Back in Capijuma the soil differs greatly between the different areas of the property. And so after we had planted already in a few locations Richard’s curiosity was sparked to investigate a little about which soil is better for planting. We didn’t have any special tools or soil testing kits available to us but luckily, while I was in Switzerland working with my brother (Thomas Rippel), I have seen a simple jar compost testing experiment that will give us an overall idea about the relative difference between our soils.
The idea is to take two samples of soil that one knows to be good as the control and two samples of each of the soils / composts you would like to be testing. In our case we compared the compost from one of our compost piles that Antonio had made in October/November of last year (2013), the soils of the African Keyhole which is a mixture of soils and composts, and the soil of our older kitchen garden.
We got six jars, washed them well, and sterilized them with hot water before we put in our soil samples. Then in each we placed a spoonful of conventional (commercial) lentil seeds. We used those because we had many of them. We watered each a little and then closed the lid of one of each of the samples and the other we covered with a net to protect it from bugs. The open containers were watered with 3 spoons full of water semi daily.
The closed containers sprouted first, possibly due to the higher humidity. In terms of quantity, most seeds sprouted in the containers with the soil from the African Keyhole. Those that sprouted grew well in both the soil from the vegetable garden and African Keyhole. After 12 days the samples in the closed containers grew a lot of mold and the seedlings were dying. This was especially true for the compost sample, possible due to the gases it has generated. On the other hand more balanced compost mixtures, as I have seen in Switzerland, generate very low levels of adverse gases. After three weeks we concluded the experiment.
Our compost piles definitely have a lot of room for improvement. For example, for the African Keyhole we didn’t used our own compost. We used our soil, humus from the forest, and the compost we got from a local governmental research institute (Incaper). You can see below that our carrots have been thriving in this mixture. This is our first step on our soil/compost pile journey, with many more to follow soon!
Very cool bro. :-)
This testing method is simple and very effective. But it is mant mainly to test wether the composting process has finished – no more gases are evaporting, all nutrients are locked up in the form of Humus and microorganisms.
It is essential that you add some clay (has 600-800m2 of active surface area per gram) to the compost! Amazonian soil has a very low nutrient retention capacity. Maybe it will be hard for you to find clay , then it is absolutely essential that you use biochar.
ahhh, yeah back in the Atlantic Forest we had very little clay. Here in the Cerrado is quite common. After 80-100cm depth there seems to be clay everywhere here. We have consistently found it in every big hole we have dug for the banana circles. Here our compost will have clay! How much do you suggest we should add?