Dairy Compost Utilization

Study 5: Soil and water quality evaluations following various rates and timings of compost applications


Evaluate soil and water quality of plots receiving dairy compost as a soil amendment.


Treatment NumberCompost Rate (ton/A)Application MethodSeeding Method
1 ~100a Incorporate Broadcast seed
2 ~100a & 1" wood chipsb No incorporation Broadcast seed
3 16 No incorporation Broadcast seed
Untreated check 0c No incorporation Broadcast seed

a Dairy compost rate of 100 ton/A is an estimation based on TxDot specification for compost manufactured topsoil (CMT) of a 1 inch application of dairy manure compost (accurate rates will be determined based on dairy compost density used). Compost will be incorporated into 3" of existing top soil and then seeded with a standard seed mix.

b Dairy compost rate of 100 ton/A is an estimation based on TxDot specification for a 1 inch application of dairy compost and a 1 inch application of wood chips. The treatment in this study will be a 2 inch application of the erosion control compost (ECC) mix as specified by TxDot standards where wood chips and dairy manure compost are blended in a 50/50 volume to volume ratio prior to application. ECC will be blended with a standard seed mix prior to application.

c Plot will receive an application of commercial fertilizer (100-100-100).


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Twelve plots were established on an embankment at the Texas A&M University Riverside campus. At the bottom of each plot, a gutter made from PVC pipe was installed to convey plot runoff to plastic buckets. The four treatments were replicated three times and randomly assigned to the 12 plots.

For treatment #1, plots were prepared by breaking up surface soil with hand implements. Subsequently, a 1 inch layer of dairy manure compost was applied, spread and incorporated into nearly 3 inches of topsoil.

For treatment #2, 50 percent dairy manure compost and 50 percent woodchips were blended by volume and mixed thoroughly. The mixture was applied as a 2 inch thick layer of erosion control blanket on top of the existing soil.

Treatment #3 consisted of an application of dairy manure compost at a rate of 16 tons per acre on undisturbed soil.

Mineral fertilizer was applied as treatment #4 at a rate of 100 lbs per acre for nitrogen (N), 44 lbs per acre as P or 100 lbs per acre as P2O5 for phosphorus (P), and 83 lbs per acre as K or 100 lbs per acre as K2O for potassium (K), respectively.

Soil and compost samples were taken from the College Station test plots prior to treatment. Rainfall was simulated over plots in November of 2003 and will be simulated again in November of 2004. Two rainfall simulators with a sprinkler nozzle were calibrated to rain at a rate of 3 inches per hour. Rainfall was maintained for 30 minutes following runoff. The first liter of runoff was collected. The remaining runoff and sediment was collected and pumped from a collection container downhill to calibrated scales. All runoff was weighed and a subsample was pulled from the entire sample following thorough mixing. Runoff samples were analyzed for nutrients to assess the quality of runoff from composted and control plots. After first rainfall simulation event, seed mix was broadcasted and surface raked in three treatments. Seed mix was standard TxDOT seed mix.

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