If you live anywhere east of Montana you know that two-thirds of the country has been roasting under record heat for the past few weeks. While the weather has been a bane to farmers and many others, it has provided us with an ideal set of conditions to begin to look at the responses in the SoMeDedTREES project.
To recap, we installed two experiments with 25-gallon container-grown ‘Bloodgood’ planetrees. In both experiments we applied one of three treatments to the root systems at planting: 1) “Shaved” the outer portion of the root system to remove circling roots, 2) “Teased” apart the outer portion of the rootball to remove circling roots and 3) “Control” where we did nothing to the root system, or “Pop and drop” to use Linda’s terminology. One set of 48 trees was planted at the MSU Beaumont Nursery where half the trees were fertilized (400 g of Osmocote 15-9-12) and half were not. The second set of trees was installed at the MSU Hort Farm. At this site I made an executive decision to change the Fertilizer treatment to a Mulch comparison based on our discussions related to a recent study that suggested mulching does not actually reduce evaporation or improve soil moisture. We applied 3” of ground red pine bark in a ring approximately 40” in diameter around each tree in the “Mulch” treatment and left the other half of the trees with bare ground.
Overview of SoMeDedTREEs site at MSU Hort farm
If I had a hammer… Summer Intern Aniko Gaal demonstrates proper form for installing TDR rods in clay soil (also works for relieving frustrations with your choice of summer employment).
Obviously this is a long-term study and we’re a long ways from any definitive results – especially with regard to the impact of the root treatments on eventual root structure – but the point of this exercise is to allow GP blog readers to come along for the ride and get a glimpse of what goes into our research. For the mulch study one of our primary objectives is to track changes in soil moisture and tree stress associated with mulching. In order to monitor soil moisture we are using a technique called Time Domain Reflectometry or TDR for short. A TDR system is basically a glorified coaxial cable tester. The system sends out an electrical pulse to a set of metal rods that are buried in the soil and then measures the return signal. The greater the moisture in the soil, the longer it takes for the signal to return. The instrument converts this information into volumetric soil moisture (% volume water/volume soil). For this study we installed rods at two depths 15 cm (6”) and 45 (18”). Rods were installed 12” from the trunk of the tree at the edge of the root ball (inside) and 24” from the trunk of the tree (outside).
Volumetric soil moisture at 15 cm and 45 cm depth of planetrees with and without mulch at MSU Hort farm, Summer 2012.
We planted the trees in mid-May and watered them from a portable water tank once a week until mid-June. Since then we’ve left the trees on their own. So far the trees actually seem to be fairing pretty well given the heat. We have one tree that is beginning to drop a few leaves but most look pretty good. Our soil moisture readings to date are consistent with a couple of related studies that we’ve done that show mulching increases soil moisture. Soil moisture was greater at the 45 cm depth than at 15 cm and the difference between mulch and no mulch was greater at the shallow depth. Still very early, obviously, but we will continue to update – sort of like FOX Radio news: “We report – you decide.”
Interesting stuff — could you throw up some error bars? I’m curious as to whether there’s more variability across the plot or between treatments.
Jeff we did account for some site variation by blocking. The differences are statistically sign. for the 45 cm on the June date. The 15 cm, are more variable as you’d expect but, as we teach our grad students NEVER to say, almost significant…
Could you please add error bars to the graphs?