National Sunflower Association of Canada Inc. Nutritional Needs of Sunflower CROP DEVELOPMENT General Ensuring the fertility needs of the crop are met is critical to maximize yield and profit. Improper application could result in crop damage and yield loss. Fertilizer applications should be made based on a soil test. Germinating sunflower seed is very sensitive to seed-placed away from the seed. No more than 6 to 10 lbs of N with potash should be placed with the seed. Dry soils can increase chances of seedling injury. When seeded with row equipment, all phosphate and potassium should be side banded 2 beside and 2 below the seed during planting. Some of all of the nitrogen can also be side-banded, provided that the total amount of fertilizer material side-banded should not exceed 300 lb/ac. Nitrogen can also be side-dressed before the plants are 12 inches tall. To assess the amount of fertilizer effect on crop stand one may use the South Dakota State University Fertilizer Seed Decision Aid. Check out this http://www.sdstate.edu/ps/extension/soil-fert/index.cfm link for the Decision Aid. Sunflowers have shown little response to micronutrient applications. Nitrogen Nitrogen is the major nutrient required by sunflowers, and has the greatest impact on seed size, size and number of leaves, test weight and yield. Insufficient N will limit crop yield, however, excess N applications can reduce oil content, and result in tall plants with large leaves more prone to lodging and disease. To help calculate the optimum quantity of nitrogen to apply, you need to develop a yield goad. It is important to be realistic when developing a yield goal and aim to be within 200 pounds of the fields highest recorded yield. Sunflowers require approximately 5 lbs of nitrogen for every 100 lbs of production yield goal. However, it is important to not apply excessive amounts of nitrogen. Nutrient uptake and removal by sunflower in Manitoba studies. Nutrient Uptake Removal Uptake Removal Lb nutrient for a 2000 lb crop Lb nutrient per cwt Nitrogen (N) 74-122 48-66 3.7-6.1 2.4-3.3 Phosphorus 24-56 18-26 1.2 2.8 0.9 1.3 (P 2 O 5 ) Potassium (K 2 O) 150-172 18-26 7.5 8.6 0.9-1.3 Sulphur (S) 8-12 3-4 0.39 0.58 0.17-0.22 Calcium (Ca) 54-94 3-4 2.7-4.7 0.15-0.23 Magnesium (Mg) 37-39 6-7 1.86-1.93 0.30-0.36 Uptake 1 = total nutrients taken up by the crop Removal 2 = total nutrients removed up by the crop From http://www.umanitoba.ca/afs/agronomists_conf/proceedings/2008/heard%20sunflower%20nutrient%20uptake-poster.pdf Page 1
lbsac Sunflower, flax and canola removal of nutrients. MAFRI. 90 80 70 60 50 40 30 20 10 0 Nitrogen Phosphate P2O5 Potassium K2O Sulphur Sunflower @ 2000 lb/ac Flax @ 24 bu/ac Canola @ 40 bu/ac Nitrogen applications can be made pre-plant, at seeding, post-seeding side-dress or a combination of these methods. Application should be timed so nitrogen is available for rapid plant growth and development. Often, logistically it is advantageous to apply nitrogen in the fall. However, the longer the time period between application and plant use, the greater the possibility for N. Fall applications are not recommended in sandy soils since the opportunity for leaching is much greater. A side-dress application of N when the sunflower plants are about 12 inches high is often preferable. Nitrogen recommendations for sunflower (based on spring band application). MAFRI. TARGET YIELD Fall Soil NO 3 -N 1750 2,000 2,250 2,500 lb/ac in 0-24 Rating NITROGEN RECOMMENTATIONS (lb/ac) 20 VL 40 85 125 170 30 L 20 60 105 145 40 M 0 35 80 120 50 M 0 10 55 100 60 H 0 0 30 75 70 H 0 0 5 50 80 VH 0 0 0 25 90 VH 0 0 0 0 100 VH + 0 0 0 0 Phosphorus deficiency is considered the second (after N) deficiency to occur within the crop. Potassium (K) is required by the crop for stalk and tissue strength. Sunflowers are a high user of potassium, with every 1t/ha yield, removing 30 kg K/ha. Phosphate and potash may be fall or spring applied before a tillage operation. These nutrients are not readily lost from the soil since they attach to the soil forming only slightly soluble compounds. Phosphorus should be applied pre-plant-broadcast, pre-plant banded, or banded at seeding. Starter applications are most efficient, especially when small amounts are applied in Page 2
