Managing plant-available N for organic sweet corn. Dan M. Sullivan Oregon State University Crop & Soil Science

Transcription

1 Managing plant-available N for organic sweet corn Dan M. Sullivan Oregon State University Crop & Soil Science PNW Vegetable Association, Nov 18, 2010

2 Today Keys to fertility management in intensive vegetable production systems

3 Nutrient management guide Sweet corn, western Oregon, Pub # EM9010-E. Oct Integrates conventional and organic management Available at: extension.oregonstate.edu/catalog/ Dan.Sullivan@oregonstate.edu

4 Section on organic management starts on page 12 in Sweet corn, western Oregon nutrient management Guide, OSU EM Pub #9010-E Available at: extension.oregonstate.edu/catalog/

5 Organic Summary for sweet corn (p. 12 in Sweet corn, western Oregon, Pub # EM9010-E) Lime to maintain ph between 5.8 and 6.2 Other nutrients: Monitor via soil testing, add when soil test indicates need Avoid buildup of excess P in soil by limiting manure or compost application Nitrogen: fine tune each year using past experience Use winter legume cover crops to provide plantavailable N from sustainable source

6 Organic nitrogen management for sweet corn 1. Sweet corn under conventional management (no organic inputs) requires 100 to 150 lb N fertilizer per acre 2. Transition to organic: supply 100 to 150 lb PAN from preplant winter cover crops + organic fertilizers. 3. Determine preplant N application: rate and source using OSU Organic Fertilizer Calculator. 4. Monitor success of N management each year. Options: 1. Mid-season soil nitrate test ( PSNT; corn 12 inches high) 2. Zero N plot 5. Gradually reduce N inputs in successive years as you gain confidence

7 Response to N fertilizer Conventional experiment station trials, corn following fallow (no organic inputs) Mid-season nitrate-n in soil: 10 ppm Yield t/a WA 2003 WA N Rate, lb/a From: Aurora, OR and Puyallup, WA. In: OSU sweet corn nutrient mgmt guide

8 Keys to sustainable management Sustainable management provides enough N for the crop maintains soil quality

9 Use soil tests ph lime requirement Phosphorus (P), Potassium (K) Tell you about health of soil in terms of supplying many nutrients Valid for all farming systems

10 Farm 9 Farm 10 Farm 11 Farm 8 Soil ph Farm 5 Farm 6 Farm 7 Farm 4 Farm 3 Farm 2 Farm Ospud project farms, 2006 Soil ph

11 Soil test P and K Farm 1 Farm 2 Farm 3 Farm 4 Farm 5 Farm 6 Farm 7 Farm 8 Farm 9 Farm 10 Farm 11 Farm 1 Farm 2 Farm 3 Farm 4 Farm 5 Farm 6 Farm 7 Farm 8 Farm 9 Farm 10 Farm Phosphorus (P) Potassium (K) Ospud project farms, 2006 Soil test K (ppm) Soil test P (Bray P1)

12 Irrigation water nitrate-n (lb N per acre-ft) Farm 1 Farm 2 Farm 3 Farm 4 Farm 5 Farm 7 Farm 8 Farm 9 Farm 10 Farm Ospud project farms, 2006 Irrigation water nitrate-n (lb/acre-ft)

13 Organic matter inputs are magical Provide all 16 plant-essential nutrients Common prescription for correcting macro/micronutrient deficiencies: add OM Food for soil life When OM inputs > OM decomposition, soil fertility increases

14 Organic matter stability rapid decomposition and nutrient release sugar, protein hemicellulose cellulose Green leafy plant material Animal manure, crop residue (straw) Compost CO 2 lignin Humus very slow decomposition ( stable ) Adapted from: SARE Handboook 4, Building Soils for Better Crops, Fig 8.1

15 New soil organic matter is most active Can bring a soil back to life via consistent organic matter additions Takes 3 to 5 years of increased organic matter addition to reach new equilibrium value for a particular cropping system

16 Denitrification N 2 or N 2 O N Cycle Ammonia NH 3 Nitrate NO3 - Plant Uptake Ammonium NH 4 + Leaching Organic Nitrogen

17 Soil Nitrate-N (ppm) Soil Nitrate-N (ppm) MF new organic farm 0 5/1 6/1 7/1 8/1 9/1 WUG established organic farm with annual organic soil amendment 0 5/1 6/1 7/1 8/1 9/1 Fallow Phacelia Vetch Rye Vetch Vetch 3 to 5+ yr amendment history may have bigger impact on soil N mineralization rate than what was done this year Andrews and Sullivan, 2009 (unpublished)

