i am working on drought stress but i have some problem that how to measure the 40 to 50 % moisture content in pots.
Hi,
If you know the water holding capacity of the soil used, i.e. how much water it can hold at saturation (w/w); then you can water pots to a desired % (40 or 50%) in reference to soil in the pots (weight basis). There will be a problem when plants gain biomass, which could add up to pot weights that you should compensate for. Hope it helps.
Dear Shakeel,
For Measuring soil moisture, you can use the TDR tools to measure. However, if you want to keep the water at the 50%, I think it would be great if you can determined the period for each of your treatment. For instance, in my work I defined my treatments as follows;
100% AW means 80%-100%
80% AW means 60% - 80%
60% AW means 40%-60%
40% AW means 20%-40%
so it is better to defined your treatment as a period such as 50% as 40% -50% because the soil moisture has a numerous fluctuations and it is out of the hand to keep at the same amount of water each time.
I hope that I can answer your question if not, please let me know,
Mohsen
Maintaining the weight of the pots at a desired value, coinciding with the value of 50% of field capacity might work. However, keeping the weight at a constant value implies a great dedication in time and care. Morover, you need to check the water potential reached at this weight... It will be different in different soil composition.
Hi
The above mentioned suggestions were excellent and the other one is using lysimeter method. Once you have your FC moisture content, you can dedicate some pots aside, some with the experimental plants and some with just the growing medium. By so doing you can easily determine how much evaporation and evapoutranspiration has taken effect in your experiment and then you can supplement the amounts to your treatments.
Hi,
The use of soil moisture sensors with closed-loop irrigation control can be employed to maintain moisture levels in a wide range of soils and substrates. The attached might be of interest where substrate moisture control has enabled water-use to be linked to environmental drivers such as VPD and solar radiation. If substrate water status is tightly controlled, water or environmental stresses can be observed when the relationship between water-use and an environmental driver breaks down.
I hope this is of interest.
Best regards,
Martin
Due to the fact that the conditions of the pot and lysimeter vary with the conditions of the farm, it is better to use the term pot capacity (PC) instead of the field capacity (FC). In measuring the humidity inside the pot or lysimeter, it is the best method to give us accurate information on the distribution of moisture inside the pot. First we need to weigh the pot with dry soil and then give the pot a little water to drain. Then, after finishing the drain, weigh the pot to determine the amount of water inside the soil (pot capacity). In this case, the soil is in a pot capacity, and other percentages of moisture can be calculated and applied to the desired treatment, for example, 40, 50 or 70 percent. During these steps, the surface of the soil should be worn to prevent evaporation. If the pot is large, it can be calibrated TDR and further used. During the growth stages, the weight of the biomass should be considered.
If you want to have only soil for your experiment with no adddition of any external soil moisture facilitator follow this You could harvest 2-3 plants to determine the plant biomass and correct for it the amount of water you would need to add to end up with the desired soil water content Weigh each pot once a week to measure evaporation and add evaporated water.Use a relation between plant height and plant weight to calculate the extra amount of water to add. Nowadays certain modelling softwares are available as well. otherwise there are certain materials which when added to soil prolong their Water holding capacity
Due to the fact that the conditions of the pot and lysimeter vary with the conditions of the farm, it is better to use the term pot capacity (PC) instead of the field capacity (FC). In measuring the humidity inside the pot or lysimeter, it is the best method to give us accurate information on the distribution of moisture inside the pot. First we need to weigh the pot with dry soil and then give the pot a little water to drain. Then, after finishing the drain, weigh the pot to determine the amount of water inside the soil (pot capacity). In this case, the soil is in a pot capacity, and other percentages of moisture can be calculated and applied to the desired treatment, for example, 40, 50 or 70 percent. During these steps, the surface of the soil should be worn to prevent evaporation. If the pot is large, it can be calibrated TDR and further used. During the growth stages, the weight of the biomass should be considered.
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