Archive for December, 2010

Quantifying biochar impact on soil

December 3, 2010

Discussions with IRRI gave some simple assumptions which can be used when assessing the impact of biochar addition on the soil.

If biochar analysis is available, then the impact of a known volume of biochar to soil can be calculated. For example, if one square metre of soil is amended with 4 kg of biochar (this is a 40 t/ha application rate), then we can assume that this represents 4% of the soil weight. This is because in 1 m at a 10 cm depth there is 100 litres of soil with an approximate bulk density of 1, which is 100 kg of soil. The properties of the biochar can then be assumed to be diluted in the soil at a 4% rate.

This assumption was then applied to the CEC (Cation Exchange Capacity) where rice husk biochar is added to the research farm soil in Siem Reap, Cambodia.
The soil has a CEC of 18.44 cmol+/kg
Biochar has a CEC of 44.5 cmol+/kg.

Therefore the CEC of the soil can be assumed to be raised to (18.44*0.96)+(44.51*0.04) = 19.48

This is a rough assumption, and should not substitute using actual data, and it assumes that there are no interactions between the soil and the biochar which could influence the CEC of the soil.

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End of project meeting, Cambodia

December 2, 2010

Although this won’t be the end of blog posts yet, we held the end of project meeting in Siem Reap 26-27.11.2010.

The aim of this meeting was to put together the end of project document, to discuss findings, and identify further areas for research. The partners from all participating countries attended: ARTI (India), IRRI (Philippines) and University of Edinburgh (representing Cambodia).

The meeting was productive, and some interesting discussions occurred, and a focused assessment of future research requirements was discussed. Particular issues where more work is required include:
– Methane emission measurements from alternative feedstock use (including degradation in the rice husk heap)
– Long term measurements on managed biochar field trial plots
– Introduction of high value cash crops (including soy beans and peanuts) into biochar trials
– Investigation into the economics of feedstock prices – for example the potential for a more developed market in rice husk following successful deployment of gasification units
– More work on the potential of biochar production from rice straw (there is relatively more work on rice husk biochar).

We are actively seeking funding to ensure that biochar research is comprehensive in that covers all potentially useful functions of biochar, and also is able to answer some of the unknowns in order to reduce risk of biochar application and production.

ARTI assist with rice harvest 25.11.2010

December 1, 2010

Dr Karve and Mr Prabunhe from ARTI (Appropriate Rural Technology Institute – India) assisted with harvesting the rice on the last of the trial plots in Chireve Commune, near Siem Reap town. The same trial design, and same treatments was used as the Nagathom farmers, and this farmer also used the same variety of seed – one of the reasons for selecting this farmer. This farm was planted over a month later however than the Nagathom farmers, and yields were significantly lower an average yield of 0.32 t/ha of paddy and 0.71 t/ha of rice straw. There was some rat damage reported by the farmer, and the height of the rice was noticeably lower (which also made it easier to harvest!). The picture shows the string which is measured to include only the part of the plot which is to be harvested for the data collection. The farmer can then harvest the remaining rice in the field – we compensate farmers for this inconvenience.

Harvesting in Chireve - within the plot boundaries. Photo by Mr Prabhune.

Some useful comments were made by the ARTI team, who suggested that simple management changes could lead to higher yields. The main comment, was that the rice was harvested early, and another 15 days would likely see higher yields. However the farmer may have been reluctant to do this since surrounding farmers were harvesting and leaving the rice in the field would lead to it being susceptible to further damage from pests. The method of threshing was also discussed. The farmers use a traditional method when the rice is wet – using their feet to pound the rice straw to break off the paddy. This led to some of the paddy being still left on the straw – which is subsequently used as fodder so not wasted, but does mean that the potential revenue for the harvest or amount for human consumption is reduced. When the rice straw and paddy is drier, it is beaten with a stick to remove the paddy which may be more effective.

Threshing rice, Chireve 25.11.2010. Photo by P. Karve.

Rice harvest 20.11.2010

December 1, 2010

Rice was harvested on two Nagathom outgrower farmers, who grow Phka Rumduol rice variety. These farmers were in Sasadom Commune which is near the Nagahtom rice mill. The variety is an improved seed, and is provided by the Nagathom Fund. Having an improved variety is useful for the trials since it is more consistent than local saved seed. The harvests across all the plots (3 replicates in each treatment – biochar 41.1 t/ha and control with no biochar), gave an average yield of 2.03 t ha of paddy and 2.42 t/ha of rice straw. In all cases the average was higher in the biochar amended plots – the results will be available in the project report which will be available early next year.

Rice harvest Nagathom farm 2. 20.11.2010. Photo by Mr Tan.