Excellent response in citrus with potassium nitrate

Citrus trees are rich in nitrogen (N) and potassium (K), with K being absorbed in greater quantities. What citrus growers strive to achieve are yield increases, more fruit per hectare, more fruit per tree and larger fruit; improved quality through increased brix, TSS, acidity, vitamin C, fewer skin defects, increased skin thickness, reduced graining and better color and by reducing crop losses by increasing disease resistance. Potassium nitrate (^Ultrasol® K ^Plus1 and ^Ultrasol® K Plus ^Acid2) has been shown to improve all the above parameters.

Fertigation programs that include potassium nitrate

It is well documented in many crops and in many soil conditions that the combination of a positive potassium cation (^K+) with the negative nitrate anion (^NO3-) acts synergistically in the uptake of each other. This charge combination maintains electrochemical balance within the roots and plant. Since citrus fruits utilize both N and K elements in the greatest amounts, this combination is very beneficial in fertigation programs. The presence of nitrates in a nutrient solution also directly and proportionally limits the uptake of excess chlorides.

Other important aspects of maximizing nitrogen-nitrate, as opposed to positive nitrogen-ammonium cation (^NH4+) or urea nutrition (converts to ammonium), are to maintain optimum pH near the roots and reduce antagonistic uptake between the positively. charged ammonium and the other positively charged cations such as ^Ca2+ and ^Mg2+ as well. Therefore, using potassium nitrate to maximize the supply of negatively charged nitrates is the ideal way to optimize ^K+ uptake, N uptake and uptake of the other cations, ^Ca2+ and ^Mg2+, in trees. The result is always a higher plant dry weight reflected in the wood and fruit (yield and quality).

Foliar applications with potassium nitrate alone or in ^combination3

Foliar applications are required under conditions where there is a recognized need. This could occur at times of peak demand and/or poor rooting conditions as a result of nutrient imbalances, nutrient fixation, salinity, cold, waterlogging, drought, incorrect fertilizer applications and root diseases.

Fruit set, or the prevention of fruit drop, is the most important factor influencing yield. Flowering and fruit set are periods of high nutrient demand, and fruit set often occurs when soil temperature is low. Foliar applications of potassium nitrate in combination with auxins at Nova, Valencia and Shamouti have been shown to improve fruit set and soluble solids, increase fruit size, weight and yield, and decrease split fruit. In Nules and Valencia, potassium nitrate applications have shown higher fruit set, higher TSS, higher fruit yield and gross revenue.

Potassium nitrate has been shown to increase the disease resistance of a citrus tree. The severity of attack is reduced by restricting the pathogen's food supply and by promoting the formation of disease inhibitory compounds such as phenols, phytoalexins and auxins. This limits the establishment and spread of pathogens within a plant.

Potassium nitrate is the preferred source of N and K in citrus nutrition, often resulting in optimal K and N uptake, stronger and healthier plants, improved fruit set and yield, larger fruit size, fewer peel problems, improved color intensity, increased disease resistance and greater tolerance to stresses such as drought, frost and salinity. For both fertigation and foliar applications, consult your agronomist for rates and timing of applications.

[1] Reg. No K5020 Law 36/1947. Registration holder Chemical and Mining Company (Africa) (Pty) Ltd [2] Reg. No K6489 Act 36/1947. Registration holder Chemical and Mining Society (Africa) (Pty) Ltd [3] All statements in this article may be substantiated by references which may be available upon request.

Content provided by Duncan Napier Technical Manager SQM Africa