Identifying sustainable land management practices within smallholder agriculture is a challenge. This is partly driven by the challenge of documenting farmers' perspectives and practices in an integrated manner with site‐specific scientific soil assessment. Smartphone applications such as LandPKS provide new approaches to quantify site‐specific soil degradation and fertility but are untested with African farm management. We surveyed 578 households in rain‐fed maize (Zea mays) production areas of Tanzania using a stratified sampling frame to encompass a wide range of soils and agroecologies. A socio‐economic survey and simultaneous sampling in focal plots documented farmer characteristics, perspectives, and management practices, along with soil properties and crop yields. For a subsample of 58 households, we additionally assessed site‐specific field status with the LandPKS application. Farmer perceptions of change in soil fertility status were consistent with soil properties, for example, a field perceived to be declining in fertility was also likely to have low SOC (1.8% relative to 2.7% for increasing fertility). LandPKS provided additional novel insights into soil limitations such as identifying poor water infiltration areas consistently associated with farmer use of erosion control practices (water infiltration of 4 mm hr−1 vs 20 all other plots). This charts a way forward to address soil fertility and land degradation challenges through the use of smartphone applications to capture site‐specific conditions and farmer concerns as the basis for land management recommendations that are highly relevant and address local conditions.

Climate change is posing severe challenges in Africa, where resilient crops are urgently needed to withstand drought periods and unreliable rainfall. Multipurpose legume species, such as lablab (Lablab purpureus (L.) Sweet), have been under-utilized yet have the potential to overcome climate challenges. While lablab is native to Africa, there are few characterized varieties and it is under-utilized by smallholder farmers due to a lack of information and access to varieties. Knowledge is especially lacking on the performance of this crop by genotype, management, and environment. We conducted a two-year field study at two sites to evaluate 29 lablab cultivars under sole and maize intercrop management, with 14 cultivars selected for in-depth study. Cultivars were evaluated on vegetative biomass and grain yield production, with N fixation assessed for one site year. Biomass and grain production differed across environments and cultivars, with only biomass affected by intercropping. Average grain yield was substantially reduced to only 37 kg ha-1 in environments with maximum temperatures greater than 33˚C, but biomass production yielded comparable amounts across high temperatures and in dry (<500 mm rainfall) environments. Tradeoffs were found between biomass and grain yield across high yielding cultivars, with the top three grain accessions averaging 612 kg ha-1 of grain and 1.97 Mg ha-1 biomass whereas the top three biomass accessions produced 327 kg ha-1 grain and 2.52 Mg ha-1 biomass across all environments. In a comparison of production and N fixation measurements, cultivars were identified which may have high performance in both. Suitability of lablab for grain and biomass production were visualized across Tanzania in a map comparing max temperature thresholds for grain and biomass against average regional livestock populations. This provides a way forward for identifying potential areas for lablab cultivation as a novel means to enhance fodder and pulse production with smallholder farmers.

Implementing sustainable production practices to rehabilitate soils is a grand challenge of our day, particularly for resource-poor farmers. The West African Sahel requires attention to balancing the need for increasing agricultural production against harsh environmental conditions. While there is much research documenting technologies for soil regeneration in the Sahel, there has been limited focus on how agricultural practices contribute or exacerbate these efforts. Previous assessments of agricultural practices in this region have been largely descriptive, and some soil ameliorating practices have been promoted with little empirical evidence on their effectiveness. Here we systematically review the literature on soil fertility and conservation practices that have been studied within West African Sahelian agricultural systems. We identified practices in the West African Sahel that have been tested to improve soil fertility and reduce land degradation, and summarized the outcomes of these practices. A unique contribution of this review is the assessment of site-specific conditions and contexts under which practices are most effective in studies which recorded these specific characteristics. We found that research in this area is dominated by chemical fertilizer and organic amendment practices, with moderate to few studies focused on soil and water conservation, crop diversification, or agroforestry. Additionally, most studies consisted of single practices rather than combining practices that target the range of biophysical limitations farmers face in agricultural production. These limitations highlight the need for increased research testing combinations of practices across long-term on-farm studies to generate stronger evidence of conditions under which practices best perform. These findings provide key lessons for research and extension on sustainable agricultural management under the challenging conditions of the Sahel.

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Effective extension systems are vital to smallholder agriculture. Education on sustainable management involves complex interactions and communication flows among information providers and practitioners. Farmer practice is often overlooked within extension knowledge systems, resulting in incompatible recommendations and barriers to sustainable agriculture. This study investigates the diversity of smallholder agricultural practices, with a focus on maize-legume systems in Tanzania, including seasonal cropping patterns and management, as well as linkages to extension recommendations and information flows. We used a mixed methods approach to assess the state of extension and farmer practice around maize-legume production in Tanzania. Household and plot-level survey data (n = 220) and focus group discussions (n = 5) and extension information was ascertained through interviews with key stakeholders (n = 12) and a survey of village-based extension advisors (n = 193). We found legume management practices were highly local. In the Southern Highlands for example, farmers produced from one to three bean crops per year, using a range of planting arrangements. Further, extension recommendations often did not take into account the varieties, fertilizer or plant spacing used by farmers. This comprehensive study of extension knowledge systems in Tanzania highlights the persistent disconnects that occur at multiple levels, acting as a barrier to sustainable intensification of smallholder farming.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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