Search This Blog


Saturday, January 23, 2010

Soil Chemistry Cookbook

Soil chemistry is the same as cooking. Both use ingredients to get an end result. As a keen pantry chef and soil scientist, I only just noticed. 

Baking a cake is the same as determining the amount of ammonium-nitrogen in soil. When we bake a cake, we gather all our ingredients, certain quantities of each. We then follow some instructions on how to combine the ingredients  and cook them to  ensure that we do it just right, for that perfect cake. If the amount of ingredients, combination or cooking is slightly wrong, we may end up with a cake that falls apart, tastes funny, is burnt, no risen or any other combinations of failure.

Similarly we follow instructions or methods measuring nutrients in the soil or result in similar failures. When we measure the amount of ammonium-nitrogen in soil, we have a list of ingredients or chemicals that we use for determination. We use in a particular quantity of each chemical. We then follow a method for the use of chemicals. For ammonium-nitrogen, we first do an extraction. An extraction is the use of a salt or water with soil to remove the nutrients we are interested in measuring. This extract is then combined with reagents; chemicals which react with the ammonium-nitrogen to produce a colour. This colour can then be measured using a spectrophotometer, which measures different absorbency of light waves.  If one step is missed or not precise, then you can result in an incorrectly measured ammonium-nitrogen, or even worse, a failed batch that can not be measured.

Just like cooking, a failed soil test can be recovered. If we have a failed cake, it is never the end of the world. We can either recreate the cake, and carefully follow the instructions or work out if the recipe is correct and if we need more eggs or flour etc. We can also use some failed cakes in other recipes. For example, a failed cake can be used in tiramisu or triffle

Over the last few months, I have had more than my share of failures in the lab that I have had to 'recover'. Ammonium-nitrogen is one memorable failure. I followed the method precisely. I took some of my soil, extracted it using a salt solution, and then added the reagents to produce colour that I could then measure. However, each time I did this I got white clouds in my solutions. This means I am unable to measure my soil. Where did I go wrong? What part of the method did I not follow? 

Failed Ammonium-Nitrogen: First, third and fourth from left with white clouds, and the second is normal.

Adding too much of one ingredient may result in a different outcome. If you add too much flour to a cake recipe, you may end up with a dry, hard cake. If you add too much milk, it will be too wet and won't bake properly. It is a matter of adjusting the recipe to get it to work correctly: add less flour or less milk. In the case of the ammonium-nitrogen, I knew that I also had to make some adjustments to the method to get it to work correctly.

Calcium-Sulphate, also known as gypsum, has a small solubility tolerance. That means, it is only soluble under particular conditions. If those conditions change, then it becomes insoluble and may be noticed as white clouds in a solution. Therefore, the white clouds in my solution was likely to be calcium-sulphate. What do I need to change to get rid of the white clouds? 

We need to understand what makes calcium-sulphate insoluble, and then how to change the method to keep it soluble. Three factors affect calcium-sulphate solubility: temperature, pH and salts. At 26 degrees Celsius or greater, it starts to become less soluble. When the pH becomes very alkaline (greater than pH 7), it also becomes less soluble. And, with lots of salts in solution, it becomes less soluble. 

I firstly tested temperature. When we add the reagents to the ammonium-nitrogen extracts, we have to do it at 36 degrees Celcius. I changed the temperature and tested at 2, 25 and 30 degrees. The white clouds still formed. We also tested the pH in all of the solutions (photographed above), they all had a pH of 12. This is necessary for the colour to develop. So, we know that changing the temperature and the pH is not possible to stop the white clouds forming. 

When you extract the ammonium-nitrogen, you do it with a salt solution. However, my soils are already filled with salt! Therefore, with the salt in my soil, plus the salt in the extract, I had increased the salt content so much that I reduced the solubility of calcium-sulphate so that it formed white clouds. How do I reduce the salt content to stop the white clouds? DILUTE! 

Ammonia-Nitrogen Win: Diluted extracts + reagents

I had to add one more step to my method. Instead of using my extract with reagents, I had to use some of my extract with water and then add reagents. This would dilute the solution, reduce the salt content and stop the white cloud in my solution.  Success.

So cooking is really just the same as soil chemistry. Both have a list of ingredients and instructions you have to follow. Both can fail if you do something wrong. And you can troubleshoot both to get the outcome you want! 

Monday, January 4, 2010


I just did a quick search for soil science blogs. Only one came up in my search. This only reminded me that in current science, soil is often forgotten about, and less than sexy. Student numbers are dwindling as catch-phrases such as 'climate change' and 'food and shortages' are thrown about. Realistically, soil science are still parts of these problems. Caring for our soil = good food, clean water and plenty of Carbon sequestration. How do we get students back in the field and playing with mud?

A few of us soilies (as we like to call ourselves) were joking in the lab about a pin-up calender for soil science. Girls in lab coats and heels, hair blowing in the wind. Men would be digging holes, bare chested, sweat dripping over their ripped torso. In reality, it is more likely that the girls will be in ripped, acid-soaked, red stained jeans with an equally revolting t-shirt, and the men will be 50 years +. Is it the image of soil science that is causing the problem? What is the image of (soil) science to youth?

We forget that (soil) science is not glamorous. Once upon a time, science was an elite field. Good money, well respected, could go into space, hot chicks etc etc. Today, science is that boring stuff about numbers and shite. Modern youth feed on excitement and 'radness'. By being keen on something, they need to know that they will have the opportunity to show their 'awesomeness' and be working on an important cause (like climate change). Is soil science rad? When we look up soil science up on the inertnet, what does it show us?

Interesting and 'sexy' soil science is difficult to find on the internet. There is plenty of information on soil science. Terms, what it is, wiki, associations, boring stuff etc. All the numbers and dots that young people don't care about. They want to know how many chicks it will score them, what the pay brackets are, how it will save the world and that they can do it all in time for an episode of Scrubs. What makes soil science interesting? Searching for 'interesting soil science' through Google only gave me similar results. This was clearly demonstrated by the lack of blogs. Further reinforced by no chat rooms. No campaigns. No hot chicks in lab coats.

Soil science is dead to modern youth and regaining its existence means making it more appealing for this generation. For modern youth if it ain't on the web, or all over the media, who the frak has heard of it anyway? And why should they waste their time thinking or talking about it with friends? Clearly it isn't cool enough if it isn't on the internet or being blasted all over TV. What youth learn on the internet will shape who they are. Young people have a strong affinity with the internet, and are more likely to Google than pick up a book. In an article by Mechthild Maczewski, it was suggested that the internet is also a means of indentifing ones self. So, if we provide information in an interesting manner, shouldn't this improve our chances at making soil science look more appealing?

In a half-humourous manner, I suggested a 'hot-new-look' and getting some 'sex-appeal' for soil science at an annual meeting. Part of this would be making soil science more readily available on the internet in different forums and formats. Myself being the youngest in the room (by at least 20 years) got glared at for 2 seconds, and the topic changed. One part of the problem is the aging population of soil scientists and their lack of understanding of both the younger generations and technology. We are now faced with techno-youth who care about how awesome something is, and scientists that do not know how to use the internetwhatsit.

Modern youth and modern technology need to be considered in adressing the lack of (soil) science students. Brainwashing them using carefully created internet sources and getting them to realise how awesome (soil) science is through media is quite possibly one of the only ways in succeeding to gain more students and interest. Eliza Dresang suggests the need to harness the internet for such a use. Blogs = one way of making soil science more appealing and sexy to modern-techno, internet-feeding frenzy generations. Let this be the start!