Sonoma Mountain Institute

Our perennial dry grassland community is dominated by Phalaris aquatica (harding grass). Phalaris aquatica has a large biomass creating a thatch layer that can be over six inches deep. The thatch build up inhibits the potential of other species to germinate and become established, leading to a monoculture of grass opposed to a variety of plant species found in a healthy native community.

Dr. Ingham’s hypothesis is thatch buildup in the grasslands is due to low fungal activity.  She believes we can achieve significant to total litter decomposition within a month’s timeframe.

In previous experiments, the biological treatments used had no appreciable effect on either thatch buildup or fungal activity biomass [see grassland experiment, Biology Analysis].  Possible explanations include, 1) fungal foods inadequate, and/or 2) the correct species composition is absent and/or the number of decomposition fungi is not adequate in our previous compost/compost tea.

In this small-scale trail, we will be looking at the effect of compost and compost tea as the biological amendments as treatments for breaking down the thatch layer of Phalaris aquatica and the leaf litter of Coast Live Oak.

Set Up

Phalaris aquatica thatch
Fill 3 bins (24-gallon totes) with 2 inches of grassland soil from the perennial dry community and cover the soil with 4 inches of Phalaris aquatica thatch. The thatch collected was ½ laying on the ground and ½ cut from standing dead plant material

Oak Leaf Litter
Fill 3 bins (24-gallon totes) with 2 inches of soil from the oak woodland and cover the soil with 2 inches of leaf litter.

Treatments
The initial phase of this trail will be a one-time treatment. The final thatch/leaf litter remaining will dictate our next step.
1.    Control Bin – this bin will receive 4 cups of water  (to establish the same amount of added moisture as the Tea Bin)
2.    Tea Bin – this bin will receive 1 cup of compost tea mixed with three cups of water to evenly distribute the tea over the top layer of thatch and leaf litter.
3.    Compost Bin – this bin will receive 2 cups of compost and 4 cups of water (the 4 cups of water is to establish the same amount of added moisture as the Tea Bin)

Testing:
Direct observation of soil (inches of soil, inches of litter)
Compost Test & Compost Tea Test

Week One: 3/17/08
Phalaris aquatica – All Bins
no change – 2 inches of soil and 4 inches of thatch
Oak Leaf Litter – All Bins
no change – 2 inches of soil and 2 inches of leaf litter

Week Two: 3/23/08
Phalaris aquatica – All Bins
no change – 2 inches of soil and 4 inches of thatch
Oak Leaf Litter – All Bins
no change – 2 inches of soil and 2 inches of leaf litter

Week Three: 4/1/08
Phalaris aquatica – All Bins
2 inches of soil and 3.5-4 inches of thatch (it appears that the thatch has settled more. Possibly  due to rains last week. No change in soil depth)
Oak Leaf Litter – All Bins
no change – 2 inches of soil and 2 inches of leaf litter

Week Four: 4/9/08