All suspected disease samples are sent to the CDFA Plant Diagnostic Lab in Sacramento for disease identification by plant pathologists to ensure accurate and complete identification. After harvest, the county agricultural commissioner office issues a certificate that is attached to the batch of seed produced in their county that is used for tracking across county or state lines. This certificate is used as proof that the seed meets foreign phytosanitary requirements for diseases that can be visually observed in the field. If additional lab tests are required for an export phytosanitary certificate, the exporting county will run the tests required according to either USDA Standards or an import permit provided by the exporter. The exporting county is not always the same as the county of origin because seed lots are moved to different counties for export. For example, seed produced in Sutter County may be moved to Yolo County for export, but all seed is tracked as to origin, to ensure regulations are met.Sunflowers have relatively large seeds and are less sensitive to seeding depth than smaller-seeded crops. However, at planting, they still need a well-worked seedbed that is smooth, fine , firm , and preferably with good soil moisture at planting, to ensure simultaneous emergence of male and female lines. It is well worth the extra effort to prepare good seedbeds. Poor and uneven seedbeds can affect the rate of seed germination, resulting in a poor “nick” and subsequent yield losses due to poor pollination. For land preparation for planting, primary tillage operations depend on field conditions and irrigation practice . On sandier soils with minimal soil compaction, beds can be reshaped after disking in the previous crop residue. However, growing racks soils with more clay, as tend to occur in the Sacramento Valley, have more problems with soil compaction and often require more extensive field preparation.

Furrow-irrigated fields are ripped to a depth of 18 inches, whereas fields with subsurface drip systems are chiseled in the furrows, to a depth of 12 inches, taking care not to destroy the drip system. Afterwards, fields are disked and ring-rolled in one operation in the fall twice to incorporate the previous crop residue and break dirt clods, taking care not to go too deep and disrupt any subsurface drip systems. A finishing disk further breaks clods and makes a fine seed bed, followed by a GPS drag scraper to smooth the ground and level fields. Afterward, beds are formed using bed-making equipment, with the bed size depending on the sunflower variety and production capability and also on the growers’ equipment preference. Subsurface drip fields are mapped with GPS technology so that the beds are always formed over the buried drip tape. Bed size will vary from single-seed rows on 30-inch beds to double seed rows on 60-inch beds, and sometimes three seed rows on 80-inch beds. The minimum soil temperature at planting is 50°F. Weeds that have germinated during the wintertime must be controlled prior to planting, either by cultivation or by an herbicide application, such as glyphosate . Fields are cultivated for weed control and to incorporate herbicides prior to planting .Overlap in flowering between male and female lines is needed in hybrid sunflower seed production to ensure good pollination by pollinators and seed set. Honey bees are used for moving pollen between the male and female parent lines at a stocking rate of 1.5–2 hives per acre. Growers commonly contract with beekeepers for hives at a current cost of $40 to $50 per hive. Hives should be set around the fields when the male plants begin to flower to ensure that the bees stay in the field. Insecticide applications for pest control should be made before the delivery of bees to the field or early in the morning before most bees are actively foraging. Male lines are usually highly branched and have more flowers to maximize pollen production and pollination, compared to the single female flower.

Poor seed set can occur when simultaneous bloom doesn’t occur, if the female parent is unattractive to bees , if the male parent line is a poor pollen producer, or if weather conditions are unfavorable for pollen production and honey bee activity. High temperatures can reduce the number of pollen grains per flower in sunflower; however, no differences in pollen germination rates at an upper limit of 88°F have been observed, indicating pollen viability is resilient. Honey bee activity and subsequent seed set can be reduced by wind or if it is too hot or too cold. Honey bee activity ceases below 55°F and above 95°F. Seed set can also be less in the center rows when wide passes of 12 or more female rows are planted due to a lack of honey bee foraging activity. Symptoms of poor pollination include empty or underdeveloped hulls. Native bees, including a digger bee and long horned digger bees , sometimes referred to as ‘sunflower’ bees, primarily collect pollen. Honey bees either forage for nectar or pollen, but not both. Native bees often jostle honey bees around in sunflower fields, causing honey bees to disperse more, making them better pollinators. Some species of native bees are solitary and nest in the ground and can be encouraged through on-farm insectary plantings . Chop and destroy the male plants once the female line is finished flowering and has set seed to prevent seed contamination of the female line at harvest. In addition, destroying the male rows before they set seed also helps reduce volunteer sunflowers that can be difficult to control in subsequent crops, especially for herbicide tolerant sunflowers, like Clearfield or ExpressSun.Prior to planting, sample the soil from 0 to 6 inches deep to determine the likelihood of crop response to phosphorus , potassium and zinc fertilizer. If soils are deficient in these nutrients, sunflowers are likely to be responsive to them. If yield differences existed within a field for the previous crop, sample and analyze these areas separately by taking 12 to 15 cores in each problem area from 0 to 6 inches deep and mixing them together to make up a composite sample. Separate samples should also be taken from areas of the field with different soil types that could affect nutrient availability. The soil pH should be from 6.0 to 8.0 for good sunflower production. Although sunflowers appear to tolerate soils with pH as low as 5.5, growing weed vertically consider liming if the pH is below 6.0 to improve nutrient availability in the soil.

