Blueberry

Nitrogen is the nutrient that promotes the growth and vigor of the plants. It is one of the fundamental elements of plant nutrition, since it is included in the composition of chlorophyll. Small fruit plants will continuously absorbs nitrogen from vegetative growth through to the beginning of ripening. Nitrogen can be absorbed by plant roots in two different forms: the ammoniacal form (NH₄⁺) and the nitrate form (NO₃^-). In the soil, ammoniacal nitrogen is gradually transformed into nitrate nitrogen by nitrification in moist soils.

During the vegetative stage up to flowering, the optimal growing temperature for small fruits is around 25°C, and the two sources of nitrogen (NO₃^- and NH₄⁺) should be in balance. Although the small fruits generally prefer ammonium to nitrate in their nutrition, the presence of ammonium can become harmful at certain growth stages. Nitrogen in the ammoniacal form generally becomes available to the plant over a period of time. This is not ideal in cases where the supply of nitrogen needs to be ‘switched off’ quickly during fruit maturation. Although nitrate is a slightly toxic anion for small fruits, it is also very mobile and can be transported to all parts of the plant. Nitrates (NO₃^-), having a negative charge, act as a “transporter” of cations to the organs (leaves, flowers, fruits), where all the elements can then perform their roles.

N deficiency symptoms generally appear on adult leaves first. With limited nitrogen availability, plants stop growing and are weak. Nitrogen deficiencies are observed as a reduction in the leaf area and a yellowing of older leaves, which may fall prematurely. The growth of the roots is also reduced and its branching is restricted in such a way that the stem to root ratio is increased. Consequently, both crop yield and quality are significantly reduced.

Phosphorus is a vital component of adenosine triphosphate (ATP), the “energy unit” of plants. ATP forms during photosynthesis, has phosphorus in its structure, and is active from the beginning of seedling growth through to the formation of fruits and maturity. Phosphorus is important for the general health and vigor of all plants including small fruits. Some specific growth benefit that have been associated with phosphorus are: a stimulation of root development, increased shoot and branch strength, improved flower formation and fruit production, more uniform and earlier ripening, improved crop quality, increased resistance to disease, and more vigorous development throughout the growth cycle.

Phosphorus is an essential nutrient for all parts of the plant as it is required for membranes, energy molecules and nucleic acids. The role of phosphorus in promoting root development means it is an essential factor in terms of successful establishment of the plants. A lower soil pH, such as that required for the cultivation of blueberries, may reduce phosphorus availability in the soil.

Phosphorus deficiency manifests itself as a reduction in plant size, accompanied by poor root growth and the coloration of the adult leaves is purple. In soils where levels of below 3 ppm of P are found, approximately 110 kg/ha of phosphorus should be applied before transplanting. In established plantations around 80 kg/ha of phosphorus should be applied during in the plant development stage (preferably using fertigation).

It is also involved in the membrane transport processes, in charge balance, in the generation of turgor pressure, in the plant transpiration and in cell elongation. The demand for potassium fluctuates throughout small fruit growth production. Potassium generally accumulates in the tissues of the stem during the vegetative stage and its content then decreases as the plant grows. However, the absorption of potassium peaks during flowering and during fruit ripening. At this time, the concentration of potassium in the leaves is low. The plant’s response to potassium fertilization obviously depends on the time of its application. In fertigation, potassium applications during the vegetative stage are less likely to have a positive impact on the crop yield. In contrast later applications of potassium during the flowering period and as the fruits start to form will usually significantly increase the yield and also the number of flowers produced. Complimentary foliar applications of potassium from flowering onwards can provide a valuable potash boost to the plants when the need for this nutrient is at its highest. In cases where insufficient potassium is available, deficiency symptoms will appear as a light green to yellow color around the margins and tips of adult leaves, which later evolve into necrosis (leaf “burn”). Potassium deficient plants are often more sensitive to diseases and more vulnerable under conditions of stress.

In the plant, it is incorporated into certain amino acids (cysteine, cysteine, methionine) and subsequently becomes part of certain enzymes (e.g. coenzyme A), vitamins (e.g. thiamine, biotin), and oils. Once in these complex molecules, sulfur is not easily mobilized within the plant. Hence in cases of deficiency, symptoms will occur in the young tissues first.

All proteins (and therefore enzymes) need sulfur to function, as disulfides bonds stabilize their structures. Sulphur also plays a key role in nitrogen metabolism. Sulfur plays a role in the aroma of certain small fruits through volatile sulfur compounds.

Annual fertilization must include at least 17 at 23 kg/ha of sulfur (S) otherwise there is a risk of deficiency. Leaf sulfur deficiency in small fruits shows up as yellowing accompanied by purple dots on the young leaves.

Calcium is also important for the stability of the cell membrane and the maintenance of fruit quality. Calcium also plays an important role in the plant’s defense by enhancing resistance to biotic and abiotic stress.

Calcium is a slowly mobile element. It is mainly absorbed by the young roots of the plant and is then transported by the flow of transpiration to the aerial parts. In fact, calcium is rather immobile in the phloem and quantities contained in the leaves will not be remobilized towards the fruits. All calcium found in the fruit reaches it through the xylem.

The peak of calcium absorption takes place during the vegetative stage, and absorption generally decreases during fruiting. Furthermore, flowers contain a significant amount of calcium, but from fruit set, the concentration decreases rapidly, probably due to the influx of photosynthates to the fruits. The concentration of calcium in the leaves, however, remains constant during the fruit development and ripening. Calcium deficiency occurs first in the apical meristems and young leaves because of the low mobility of calcium. Deficient leaves are chlorotic, and at later stages, they show signs of necrosis at the margins. Temporary calcium deficiencies can occur when the levels of this element in the xylem are low, due to the reduction in the rate of transpiration caused by high relative humidity, cloudy days or low water availability. Exogenous application of calcium will help prevent deficiency but it will not serve a corrective measure.

