September 1, 2005
A joint mission between the USDA Foreign Agricultural Service (FAS) and the USAID FEWS NET Project conducted a crop tour in Kenya and northeastern Tanzania from June 23-July 5, 2005. The purpose of the crop tour was to assess current crop conditions, collect ancillary data from local industry sources, and validate several operational crop models currently used by FEWS NET and USDA/FAS analysts. Digital photos and spatial model images from this year's crop tour are presented at “WRSI Relative Yield Model Compared to Ground Conditions” and "2005 Kenya-Tanzania Crop Tour Pictures". In addition, recent Kenya and Tanzania corn production estimates derived from the 2005 crop tour are described in the PECAD articles titled, "Record Corn Area Increases Production in Tanzania" and “Kenya’s Corn Production Greater than Last Year”.
Georeferenced digital photos from the crop tour can be viewed at "2005 Kenya-Tanzania Crop Tour Pictures". A new GPS-photo link software package was utilized that linked the time stamps from digital photos to the time log from GPS track routes. The linking process takes about 45-minutes which includes downloading the digital photos; downloading the GPS track route; and linking the digital photos to GPS track routes so that the digital photos are georeferenced with latitude/longitude coordinates. In addition, the software creates two ESRI shape files (GPS route and georeferenced photos); provides two extensions for hotlink display of photos in ArcView or ArcGIS; adds latitude/longitude watermarks to the photos; creates a web page with metadata for viewing the photos; and links the pictures to Mapquest or other web mapping utilities.
It is envisaged that future crop tours conducted by FEWS NET and USDA/FAS will georeference all digital photos for continuous crop model validation from year-to-year. USDA/FAS has been conducting similar studies in South Africa (2004 and 2005) and these crop surveys have shown that, in most cases, the operational FEWS NET spatial models closely reflect ground conditions.
Africa Data Dissemination Service (ADDS) provides operational crop model products for Start of Season (SoS), Season Progress, and Water Requirement Satisfaction Index (WRSI). These spatial products were validated by making field observations; conducting interviews with government personnel, agronomists, traders, and farmers; and utilizing GPS units and digital cameras.
The SoS algorithm is based on 45-millimeter rainfall accumulation over a one-month period, and initializes the Season Progress and WRSI relative-yield models. In addition, a SoS anomaly image is produced by subtracting the current SoS images from the average SoS image derived from long-term average rainfall data. The SoS anomaly image helps to depicts whether the current season arrived earlier or later than average SoS values. However, it should be noted that the SoS model does not always model the exact planting dates as different agroclimatic conditions and local practices may require farmers to plant seeds in dry soil several weeks before rains are scheduled to arrive while other farmers may plant several weeks after the rains have arrived and soil moisture conditions are very moist.
For
In Tanzania, the SoS product had difficulty near the highland regions near Arusha where the unimodal (one rainy period during the year) and bimodal (two rainy periods per year) rainfall patterns merged together and the dividing line between the two patterns tends to be a function of elevation. Reports from local experts confirmed a GIS rainfall analysis that shows highland regions near Arusha are unimodal (with one long growing season caused by slow plant growth from cooler temperatures), and lowland regions tend to be bimodal (with two shorter growing seasons and rapid plant growth from warmer temperatures).
Digital photos comparing the WRSI relative-yield model to crop conditions on the ground can be viewed from “WRSI Relative Yield Model Compared to Ground Conditions” .
The Season Progress model
from ADDS is largely dependent
on SoS and Length of Growing Period (LGP) data layers.
The LGP database for
In
One important field technique was to estimate "average" crop stages across a valley as several different crop stages may be recorded within the same general vicinity. In view of this procedure, the mission team found a comprehensive crop tour in late June or early July was an ideal time for crop assessment tours in Kenya as most of the corn crop was in advance stages in the lowland regions and beginning to tassel in the highland regions.
The main conclusions from the Kenya-Tanzania 2005 crop
tour include:
Additional WRSI model improvements recommended include:
Kenya/Tanzania Crop Tour Route from June 23-July 5, 2005 and 3-D View
WRSI Relative Yield Model Compared to Ground Conditions
2005 Kenya-Tanzania Crop Tour Pictures (digital pictures georeferenced with GPS data)
Season Progress Product from ADDS and 3-D View
WRSI (August 20, 2004) for Kenya's long rain season
WRSI (May 31, 2005) for the unimodal rainfall regions of Tanzania
Length of Growing Period (LGP) Revision
Start of Season Products from ADDS
"Relay planting" region in Kenya with high annual rainfall and long Length of Growing Period (LGP)
FAO's Africover crop mask helps to identify only crop regions.
Greater Horn of Africa (GHA) Food Security Bulletin (July, 2005)
Daily MODIS (250-meter resolution) Satellite Images over Africa
Africa Data Dissemination Service (ADDS)
NOAA's Rainfall Estimate (RFE) product
Length of Growing Period (LGP) for East Africa as defined by FAO
Unimodal and Bimodal Rainfall Regions in East Africa
South Africa 2005 Crop Tour Summary
South Africa 2004 Crop Tour Summary