Samuel Eze, Andrew Dougill, Steven Banwart, Susannah M. Sallu, Rashid N. Mgohele, Catherine J. Senkoro
Food insecurity remains a major challenge globally, particularly in Africa where farmers depend on rain-fed agriculture, which is vulnerable to climate change and extreme weather events such as flooding and drought. With growing demand for food due to rising population, there is an urgent need to deploy all necessary measures to improve and sustain agricultural production. One key strategy for sustaining agricultural production is improved monitoring the health status of soils, utilising both local and scientific knowledge, in order to make land management decisions that are appropriate and location-specific.
Landslide on a farm in the East Usambara Mountains, Tanzania.
To monitor soil health, sensitive soil attributes that influence the soil’s water retention and nutrient cycling are targeted and are referred to as soil health indicators. There are both ‘traditional’ (qualitative or visual) and ‘scientific’ (quantitative) techniques for monitoring soil health. The visual techniques involve physical observations to assess properties such as the “feel” of the soil, wetness or dryness, size of aggregates, root presence, and soil fertility based on nutrient deficiency or toxicity symptoms in plants. Scientific techniques tend to be most preferred for monitoring soil health because they provide accurate and verifiable information about the soil in different regions. Consequently, conventional soil assessments by Governments and Donors remain mostly carried out in the laboratory by trained scientists and technicians, whilst farmers rely on the visual techniques with only few attempts to integrate these measures. In a recent AFRICAP project study in Tanzania, we evaluate how useful and useable are farmers’ soil assessments in terms of achieving more sustainable and climate-smart land management practices?
During our discussions with farmers in the East Usambara Mountains (EUM) of Eastern Tanzania, their statements such as “We farm based on experience” and “Even though I applied recommended fertilizer, crop yield did not increase” were a constant reminder that farmers’ experiences need to be considered in land management planning.
This led to us to conduct a number of studies in African Mountain Systems to understand the importance of farmer’s visual soil assessments. Farmers’ awareness and use of soil health indicators in making land management decisions were first assessed in a paper using data collected in Tanzania and from a review of existing literature. Last month we have extended our analysis in a further paper assessing changes in soil health indicators under a range of climate-smart practices across the East Usumbara Mountain sites in Tanzania. Conventional soil testing techniques and farmers’ observations of soil health indicators of fields under three common SWC practices in the EUM were compared with those of fields with no SWC practice. The three practices evaluated were: addition of farmyard manure, incorporation of crop residues in soil, and Fanya juu terracing stabilized with Guatemala grass strips across steep slopes.
Soil & Water Conservation measures, including Fanya juu terraces and grass strips in East Usambara, Tanzania.
Farmers across the African Highlands use observable characteristics of soils and plants as indicators of soil health. Soil colour (a proxy for organic carbon) and vegetation performance (linked to soil nutrient availability) were the most frequently reported indicators. In our Tanzanian sites, soil colour and vegetation performance were the only two soil health indicators that influenced farmers’ land management decisions. When soils turn red, an indication of low fertility, or there is a decline in crop yield, farmers reported adding farmyard manure and/or incorporating crop residues in the soil to address the soil health problems.
The farmers in the East Usambara Mountains did not observe any improvement in soil health after two to four years of adding organic manure to their fields, but they observed significant increases in crop yield where organic manure addition was combined with Fanya juu terracing. Fanya juu terracing is the practice of digging trenches across slopes with excavated soils thrown uphill to form an embankment. In the highlands, erosion control measures, such as terracing, are necessary to help retain water and nutrients for the crops. The results of conventional soil testing showed improvements in soil structure resulting from the SWC, which corroborates farmers’ observations in terms of soil colour and crop yield.
Farmer discussions on terracing, crop residue management and soil health.
To address the growing challenges of food insecurity and land degradation, locally-appropriate comprehensive soil health monitoring programmes are required to inform the selection and adoption of sustainable land management practices that are most suitable for enhancing crop yields without degrading the environment. This can be best achieved by integrating farmers’ observation techniques with conventional scientific soil health analyses to identify the most appropriate sustainable land management practices.
The newly established Climate Smart Agriculture Alliance in Muheza District, a registered community-based organization that brings stakeholders together to jointly identify, discuss and find appropriate solutions to challenges emanating from climate change in agriculture, demonstrates local commitment for such initiatives.
See full paper at – https://onlinelibrary.wiley.com/doi/epdf/10.1002/ldr.4339