Does crop-livestock integration lead to improved crop production in the savanna of West Africa?

Integrated crop-livestock farming in the Guinea savanna of West Africa is often assumed to lead to synergies between crop and livestock production, thereby improving the overall productivity and resilience of agricultural production. Whether these synergies actually occur remains poorly studied. On-farm trials were conducted in northern Nigeria over a period of four years to assess the agronomic and economic performance of maize-legume systems with and without the integration of livestock (goats). Groundnut-maize rotations with livestock achieved the highest carry-over of nutrients as manure from one season to the next, covering approximately one-third of the expected N, P and K uptake by maize and reducing the demand for synthetic fertilizers. However, the advantage of lower fertilizer costs in rotations with livestock was offset by higher labour costs for manure application and slightly lower values of maize grain. Overall, no clear agronomic or economic benefits for crop production were observed from the combined application of manure and synthetic fertilizer over the application of synthetic fertilizer only, probably because the amounts of manure applied were relatively small. Legume-maize rotations achieved higher cereal yields, a better response to labour and fertilizer inputs, and a higher profitability than maize-based systems with no or only a small legume component, irrespective of the presence of livestock. Livestock at or near the farm could nevertheless make legume cultivation economically more attractive by increasing the value of legume haulms. The results suggested that factors other than crop benefits, e.g. livestock providing tangible and non-tangible benefits and opportunities for animal traction, could be important drivers for the ongoing integration of crop and livestock production in the savann

Quantifying the prevalence of (non)-response to fertilizers in sub-Saharan Africa using on-farm trial data

Open Access Article; Published online: 21 Oct 2021Poor and variable crop responses to fertilizer applications constitute a production risk and may pose a barrier to fertilizer adoption in sub-Saharan Africa (SSA). Attempts to measure response variability and quantify the prevalence of non-response empirically are complicated by the fact that data from on-farm fertilizer trials generally include diverse nutrients and do not include on-site replications. The first aspect limits the extent to which different studies can be combined and compared, while the second does not allow to distinguish actual field-level response variability from experimental error and other residual variations. In this study, we assembled datasets from 41 on-farm fertilizer response trials on cereals and legumes across 11 countries, representing different nutrient applications, to assess response variability and quantify the frequency of occurrence of non-response to fertilizers. Using two approaches to account for residual variation, we estimated non-response, defined here as a zero agronomic response to fertilizer in a given year, to be relatively rare, affecting 0–1 and 7–16% of fields on average for cereals and legumes respectively. The magnitude of response could not be explained by climatic and selected topsoil variables, suggesting that much of the observed variation may relate to unpredictable seasonal and/or local conditions. This implies that, despite demonstrable spatial bias in our sample of trials, the estimated proportion of non-response may be representative for other agro-ecologies across SSA. Under the latter assumption, we estimated that roughly 260,000 ha of cereals and 3,240,000 ha of legumes could be expected to be non-responsive in any particular year

Assessing and understanding non-responsiveness of maize and soybean to fertilizer applications in African smallholder farms

Open Access Article; Published online: 05 Oct 2020Use of mineral fertilizers is essential to enhance crop productivity in smallholder farming systems of Sub-Saharan Africa, but various studies have reported ‘non-responsiveness’ where application of inorganic fertilizers does not lead to satisfactory yield gains. This phenomenon is not well defined nor are its extent and causes well understood. In order to close these knowledge gaps, we assessed the effects of commonly recommended nitrogen (N), phosphorus (P) and/or potassium (K) fertilizer inputs on maize grain and soybean production on farmer fields across prevalent land slope and/or soil texture gradients (2 × 2 matrix) in four agroecosystems over two growing seasons. The extent of the problem in the two cropping systems was compared by decomposing frequency distributions into various ranges of fertilizer effect sizes that represent specific degrees of non-responsiveness and responsiveness. Key soil properties and rainfall variables for field trials were also determined to identify the factors that are limiting crop yield increases by mineral fertilizer input. Significant differences were found in mean fertilizer effect on crop productivity and frequency of non-responsiveness among the study areas and growing seasons, with some explicit contrasts between maize and soybean. The application of mineral fertilizers failed to increase maize yields by more than 0.5 t ha−1 in up to 68 % of farmer fields and soybean yields by more than 150 kg ha−1 in up to 65 % of farmer fields for specific study areas and/or growing seasons, while for others crop responses exceeded those levels. Unlike hypothesized, there were no consistent differences in crop fertilizer responses between the soil texture and land slope classes at any of the study sites. The variation in fertilizer effects on maize grain productivity across the study areas and growing seasons was most strongly related to the soil silt and clay content, and exchangeable cation balances of calcium (Ca), magnesium (Mg) and K, whereas fertilizer effects on soybean were most strongly influenced by the evenness in rainfall during growing seasons, and the soil silt content, extractable P, and ratio of total C and total N. Findings from our study emphasize that non-responsiveness by maize and soybean crops in African smallholder agroecosystems is dependent on multiple interacting factors, and requires careful scrutiny to ensure returns on investments