It plays an important role in the regulation of cellular pH and the anion-cation balance. Undoubtedly, the most important function of magnesium is as a constituent element of chlorophyll that intervenes in carbohydrate synthesis. It has an important role to play in energy metabolism (photosynthesis, glycolysis, Krebs cycle), since magnesium ions are crucial in the phosphorylation of protein kinases. Adequate levels of magnesium will increase the intensity in the green color of leaves and contribute to increase the performance of the plant (increased photosynthetic activity in the leaves). In addition, good levels of magnesium will improve the accumulation of reserves for next season.

Application of magnesium is recommended when the concentration of this element in the soil is less than 1 meq/100 g. In such cases, an application of around 50 kg magnesium (Mg) per hectare is recommended. Magnesium deficiency can occur in light, acidic soils that are prone to leaching or in soils that have received high rates of potassium fertilizers. Deficiency generally shows up as internervenal necrosis in the older leaves.

Each litre of Thio-Sul provides approximately 160 g of nitrogen and 346 g of sulfur, delivering a concentrated and efficient source of both nutrients. Its liquid formulation is easy to handle and integrates readily into modern crop nutrition programmes across a wide range of crops and production systems.

By supplying nitrogen and thiosulfate sulfur together, Thio-Sul helps maintain an appropriate nitrogen-to-sulfur balance, supports protein formation and promotes more efficient use of applied nitrogen. Its sulfur becomes available progressively as thiosulfate is converted in the soil, helping support crop nutrition throughout key growth stages.

Thio-Sul can be applied through irrigation systems, banded, broadcast, injected into the soil or incorporated into compatible liquid fertiliser blends. This application flexibility makes it a practical solution for improving sulfur nutrition and complementing nitrogen fertilisation.

Each litre of KTS supplies approximately 360 g of potash and 252 g of sulfur, providing a highly concentrated source of soluble potassium and sulfur. Its nitrate-free and chloride-free formulation allows potassium to be supplied without adding unnecessary nitrogen or chloride.

Potassium supports water regulation, enzyme activity, carbohydrate transport and the development of crop yield and quality, while sulfur contributes to protein and enzyme formation. KTS is particularly valuable during periods of rapid growth, reproductive development and crop filling, when potassium requirements can increase substantially.

KTS can be used through fertigation, in starter or side-dress programmes, in compatible liquid fertiliser blends and as a foliar treatment on selected crops. Its versatility allows potassium and sulfur to be delivered at critical stages within a wide range of crop nutrition programmes.

Each litre of CaTs supplies approximately 75 g of calcium and 125 g of sulfur, providing both nutrients in a fully soluble liquid form. CaTs combines crop nutrition with soil-management benefits and can be incorporated into a broad range of fertilisation programmes.

Calcium contributes to cell-wall strength, root development and the structural integrity of growing plant tissues, while sulfur supports protein and enzyme formation. A consistent calcium supply is especially important during periods of rapid vegetative growth and fruit development, helping support crop quality, firmness and marketability.

CaTs can be applied through irrigation systems, banded, broadcast or blended with compatible liquid fertilisers. It may also be used as a soil amendment to provide soluble calcium, support soil aggregation and water infiltration, and help manage the effects of excess sodium in saline or sodic soils.

Its fine crystalline formulation dissolves rapidly and completely, producing a clean spray solution with minimal residue. This makes K-Leaf particularly suitable for precision spraying and for situations in which crops require a rapid supplementary supply of potassium and sulfur.

Applied directly to the foliage, K-Leaf helps prevent or correct potassium and sulfur deficiencies during critical growth stages. Potassium supports water regulation, photosynthesis, carbohydrate movement and crop quality, while sulfur contributes to protein synthesis and essential metabolic processes.

K-Leaf can supplement soil fertilisation when nutrient uptake through the roots is restricted or when crop demand temporarily exceeds soil supply. It is suitable for a wide range of broad-acre, fruit and vegetable crops and can be combined with many compatible soluble fertilisers and crop-protection products following a compatibility test.

SoluPotasse provides potassium and sulfur without nitrogen or chloride, allowing both nutrients to be managed independently within the crop nutrition programme. Its fine crystalline form dissolves rapidly and completely, making it suitable for demanding fertigation applications.

Potassium supports water-use regulation, enzyme activation, carbohydrate transport and crop quality, while sulfur contributes to protein formation and nutrient metabolism. SoluPotasse is particularly useful when crops require additional potassium but no further nitrogen, including during fruit, tuber and grain development.

SoluPotasse can be applied through fertigation and other systems designed for fully soluble fertilisers. Its low-chloride, nitrogen-free composition makes it well suited to chloride-sensitive crops, saline growing conditions and fertilisation programmes requiring precise control of nitrogen and potassium inputs.

The chloride-free, nitrogen-free formulation of GranuPotasse provides an efficient source of potassium and sulfur, making it ideal for chloride-sensitive crops and high-value production systems. The uniform, free-flowing granules ensure accurate spreading, easy handling and consistent field performance.

By supplying potassium and sulfur in readily available forms, GranuPotasse supports water regulation, enzyme activation, carbohydrate transport and protein synthesis, helping improve crop yield, quality and marketability. It is particularly beneficial for fruit, vegetable and other high-value crops where crop quality, storage life and export potential are essential.

GranuPotasse® is suitable for pre-plant, basal and in-season applications and can be broadcast, banded or incorporated into the soil. It also blends readily with many granular fertilizers, providing growers with a flexible solution for balanced potassium and sulfur nutrition across a wide range of cropping systems.