Micronutrient functions in plants: B Forms stable organic complexes in cell walls, immobile Meristem cell differentiation Pollen viability & pollen tube growth Deficiency Terminal death or slow growth Shorter internodes; thicker & misshapen leaves, stems, & petioles Poor flowering, pollination, fruit development Decreased cotton fiber elongation Boron: general issues. As an immobile nutrient, it can have severe effects on newly developing shoots, flowers, fruits, and seeds.

B Boron deficiency in cotton leads to abnormal leaf expansion (cupping) as well as petiole striations.

B Boron deficiency in soybean leads to abnormal leaf expansion (cupping).

B Boron deficiency in tobacco leads to abnormal apex development and leaf expansion (cupping).

Micronutrients: Boron (lb B/ac) Source Conc B’cast Band Foliar Borax 11 0.8 - - - 0.2 Solubor 20 Sodium tetraborate 14-20 Organic B+N 3 Potential B sources are shown. Toxicity can occur, so limit rates broadcast to the soil to approximately 0.8 to 1 lb B/ac and limit rates sprayed on foliage to 0.2 to 0.4 lb B/ac.

Micronutrient price survey: B (summary of 3 dealers, fall 2007) Material Cost Application rate Treatment cost (% B) $/lb B lb B/ac $/ac Granular borate (10%) $2.55 1 Solution (9%) $11.06 0.2 $2.21 A 2007 survey of fertilizer dealers found similar costs for soil and foliar treatments.

Micronutrient functions in plants: Cu Photosynthetic & mitochondrial electron transport Enzyme activator Lignin production Immobile in plant Deficiency Chlorosis, necrosis espec. young tissue Poor reproductive growth Shoot bending, lodging Copper is involved in several metabolic activity functions and since it is relatively immobile in the plant, deficiencies tend to affect young tissues at the apex or reproductive structures.

Cu Copper deficient corn plants. In the field, this can occur on organic soils where little copper is present naturally and where soil organic matter complexes make copper even less available.

Copper deficiency in soybean, with severely affected flower buds and apical growth. Cu

Cu Copper deficiency in wheat growing on an organic soil. Severe deficiency symptoms often occur at the onset of rapid late winter/early spring growth.

Cu timing (Younts, 1964) [LSD, p<0 Cu timing (Younts, 1964) [LSD, p<0.05=12 bu/ac] Rec: organic soil 6 lb Cu/ac Copper deficiency in wheat can be corrected if fertilizer is applied during the fall or winter, substantial yield reductions can result from delaying applications until spring. 0 w/o Cu

Cu source (Barnes & Cox, 1973) Hyde Co. , 49% O. M. , pH 4 Cu source (Barnes & Cox, 1973) Hyde Co., 49% O.M., pH 4.3 + 2 ton lime/ac sulfate as effective as Cl- & organic-complexes Yield response was similar to copper sulfate and to two complexed copper forms in this study.

Cu Source (Forsee et al. , 1954) Florida Everglades peat, pH 5 Cu Source (Forsee et al., 1954) Florida Everglades peat, pH 5.5, greenhouse [oxide = sulfate when thoroughly mixed pre-plant] Yield response was similar to copper oxide and copper sulfate forms in this study. Oxide forms are typically less expensive and are less water soluble, but should be effective if they are applied pre-plant and incorporated into the soil.

Micronutrients: Copper (lb Cu/ac) Source Conc B’cast* Foliar Cu sulfate 25-35 2-6 0.25 Cu oxide 75 - - - Cu chelate 9-13 Potential copper sources are shown, along with suggested rates to correct deficiency and avoid toxicity. Apply the highest rates to organic soils. Reduce rates if banding the soil application. Highest rates for organic soils, lowest for mineral soils Reduce rates ½ or 1/3 if banding

Micronutrient price survey: Cu (summary of 3 dealers, fall 2007) Material Cost Application rate Treatment cost (% Cu) $/lb Cu lb Cu/ac $/ac Granular Cu oxysulfate (15%) $5.77 Min 2 M-O 4 Org 6 $11.54 $23.08 $34.62 Granular Cu sulfate (25%) $4.80 $9.60 $19.20 $28.80 Solution (8%) $12.81 Foliar 0.25 $3.20 Copper prices are relatively high compared to other micronutrients. Note that granular copper rates can be reduced by ½ to 1/3 if banded, and that foliar treatments are less expensive per acre, but leave less residual copper for future uptake.