Flowering, fruit set and crop yield

Poor seed set in sunflower has several common causes, including poor pollination, heat or water stress at flowering, and boron shortage, to which sunflower is known to be sensitive. A soil and leaf test for boron, together with a check on pollination and weather at flowering, will narrow it down.

If a test confirms low boron, common sources include Boric Acid, Di Sodium Octaborate Tetrahydrate and Borax Anhydrous. How these differ is set out in boron sources compared. Boron has a narrow range between too little and too much, so the rate must come from an agronomist.

Some flower and square shedding is normal in cotton, but heavy shedding is commonly linked to water stress, high temperature, pests, too much nitrogen, or boron shortage. Regular fertilizer may not supply boron. Check pests and irrigation first, then test soil and leaves for boron.

Boron sources Taskon makes include Boric Acid and Di Sodium Octaborate Tetrahydrate. Because boron becomes harmful above a narrow range, any application should follow a test and an agronomist’s advice.

Lush leaves with small fruit often point to too much nitrogen relative to potassium and phosphorus, or to potassium shortage at fruit fill, though water stress, crop load and pollination also matter. A soil and leaf test taken at fruiting will show whether the balance is the problem.

Growers who need to shift the balance toward potassium commonly use sources such as Potassium Sulphate, Potassium Nitrate and Mono Potassium Phosphate. The balance for your crop and stage should be set by an agronomist.

A crop that grows well but yields poorly usually ran short of something during flowering and grain or fruit fill: water, potassium, phosphorus, a micronutrient, or it was hit by heat, pests or disease at that stage. Leaf tests taken at flowering, not only at planting, show whether nutrition was the limit.

Feeding needs change through the season, so a programme set only at sowing may miss the demand at fill. An agronomist can match feeding to crop stage. Taskon’s nutrient sources are listed in the NPK fertilizers, phosphates and sulphates ranges.

Heavy fruit drop after good flowering is commonly caused by water stress, heat, poor pollination or pests, and nutrition is only one possible factor. Where nutrition is involved, boron, calcium and potassium are the ones most often checked. A leaf test at fruit set will show whether any is low.

Sources Taskon makes for these nutrients include Boric Acid, Calcium Nitrate and Potassium Sulphate. Please treat nutrition as one line of inquiry alongside irrigation and pest checks, not the only one.

A yield plateau under a fixed feeding schedule often means the schedule no longer matches the crop, or that salts have built up in the growing medium. Testing the drain or runoff water and the medium, alongside leaf analysis, shows whether the feed is out of balance.

Salt build-up, water quality changes and climate control can all cap yield as surely as nutrition. An agronomist can compare the feed going in with the drain coming out. Water-soluble sources Taskon makes include Calcium Nitrate, Potassium Nitrate, Mono Potassium Phosphate and Magnesium Sulphate Heptahydrate.

Slow growth under regular NPK feeding is often caused by something NPK does not supply, such as calcium, magnesium or micronutrients, or by root zone problems like wrong pH, salinity, poor aeration or low temperature. Test the medium and the water, and check the roots.

NPK covers three nutrients out of many a crop needs. Taskon makes secondary and micronutrient sources including Calcium Nitrate and Magnesium Sulphate Heptahydrate and the EDTA chelated micronutrients range.

Slow, uneven seedlings are most often caused by the growing medium, watering, temperature or light rather than a missing fertilizer, and seedlings are easily damaged by too much feed. Check the medium’s pH and salt level and the growing conditions before adding nutrients.

Where a test shows the medium is short of nutrients, nurseries commonly use a mild, fully soluble feed. Taskon makes NPK 100% Water Soluble Fertilizer. The strength for young seedlings should come from a nursery specialist or agronomist.

Weak, thin roots despite good watering often point to overwatering and poor oxygen in the root zone, high salinity, root disease or nematodes, rather than a nutrient shortage. A check of the medium’s drainage, salt level and a root inspection should come before any change in feeding.

Phosphorus supports root development, but adding it will not fix a drainage, salinity or disease problem. Confirm the cause first. Phosphorus sources Taskon makes include Mono Potassium Phosphate and Mono Ammonium Phosphate.

Foliar feeding supplies small amounts through the leaf and can act quickly for some nutrients, but it cannot replace soil feeding for the major nutrients, and results depend on the nutrient, leaf surface, weather and timing of the spray. Symptoms already on old leaves may not visibly clear.

Foliar sprays are commonly used for micronutrients or to correct a shortage quickly during the season. Spray timing, water quality and leaf condition all affect how much is taken up. An agronomist can say whether foliar, soil or both suits your crop. See also EDTA chelates vs sulphate salts.

Different results from similar sprays usually come from differences in the product’s form, the spray water, the time of day, the leaf condition or the underlying cause of the yellowing. If the yellowing is not caused by the nutrient you are spraying, no spray of it will green the crop.

Before comparing products, confirm with a leaf test that you are correcting the right nutrient. Hard or alkaline spray water and spraying in hot sun can also reduce uptake. An agronomist can check the cause and the method.

Fungal disease that no longer responds to a usual spray may indicate resistance, the wrong product for the disease, poor coverage or timing. This is a crop protection question for a plant pathologist or agronomist, who can identify the disease and recommend an approved treatment.

Taskon Industries supplies chemicals, not formulated crop protection products, and this page does not advise on fungicide choice. Please consult your state agriculture department or a qualified plant protection specialist, and use only products approved for your crop.