Yield lb/ac Yield lb/ac fields low in available phosphorus. Potassium deficiencies normally only occur in sandy soils. Potassium that is band placed is about twice as efficient as broadcast applications. Phosphorus, potassium and sulfur recommendations for sunflower based on soil test levels and placement. MAFRI. PHOSPHORUS POTASSIUM SULPHUR Fertilizer Phosphate Fertilizer Potash (K 2 0) Soil Sulphate- Sulphur (0-24 ) Fertilizer Sulphur (S) Soil Phosphorus (0-6 ) (P 2 O 5 ) Recommend ed (lb/ac) Soil Potassium (0-6 ) Recommende d (lb/ac) Recommende d (lb/ac) ppm lb/ac Rating Sb 2 PPI 3 pp lb/ac Rating Sb 2 PPI 3 lb/ac Rating N/A 3 m 0 0 VL 40 40 0 0 VL 30 60 0 VL 20 5 VL 40 40 25 50 VL 30 60 5 VL 20 5 10 L 40 40 50 100 VL 15 30 10 VL 20 15 L 35 35 75 150 L 15 30 15 L 20 10 20 M 30 30 100 200 L 0 0 20 L 20 25 M 20 20 125 250 M 0 0 25 M 20 15 30 H 15 15 150 300 M 0 0 30 M 20 35 H 10 10 175 350 H 0 0 35 H 0 20 40 VH 10 10 200 400 VH 0 0 40 VH 0 20 + 40 + VH + 10 10 200 + 400 + VH + 0 0 40 + VH + 0 Sb 2 = Side Banded PPI 3= broadcast and pre-plant incorporated N/A 3 = placement does not influence effectiveness of sulphate forms of sulphur fertilizer Adapted from the Manitoba Agriculture Food and Rural Initiatives 0 lbs/ac 3000 0 lbs/ac 2500 45 lbs/ac 2500 90 lbs/ac 2000 2000 1500 1500 1000 1000 500 500 0 Low P Medium P High P Very High P 0 Low K Very High K Soil P Level Soil K Ratings Page 3
Plant Tissue Analysis Plant tissue analysis is an important tool in assessing nutrient status of the growing crop. Following are plant tissue analysis interpretive criteria used by the former Manitoba Agriculture Provincial Testing laboratory. These levels should be used for the top one to three most mature leaves collected at the bud stage. AgVise labs have a comprehensive tissue sampling guide http://www.agviselabs.com/pdf/plantsample.pdf. However if a deficiency is detected at this stage, yield potential has already been affected. This sampling is best used as an auditing tool to determine of your fertility program is sufficient for the yield potential. If nutrient deficiency is suspected earlier, sample plants and soil from the affected area and contrast results with plant and soil samples from an adjacent normal looking area. This is considered diagnostic sampling and could be used to correct some in-season deficiencies. Consult with your soil and plant tissue laboratory for guidelines when sampling at other growth stages. It is more efficient to assess soil sample results in the spring prior to planting and ensure the crop receives adequate fertilizer to last throughout the growing season. Sunflower tissue analysis interpretation Content Nutrient Low Marginal Sufficient High Excess Nitrogen % N 1.4 1.5-1.9 2.0-3.4 3.5-3.9 4.0 Phosphorus %P 0.14 0.15-0.25-0.5-0.8 0.24 0.49 0.79 Potassium %K 0.9 1.0-1.4 1.5-2.9 3.0-4.9 5.0 Sulphur %S 0.14 0.15-0.2-0.39 0.4-1.0 0.19 0.99 Calcium %Ca 0.19 0.2-0.29 0.3-1.9 2.0-2.4 2.5 Magnesium 0.09 0.1-0.19 0.2-1.4 1.5-1.9 2.0 %Mg Zinc ppm ZN 11 12-14 15-69 70-149 150 Copper ppm 2 3-5 6-24 25-74 75 (Cu) Iron ppm (FE) 14 15-19 20-249 250-500 499 Manganese ppm (Mn) 9 10-14 15-99 100-249 350 Boron No provincial guidelines developed. Consult analytical companies Page 4