Nitrogen budgets and nitrogen use efficiency as agricultural performance indicators in Lake Victoria basin

Open Access JournalToo little nitrogen (N) is a threat to crop productivity and soil fertility in subSaharan Africa (SSA). Nitrogen budgets (NB) and nitrogen use e ciency (NUE) are critical tools for assessing N dynamics in agriculture and have received little or no attention in the region. Data were collected from smallholder farmers clustered into two categories, farmers applying and farmers not applying N fertilizers. NB were calculated using the Coupled Human and Natural Systems (CHANS) model approach for field and farm spatial scales. The results showed spatial variabilities in NB and NUE at the field level (maize and rice) across all the catchments. At the field level, N balances were negative for the two crops in all the catchments. Similarly, at the farm gate, a deficit of −78.37 kg N ha−1 was observed, an indicator of soil N mining. NUE values at the field scale varied across the catchments for both crops, with values for maize grown without N ranging from 25.76 to 140.18%. Even with the application of mineral N at higher levels in rice fields compared to maize fields, NUE values ranged between 81.92 and 224.6%. Our study revealed that the Lake Victoria region suers from ine cient N cycling due to depleted soil N pools and low synchrony between N input and N removal. Therefore, a challenge lies in exploiting more sustainable N sources for farmers in the region for sustainable farming systems. The NB and NUE provide critical information to agriculture stakeholders to develop environmental, agronomic, and economically viable N management solutions

Assessment of the 2006 Abuja fertilizer declaration with emphasis on nitrogen use efficiency to reduce yield gaps in maize production

Open Access Journal; Published online: 01 Feb 2022The Abuja Fertilizer Declaration in 2006 recommended the increase of fertilizer use from the current practice for Sub-Saharan Africa (SSA) to achieve food sufficiency and improve soil fertility status. However, the current recommended rates of fertilizer have not been evaluated for specific crops on their potential to reduce the yield gap and optimize nitrogen use efficiency (NUE). In this study, with nitrogen (N) being a significant yield-determinant nutrient, four N use scenarios were drawn from existing recommendations and were evaluated under field conditions for maize crops in two catchments of the Lake Victoria basin. The scenarios included Business as Usual (BAU, 0 kg N ha−1), 25% of the Abuja declaration (ADS 12.5 kg N ha−1), 50% of the Abuja declaration (ADS 25 kg N ha−1), and Abuja declaration–Abuja scenario (ADS, 50 kg N ha−1). The results revealed that increasing N input levels significantly influenced the growth and yield of maize crops. The ADS scenario recorded the highest grain yield increase (167.39%) in Nyando and 103.25% in Rangwe catchments compared to the BAU scenario. N deficits were observed in all the N use scenarios with a range of −66.6 to −125.7 kg N ha−1 in Nyando and −62.5 to −105.4 kg N ha−1 in Rangwe catchments with the 50% ADS scenario having the highest deficits. The deficits imply that the added N input is insufficient to create an N balance for optimal NUE with consequent high risks of soil N mining. In both catchments, all N use scenarios were within the recommended agro-physiological N efficiency (APEN) level of between 40 and 60 kg kg−1 N. The partial N balance obtained at Nyando (1.56–3.11) and Rangwe (1.10–4.64) was higher than the optimal values, a sign of insufficiency of N inputs and possible risk of soil N depletion in all the scenarios. Our findings conclude that the proposed N rates in the region are still very low for food sufficiency and optimized NUE. Therefore, there is a need to explore other sources of N such as biological N fixation and organic manure and inform policy- and decision-makers to recommend higher rates beyond the “Abuja declaration” with the prospect of reaching target yield and optimizing NUE values based on specific crop recommendations

Agro-ecology, resource endowment and indigenous knowledge interactions modulate soil fertility in mixed farming systems in central and western Ethiopia

Open Access Article; Published online: 14 Feb 2021Site‐specific soil fertility management requires a fundamental understanding of factors that modulate soil fertility variability in the local context. To verify this assumption, this study hypothesized that soil fertility variability across two regions in Central and Western Ethiopia is determined by inter‐related effects of agro‐ecological zones and farmers’ resource endowment (‘wealthy’ versus ‘poor’ farmers). Mid‐infrared spectroscopy coupled to partial least squares regression (midDRIFTS‐PLSR) and wet‐laboratory analyses were used to assess the soil fertility (soil pH, total soil carbon [TC] and nitrogen [TN], plant‐available phosphorous [Pav] and potassium [Kav]) across four agro‐ecological zones: ‘High‐Dega’ (HD), ‘Dega’ (D), ‘Weina‐Dega’ (WD) and ‘Kola’ (K). MidDRIFTS peak area analysis of spectral frequencies (2,930 [aliphatic C‐H], 1,620 [aromatic C = C], 1,159 [C‐O poly‐alcoholic and ether groups] cm‐1) was applied to characterize soil organic carbon (SOC) quality and to calculate the SOC stability index (1,620:2,930). Higher TC in HD, as well as higher TN and Kav contents in K were found in fields of wealthy compared with poor farmers. Resource endowment dependent soil fertility management options revealed SOC of higher quality in wealthy compared with poor farms in D. Agro‐ecological zones distinctions contributed to these soil fertility differences. Farmers distinguished visually fertile and less fertile fields based on soil colour. Higher pH in K and WD as well as Pav in K and HD were found in fertile (brown/black) than less fertile (red) soils. To conclude, tailor‐made soil fertility management in the local context must consider agro‐ecological zones and resource endowment interactions along with farmers’ indigenous knowledge

