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Scalable yield gap analysis
David B. Lobell
Associate Professor, Department of Environmental Earth System Science
Associat...
•

In 2004, Ivan and I gave a talk in El Batan about how remote
sensing could be really useful

•

A lot has changed since...
When is remote sensing useful?
Type of cropping system

Applications that are likely useful

1) Low input, subsistence
sys...
The goals of yield gap analysis
To answer questions such as:
•How big are exploitable yield gaps?
•What key factors cause ...
Scalable yield gap analysis
What do I mean by scalable?

•Can be rapidly applied in a new area
•Does not rely on field sam...
1. Automated yield estimation
100+ sets of crop
model parameters
(sow date, density,
fertilizer, etc.)

Daily
Weather
Data...
Wheat yield estimates derived from
Landsat in Yaqui Valley, Mexico

~7.0 ton/Ha
~4.0 ton/Ha

-1

M e a n S a te llite -B a...
2002 Wheat Yield in Punjab (Mg/ha)

Faridkot

Moga

Faridkot
Sangrur

Mukstar

Sangrur
Bhatinda
Mansa

Mansa
25

Moga

Muk...
Maize yields in North China Plain

R2 = 0.48
Outline
Our current approach is a 4-step process
1. Yield estimation for individual fields for 3+ years
2. Analysis of the...
Not all yield differences are persistent
Measures of yield persistence can help identify how
much of overall yield gap is driven by persistent factors
Measures of yield persistence can help identify how
much of overall yield gap is driven by persistent factors
Can also readily do things like look at between vs.
within field yield variation
Estimated maize yields (t/ha) in part of ...
Outline
Our current approach is a 4-step process
1. Yield estimation for individual fields for 3+ years
2. Analysis of the...
Some factors typically emerge as important,
others not
Wheat yields in Indian Punjab vs. distance to roads or canals

Lobe...
Outline
Our current approach is a 4-step process
1. Yield estimation for individual fields for 3+ years
2. Analysis of the...
Farmer surveys in Quzhou China
My questions:
The next five years should be very exciting, but there is finite time
and resources. So…

•

How much intere...
Acknowledgements
Most of this work was inspired by and done in collaboration with
Ivan Ortiz-Monasterio
Funding from NASA,...
Scalable yield gap analysis
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Scalable yield gap analysis

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Remote sensing –Beyond images
Mexico 14-15 December 2013

The workshop was organized by CIMMYT Global Conservation Agriculture Program (GCAP) and funded by the Bill & Melinda Gates Foundation (BMGF), the Mexican Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA), the International Maize and Wheat Improvement Center (CIMMYT), CGIAR Research Program on Maize, the Cereal System Initiative for South Asia (CSISA) and the Sustainable Modernization of the Traditional Agriculture (MasAgro)

Published in: Education, Technology
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Scalable yield gap analysis

