May Field Updates

A research meeting with Robilert and Alex

Warm greetings to all!

I hope this finds you well.

I wanted to start by sharing an update on the basket/grain mill project from last year. Many of you generously purchased baskets from refugees and hosts in Imvepi. Hopefully you have enjoyed them in your home or have passed them on as gifts. All of the money received from basket purchases (almost $1500!) was used to support my assistant Alex (pictured right below) and his youth entrepreneurship group purchase a grain mill. They plan to grind maize, cassava, and sorghum for their neighbors as a supplementary income source.

In early May, Robilert assisted Alex in buying the grain mill from Arua and arranging for transport back to Imvepi. Currently the grain mill is stored in Alex's home as he finishes constructing an outdoor shelter where it will be used in the community. Many thanks to all for helping to turn this idea into reality!

Robilert, Alex, and the grain mill

As you may recall from my previous post, we have started off this field season by establishing experimental field trials to test whether 1) agroforestry and 2) application of biochar (a carbonized soil amendment) can improve agricultural growing conditions and diversify crop yields in Imvepi. We are using a randomized controlled block design (RCBD) with the same experiment replicated four times. Within each replication are 11 experimental sub-plots, with each sub-plot having a a unique "treatment," or a particular combination of crops, trees, and/or biochar. We are testing crop interactions with three nitrogen-fixing tree/shrub species: Albizia gummifera, pigeon pea (Cajanus cajan) and Calliandra calothyrsus. The layout of the plots is randomized and differs within each replication. Below is the general layout of our experiment:

RCBD layout for agroforestry and biochar field trials

Plot measurement, tilling, and fencing

Step one was to complete primary cultivation of the field sites, which are three acres in total, divided between two separate locations in Imvepi. We hire mixed refugee-host teams to help with the labor, which has been a good employment and community-building opportunity for folks living near the experimental sites. All field sites were cultivated by hand with hoes. Next Robilert and Alex carefully measured out individual sub-plots according to the design shown above. Each sub-plot is 9 meters by 10 meters. Robilert and Alex are really attentive to details and did a wonderful job setting out the sub-plots, which are demarcated by corner pegs and string along the boundaries.

Fencing will be needed to protect the field sites from stray animals. Originally we considered barbed wire fencing, but the cost of fencing three acres was far outside of our budget. Instead, we adopted the local practice of heaping thorny tree branches along the boundary of the field sites to discourage animals from entering. We will continue bolstering these throughout the season.

(left to right) Primary cultivation, Robilert and Alex measuring sub-plots, thorny branch fencing

Sub-plot marking, soil samples, and soil measurements

Next, each sub-plot was clearly labeled with garden signs I brought from the US. I spent several days collecting baseline soil samples from each of the 44 sub-plots, which will be brought to a soil science lab at Gulu University for analysis of nitrogen, carbon, phosphorus, potassium, etc. I collected nine mini samples per plot, mixed them in a bucket, then filled labeled bags. Once I got home, I dried the soil outdoors so that it can be stored until I travel to Gulu.

I also also ran tests on soil aggregate stability using an iPhone app called "SLAKES." Soil aggregate stability refers to how well soil particles hold their form under external forces like wind and water. Three small clumps of soil from each sub-plot are left to air dry in a petri dish for 24 hours, then soaked in water for 10 minutes as the phone records the extent to which the soil holds form. The app gives each sample an aggregate stability score. Finally, I took six measurements of soil moisture content and temperature within each sub-plot, and averaged the measurements, being careful to record the date and time of day which will be important for follow-up measurements next year.

Robilert marking a plot, soil samples collected, air-dried, then bagged up. Soil clumps for aggregate stability testing in petri dishes, and soil moisture/temperature measurement tools

Applying biochar, planting trees and crops

Over the winter Robilert, Alex, and some assistants produced all of the biochar needed for the experimental plots (176 sacks in total!). We needed to transport half the biochar (~88 bags) to one of our experimental sites using a tricycle, which carried 15 bags per trip. After the biochar was distributed and tilled into the correct sub-plots, we began planting trees and crops.

Robilert instructed folks on how to dig sizeable pits for planting Albizia seedlings, while pigeon pea and calliandra were direct seeded. After one week, we returned to plant maize and cassava, using marked ropes to ensure consistent spacing across plots. We also planted maize and pumpkins in unused corners of the field sites. All of the crops and trees will eventually be left to the landowners, in exchange for allowing us to use the land for this experiment.

Biochar loaded in a tricycle, Robilert demonstrating how to dig seedling pits, Alex planting an Albizia seedling, cassava and maize planting, and sprouting pumpkins

I am currently setting off for a week-long science agroforestry education event in Nairobi, Kenya. Looking forward to sharing about that and more in my next post! In the meantime, please stay well,

Sarah