Cameroon trial data show strong improvement in maize yield - summary report
Kumba, Cameroon, September 10, 2009 -
Since December 2008, more than 1500 subsistence farmers in Cameroon's South-West Region (SWR) have been participating in the largest-ever field trial testing the effects of biochar on crop productivity. The first results of this ongoing experiment, based on maize planted in a large series of plots, are now available. The data can be described as 'remarkable', in that they demonstrate how biochar consistently helps to boost crop productivity in tropical soils, sometimes in a spectacular manner.
The preliminary results suggest that biochar may offer a solution to hunger and food insecurity amongst the world's poorest, as well as to soil depletion and tropical deforestation.
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Results
Out of 75 test plots, 41 yielded complete data on biomass development, whereas 37 offer complete data on grain yields. 31 data-sets are complete for both biomass and grain yield data. Incomplete data series can be explained by a range of factors: theft of healthy maize cobs is the most common problem, with some groups whose plots were located deep in the forest reporting that all their maize was stolen (because it looked so good, in their own words). Other losses were due to observable bird and pest attacks, and misunderstandings on how to conserve and prepare the maize and the biomass correctly for measurements. Some groups sold or consumed the maize before we could collect data.
Despite these losses, we think the series of data presented here are sufficiently large to draw conclusions on the effectiveness of biochar as an agricultural soil amendment in the tropics, and in particular on maize in relatively infertile soils.
Biomass yield
The relative biomass yield (roots, stems, cobs, maize grain) for all test plots shows that all combinations of soil inputs perform better than the control (general data, figure 1 Biochar food security maize yield terra preta carbon dioxide climate change soil fertility).
The addition of 10 tons of char per hectare (C10) will increase biomass yields by around 40%, which is as much as the addition of either organic or mineral fertilizers (O = 33%, F = 46%). This shows that for the individual farmer, char may function as efficiently fertilizers, even though biochar is not a fertilizer in itself. The addition of char at a higher rate, equivalent to 20 tonnes per hectare, results in an even bigger increase (C20, an increase of 52%).
The combination of organic and mineral fertilizers (OF) greatly increases biomass yield as compared to the control, almost doubling it (a 90% increase). However, when char is added, at either the equivalent of 10 or 20 tons, the effect will be even more outspoken (C10OF = 119%, C20OF = 113%). This demonstrates that char boosts the efficiency with which a soil makes nutrients available to the maize plant.
Interestingly, the combination of C10 with mineral fertilizer (C10F = 84% increase in biomass yield) and the combination of C20 with organic (C20O =74%) or mineral fertilizer (C20F = 94%) alone, results in as high an increase in biomass yields as OF. In practise this means that a farmer has to use only one of either mineral or organic fertilizers and combine it with char (C10F, C20O or C20F), in order to obtain the same effect as the combination of both these expensive soil inputs without char (OF).
When we look at individual test plots (general data, figure 9 Biochar food security maize yield terra preta carbon dioxide climate change soil fertility), we observe that in a small minority of cases (3 out of 41) the addition of any type of soil input will have a negative effect on biomass yields (Takie Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Unity & Progress Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, and Njinjong Biochar food security maize yield terra preta carbon dioxide climate change soil fertility). This may be due to the natural fertility of the soil, with additions of inputs distorting this balance. However, with soil analyses currently in progress, it is too early to discuss these exceptions.
In about five cases the addition of char yields a slightly negative (< 5% decrease) ( (Main dans la Main Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Firm Hand Farmers Biochar food security maize yield terra preta carbon dioxide climate change soil fertility) to a negligible effect (<3% increase or decrease) (Ntukia Women Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Rainbow Farmers Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Juliette Biochar food security maize yield terra preta carbon dioxide climate change soil fertility) on biomass productivity.
On the other end of the scale: in 12 cases the addition of char alone resulted in an increase in biomass productivity larger than 50%. Seven plots showed more than a doubling in biomass yields. In three cases, already identified as plots with poor oxisols (Oben Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Man Must Try Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Mekora Biochar food security maize yield terra preta carbon dioxide climate change soil fertility), the addition of char at a rate of 20 tons per hectare even yielded a 'spectacular' boost in biomass productivity, with an increase bigger than 250%.
Grain yield
The main goal of both the Biochar Fund and Key Farmers Cameroon is the maximization of food production and the reduction of hunger. However, in a scenario in which carbon storage in soils based on the production of biochar obtained from farm residues is rewarded with a form of carbon compensation (carbon credits or other), it is interesting to assess the value of biomass productivity as it relates to grain yield. We will do this, below, by looking at the residue-to-product ratio. But let us first focus on food - the maize.
