Towards closing cassava yield gap in West Africa : Agronomic efficiency and storage root yield responses to NPK fertilizers

Nutrient management of cassava has received little attention compared with cereal crops. We evaluated cassava yield potential and nutrient use efficiency when supplied with nitrogen, phosphorus and potassium at high rates and when supplied with increasing rates of K. On-farm experiments were conducted at six locations in Nigeria across the major cassava growing agro-ecologies of Western Africa (Tropical Rainforest – Cross River, Forest Transition Savanna – Edo, and Guinea Savanna – Benue) during two seasons (2016–2017 and 2017–2018). Nitrogen, P and K fertilizers were applied at various rates, including treatments with and without added secondary and micronutrients. Storage root dry matter (DM) yields ranged between 11 and 35 t DM ha−1. The largest yields were obtained with a mean agronomic efficiency of 60, 162 and 51 kg DM of storage roots per kg of N, P and K applied, with average uptakes of 364, 44 and 242 kg N, P and K ha−1 respectively. Storage root yield responses to applied N, P and K fertilizers (2–18, 3–16 and 3–22 t DM ha−1, respectively) varied across the locations, reflecting variability in potential yields and applied NPK ratios. Addition of a mixture of secondary and micronutrients did not affect cassava yields. We found that the caloric energy yield of cassava per kg of N applied is 2.7 times larger than the value reported for maize. Increasing the supply of K gave a high agronomic efficiency of N even when supplied at high rates, supporting the theory of “increasing returns to scale” of De Wit. We conclude that cassava has a major role in future food security of sub-Saharan Africa, with potentially larger DM yields, a better recovery of applied nutrients and larger energy yield per kg of applied N fertilizer when compared with grains.</p

Effects of expanding cassava planting and harvesting windows on root yield, starch content and revenue in southwestern Nigeria

Open Access Article; Published online: 28 Jul 2022Cassava (Manihot esculenta Crantz) is an important staple crop in Nigeria. It provides approximately 80 % of the caloric intake in Nigeria. High starch content and fresh root yields are important for the commercialization of cassava. Cassava is a perennial crop, and it can be produced all year round. However, cassava fresh root yield and starch content are strongly influenced by environmental conditions such as rainfall. Therefore, it is important to identify planting and harvest periods to attain maximum yields and starch content and to increase profitability. The present study aimed at (i) comparing changes in fresh root yields and starch contents of cassava planted and harvested at different times around the year (ii) identifying the cassava harvest phase attaining maximum fresh root yields and starch content (iii) assessing how price fluctuations and root yields affect the revenue and income generation across the year. This study was carried from 2017 to 2019 in southwestern Nigeria. Existing cassava fields planted at different months were visited and the planting dates were recorded. Harvesting for each planting month was done at 9, 11 and 13 months after planting (MAP). Fresh root yield and starch content varied across planting months. For all crop ages, the highest fresh root yields were recorded when planted in September and December. The highest root starch content was observed in 9- and 13-months old cassava when planted in March and November, respectively. Cassava fresh root yield and starch content varied across Julian day of harvest with lowest yields obtained between Julian day 60–120 (March and April) which coincides with the beginning of rainfall. Highest fresh root yields and starch content were attained between Julian day 180–330. Revenue showed seasonal variation and was dependent Julian day of harvest. Gross revenue was lowest between Julian day 60 and 120 (March and April) and highest from Julian day 180 (July). Lowest incomes or profits were recorded when cassava was harvested between Julian day 60 and 120 (March and April). About 9.1 % of farmers had negative revenues or lost income when they harvested at 9 MAP hence losing between 150 and 200 USD ha−1 compared with 2.8 % of farmers that lost income when harvesting was done at 11 and 13 MAP losing between 100 and 150 USD ha−1. Thus, farmers’ income generation critically depends on cassava planting and harvest dates. Choosing the right time to plant and harvest cassava is one of the most important decisions farmers can make to maximize profit

Cassava-maize intercropping systems in southern Nigeria: radiation use efficiency, soil moisture dynamics, and yields of component crops

