Plant nutrition forms the basis of a healthy productive crop. Plants get this through three ways: nutrients present in the soil, recycling of nutrients (such as dead leaves falling back to the soil) and through the application of fertilizers. Sugarcane consumes both large and small amounts of nutrients. Nitrogen, phosphorous and potassium are examples of three elements consumed in large amounts (known as macronutrients). Magnesium, boron and iron are examples of elements consumed in small amounts (known as micronutrients).
SIRDI, with the assistance from the European Union, conducted a field soil and crop review study last year. Soil samples were selected from twenty five sites representative of the sugar
industry. Each site was carefully selected to represent a soil type.
Nitrogen deficiency in the leaf means that insufficient nitrogen is reaching the roots of sugarcane plants. The causes of Nitrogen deficiency are high because our soils are basic
(sugarcane prefers slightly acidic soils instead of basic soils), the high levels of calcium in soil and the forms of fertilizer application. Traditionally, fertilizers used in the sugar industry are urea based: Urea-based fertilizers, which contain nitrogen, are very inclined to nutrient loss through volatilization. This is loss is made quicker through the high pH and high Calcium concentration in the soil. Most farmers use fertilizers that do not contain Potassium. The most common are 18-46-0, 28-28-0, 46-0-0 and 34-18-0. All of these fertilizers have zero potassium,
represented by the zero at the end of each blend. This has severely depleted potassium soil reserves and consequently, the leaf analysis has shown severe deficiencies. It is important that the industry nutritional program includes high levels of potassium to correct the Potassium deficiency.
To correct the problem, farmers are encouraged to switch to ammonium nitrate or better
yet, ammonium sulfate based fertilizers. Ammonium nitrate and ammonium sulfate are much
less inclined to volatilization and are taken in faster by the soil. Ammonium sulfate can also
correct the 1/3 of the industry that is showing sulfur de ficiencies. The sulfate will also, with
continuous use, lower the soil pH to desirable levels.
Contributor: Adrian Zetina