Status and challenges of soil management in Africa Bernard Vanlauwe International Institute of Tropical Agriculture Nairobi, Kenya b.vanlauwe@cgiar.org
The challenge Food security for 9 billion people? Closing the yield gap Increasing production ceilings Expanding aquaculture Reducing waste ( 30-40% of the produce) Changing diets Demography
The yield gap Maize yield reduction (% of potential) J. Koo, 2010 FAO and IFDC, 2002
The Coca-cola paradox $ 200-500 /tonne urea world market 2010-2011 $ 900-1.400 /tonne urea in Bukavu (DRC)
The Coca-cola paradox $ 1.5-2 in Europe $ 0.5 in Bukavu (DRC)
Lack of organic resources Crop Oilpalm Imperata Manure residues leaves Availability? Acceptability? Quality?
Variability in soil fertility
Variability in soil fertility Same farm Same variety Same inputs Same management Same weather
Non-responsive soils Occurrence: Non-responsive soils appear to occur in most densely populated areas where resources are scarce.
Importance of policy and good governance In Africa, there are good recent examples of where policy is making a difference in farmer livelihoods (e.g., Malawi, Rwanda, Kenya)
70 s: First paradigm: Overcome soil constraints to fit plant requirements through purchased inputs When mechanization is feasible and fertilizers are available at reasonable cost, there is no reason to consider the maintenance of SOM as a major management goal Sanchez, 1976
80 s: Focus on biological mgt of soil fertility
80 s: First signs of no-till farming
90 s: 2 nd Paradigm (Sanchez, 1994): Overcome soil constraints by relying on biological processes by adapting germplasm to adverse soil conditions, enhancing soil biological activity, and optimizing nutrient cycling to minimize external inputs and maximize their use efficiency The revival of green manures in East Africa (e.g., Tithonia diversifolia; Crotalaria sp)
90 s: First signs of uptake of CA in Brasil 1990
The destination is clear, less so the road to follow Productivity X Natural resource status
Fertilizer works (and interacts with improved varieties) FAO fertilizer program (FAO, 1989) : Average response of 750 kg grain/ha to medium NPK rates Value to Cost ratios between 1.1 and 8.9, usually above the required ratio of 2 Maize yield in East DR Congo
Agro-ecological principles Desired Outputs (e.g. Yield) or Undesired Outputs (e.g. N loss, GHG loss) Riskadjusted Optimum Economic Optimum Biological Optimum Keating, 2011 Inputs (nutrients, water, labour, agro-chemicals, energy etc.)
Fertilizer is best applied in combination with organic inputs!
Impact of fertilizer x variety on soil C 60 50 Commercial Communal Total C (t ha -1 ) 40 30 20 10 0 20 40 60 80 100 Zingore, Manyame, Nyamugafata and Giller (2002) Time, years
Now: Integrated Soil Fertility Management The application of soil fertility management practices, and the knowledge to adapt these to local conditions, which maximize fertilizer and organic resource use efficiency and crop productivity. These practices necessarily include fertilizer and organic input management in combination with improved germplasm
Now: Integrated Soil Fertility Management
Principles of Conservation Agriculture 1. Minimize soil disturbance by reduced or zero-tillage 2. Keep the soil covered with organic materials (crop harvest residues or cover crops) at least 30% soil cover 3. Use crop rotations/associations Important additional rule: No minimal tillage without mulch retention! 4. Use fertilizer [additional principle for Africa]
Time to CA http://www.fao.org/ag/ca/5.html
Niches for CA Tillage x residue management in Central Kenya Good Residue cover (%) 100 80 60 40 20 30% Good - with tillage Medium - with tillage Poor - with tillage Good - without tillage Medium - without tillage Poor - without tillage SED Medium Poor 0 0 5 10 15 20 Time (weeks) Guto et al. (2011), Agron. J. Guto et al. (2011), Agron. J.
The destination is clear, less so the road to follow Productivity Agronomic efficiency Increase in knowledge A C Responsive soils B Poor, less-responsive soils Current practice Germplasm & fertilizer Move towards ISFM Germplasm & fertilizer + Organic resource mgt Germplasm & fertilizer + Organic resource mgt + Local adaptation Full ISFM X Natural resource status
Importance of enabling conditions Role of input and output markets: ISFM requires investments in production factors; income is a requirement to move towards full ISFM. Models: Many interesting models to link smallholders to input supply chains and profitable markets are being piloted/implemented at scale.
Organic agriculture is constrained by organic inputs; OK for niche markets N: Some BNF Low use efficiency! P: Rock phosphates Availability? K: K salts; roots and tubers Availability? Other (micro)nutrients: S, Zn, Mg, etc??
The confusing life of a policymaker??
Farmer first! Interview Prem Warrior, BMGF, 17 Oct 2012 Question: What s the right thing to do for smallholders in Africa? Response: It s for her to decide! Thank you! Merci beaucoup! Asante sana!