Open Access Article; Published online: 30 Apr 2022Efficient utilization of incident solar radiation and rainwater conservation in rain-fed smallholder cropping systems require the development and adoption of cropping systems with high resource use efficiency. Due to the popularity of cassava-maize intercropping and the food security and economic importance of both crops in Nigeria, we investigated options to improve interception of photosynthetically active radiation (IPAR), radiation use efficiency (RUE), soil moisture retention, and yields of cassava and maize in cassava-maize intercropping systems in 8 on-farm researcher-managed multi-location trials between 2017 and 2019 in different agro-ecologies of southern Nigeria. Treatments were a combination of (1) maize planting density (low density at 20,000 maize plants ha-1 versus high density at 40,000 maize plants ha-1, intercropped with 12,500 cassava plants ha-1); (2) fertilizer application and management targeting either the maize crop (90 kg N, 20 kg P and 37 kg K ha-1) or the cassava crop (75 kg N, 20 kg P and 90 kg K ha-1), compared with control without fertilizer application. Cassava and maize development parameters were highest in the maize fertilizer regime, resulting in the highest IPAR at high maize density. The combined intercrop biomass yield was highest at high maize density in the maize fertilizer regime. Without fertilizer application, RUE was highest at low maize density. However, the application of the maize fertilizer regime at high maize density resulted in the highest RUE, soil moisture content, and maize grain yield. Cassava storage root yield was higher in the cassava fertilizer regime than in the maize fertilizer regime. We conclude that improved IPAR, RUE, soil moisture retention, and grain yield on nutrient-limited soils of southern Nigeria, or in similar environments, can be achieved by intercropping 40,000 maize plants ha-1 with 12,500 cassava plants ha-1 and managing the system with the maize fertilizer regime. However, for higher cassava storage root yield, the system should be managed with the cassava fertilizer regime

Developing recommendations for increased productivity in cassava-maize intercropping systems in southern Nigeria

Open Access Article; Published online: 31 Aug 2021Cassava-maize intercropping is a common practice among smallholder farmers in Southern Nigeria. It provides food security and early access to income from the maize component. However, yields of both crops are commonly low in farmers’ fields. Multi-locational trials were conducted in Southern Nigeria in 2016 and 2017 to investigate options to increase productivity and profitability through increased cassava and maize plant densities and fertilizer application. Trials with 4 and 6 treatments in 2016 and 2017, respectively were established on 126 farmers’ fields over two seasons with a set of different designs, including combinations of two levels of crop density and three levels of fertilizer rates. The maize crop was tested at low density (LM) with 20,000 plants ha−1 versus high density (HM) with 40,000 plants ha−1. For cassava, low density (LC) had had 10,000 plants ha−1 versus the high density (HC) with 12,500 plants ha−1.; The fertilizer application followed a regime favouring either the maize crop (FM: 90 kg N, 20 kg P and 37 kg K ha−1) or the cassava crop (FC: 75 kg N, 20 kg P and 90 kg K ha−1), next to control without fertilizer application (F0). Higher maize density (HM) increased marketable maize cob yield by 14 % (3700 cobs ha−1) in the first cycle and by 8% (2100 cobs ha−1) in the second cycle, relative to the LM treatment. Across both cropping cycles, fertilizer application increased cob yield by 15 % (5000 cobs ha−1) and 19 % (6700 cobs ha−1) in the FC and FM regime, respectively. Cassava storage root yield increased by 16 % (4 Mg ha−1) due to increased cassava plant density, and by 14 % (4 Mg ha−1) due to fertilizer application (i.e., with both fertilizer regimes) but only in the first cropping cycle. In the second cycle, increased maize plant density (HM) reduced cassava storage root yield by 7% (1.5 Mg ha−1) relative to the LM treatment. However, the negative effect of high maize density on storage root yield was counteracted by fertilizer application. Fresh storage root yield increased by 8% (2 Mg ha−1) in both fertilizer regimes compared to the control without fertilizer application. Responses to fertilizer by cassava and maize varied between fields. Positive responses tended to decline with increasing yields in the control treatment. The average value-to-cost ratio (VCR) of fertilizer use for the FM regime was 3.6 and higher than for the FC regime (VCR = 1.6), resulting from higher maize yields when FM than when FC was applied. Revenue generated by maize constituted 84–91% of the total revenue of the cropping system. The highest profits were achieved with the FM regime when both cassava and maize were grown at high density. However, fertilizer application was not always advisable as 34 % of farmers did not realize a profit. For higher yields and profitability, fertilizer recommendations should be targeted to responsive fields based on soil fertility knowledge

Effect of banana leaf pruning on banana and legume yield under intercropping in farmers' fields in eastern Democratic Republic of Congo