Data on the relative grain yield for all plots show that, again, the introduction of any type of input yields more grain than plants on the control. Organic (O) and mineral (F) fertilizers increase grain yield by about 60%. The combination of both (OF) roughly doubles output (+94%).
When char alone is added to the soil, at either the equivalent of 10 or 20 tonnes per hectare, grain yields are almost doubled (C10 = +85%; C20 = +89%). This means that char alone performs as well as the combination of organic and mineral fertilizers (OF). Biochar being considerably less expensive than these traditional inputs and yielding potential carbon compensations, the individual farmer may easily choose for the introduction of char to manage his soils and crop productivity.
When char is combined with organic or mineral fertilizers, grain yields get a boost of between 116% (C20F) to 168% (C20OF). This demonstrates again that biochar helps improve the efficiency of nutrient storage and exchanges in the soil. Interestingly, the difference between the combination of char at a low input rate (C10) with other inputs (C10O, C10F) and char at a higher input rate (C20O, C20F) is small. At the C20 rate, mineral fertilizers even seem to perform less strongly on grain yield (C20F = +116%) than when combined with C10 (C10F = +144%). When all inputs are combined, maize grain yields increase by 145% (C10OF) to 168% (C20F). Increasing grain yield by two and a half times is obviously a very attractive prospect for subsistence farmers. Economics however will determine whether these combinations are cost-effective for them.
Looking at individual test plots (general data, figure 10 Biochar food security maize yield terra preta carbon dioxide climate change soil fertility), we can observe great differences in the maize grain yield. In five cases (Yamba Women Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Humble Ladies Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Etoko Women Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Nature is Life Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Agbor Biochar food security maize yield terra preta carbon dioxide climate change soil fertility), the addition of C10 brought about a lower grain yield than the control. In only four cases (Humble Ladies Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Etoko Women Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Unity and Progress Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, and Nature is Life Biochar food security maize yield terra preta carbon dioxide climate change soil fertility) did the introduction of C20 affect grain yield negatively. In two cases (Rainbow Farmers Biochar food security maize yield terra preta carbon dioxide climate change soil fertility, Ayuk Biochar food security maize yield terra preta carbon dioxide climate change soil fertility), the addition of biochar (either C10 or C20) had no effect whatsoever. In all the other test fields, char helped improve grain yields.
In fifteen cases, the utilization of biochar alone, at a rate of ten tons per hectare (C10), showed an increase of more than 50%. In eight of these, grain yields were more than doubled because of C10. Extreme results on the C10 sub-plots: +211% (Mekora Biochar food security maize yield terra preta carbon dioxide climate change soil fertility), +240% (Tecla Biochar food security maize yield terra preta carbon dioxide climate change soil fertility), +300% (Bih Biochar food security maize yield terra preta carbon dioxide climate change soil fertility), +360% (Bate - to be uploaded) and +400% (Kofapru Biochar food security maize yield terra preta carbon dioxide climate change soil fertility).
With char added at 20MT/ha, we see a (more than) doubling in grain yield in eight cases. Extreme results were obtained at the plots of Antaze Dynamic Biochar food security maize yield terra preta carbon dioxide climate change soil fertility (+249%), Kofapru Biochar food security maize yield terra preta carbon dioxide climate change soil fertility (+300%), Mekora Biochar food security maize yield terra preta carbon dioxide climate change soil fertility (+288%), Bate (+360% - to be uploaded), and Oben Biochar food security maize yield terra preta carbon dioxide climate change soil fertility (+675%).
Figure 6 Biochar food security maize yield terra preta carbon dioxide climate change soil fertility in the general data page shows the absolute grain yield for all plots in the experiment. Currently, the subsistence farmers who participate in the trial produce less than 1,7 tons of maize per hectare on average. This can be considered to be a low yield. When post-harvest losses are considered, the final yield may be below 1,5 tons (compare this with maize yields in the EU or the US, which are between 7 and 9 MT/ha). With the addition of soil inputs, the picture changes. The farmer will be able to produce one ton more food per hectare, by adding either a combination of non-char inputs (OF) or biochar alone. Grain output can be doubled when organic and mineral fertilizers are combined with char.
In conclusion: biochar may help farmers boost the grain yield of maize, particularly when combined with other inputs. In some notoriously poor soils, charcoal will greatly help retain nutrients and keep them available for the crop. In the tropical soils and under the specific agro-ecological conditions encountered in this experiment, biochar functions as effectively in the soil as more traditional inputs such as organic and mineral fertilizers. This means a farmer can grow more food, without introducing chemical fertilizers. A future of improved food security based on organic soil management thus becomes possible.
Biochar Fund - fighting hunger, deforestation, energy insecurity and climate change - Biochar works: Cameroon trial data show strong improvement in maize yield
