and 10.96) was maximum with control (no residue) in the SW system. In wheat there was 37.85% improvement in irrigation water use efficiency (WUE) in raised bed planting than flat planting and 28.57% of irrigation water was saved. The study suggested that ZT either bed or flat planting to both the crops can successfully adopted along with application wheat + soybean residue together with full recommended dose of NPK fertilizers to the system for improving productivity, profitability, soil health and sustainability of SW system in the IGPs of South Asia.

Soil Organic Carbon (SOC) is a major indicator of soil fertility in the tropics and underlies variability in crop response to mineral fertilizers. Critical SOC concentrations that interact positively with N fertilizer for optimal crop yield are less understood. A study was conducted on a Ferralsol in sub-humid Uganda to explore the critical range of SOC concentrations and associated fractions for optimal maize (Zea mays L.) yield response to applied mineral N fertiliser. Maize grain yield response to N rates applied at 0, 25, 50 and 100 kg N ha−1 in 30 fields of low fertility (SOC < 1.2%), medium fertility (SOC = 1.2–1.7%) and high fertility (SOC > 1.7%) was assessed. Soil was physically fractionated into sand-sized (63–2000 µm), silt-sized (2–63 µm) and clay-sized (<2 µm) particles and SOC content determined. Low fertility fields (<1.2% SOC) resulted in the lowest response to N application. Fields with >1.2% SOC registered the highest agronomic efficiency (AE) and grain yield. Non-linear regression models predicted critical SOC for optimal yields to be 2.204% at the 50 kg N ha−1 rate. Overall, models predicted 1.9–2.2% SOC as the critical concentration range for high yields. The critical range of SOC concentrations corresponded to 3.5–5.0 g kg−1 sand-sized C and 9–11 g kg−1 for clay-sized C.