Areas of known or suspected high salinity or boron should be sampled at depths of 0 to 6, 6 to 12, and 12 to 24 inches if there is reason to suspect toxicity problems.Knowledge of field history and past nutrient deficiencies or toxicities should be taken into consideration before planting sunflowers.Sunflowers have a deep taproot and are good scavengers of nitrogen . Some N will be available from the previous crop, long-term fertilization practices, and N release from soil organic matter. For example, more N will be available in the soil after a tomato crop, than after corn or wheat. If N is deficient, the older sunflower leaves will turn uniformly pale green to yellow, plant growth will be reduced, flowers may not develop, and heads will fill poorly. As a starting point for determining N needs in sunflowers, the seed has an average N content of 3.7 percent. For a yield of 1,400 pounds per acre, the seed will need at least 52 pounds of N per planted acre to account for crop removal. An additional 25 pounds of N per acre will be needed for the plant . Adding 25 percent more N for male acreage , the total N needed by a sunflower crop producing 1,400 pounds per acre yield is approximately 100 pounds of N per acre, with yield calculated on a whole-acre basis. Fertilizer trials in sunflowers have generally not shown yield benefits at N application rates exceeding 100 to 150 pounds N/acre. To ensure good hybrid sunflower seed production, fertilization begins with a starter fertilizer of 8-24-6 with 1-2% Zn band-applied during planting, 2 inches below and 2 inches to the side of the seed row. Apply about 100 pounds of dry fertilizer or 10 gallons of liquid fertilizer of similar analysis per acre. The starter fertilizer is particularly important for spring plantings with cooler soil temperatures, when phosphorus and zinc are less available. Exercise particular care with starter fertilizer placement in order to avoid salt damage or ammonia toxicity to the germinating seed. Do not use urea or diammonium phosphate, either 18-46-0 or 16-48-0. Do not place any fertilizer in direct contact with the seed. As a general rule, a monoammonium phosphate is the preferred base fertilizer and should be placed no closer than about 2 inches to the side and about 2 inches below the sunflower seed. At lay by, when the plants are about 12 inches tall, fertilize the fields with N so that it is readily available for rapid plant growth and development. Prior to the N application, residual N levels in the soil should be determined about 10 to 15 days prior to the planned side-dressing. This allows for the rate of applied N to be based on the available nitrate-N in the top 24 inches of the soil . Take soil samples from 0 to 6 inches, 6 to 12 inches, and 12 to 24 inches deep at 2 to 3 locations in each field, as described in Geisseler and Horwath , and request analysis for nitrate-N. For furrow-irrigated systems, N should be side-dressed during a cultivation for weed control, with aqua ammonia or a similar N fertilizer. If using subsurface drip, start injecting N in the drip line when the plants are about 12 inches tall and continue until the sunflowers begin to head out . Nitrogen rates can also be reduced somewhat if the irrigation water contains high nitrate levels. Calculate the number of pounds of N per acre-foot of irrigation water by multiplying the parts per million nitrate-N in the irrigation water by the factor 2.72. Have your water tested, because irrigation water sources vary considerably in nitrate-N concentration. Excess N applications may delay flowering, leading to yield and quality reductions.Phosphorus can be especially important for sunflower production in California due to the relatively early planting dates and cooler soil temperatures that reduce P solubility and uptake. Phosphorus is particularly important in the early stages of plant growth because it promotes the development of extensive root systems and vigorous seedlings, which also helps the plants out compete weeds. A phosphorus deficiency is characterized by slow plant growth, poor tap root development, thin stems, and older leaves that turn yellow and drop prematurely, while the new leaves are small and dark green. If a representative soil test prior to planting indicates a P deficiency, apply a starter fertilizer at the rate indicated in table 4 as pounds of P2 O5 per acre. The soil test using the Olsen bicarbonate extract should be used on soils with a pH of 6.5 or greater, while the Bray #1-P extract should be used for soils with a pH less than 6.5. Soil tests showing very low and low extractable P levels would be expected to show a yield response to P fertilization. Crops grown in soils that have test levels in the moderate range are less likely to respond to P fertilizer applications.Potassium is essential for translocation of sugars, starch formation, and for regulating the opening and closing of stomata, which helps water use efficiency. Potassium additionally promotes root growth, produces larger, more uniformly distributed xylem vessels throughout the root system, and increases plant resistance to diseases. Sunflowers also need relatively large amounts of K for stalk and tissue strength, since it is a tall plant. When K is limiting in sunflowers, deficiencies include smaller leaves, yellowing and necrosis of the lower leaves, stunting, and thinner stems that make the plant more susceptible to lodging. If a representative soil test indicates a K deficiency, correct it using a starter fertilizer containing K at the rate indicated in table 5 as pounds of K2 O per acre. Soil test results that fall in the low range indicate that plants should respond to K fertilization; test levels in the medium range indicate that the plants are less likely to respond to K fertilization.