ICARDA
Question
Asked 2nd Jun, 2015
How do I determine field capacity?
I would like to do pot experiment on irrigation interval on growth and yield of rice. Treatments are continuous flooding, irrigation at field capacity, 90% field capacity and 80 % field capacity. I need to determine field capacity, 90% FC, 80% FC for irrigation.
Most recent answer
Preliminary Steps
- Soil Analysis: Start with an analysis of the soil in which you plan to grow the rice. This will help you understand its texture, which directly impacts its water-holding capacity.
- Calibration: Calibrate your irrigation system to know exactly how much water is applied in a given time period. This will help you standardize treatments.
- Initial Saturation: Initially, saturate the soil in the pots and then allow drainage to achieve natural field capacity.
Determining Field Capacity
- Water Saturation: Saturate the soil in the pot until it reaches its water-holding capacity. Make sure there is free drainage from the bottom.
- Drainage Time: Let the soil drain freely until no more water drains from the pot. Usually, this might take 24-48 hours depending on the soil type.
- Soil Weight: After the drainage time, weigh the pot to determine the weight of the soil at field capacity.
- Calculation: Use the weight of the soil at field capacity minus the dry weight of the soil to calculate the amount of water it holds at field capacity.
Calculating 90% and 80% Field Capacity
Once you have determined the field capacity (FC) of the soil, calculating 90% and 80% FC is straightforward.
- 90% FC: Multiply the weight of water at field capacity by 0.9.9090
- 80% FC: Multiply the weight of water at field capacity by 0.8.8080
Implementing Treatments
- Continuous Flooding: Keep the soil submerged under a few centimeters of water throughout the experiment.
- Field Capacity: Irrigate the pot back to the calculated field capacity weight whenever the soil dries out.
- 90% FC: Irrigate the pot back to 90% of the calculated field capacity weight when the soil moisture reaches this level.
- 80% FC: Irrigate the pot back to 80% of the calculated field capacity weight when the soil moisture reaches this level.
3 Recommendations
Popular answers (1)
University of Udine
1) fill a bare soil area with excess water inducing drainage.
2) cover the wet soil with a plastic cover
3) wait about 2-3 days
4) collect a soil sample
5) weigh moist soil, dry in a oven at 105°C till to constant; weigh (after about 24 hours) and weigh the dry soil.
6) Calculate moisture at field capacity
17 Recommendations
All Answers (11)
Huazhong Agricultural University
you can find the solution at here: http://www.agvise.com/educational-articles/water-holding-capacity/
best
Hi Thant Wai
I believe that you should use tensiometers
You should discuss this with soil physics scientists in you University.
Kind regards
1 Recommendation
King Saud University
In addition to the methods mentioned by the colleagues above, you can estimate the field capacity from the published data according to the soil texture.
I have summarized the data of three good references in the following table.
6 Recommendations
University of Udine
1) fill a bare soil area with excess water inducing drainage.
2) cover the wet soil with a plastic cover
3) wait about 2-3 days
4) collect a soil sample
5) weigh moist soil, dry in a oven at 105°C till to constant; weigh (after about 24 hours) and weigh the dry soil.
6) Calculate moisture at field capacity
17 Recommendations
Navsari Agricultural University
Hi Thant Wai
All the above researchers suggest appropriate methods for FC determination depending on the facility/experience available. Field method as suggested by Francesco Danuso is more appropriate for undisturbed soils under field condition. However, in pot trial, you will also determine the FC of disturbed soil as follows.
Take a pot that you will use in experiment. Cover surfaces of pot by thin plastic film with proving several holes at bottom of pot to drain free water (soil particles must not remove with drain water). Take a known quantity of soil in pot. Saturate the pot soil for several hours with excess water (hence, all micro pores will filled up by water) and cover the top of pot to avoid evaporation. When the gravitational water will seizes (probable overnight), weigh net weight of moist soil. Calculate the amount of water held by soil i.e. 100 % FC. Subsequent calculate Water held at 80 and 90 % of FC. Further, looking your treatment, you might miss MWHC treatment in-between continuous flooding and 100 % FC.
4 Recommendations
G. B. Pant University of Agriculture and Technology, Pantnagar
Dear Sir,
The field capacity of soil can also be determined easily with the help of time domain reflectometer (TDR). For this, the soil in the pot is saturated with water in such a manner that excess water is drained out from the bottom holes of pot. The pot is covered with plastic sheet for 2 days to prevent evaporation and to allow downward redistribution of water. The TDR probes are then inserted vertically from the soil surface to determine field capacity.
Best regards
10 Recommendations
School of Agriculture; The PNG University of Technology; Papua New Guinea
We put a small amount of soil in a small pot, flood the soil and allow it to drain overnight or for a few days, then take the wet weight. The same sample is oven-dried and uses these data to calculate field capacity. For those in the pots, using this information, set to 100 FC, and rest are maintained based on the weight basis, following dry down. After that, just add water to maintain the desired FC.
Michael, P. S., Fitzpatrick, W. R. and Reid, J. R. (2017)*. Effects of live wetland plant macrophytes on acidification, redox potential and sulfate content in acid sulphate soils. Soil Use and Management 33, 471-481
4 Recommendations
ICARDA
Preliminary Steps
- Soil Analysis: Start with an analysis of the soil in which you plan to grow the rice. This will help you understand its texture, which directly impacts its water-holding capacity.
- Calibration: Calibrate your irrigation system to know exactly how much water is applied in a given time period. This will help you standardize treatments.
- Initial Saturation: Initially, saturate the soil in the pots and then allow drainage to achieve natural field capacity.
Determining Field Capacity
- Water Saturation: Saturate the soil in the pot until it reaches its water-holding capacity. Make sure there is free drainage from the bottom.
- Drainage Time: Let the soil drain freely until no more water drains from the pot. Usually, this might take 24-48 hours depending on the soil type.
- Soil Weight: After the drainage time, weigh the pot to determine the weight of the soil at field capacity.
- Calculation: Use the weight of the soil at field capacity minus the dry weight of the soil to calculate the amount of water it holds at field capacity.
Calculating 90% and 80% Field Capacity
Once you have determined the field capacity (FC) of the soil, calculating 90% and 80% FC is straightforward.
- 90% FC: Multiply the weight of water at field capacity by 0.9.9090
- 80% FC: Multiply the weight of water at field capacity by 0.8.8080
Implementing Treatments
- Continuous Flooding: Keep the soil submerged under a few centimeters of water throughout the experiment.
- Field Capacity: Irrigate the pot back to the calculated field capacity weight whenever the soil dries out.
- 90% FC: Irrigate the pot back to 90% of the calculated field capacity weight when the soil moisture reaches this level.
- 80% FC: Irrigate the pot back to 80% of the calculated field capacity weight when the soil moisture reaches this level.
3 Recommendations
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