  1. 1. Scalable yield gap analysis David B. Lobell Associate Professor, Department of Environmental Earth System Science Associate Director, Center on Food Security and the Environment dlobell@stanford.edu
  2. 2. • In 2004, Ivan and I gave a talk in El Batan about how remote sensing could be really useful • A lot has changed since, but these resources are still generally underutilized • Technology has advanced a little slower than many of us expected, but the pace of progress seems to be picking up
  3. 3. When is remote sensing useful? Type of cropping system Applications that are likely useful 1) Low input, subsistence systems •Providing basic statistics on area and production •Early warning of shortfalls •Tracking impacts of interventions 2) High input, low input use efficiency 3) High input, high input use efficiency •Real-time management assistance •Yield gap analysis
  4. 4. The goals of yield gap analysis To answer questions such as: •How big are exploitable yield gaps? •What key factors cause yield gaps? •On what practices should research and extension efforts focus for biggest yield gain? (From Van Ittersum et al. 2013) •Which fields are especially good or bad for a particular crop or variety?
  5. 5. Scalable yield gap analysis What do I mean by scalable? •Can be rapidly applied in a new area •Does not rely on field samples to calibrate yield estimates Our current approach is a 4-step process 1. Yield estimation for individual fields for 3+ years 2. Analysis of the temporal consistency of spatial patterns 3. Comparison of average yields with other readily available spatial datasets, such as on soil types, roads, and irrigation infrastructure 4. Targeted field surveys that focus on areas with highest and lowest average yields
  6. 6. 1. Automated yield estimation 100+ sets of crop model parameters (sow date, density, fertilizer, etc.) Daily Weather Data Available satellite images for year T Daily time step crop model (e.g. APSIM, Hybrid-Maize) Surface Reflectance Data inputs Crop Model Prescribed Parameters Outputs / Intermediate Variables Simulated yields and veg. indices (N > 100) Veg. Indices (WDRVI) Crop Classification Maps Regressions that link VIs on image date(s) to final yields Annual maps of crop yields
  7. 7. Wheat yield estimates derived from Landsat in Yaqui Valley, Mexico ~7.0 ton/Ha ~4.0 ton/Ha -1 M e a n S a te llite -B a s e d Y ie ld (to n h a ) 1 km 8 2 R = 0 .7 8 -1 rm s = 0 .3 7 to n h a 7 2002-03 6 5 1 :1 lin e 4 4 5 6 7 8 -1 F a rm e r R e p o rte d Y ie ld (to n h a ) 2001-02 2000-01 ~7.0 ton/Ha 1999-00 1993-94 ~4.0 ton/Ha
  8. 8. 2002 Wheat Yield in Punjab (Mg/ha) Faridkot Moga Faridkot Sangrur Mukstar Sangrur Bhatinda Mansa Mansa 25 Moga Mukstar Bhatinda 0 2002 Planting Date in Punjab 50km 5.5 Dec 25 4.0 2.5 5 km Nov 19 Oct 15
  9. 9. Maize yields in North China Plain R2 = 0.48
  10. 10. Outline Our current approach is a 4-step process 1. Yield estimation for individual fields for 3+ years 2. Analysis of the temporal consistency of spatial patterns 3. Comparison of average yields with other readily available spatial datasets, such as on soil types, roads, and irrigation infrastructure 4. Targeted field surveys that focus on areas with highest and lowest average yields
  11. 11. Not all yield differences are persistent
  12. 12. Measures of yield persistence can help identify how much of overall yield gap is driven by persistent factors
  13. 13. Measures of yield persistence can help identify how much of overall yield gap is driven by persistent factors
  14. 14. Can also readily do things like look at between vs. within field yield variation Estimated maize yields (t/ha) in part of Madison, Nebraska 2002 2004 2003 Estimated maize yields (t/ha) in part of Madison, Nebraska 2007 2008 2011 2012 2009 2005 2010
  15. 15. Outline Our current approach is a 4-step process 1. Yield estimation for individual fields for 3+ years 2. Analysis of the temporal consistency of spatial patterns 3. Comparison of average yields with other readily available spatial datasets, such as on soil types, roads, irrigation infrastructure, crop rotation, etc. 4. Targeted field surveys that focus on areas with highest and lowest average yields
  16. 16. Some factors typically emerge as important, others not Wheat yields in Indian Punjab vs. distance to roads or canals Lobell et al. 2010, Field Crops Research
  17. 17. Outline Our current approach is a 4-step process 1. Yield estimation for individual fields for 3+ years 2. Analysis of the temporal consistency of spatial patterns 3. Comparison of average yields with other readily available spatial datasets, such as on soil types, roads, and irrigation infrastructure 4. Targeted field surveys that focus on areas with highest and lowest average yields Note: this is the most time consuming step, but it comes last and is guided by the first three.
  18. 18. Farmer surveys in Quzhou China
  19. 19. My questions: The next five years should be very exciting, but there is finite time and resources. So… • How much interest exists at CIMMYT for yield gap analysis, or is there more interest on other uses, like real-time management, estimating crop areas, and impact evaluation? • Is it better to continue in ‘research mode’ where estimates are made for areas with specific questions and projects in mind, or in “public good mode” where we simply try to map all wheat and maize systems of the world and make it available to researchers (and farmers)?
  20. 20. Acknowledgements Most of this work was inspired by and done in collaboration with Ivan Ortiz-Monasterio Funding from NASA, Fundacion Sonora, Stanford University Students/ Research Assistants: Adam Sibley, Yi Zhao, Nancy Thomas, Christopher Seifert Thanks for your attention!

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