Problem Set #2 Questions

Here you can post questions about Problem Set #2.

Question 1 part b asks for the water potential gradient between the two depths. I got a negative number for this and I am not sure if this is correct. Since water always moves from high potential to low potential, is the potential gradient supposed to be positive all the time? Thank you!

There is nothing wrong with total water potential being negative. It

For the 3rd question, is it asking us to find the gravimetric water content and volumetric water content of the moist soil or the oven dried soil?

For gravimetric water content you need to know mass of oven dry soil Volumetric water content you need to know volume of water & total volume of soil

Q.For question 3c, do I need to calculate the bulk density or just estimate to 2.65? Since in 3b, the soil is unsaturated, so the density maybe different.

A. You should assume particle density of 2.65 g/cm3 (and this is particle density, not bulk density). Particle density is NOT affected by the water content.

Q. re. question 4b, I don't really know the soil condition of BC forest, is that just because there is too much rain, so the Al ions are washed away, so it's less acidic? Or anything else?

A. Pls refer back to the lecture slide (shown on Friday Feb 7)showing the most common ranges of pH values in soils in humid & arid regions. I went over this explanation in the class and there is similar explanation in the textbook from where that slide was taken. Hint - coastal BC has a humid climate and Al is not as easily washed out of the soil as some other ions (e.g. Ca, and Mg).