Hi I have a plant growth experiment in pots whereby the measured gravimetric soil moisture at "pot capacity" is 60%, but the theoretical calculated field capacity from a soil moisture curve is only 26.4% (at 5kpa). Permanent wilting point (gravimentric) is at 14% (1500kpa).
I wish to apply 3 moisture treatments to this experiment, Wet, Moderate and Dry. What gravimetrics should I apply?
I fail to understand, what is this pot capacity of 60%. The available water content of your soil comes out to be 12.4%.Two and half folds of PWP ( 30% soil moisture) moisture of your soil should be considered as wet soil moisture .While 24% as 10 % less than FC soil moistureshould be considered moderate soil moisture and 30% less than FC soil moisture (18- 19% soil moisture) should be dry soil moisture , better PWP soil mosture. Most important at all these three soil moisture levels , plant should be able to display differential growth respinse. Another important issue is how to regulate these three soil moisture levels. Weighed pots procedure could be one practical way or alternatively, standardizing these three soil moisture levels as per daily evaporation rate....
Actual pot capacity is often much greater than theoretically calculated field capacity. To measure pot capacity I saturated the soil in the pot (3 replicates), let stand for 24 hours and weighed. Pot capacity (gravimetric) is weight soil moisture/ weight dry soil equalled 60 percent.
Theoretical field capacity from moisture curve only 26.4 percent. What to do?
Michael, I am really impressed , the way , you are conceptualizing. If I am in your place , I would take up two setup of experiment to see , which concept throws out the better and realistic results . In field , pot like situation never exists , water has three dimensional movement .However , I will restrict myself preferably with FC of your soil which will actually interact with the plants, you grow in these pots...
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