Assessment of sustainable land use: linking land management practices to sustainable land use indicators

Open Access Article; Published online: 22 May 2021Land degradation threatens food production especially in smallholder farming systems predominant in sub-Saharan Africa. Monitoring the effects of agricultural land uses is critical to guide sustainable intensification (SI). There are various indicators of sustainable land use (SLU), but conventional methods to quantify their metrics are complex and difficult to deploy for rapid and large-scale assessments. Considering that SLU indicators are dependent on agricultural practices, which can be rapidly identified and quantified, we propose a framework for SLU assessment that includes indirect quantifications of prioritized indicators (crop productivity, soil organic carbon (SOC), acidification, erosion, nutrient balance) using agricultural practices; and a SLU index derived from the integration of these indicators. The application of the framework to a case study, consisting of 1319 farm plots in Tanzania, reveals that SOC and N balance were the main contributors to the SLU gap. Only 2.2% of the plots qualified as being used sustainably. The framework proved to be sensitive to practices commonly used by farmers, thus providing an opportunity to identify practices needed to revert land degradation. Further application of the framework as a decision-support tool can enhance the efficiency of SI investments, by targeting practices which effectively enhance food production and preserve land

Integrated soil fertility management in sub-Saharan Africa: unravelling local adaptation

Intensification of smallholder agriculture in sub-Saharan Africa is necessary to address rural poverty and natural resource degradation. Integrated Soil Fertility Management (ISFM) is a means to enhance crop productivity while maximizing the agronomic efficiency (AE) of applied inputs, and can thus contribute to sustainable intensification. ISFM consists of a set of best practices, preferably used in combination, including the use of appropriate germplasm, the appropriate use of fertilizer and of organic resources, and good agronomic practices. The large variability in soil fertility conditions within smallholder farms is also recognised within ISFM, including soils with constraints beyond those addressed by fertilizer and organic inputs. The variable biophysical environments that characterize smallholder farming systems have profound effects on crop productivity and AE and targeted application of limited agro-inputs and management practices is necessary to enhance AE. Further, management decisions depend on the farmer's resource endowments and production objectives. In this paper we discuss the "local adaptation" component of ISFM and how this can be conceptualized within an ISFM framework, backstopped by analysis of AE at plot and farm level. At plot level, a set of four constraints to maximum AE is discussed in relation to "local adaptation": soil acidity, secondary nutrient and micro-nutrient (SMN) deficiencies, physical constraints, and drought stress. In each of these cases, examples are presented whereby amendments and/or practices addressing these have a significantly positive impact on fertilizer AE, including mechanistic principles underlying these effects. While the impact of such amendments and/or practices is easily understood for some practices (e.g., the application of SMNs where these are limiting), for others, more complex interactions with fertilizer AE can be identified (e.g., water harvesting under varying rainfall conditions). At farm scale, adjusting fertilizer applications within-farm soil fertility gradients has the potential to increase AE compared with blanket recommendations, in particular where fertility gradients are strong. In the final section, "local adaption" is discussed in relation to scale issues and decision support tools are evaluated as a means to create a better understanding of complexity at farm level and to communicate best scenarios for allocating agro-inputs and management practices within heterogeneous farming environments

Understanding nutrient imbalances in maize (Zea mays L.) using the diagnosis and recommendation integrated system

Open Access Journal; Published online: 06 Aug 2021Low nutrient use efficiency in maize as a result of imbalanced nutrition has been reported to drastically reduce yield. We implemented a nutrient omission experiment to assess the effect of nutrient application on maize yield and nutritional balance. Maize ear leaves were analyzed for nutrients, to identify nutrient balance status using the Diagnostic and Recommendation Integrated System (DRIS) approach. Results indicated that omission of N or P resulted in highly imbalanced DRIS indices respectively, and significantly lower grain yield. A strong inverse relationship between K ear leaf content with DRIS index suggests that K application negatively increases K imbalance in many situations. Imbalances of Mg, Ca and Cu were more associated with higher yielding treatments. A Which-Won-Where result show that nutrient imbalances in the diagnosis were systematically frequent when N was omitted. All the diagnosed nutrients were imbalanced even under the highest yielding NPKZn treatment; indicating further opportunity for yield increase with more balanced nutrition. Balanced nutrition of maize in the maize belt of Nigeria should target application of varying rates of N, P, K, Mg, S and Zn, depending on the soil conditions. But, because of complexities of nutrient interactions during uptake, it is hardly possible to realize a balanced nutrition. However, differentiating the application of antagonistic nutrients into foliar or soil-based methods is recommended for a more balanced maize nutrition