This past week we harvested our second round of biochar test plots. We planted sorghum using the same techniques and nutrient inputs as we did with finger millet during the long rains season. The primary difference this round was that we did not add any new biochar. That means the biochar + human urine solution test plots only received a new helping of urine this season. No new biochar.
What we wanted to test was biochar’s impact in its second season. After harvest we looked at our results and were blown away.
Not only did the effect of biochar not diminish, it substantially grew! One of the likely causes was higher nutrient retention rates in soils with greater amount of biochar added last season. What this basically means is less long rains (last season) nutrients were lost from the soil heading in to the short rains season (this season) in plots with more biochar. So, when we added human urine to our 6000kg/acre biochar test plot it likely had greater reserves of nitrogen and phosphorus available than the 2000kg/acre or 400kg/acre plots. This compound effect can be seen in the below graph.
This season we had twelve (12) test plots outperform the baseline DAP plot. DAP (di-ammonium phosphate) is the most commonly used inorganic fertilizer in western Kenya. The 50KG/Acre application rate is recommended by most distributers. All but one of these twelve plots were amended with biochar, and five of those eleven were 100% organic (an improvement from two last season).
Once again the 6000KG Biochar + 5000L 15% Human Urine Solution plot took gold. Last season it beat DAP by 27%. This season this organic biochar plot beat the DAP plot by 144%. Additionally, last season’s 400KG/Acre application of biochar allowed us to reduce our DAP use by 50% and while improving our yield 17% (versus a full application of DAP with no biochar).
The primary observation this season was the compound effect of a biochar application in its second season, likely resulting from improved nutrient retention and overall soil health (microbial activity, water infiltration, aeration, etc). The average impact of 400KG/Acre, 2000KG/Acre, and 6000KG/Acre biochar applications versus the control more than doubled in their second season, and in some cases more than tripled, as compared to the first season (11%, 31%, and 54% versus 40%, 95%, and 140% respectively).
These results aren’t limited to our test plots; customers from all over western Kenya are reporting substantial yield improvements and reductions in dependency on inorganic fertilizer.
Every kiln sold is another step toward carbon negative food security for the region and every season provides further proof of biochar’s impact on farmer livelihoods and long term soil health.