1. Effects of Cover Crop Management on Corn Production Brian Jones Agronomy Extension Agent 245-5750 brjones8@vt.edu http://www.valleycrops.cses.vt.edu

2. Benefits of Cover Crops - Review  Cut fertilizer costs “Fix” atmospheric N (legumes) Scavenge / redistribute nutrients (grasses, some legumes) How much??  Big question  Depends on: time of killing, season, etc.  More later…

3. Benefits of Cover Crops - Review  Suppress weeds / other pests Smother early emerging annuals Competition for water, light and nutrients Root exudates or compounds provide natural chemical and nematode control (sometimes) Encourage beneficial insects

4. Benefits of Cover Crops - Review  Improve yields Increased infiltration (less runoff) Decrease compaction Improve soil structure Increase organic matter Improve nutrient cycling

5. Benefits of Cover Crops - Review  Prevent erosion Dense roots hold soil in place Prevents the “splash” effect Cover over the winter months

6. Benefits of Cover Crops - Review  Conserve soil moisture Residue increases infiltration  Surface and root zone Reduce evaporation from bare soil Must avoid killing too late  Problem with mechanical control systems

7. Challenges of Cover Crops  Main Challenge: Fitting them into your system Have to have the feed…  Nutrient cycling How much N? May be variable and will need to test (PSNT) N tie up with high C:N cover crops  Rye killed late May not see N until following year

8. Challenges of Cover Crops  Cropping challenges Allelopathy may affect cash crop Stand / emergence issues Planting equipment adjustments Mechanically killing for some Good environment for harmful insects Cost of production

9. Challenges of Cover Crops  Need to understand these questions with our systems and conditions  No perfect cover Depends on rotation, needs, etc.  Need local research…

10. Objectives 1. Quantify the effects of cover crop species on soil fertility and nutrient cycling 2. Determine how cover crop kill date affects cover crop biomass, corn yield and nutrient cycling – Part of a larger study looking at low-input cover crop management – Funded by the Shenandoah RC&D Council

11. Methods  Project established in 2006 in Rockingham County  Planted seven different cover crop treatments in fall of 2006 Three replications of each  Each treatment was killed at three different timings Residue rolled flat  Cover crop biomass, soil samples, and cover samples were taken prior to each rolling  Corn was planted no-till after each rolling 0 lbs N applied to corn  Whole plot was harvested with chopper and yield determined

12. Methods 40’ 10’

13. Methods  Timing of killing was based on small grain development: May 10 (boot stage) June 1 (soft dough) June 11 (hard dough)  Only talk about data from May 10 and June 1 treatment today Latest that most of us will be planting corn

14. Results: Cover Crop DM and Yield

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16. Daicon Radish  Not a traditional radish  Being marketed as biological compaction relief  Some evidence of increased microbiological activity as a cover crop

17. QUESTIONS?

18. Total N from Cover Crop a a a a a a

19. Available N From Cover  Total N is not all available for mineralization and crop uptake Loss factors include:  Volatilization (loss to atmosphere)  Immobilization (tied up by bacteria)  Leaching (loss to groundwater)

20. Available N From Cover  Volatilization losses Depend largely on whether or not cover was incorporated Without incorporating cover crop in our climate figure approximately 50% loss due to volatilization

21. Available N From Cover  Immobilization losses Depend largely on the carbon to nitrogen ratio (C:N) of the cover crop species Low C:N (<25) bacteria quickly break down vegetation making N available immediately High C:N (>25) N will become available, but may not be until the following growing season  Also, bacteria will tie up soil N in order to digest high carbon residue  Often see this with the yellowing of corn in early spring with high residue

22. Available N From Cover Net Loss of PAN from immobilization Net gain of PAN from mineralization

23. Available N From Cover

24. Available Soil N  Sampled the NO3-N and NH3-N fraction at the time of kill and corn planting to see how much was potentially available These are highly mobile Most of crop uptake

25. Available Soil N

27. QUESTIONS?

28. Crop Response  So how much N was actually available to the corn crop from our cover crop treatments?  Best observed by looking at the plant itself Ear leaf samples show the % N in the plant at silking and provide a good “in-season” analysis of N uptake

29. Crop Response – Ear Leaf N a a a

30. Crop Response – Silage Yield a a a a

31. QUESTIONS?

32. Economics  Bottom line  Seed and establishment not cheap

33. Economics – Yield Advantage

34. Economics – N Advantage

35. Economics – $ Advantage

36. THANK YOU! QUESTIONS?