Renewed Interest in Blueberry N Sources for North Carolina Production David H. Hardy NCDA&CS Agronomic Division SERA 6 Annual Meeting June 14, 2010

Today’s Presentation General overview of production General overview of production Standard fertilizer program Standard fertilizer program Fertility interests to pursue Fertility interests to pursue Challenges in blueberry fertility Challenges in blueberry fertility Overview of 2009 study Overview of 2009 study Future work Future work

N.C. Blueberries 4,200 acres $3.7 million in th largest producer in U.S. 5 th highest yield in U.S.— 5430 lb/A

N.C. Highbush & Rabbiteye — 80% Highbush concentrated in Bladen, Pender Duplin, & Sampson counties

Preferred Soil pH Levels  Highbush4.0–5.0  Rabbiteye4.5–5.3 Dr. George Cummings, 2005 N.C. Blueberry Council Proceedings

Soil types in southeastern NC may vary greatly and have a major fertility impact.

Nitrogen and phosphorus are the two most important nutrients.

The micronutrient copper is often deficient.

Standard Fertilizer Program bud break about mid-March bud break about mid-March –100 to 150 lb per acre in early May in early May –75 lb per acre (DAP) in late July or early August (DAP) in late July or early August –50 lb per acre

Standard Fertilizer Program Developed from work of Cummings Developed from work of Cummings –Older varieties Successful and well adopted Successful and well adopted Fertilizer relatively inexpensive Fertilizer relatively inexpensive

Grower Interest in Fertility Newer variety responses to fertilizer Newer variety responses to fertilizer –Star, Duke, Reveille, O’Neal

Grower Interest in Fertility Newer variety responses to fertilizer Newer variety responses to fertilizer –Star, Duke, Reveille, O’Neal Possible benefit from N during fruiting Possible benefit from N during fruiting

Grower Interest in Fertility Newer variety responses to fertilizer Newer variety responses to fertilizer –Star, Duke, Reveille, O’Neal Possible benefit from N during fruiting Possible benefit from N during fruiting Better use of liquid vs. dry fertilizer Better use of liquid vs. dry fertilizer – liquid – liquid

Challenges in Fertility Work Blueberry is a perennial plant Blueberry is a perennial plant –Plant takes up N in one season –Response may take several seasons Application of fertilizer during fruiting may dislodge berries from plant Application of fertilizer during fruiting may dislodge berries from plant –Slow release N to avoid this

Challenges in Fertility Work Blueberries are grown on mineral and organic soils Blueberries are grown on mineral and organic soils –Range of N from organic matter Leon Lynn Haven Murville Pamlico

Challenges in Fertility Work Low soil pH may affect soil N reactions Low soil pH may affect soil N reactions –Conversion to nitrate –Where does N go???

Blueberry N Use & Source Fairly inefficient in using N Fairly inefficient in using N Ammonium (NH 4 + ) preferred over nitrate (NO 3 - ) Ammonium (NH 4 + ) preferred over nitrate (NO 3 - ) Mostly ammonium N in Mostly ammonium N in Studies showing higher yields with sulfur- coated urea Studies showing higher yields with sulfur- coated urea

Research Objective in 2009 Evaluate plant nutrition and overall plant growth –Standard dry and liquid grower fertilizers –Slow-release N products  Mixed with P and K sources to give similar rates of all nutrients

Research 2009 Castle Hayne Station Castle Hayne Station 7 fertility treatments per row 7 fertility treatments per row –(6 plants / treatment) Duke, O-Neal, Star varieties Duke, O-Neal, Star varieties –2 rows of each variety for total of 6 rows –Variety / row = replications

Research in 2009 (7 treatments) 1. Control (no fertilizer) 2. Standard fertility (dry & ) liquid (increase efficiency by placement) Slow-release N treatments Slow-release N treatments (potential increase in N availability during fruiting) (potential increase in N availability during fruiting) 4. Urea 5. Sulfur-coated urea 6. Nitamin 30L (urea polymer, triazone, liquid N) 7. Florikan ( , 92% 7. Florikan ( , 92% polymer-coated NH 4 + & NO 3 - )

Fertilizers Urea Sulfur-coated UreaFlorikan

Research 2009 Soil sampled for nitrate and fertility Soil sampled for nitrate and fertility –4 times (Mar 26, May 4, Jun 26, Aug 5) Plant tissue sampled Plant tissue sampled –Jun 26 Growth Growth –Oct 29 — measurements (H × W) –Dec 22 — pictures

Results

Soil Fertility in Top 12 Inches HMW/VCECpHBSKP %g/cc meq/100 cc % --mg dm --mg dm  Appears to be no differences in treatments for a given depth  Note P differences between depths

Treatment NPKCaMg % Grower Std ( )1.51 a0.13 ab0.48 a0.68 b0.18 b Liquid1.53 a0.13 ab0.49 a0.66 b0.18 b Urea-N1.58 a0.13 ab0.47 a0.63 b0.17 b Sulfur-coated Urea1.6 a0.13 ab0.45 a0.62 b0.17 b Nitamin1.58 a0.14 ab0.47 a0.62 b0.17 b Florikan ( )1.64 a0.15 a0.47 a0.67 b0.19 b Check1.46 a0.12 b0.40 b0.86 a0.23 a Plant Nutrient Levels

Sufficiency Plant Nutrient Levels SourceNPKCaMg % SERA 6- Rab1.20 – – – – – 0.20 UGA- High UGA- Rab Pl. An. Hdbk II High- Prod Pl. An. Hdbk II High- Res Study Average

Growth as Affected by Treatment

Replications of Star Gr. Std Dry Gr. Std Liquid Urea S-Coated Urea NitaminFlorikanCheck Gr. Std Dry Gr. Std Liquid Urea S-Coated Urea NitaminFlorikanCheck

Replications of O’Neal Gr. Std Dry Gr. Std Liquid Urea S-Coated Urea NitaminFlorikanCheck Gr. Std Dry Gr. Std Liquid Urea S-Coated Urea NitaminFlorikanCheck

Replications of Duke Gr. Std Dry Gr. Std Liquid UreaS-Coated Urea Nitamin Florikan Check Gr. Std Dry Gr. Std Liquid Urea S-Coated Urea Nitamin Florikan Check

Thoughts on the Study One-year of data – –No conclusions can be drawn Considerable variability in plant growth – –Treatments look promising – –Differences may become more pronounced over the next few years Soil nitrate data puzzling – –Soil heavily amended with pine bark

Further Studies Expand this study to grower fields on different soil types Expand this study to grower fields on different soil types Implement incubation studies in glass flasks with sampling intervals to determine N reactions at low pH Implement incubation studies in glass flasks with sampling intervals to determine N reactions at low pH Study rock phosphate Study rock phosphate –Potential slow release of P on organic soils