Banana-legume intercropping systems are commonly practiced in the highland zones of the eastern Democratic Republic of Congo to maximize land use and intensify crop production. However, banana leaves are pruned during legume intercropping to improve sunlight penetration for the legume. On-farm experiments were conducted in South Kivu province to determine the effect of banana leaf pruning on banana (Musa sp.), bush and climbing beans (Phaseolus vulgaris L) and soybean (Glycine max L) yield. Legumes were planted in existing farmers’ fields of East African highland beer banana genotype ‘Nshikazi’ (Musa sp., AAA-EA) during four cropping seasons covering 30 months. The experiments were established using a split-plot design, with the main plot treatments consisting of two levels of banana leaf canopy pruning (leaving only seven leaves or leaving all leaves) and the split plot treatments consisting of improved or local leguminous crop cultivars (the bush bean ‘MLB49’, the climbing bean ‘AND10’ and soybean ‘SB24’ planted in the banana plot. Each farmer’s banana plot was a replicate). A total of 24 replicates, each of improved and local soybean, improved and local climbing bean and improved and local bush bean were planted in established farmers’ fields located in four sites. Bean yields were assessed during four consecutive cropping seasons (2010B, 2011A and B, 2012A) and one cycle of banana cultivation. Banana leaf pruning did not have a significant effect on banana bunch weight or yield, but legume type affected banana fruit weight and yield in Burhale and Lurhala, which have poor soil fertility. Banana leaf pruning enhanced legume grain yield for the four seasons at all sites

The effect of communication media on the uptake of agricultural innovations in selected states of Nigeria

Open Access Article; Published online: 21 Sep 2022Purpose Poor uptake of agricultural innovations on weed management practices is a major factor responsible for low productivity. This paper examines how communication media can help improve farmers’ adoption behaviour. Methodology A sample of 725 Nigerian cassava farmers, exposed to agricultural innovation on weed management practices from varying sources, were asked, through a structured questionnaire, to indicate their knowledge, attitudes, and practices of cassava weed management. The responses were compared with a sample of 190 cassava farmers who were not exposed to the information (control group). The data were analysed using frequency counts, percentages, mean, analysis of variance, and multivariate probit regression. Findings Farmers exposed to the agricultural innovation in weed management practices indicated more positive behaviour (57.7%) towards improved weed management practices than the control group (26.8%). The mean knowledge, attitude, practice, and behaviour of the farmers exposed to the innovation through demonstration was significantly higher than for other sources. Practical implications On-farm demonstrations as a means of communication will enhance the uptake and effectiveness of agricultural innovation on weed management practices. Theoretical implications Findings on the influence of communication media on improved weed control and agronomy are significant, given that there is little well-documented data on how communication media enhances technology and innovation adoption in arable crop farming. Originality/value This study generates important data that reinforces the imperatives of communication and media choices, and further underpins the debate that technology alone cannot lead to uptake by farmers but needs to be communicated

Looking back and moving forward: 50 years of soil and soil fertility management research in sub-Saharan Africa

Article purchased; Published online: 02 Nov 2017Low and declining soil fertility has been recognized for a long time as a major impediment to intensifying agriculture in sub-Saharan Africa (SSA). Consequently, from the inception of international agricultural research, centres operating in SSA have had a research programme focusing on soil and soil fertility management, including the International Institute of Tropical Agriculture (IITA). The scope, content, and approaches of soil and soil fertility management research have changed over the past decades in response to lessons learnt and internal and external drivers and this paper uses IITA as a case study to document and analyse the consequences of strategic decisions taken on technology development, validation, and ultimately uptake by smallholder farmers in SSA. After an initial section describing the external environment within which soil and soil fertility management research is operating, various dimensions of this research area are covered: (i) ‘strategic research’, ‘Research for Development’, partnerships, and balancing acts, (ii) changing role of characterization due to the expansion in geographical scope and shift from soils to farms and livelihoods, (iii) technology development: changes in vision, content, and scale of intervention, (iv) technology validation and delivery to farming communities, and (v) impact and feedback to the technology development and validation process. Each of the above sections follows a chronological approach, covering the last five decades (from the late 1960s till today). The paper ends with a number of lessons learnt which could be considered for future initiatives aiming at developing and delivering improved soil and soil fertility management practices to smallholder farming communities in SSA

CGIAR’s role in digital extension services

CGIAR’s digital extension services bridge the gap between the development and the adoption of new climate change adaptation strategies. These services include new ways to disperse information on rainfed systems of agriculture, nutrition, pest control, new crop varieties, crop management practices, and more