Soil Testing in Tanzania

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Dr. Gene Stevens used a Garmin GPS receiver to navigate between soil sample grid points in Tanzania.

In July 2014, I collected soil samples on a 8,000 acre research/demonstration farm near Mombo, Tanzania.   Shallom Farm is being co-developed by Dr. Parseko Kone, a Tanzania Regional Commissioner,  and Floyd Hammer, founder of  Outreach International.  Much of the farm is covered with small trees and thorny vines.  To avoid getting lost and having a record of where I collected samples, I used GPS to navigate between sampling locations. Angelo Lopes, a student from Brazil, helped me develop a grid point system for the farm and saved the way points on my Garmin GPS receiver before I left the United States.  The farm was divided into 25 acre cells.  Each cell has a letter and number.  They are  labeled west to east with letters (A to Z) and north to south with numbers (1 to 14).

Grid points for soil sampling.
Grid points for soil sampling in Tanzania.

The most suitable areas for growing maize on the farm are in the northwest and southwest corners so I focused my sampling in those locations. The headquarters (Boma) is located close to the center of the farm on a hill.  Each afternoon, the Maasai herdsmen from a local village drive the cattle into pens.  In the morning, they turn them out to graze.

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Cattle are held in pens made from tree branches.
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A Maasai man sharpens a knife on a rock.

The east side of the farm has stream channels that are dry most of the year.  In the rainy season, which is October to March, water flows in the streams. If berms could be constructed to hold water in reservoirs , irrigation might be used to water crops in the dry season.

Topography

I collected soil samples in the dry season.  In most locations, the  ground was hard and we had to use a hammer to drive the probe into the soil. Oscar, the young man holding the probe, moved from South Africa with his uncle to work on the farm. 

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In my luggage, I carried a portable pH meter, potassium ion electrode, and test kit for measuring phosphorus.  Outreach rented a house at Rosminian Health Center.  It is a charity hospital managed by Sister Jennifer Raduck and Father Ambrose Chuwa.  To analyze the soil samples, I converted the  kitchen in the house into a temporary laboratory.  Most of the soil samples from Shallom Farm were either black shrink-swell clay or red loam soil high in oxidized iron.

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Equipment was not available dry the samples so I let them dry in the sun and used a rolling pin to crush the clods.

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Soil pH was measured in a 1:1 soil/water solution.   The pH meter was calibrated with a pH 7.0 solution.  I used a aluminum sulfate extraction solution for potassium and filtered the liquid before testing it with an ion specific electrode.  The potassium meter was calibrated with 20 and 200 ppm K solutions.

 

Measuring soil pH for acidity in 1:1 water solution.

Measuring soil pH for acidity.
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Portable potassium ion specific electrode.
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Phosphorus was measured using a purple indicator and the intensity of color was matched to a scaled chart.

Most of the samples contained adequate potassium for maize production. The pH levels were usually above 6.0 which is good.  I had difficulty accurately determining the phosphorus levels with the color indicator.  In follow up testing in a conventional laboratory,  we determined that soil phosphorus and sulfur were below critical levels in some of the samples.

P1000378Visiting Tanzania was an enjoyable experience.  I learned several Swahili greeting words such as jambo (hello), habari (how are you?) and mzuri (fine).  Mzuri is pronounced like my home state of Missouri.  I spent time in Mombo, Moshi, and Arusha.  All of the people that I met in Tanzania were very friendly and I hope to go back someday.