Hi, I am doing soil water-filled pore space (WFPS). I don't know why researchers tend to make soil bulk density at 1.1 g/cm3 during the test? Besides, what factors will affect the results of WFPS? Is WFPS the constant for a specific soil?
Thank you very much.
How to establish comparable soil moisture conditions in incubation studies is a challenging topic. I'm aware of three main approaches (which have been used for disturbed and undisturbed samples):
1) By far the most favourite method among soil microbiologists is to use a fixed percentage of the water holding capacity. The main appeal of this method is its simplicity. Measuring water holding capacity is fast, cheap and easy (see numerous textbooks). However, from soil physics we know that this method clearly is not appropriate to standardize over different soils.
2) Especially if the research topic strongly depends on gas exchange, a percentage of WFPS is often used. There has been some success to explain nitrous oxide emission, i.e., moisture optima of nitrification and denitrification, with WFPS.
3) Especially if the incubation system offers the possibility to adjust water tension using this as a way to standardize moisture conditions seems logical. However, one needs to be aware that this is still a gross state variable as Fulvio has pointed out. Furthermore, measuring water-retention curves (in case you are not able to adjust it in your microcosms) is not easy and can take a long time (especially for clay soils).
Recommended reading:
Cook, F.J., Orchard, V.A., 2008. Relationships between soil respiration and soil moisture. Soil Biol. Biochem. 40(5), 1013-1018.
Thank you @Fulvio M. Rivano.I want to give soil 60% WFPS, so firstly I need to know the WFPS. What I am confused is whether WFPS is not a constant coefficient for a specific soil. If WFPS is only an expression for volumetric soil water content, then what's the difference from the gravimetric water?
Article Microbial activity in response to water-filled pore space of...
How to establish comparable soil moisture conditions in incubation studies is a challenging topic. I'm aware of three main approaches (which have been used for disturbed and undisturbed samples):
1) By far the most favourite method among soil microbiologists is to use a fixed percentage of the water holding capacity. The main appeal of this method is its simplicity. Measuring water holding capacity is fast, cheap and easy (see numerous textbooks). However, from soil physics we know that this method clearly is not appropriate to standardize over different soils.
2) Especially if the research topic strongly depends on gas exchange, a percentage of WFPS is often used. There has been some success to explain nitrous oxide emission, i.e., moisture optima of nitrification and denitrification, with WFPS.
3) Especially if the incubation system offers the possibility to adjust water tension using this as a way to standardize moisture conditions seems logical. However, one needs to be aware that this is still a gross state variable as Fulvio has pointed out. Furthermore, measuring water-retention curves (in case you are not able to adjust it in your microcosms) is not easy and can take a long time (especially for clay soils).
Recommended reading:
Cook, F.J., Orchard, V.A., 2008. Relationships between soil respiration and soil moisture. Soil Biol. Biochem. 40(5), 1013-1018.
Dear Xin,
I hope all is well with you.
As you mentioned, Water-filled pore space (WFPS, %) was calculated according to the following relationship, 100× (gravimetric moisture content× soil bulk density)/ total soil porosity;
where total soil porosity= 1- (soil bulk density/soil particle density).
Well, you can find the parameters you need to regulate.
Best wishes,
Ping
Dear Ping,
Thank you for your help. I am fine. How are you?
Your paper do me a great favor. Probably the problem is the soils which are sieved, so I don't know the bulk density. If I hypothesize the bulk density is 1.1 g/cm3 , and I can test the gravimetric water content. Thus calculate the WFPS by the formula. Is this practical?
Best regards
Xin
Shu, since you don't seem to know that: If you've sieved the soil, you should establish a defined bulk density when filling it into you incubation device. Usually, one would adjust to some approximate of the field bulk density. For this you'd mark a desired volume on your incubation devise, sub-divide it into, e.g., 4 layers, fill the corresponding (dry) soil mass in each layer and compact it to the desired subvolume. In the end this should result in a somewhat homogeneous bulk density.
Hi Roland, your suggestion is working. Thank you. By the way, I am doing the calculation, but a little confusion. If the WFPS I have is 0.70 m3/m3, and the soil water content is 0.4 g/g dry soil. I want to incubate the soil at 60% WFPS, so how much water should I add in 100 g fresh soil? Thank you.
Dear All,
I am still a little confused about the calculation. For example, the bulk density of a soil is 1.1. g / cm3, and water content is 0.2 g / g dry soil, so at present it's WFPS is 38%. If we want to make the WFPS to 60%, then we need to add water into it. But how to add the water? Most people prefer adding water to the air dried soil. If soil is air dried, and then add the water into it, do you think the soil is stressed by dry-rewetting? Do you think this will affect the microbial activity? Probably some microorganism will die because of the desiccation. Can we add the water into the fresh soil? Therefore, I am wondering how to calculate the addition of water. If you can give me a hand, that would be appreciated.
Cheers.
Xin
Article Response of ammonia oxidizing archaea and bacteria to changi...
- Badges
- Science topic
- Similar topics
- Agriculture
- Soil Science