SPECIAL FERTILITY CONSIDERATIONS Sunflowers have deep tap roots that can obtain water and nutrients five to six feet (1.5 to 1.8 meters) deep in the soil. These reserves of water and nutrients are unavailable to most other annual crops, making sunflower a good rotational crop. Sunflowers have the ability to scavenge nitrogen that has leached below the rooting depth of other crops. Effect of Frost on Sunflower Crops differ in how sensitive they are to frost based where the growing points are and what inherent mechanisms the plant has to prevent ice crystal formation. Broadleaf crops (eg. soybean, canola and sunflower) that have their growing point at the top of the plant are more sensitive to frost than grass species. In grassy species, the growing point often remains below the ground, protected until initiation of the reproductive growth stage (bolting). Sunflowers are most frost tolerant when emerging and in the cotyledon stage. During this early grow th stage, plants can withstand temperatures in the 25 to 26 o F (-3.3 to -3.8 o C) range for short periods. As the plants develop through the vegetative stages, V2-, V4-, V6- they become progressively more sensitive to frost and terminal bud damage can occur. At the V2- stage, the lowest temperature plants can withstand is 26 to 27 o F (-2.7to -3.3 o C) degrees, but for the V4-, V6- stages, 28-29 o F (-1.6 to -2.2 o C) degrees is the lower limit. If planted early, the crop could just be getting established with the strong possibility of a deep frost in mid-may. What would be the aftermath? Cool temperatures (33 to 34 o F or 0.5 to 1.1 o C) over several days, coupled with wet soils and dew helps reduce frost damage. Growth may slow delaying maturity with minimal effect on yield. Most damage can be expected if temperatures change rapidly between extremes. Frost damage can result in loss of apical dominance causing branching from axillary buds and multiple heads later in the season. Yield and quality are affected greatly. The disk flowers are very sensitive to frost. During flowering, temperatures of 28 to 30 o F (-1.1 to -2.2 o C) can result in damaged buds and sterile sections or rings in the flowering head. After pollination and petal drop, sunflower can withstand temperatures as low as 25 o F (-3.8 o C) with minor damage. A killing frost (23 to 25 o F (-3.8 to -5 o C) for 6 or more hours) prior to the R-8 stage can cause minor damage which includes reduced yield, oil content and seed quality/test weight. During the final stages of crop development, a killing frost will only cause minor damage, including reduced yield, oil content and seed size or grade. V-1 V-2 V-6 R-2 R-4 Page 5
R R-5.5 R-5.8 R-6 R-8 Crop Development Page 6
A. A. Schneiter and J. F. Miller in 1981 (Schneiter and Miller. 1981. Description of Sunflower Growth Stages. Crop Science 11: 635-638). Rotation Crop rotations are essential in farm management. Extended crop rotations help to reduce disease inoculum loads in the soil, allow for herbicide rotation, manage overwintering insect populations, weeds, water usage and fertility management. Growers with inadequate crop rotations will likely be confronted with one or more of the following yield-reducing problems: 1) Disease and disease-infested fields (e.g. increased sclerotinia) 2) Increased insect risk 3) Increased populations of certain weed species 4) Increased populations of volunteer sunflowers 5) Soil moisture depletion 6) Allelopathy or phytotoxicity of the sunflower residue to the sunflower crop Rotations can be used to alter weed populations. Populations of certain weed species can be suppressed by competition from the crop raised or by the selective use of herbicide. Such that broadleaf weeds are easier to control in grassy crop types and vice versa. Thus, the alteration between crop types allows for control of weed types for subsequent years when weed control could be more difficult. Weed populations can also become adapted to the seeding schedule of crops. For example, winter annuals may increase in population in a field where a fall crop has been grown consecutively. Changing to a spring seeded crop that allows for a spring non-selective herbicide application may kill the winter annual plant and disrupt the population. Page 7
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