Cropping Practices and Organic Matter

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Cropping Practices and Organic Matter

• By
• Cody Petersen and
• Seth Marable

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Objectives

• To show how cropping practices affect the Organic
  Matter of soil
• Greater OM content, greater water holding
  capacity
• Less erosion
• All around soil health-Tilth
• Serves as buffer

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Hypothesis

• We hypothesize that with intensive cropping
  practices and irrigation, organic matter will be
  a smaller percentage of the soil composition.
• Other factors affecting OM
• Crop selection
• Stem types
• Leaves
• Roots

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Field ProceduresSamples collected from ARS farm
in Bushland

• Row water Maize
• Drip Maize
• Fallow dryland Maize
• Linear irrigated Maize
• Irrigated Beets
• Buffalo Grass

• Surface/drip Soybeans
• Sub/drip Soybeans
• Fallow dryland wheat/No-till
• Irrigated wheat
• Pivot Irrigated Cotton
• Row water Cotton

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Lab Procedure

• Weight bulk sample
• Oven dry
• Weight dry samples
• 2mm Sieve samples
• Prepare for dry combustion
• Bake boats
• DC procedure
• Run DC over night
• Transform Carbon percent into OM percent

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Dry Combustion

• .5 gram samples into boats
• Standard samples-used for calibration
• Run all samples twice
• Standards at beginning and end
• Blanks in middle
• Results are Carbon and Nitrogen gas found after
  900C
• Standards set the reference point for all samples
  to convert to percentages

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Results

• Organic C varied about 0.25 in intensive
  cropping and irrigation practices
• Cropped soils had less soil organic C than native
  grass

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Other Results

• Direct correlation between Nitrogen and Organic
  Matter in all samples (The CN in most soils is
  usually about 10)
• Bulk density is mostly affected by tillage
  practices