How Do Cover Crops Affect Fertilizer Recommendations? Newell Kitchen USDA-ARS Cropping Systems and Water Quality Research Unit, Columbia, MO 2014 Advanced Nutrient Management Course Bradford Technology Transfer Center Feb 3-4 2014
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion 2. Increased soil organic matter 3. Enhanced infiltration 4. Enhanced aeration with improved soil structure/aggregation 5. Preventive of soil compaction 6. Reduced evaporation potential 7. Recycle nutrients 8. Fix N with legumes
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion
What nutrient losses should we be concerned about? 70% of N and P transported in the basis are tied to agricultural sources (Alexander et al., 2008). 52% of N and 25% of P come from corn and soybean production; 37% of P from animal manure on pasture and rangeland.
Percent Reduction in Phosphorus in Runoff (summary of studies; Sharpley and Smith; 1991)
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion 2. Increased soil organic matter
Cover Crop Effects on Soil Quality Indicators Property and units 2003 2007 ph 6.18 6.34 P, mg/kg 7.6 15.1 K, mg/kg 60.9 133.6 SOC, g/kg 11.5 12.4 POM-C, g/kg 1.49 2.51 MnOxC, g/kg 0.344 0.342 Total N, g/kg 1.07 1.18 POM-N, g/kg 0.117 0.166 Highlighted items are significantly different between samplings
Role of Organic Matter on Nutrients Organic matter is a reservoir of nutrients that can be released to the soil. Each percent of organic matter in the soil releases 20 to 30 pounds of N, 4.5 to 6.6 pounds of P 2 O 5, and 2 to 3 pounds of sulfur per year. The nutrient release occurs predominantly in the spring and summer, so summer crops benefit more from organic-matter mineralization than winter crops.
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion 2. Increased soil organic matter 3. Enhanced infiltration
Improved Water Infiltration
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion 2. Increased soil organic matter 3. Enhanced infiltration 4. Enhanced aeration with improved soil structure/aggregation
Soil Aggregate Stability 70 60 Min. Till CS (1) No Till CS (2) ICM No Till CSW (5) CRP (6) Aggregate stability, % 50 40 30 20 With Cover Crop Without Cover Crop 10 0 Footslope Backslope Summit Landscape
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion 2. Increased soil organic matter 3. Enhanced infiltration 4. Enhanced aeration with improved soil structure/aggregation 5. Preventive of soil compaction
Cover Crops and Soil Compaction http://www.grdc.com.au/research-and-development/grdc-update-papers/2009/10/using-rotation-crops-to-improve-soil-quality
Do Cover Crops Always Reduce Compaction?
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion 2. Increased soil organic matter 3. Enhanced infiltration 4. Enhanced aeration with improved soil structure/aggregation 5. Preventive of soil compaction 6. Reduced evaporation potential
Effect of Cover on Evaporation
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion 2. Increased soil organic matter 3. Enhanced infiltration 4. Enhanced aeration with improved soil structure/aggregation 5. Preventive of soil compaction 6. Reduced evaporation potential 7. Recycle nutrients
Cover Crop Effects on Soil Quality Indicators Property and units 2003 2007 ph 6.18 6.34 P, mg/kg 7.6 15.1 K, mg/kg 60.9 133.6 SOC, g/kg 11.5 12.4 POM-C, g/kg 1.49 2.51 MnOxC, g/kg 0.344 0.342 Total N, g/kg 1.07 1.18 POM-N, g/kg 0.117 0.166 Highlighted items are significantly different between samplings
Recovered Nitrogen after Drought 0 Profile Depth (cm) 20 40 60 80 91 lbs/a captured If 50% of captured N available $27/A of N saved @ $.60/lb N Avg. NO 3 -N (kg ha -1 90cm -1 ) Cover: 16.7 No-Cover: 118.8 $2,430 of N for 90 acre field 0 20 40 60 NO3-N (kg ha -1 )
Percent Reduction in Nitrate Leaching (summary of studies; Meisinger et al., 1991) 100 90 80 70 60 50 40 30 20 10 0
Summary of Typical Positive Impacts from Cover Crops on Soil Physical/Chemical Properties 1. Greatly reduced erosion 2. Increased soil organic matter 3. Enhanced infiltration 4. Enhanced aeration with improved soil structure/aggregation 5. Preventive of soil compaction 6. Reduced evaporation potential 7. Recycle nutrients 8. Fix N with legumes
Cover Crop and Kill Date on Plant Available N Source: D. Sullivan.
1. Greatly reduced erosion 2. Increased soil organic matter 3. Enhanced infiltration 4. Enhanced aeration with improved soil structure/aggregation 5. Preventive of soil compaction 6. Reduced evaporation potential 7. Recycle nutrients 8. Fix N with legumes
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