Fertilizer and Ag Lime Grants
Title: P and K Fixation by Missouri Soils
Principal Investigators: Peter Scharf, Randy Miles, and Manjula Nathan
Departments of Agronomy and Soil and Atmospheric Sciences, University of Missouri
Objectives for 2001:
- Conduct the laboratory incubation to measure P and K fixation of forty different Missouri soils.
- Evaluate whether P and K fixation differ widely between north and south Missouri soils.
- Evaluate whether other soil measurements, such as extractable aluminum, can be used to predict P or K fixation by different soils.
- Use results to plan appropriate field experiments that would lead to improved P and K recommendations; these might be region-specific, or based on an additional lab test such as extractable aluminum.
Methods:
- Obtain 20 soil samples representative of each region (north Missouri + Mississippi River valley is one region, south Missouri is the other), and for which the soil series is known.
- All samples will be surface soils, 0 to 6 inch depth. This is the soil zone to which fertilizer is applied and where fixation of fertilizer nutrients may be an important process.
- Mix small samples (200 grams) of each soil thoroughly with either:
- 10 mg of P solution (this should raise Bray 1 soil test P by about 25 lb/acre)
- 10 mg of K solution (this should raise soil test K by about 20 lb/acre)
- distilled water
- evenness of nutrient-soil mixing is the reason for using solutions
- All treatments will be replicated three times. Because this study is exploratory, surveying a range of Missouri soils, we felt that it was best to allocate our resources to looking at more soils and use a minimum number of replications.
- Incubate in the lab, keeping the soil moist, and measure the amount of extractable P (Bray 1 method) and K (ammonium acetate method) after six months, along with soil pH.
- Measure extractable aluminum in the extracts also; Vermont research has shown that this can be a useful predictor of P fixation.
- Make soil clay mineralogy measurements (X-ray diffraction, selective chemical dissolution).
- Use statistical analysis of covariance to see whether soil region, soil aluminum, soil pH, or soil mineralogy can be useful in predicting how much P & K are fixed by different soils. Within a soil region, look for patterns that suggest what types of soils should be represented in future field experiments.
Soils collected for P & K fixation study
County | Soil |
Linn | Lagonda |
Boone | Mexico |
Mississippi | Commerce silty clay loam |
Gentry | Grundy Silt Loam |
Saline | Haynie silt loam |
Lafayette | Higginsville silt loam, eroded |
Stoddard | Lilbourn(2)fine sandy loam |
Stoddard | Loring silt loam |
Monroe | Mexico silt loam |
Monroe | Putnam- Pasture |
Knox | Putnam silt loam |
New Madrid | Sharkey clay |
Ray | Sharpsburg silt loam-9% slope, eroded |
Scott | Commerce silty clay loam |
DeKalb | Grundy silt loam, 1 to 5 % slopes |
Ray | Leta silty clay |
Stoddard | Lilbourn fine sandy loam |
Stoddard | Loring silt loam, eroded |
Lafayette | Marshall silt loam |
Monroe | Mexico silt loam |
Montgomery | Mexico silt loam |
Pemiscot | Portageville Clay |
Monroe | Putnam |
Stoddard | Sharkey silty clay loam |
Lewis | Westerville silt loam |
Lawrence | Creldon silt loam |
Vernon | Barco loam |
Vernon | Barden Silt Loam-Soybean |
Vernon | Barden Silt Loam |
Christian | Clarksville very cherty silt loam |
Polk | Goss gravelly silt loam |
Vernon | Osage silty clay |
Laclede | Viraton silt loam |
Vernon | Barco loam |
Vernon | Barden Silt Loam |
Wright | Cedargap cherty silt loam |
Cass | Haig silt loam |
Henry | Hartwell silt loam, 2 to 4 % slopes |
Lawrence | Huntington silt loam |
Lawrence | Keeno cherty silt loam |
Bates | Kenoma silt loam, 1 to 4 % slopes |
Barton | Parsons silt loam , 0 - 1 % slopes |
Results for 2001:
- Forty-two soils have been collected from all over the state, representing many major agricultural soil types (see map and table).
- Soils have been dried and ground, and initial soil tests have been run.
- Soils were analyzed for water content at field capacity, so that we would know how much water to add to each soil during the incubation procedure.
- Incubation study was initiated in July, 2001.
- Soil clay mineral analyses are in process.
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