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Reducing bulk density with biochar

4. 6. 2024

Reducing bulk density with biochar

MASH Biochar Graph

Graph: As seen in the graph above, the bulk density decreases as more biochar is added to the soil. The experimental value is shown here against standard value, a benchmark figure derived from established literature. The projected value is a theoretical result calculated using models and simulations.


A recent microanalysis showed that MASH Makes biochar can greatly benefit soil health and agricultural productivity – especially when it comes to bulk density.

What does that mean for farmers and the crops they produce? First, let’s start with the basics of what biochar is and how it can improve soil. 

What is biochar?
Biochar is a charcoal-like material that we produce from agricultural residues through a thermochemical process called pyrolysis, which involves heating the material without oxygen. Biochar is porous, meaning that it has a lot of microscopic holes that allow it to hold on to moisture and nutrients for plants. 

What is bulk density?
Bulk density is a measure of how compact the soil is, and it is measured by how much it weighs in a given space (g/cm³). Lower bulk density means more space for air and water to move, allowing roots to grow better and deeper and overall healthier plants. For farmers, managing bulk density is crucial, since it directly affects crop yields and soil health.


The analysis

To test how MASH Makes biochar affects bulk density, we conducted an experiment at our research centre in Mumbai. The procedure for measuring biochar bulk density involved compacting the soil by tapping it four times, with each tap lasting 30 seconds, resulting in a total duration of two minutes. Our results showed that bulk density decreased as biochar was put into the soil, with especially positive results when 10% of biochar is added (See graph below). 

Why? Because biochar is lighter than soil, mixing it in makes the soil less dense. This is especially noticeable when the weights of biochar and soil differ significantly. Biochar also helps soil particles stick together better, creating more space for air, water, and nutrients.


Key findings of the analysis 

This discovery is important because adding biochar helps prevent soil from getting too compact, improving its structure. Soil with biochar doesn't compact as easily and stays lighter.  Biochar is lighter than soil, which helps keep the soil from getting too dense. This is especially true for clay soils, where there aren’t many spaces for air and water. As a result, biochar helps keep the soil loose, which is good for holding water and nutrients. Adding 10% biochar reduced the soil density to below 1.1 g/cm³ (as stated by NRCS USDA), which is perfect for plant roots to grow.

Can these results be reproduced on any farm?

From these results, it’s clear that MASH Makes biochar can have a positive effect on bulk density in soil. But it’s important to note that our experiment is valid under specific conditions. 

The technical details

  • Soil Type: Our analysis was done on clay soil with particle sizes typically between 1 to 3 mm.
  • Biochar Particle Size: More than 90% of particles were between 1 mm and 3 mm.
  • Soil Condition: The soil was kept for no more than 15 days before the experiment. 
  • Moisture content: Soil moisture content was  10-12% at the time of experiment, and the experiment was conducted at room temperature. 

It’s important to note that our findings are based on short-term experiments that were done under specific conditions. One limitation is that we did not investigate the pore space of biochar, which is important for determining if the pores stay empty. 

We used standard protocols from the Indian Fertilizer Control Order of 1985 for our experiments. These values should be reliable, but the effect on soil bulk density might change with different soil types. Results could vary for sandy soil or smaller-sized biochar, for example.

Overall, though, our analysis shows that incorporating biochar into soil can significantly reduce bulk density, enhance soil structure, and promote healthier plant growth. While these insights are definitely promising, we must research further to explore the long-term effects and applicability across various soil types. 


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