18 Legumes: key to providing enough N for rotation Half of legume N converts to plant-available N rapidly (30 days) Other half of legume N contributes to longterm fertility Legume N converted to nitrate-n by soil biology Nitrate-N from legumes or any other source subject to leaching loss

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20 Above-ground N in winter cover crop Garrett and Luna, 2007 Lewis Brown farm

21 Cover crop effect on nitrate-n Lab incubation in moist silt loam soil (72 o F) Garrett thesis, 2009

22 Fertilizer N equivalency of winter vetch cover crop for summer organic broccoli Vetch winter cover Winter Fallow Broccoli yield (ton/acre) Feather meal N rate (lb total N per acre) Vetch winter cover crop = 100 lb feather meal N/ac Garrett and Luna, 2007 Lewis Brown farm

23 Cereals recycle N. Cereal crop residues may temporarily immobilize N. oats, wheat, rye, barley, sorghum-sudan Recycle N within cropping systems Can be used to trap N that would otherwise be lost by leaching (fall rains in western OR) For significant fall N uptake, seed by Oct 1 Cereals do not provide significant amount of additional PAN for next crop May cause short-term tie-up of plant available N (for 3 to 6 weeks after incorporation in spring)

24 Winter cereal cover crop captured N, preventing it from leaching Six year leaching study (passive lysimeter) N leached in winter following sweet corn Fertilizer N rate for sweet corn No winter cover crop Cover crop b (lb/a) Leachate nitrate-n concentration (mg/l or ppm) Annual nitrate-n loss via leaching (lb/a) Average for 6 sweet corn crop years. Willamette silt loam soil, Aurora, OR. Adapted from: Feaga et al. (2010). Soil Sci. Soc. Am. J. 74:

25 The greener the crop residue, the more N is mineralized following the crop Higher N concentration in leaves than in stems Legumes: 2.5 %N (mature) to 5% N (young) Non-legume: 1% N (mature) to 3% N (young)

26 PAN from cover crop residue (lab incubation in soil at 22 o C) Plant available Plant-available N from N decomposition (PAN), % (% of total N applied) after 10 weeks after 4 weeks Breakeven crop residue N% (4 wk) below 2% = immobilization (negative PAN) above 2% = mineralization (positive PAN) Nitrogen concentration in cover crop residue (%) From: Datta, Sullivan and Andrews, unpublished, 2010

27 OSU Calculator: Estimates PAN release from organic fertilizer and cover crops

28 Crops use most N during rapid vegetative growth Seedling, early growth (low N demand) Rapid vegetative growth (high) Reproductive growth (no N demand) Specialty organic fertilizers applied preplant do reasonable job of supplying N when it is needed (rapid vegetative growth)

29 Sweet corn growth (biomass/day) and plant N uptake (lb/acre/day) Peachey and Hart, In: OSU sweet corn nutrient mgmt guide

30 PNW 513. Available online: OSU Extension and Experiment Station Publications.

31 Sweet corn: Midseason nitrate-n test From Gale, In: OSU sweet corn nutrient mgmt guide.

32 Soil nitrate-n vs. table beet yield Table beet yield (Mg/ha) MF Farm Fallow Fallow + feather meal Phacelia Vetch (PV) PV + feather meal Rye Vetch (RV) RV + feather meal Vetch (V) V + feather meal Soil nitrate-n (mg/kg) on May 18, 2009 Andrews, Poole and Sullivan, unpublished

33 Leave a zero N plot in your field to see impact of current season N inputs You might be surprised at how much N is being provided by soil reserves In-season soil nitrate testing also valuable monitoring information

34 Zero N experiment across six organic farms: whole potato plant N uptake Crop Nitrogen Uptake (lb/acre) 250 crop N uptake = 2 lb N per acre per day Days after planting shows crop response to mineralized N with no current season N fertilization or N min from winter cover crop From: Sullivan et al., OSU Extension EM8949-E (2008)

35 Sustainable Management Keys 1. Get and use basic soil tests 2. Organic inputs are magical 3. New organic matter is most active 4. Legumes: key to providing enough N for rotation 5. Cereals recycle N. Cereal crop residues may temporarily immobilize N 6. The greener the crop residue, the more N is mineralized 7. Crops use most N during rapid vegetative growth 8. Leave a zero N plot in your field to see impact of current season N inputs

36 Dan M. Sullivan Oregon State University Crop & Soil Science