Returns to fertilizer and program efficiency: Estimation techniques & results from crop simulation
- 1. 1 Returns to fertilizer and program efficiency: Estimation techniques & results from crop simulation Andrew Dorward & Ephraim Chirwa, School of Oriental and African Studies, University of London Wadonda Consult
- 2. Outline Background – policy importance Returns to fertiliser (kg grain yield per kg fertiliser or nutrient N &/or P) are critical to the production benefits & economic returns to the programme Therefore ….. What is the yield response? Estimation techniques’ results & reliability How can it be improved? Crop simulation modelling results & policy implications 2 July 2014
- 3. Returns to fertiliser: yield response 3 July 2014 - 0.50 1.00 1.50 2.00 2.50 - 50 100 150 200 250 300 30% 40% 50% 60% 70% 80% 90% 100% 110% 120% US$mill % of Simulation NUE (23.4 kg/kg hybrid, 18.0 local) NPV (US$ mill) BCR Fiscal Efficiency
- 4. What is the yield response? Difficult to obtain reliable information on smallholder yields and yield responses Different data sources & methods with different reliability and bias Variability across years (rainfall, population growth, changes in varieties & cropping methods) Variation between areas & across farms (rainfall, population density, varieties, soils & cropping methods) 4 July 2014
- 5. Data sources – methods & reliability 5 Farm surveys • General random errors from farmer & enumerator errors, especially small plots • (Omitted variables over-estimate yield response) • Farmer estimates area • Under-estimates of smaller plot areas & over- estimates of larger plot areas – average over- estimate • Clustering in acre fractions • GPS area • Should be reliable • Farmer estimates production • Possible over- or under- estimates from farmer reporting & measurement units. • Possible under estimates from omission of green maize & multiple respondents • Differential bias effects on yield response? • Crop cutting • Over estimates of yield: production & yield response affected by bias in area estimates • Fertiliser use • Under reporting of sales & purchases leads to under-estimates of yield response On farm trials • Common over-estimate of yield & yield response due to farmer selection & crop management Crop simulations • Model over- or under- estimates yield response • Over estimate of yield response, no pest & disease
- 6. Yield response estimates Study Response kg/kgN Yield (kg/ha) Local Hybrid Local Hybrid Chibwana et al (2010) (subs) 2008/9 12 13 1,312 1,510 Holden & Lunduka (2010,3) 2006,7,8 9? 14? 1,609 IHS2 – AISS2 (adjusted yield) 2004,6,8 6.6 – 13.9 682 NACAL (pure stand only) 2006/7 n.a. 928 1,803 Crop simulation (with subs) 2012/13 18 23 1,392 1,921 Makumba (2013) hybrid 2010/11 16.8 0 Fert 2,483 Fert 4,003 Kamanga (2013) CR hybrid 2003/4 29 1 weed 900 2 weed 1,300 SOAS (2008) Summary/review ‘median’ 15 22
- 7. National food security: consumption, 7 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000 3500 4000 2001/2 2002/3 2003/4 2004/5 2005/6 2006/7 2007/8 2008/9 2009/10 2010/11 2011/12 2012/13 2013/14 '000MT Total consumption (MT)
- 8. National food security: consumption, production with subsidy 8 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000 3500 4000 2001/2 2002/3 2003/4 2004/5 2005/6 2006/7 2007/8 2008/9 2009/10 2010/11 2011/12 2012/13 2013/14 '000MT Total consumption (MT) Production with subsidy (MT)
- 9. National food security: consumption, production & surplus/deficit with subsidy 9 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000 3500 4000 2001/2 2002/3 2003/4 2004/5 2005/6 2006/7 2007/8 2008/9 2009/10 2010/11 2011/12 2012/13 2013/14 '000MT Domestic surplus (deficit) before subsidy (MT) Domestic surplus (deficit) with subsidy (MT) Total consumption (MT) Production with subsidy (MT)
- 10. 10 July 2014 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000 3500 4000 2001/2 2002/3 2003/4 2004/5 2005/6 2006/7 2007/8 2008/9 2009/10 2010/11 2011/12 2012/13 2013/14 '000MT Domestic surplus (deficit) before subsidy (MT) Domestic surplus (deficit) with subsidy (MT) Domestic surplus (deficit) without subsidy (MT) Total consumption (MT) Production with subsidy (MT) Production without subsidy National food security: consumption, production & surplus/deficit without subsidy
- 11. Crop simulation Commissioned maize simulation study under smallholder conditions (Anthony Whitbread et al, Goettingen University, now at ICRISAT) Review & meta-analysis of response studies: limited / conflicting/ weak information Hybrid 30-80 kg grain/kg N @ 15-30 kg N/ha Local 10-30 kg grain/kg N @ 15-30 kg N/ha APSIM model calibrated for smallholder conditions (eg weeds) historical (1927-2004) daily climate information for Kasungu 4 sandy or sandy clay loams (deep & shallow soils) Centre & South Range of management practices matching 2008 AISS2 observations Planting date & density, N & P rates & times, good & poor weeding Used results to generate regression estimates of crop responses Evaluated crop responses using regression coefficients at observed 2012/13 crop management means 11 July 2014
- 12. Crop simulation findings Influences on yield & yield response Mean yield and fertiliser response estimates 12 July 2014
- 13. Illustrative N Response, HYBRID by plant population & weeding, without & with P 13 July 2014 0 1000 2000 3000 4000 5000 0 15 30 60 120 Grainyield(kg/ha) Fertiliser N rate (kg/ha) Low Good Low Poor Mod Good Mod Poor High Good High Poor Chitala 0P Variety: Hybrid 0 1000 2000 3000 4000 5000 0 15 30 60 120 Grainyield(kg/ha) Fertiliser N rate (kg/ha) Chitala 10P Variety: Hybrid Source: Whitbread et al 2013
- 14. 0 1000 2000 3000 4000 5000 0 15 30 60 120 Grainyield(kg/ha) Fertiliser N rate (kg/ha) Low Good Low Poor Mod Good Mod Poor High Good High Poor Chitala 0P Variety: Local 0 1000 2000 3000 4000 5000 0 15 30 60 120 Grainyield(kg/ha) Fertiliser N rate (kg/ha) Chitala 10P Variety: Local Illustrative N Response, LOCAL by plant population & weeding, without & with P 14 July 2014 Source: Whitbread et al 2013
- 15. Simulated yield response Importance of hybrid seed early planting good agronomy potential for lower N application rates variable returns to N Good potential returns to N and impact Nutrient responses with average smallholder management Local 18 kg grain/kg N (@37 kg N/ha) Hybrid 22 kg grain/kg N (@47 kg N/ha) Hybrid without fertiliser + 600kg/ha 15 July 2014
- 16. 16 Returns to fertilizer and program efficiency: Estimation techniques & results from crop simulation Andrew Dorward & Ephraim Chirwa, School of Oriental and African Studies, University of London Wadonda Consult