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Barley [photo] 

Expertise

Boosting your sugarcane yield by mastering the basics of nutrition

By Marcel Heine (Agronomist: KwaZulu-Natal) and Johan Campher (Agronomist: Lowveld)

World sugar production has grown from around 50 million tonnes in 1965 to roughly 175 million tonnes today.

South Africa has been facing one of the worst droughts in farming history which has seen yields drop throughout the sugarcane industry. Total saleable sugar production is normally in the region of 2 million tonnes, but has dropped to a forecast of 1.6 million tonnes for the 2016/2017 season (SASA).

It is increasingly important to ensure that every aspect of sugarcane production is fine-tuned so that the yields and turnover are a true reflection of the potential achievable, given the amount of available water. One of these factors is nutrition, something that can be manipulated in order to achieve the desired output.

Water is required for the uptake of nutrients. Fortunately sugarcane has a long growing season and the ability to respond over a much longer period after fertilizer is applied. However, the uptake pattern of nutrients, coupled with the placement thereof, can influence the nutrient use efficiency (NUE).

The macro nutrients nitrogen (N), phosphorus (P) and potassium (K) are often given the most attention in recommendations, but sulphur and micronutrients are also needed by the plant to ensure optimal yields. N is mainly responsible for vegetative growth which has an essential role in the photosynthesis process responsible for the production of sugar. Timing is important as too much N applied late in the season can cause a drop in sugar production. P promotes early growth and is essential for the formation of a strong and vigorous root system, as well as many other processes in the plant. K enables the plant to use other nutrients and water more efficiently and controls the movement of sugars throughout the plant. Sulphur (S) is an often overlooked nutrient, but is of high importance and can result in yield increases (Fig. 1). S is necessary for the formation of amino acids, which forms part of protein structure, and also for the synthesis of certain enzymes and chlorophyll (Havlin et al., 2005).

N and K are required in large amounts and their uptake corresponds to the pattern of biomass accumulation. Time of application should be early for these nutrients, but will depend on the production area. P and S uptake follow a much flatter curve, but both are also needed for good growth early in the season (IPI, 2013). The placement of the less mobile nutrients P and K deserves special attention, preferably in or near the root zone. A ratoon crop is at a greater risk of deficiencies of P during the later ratoon cycles as fertilizer applied at planting can be depleted or fixed over time. The use of ripper tines for subsoil placement between sugarcane rows is becoming popular and this is one way to ensure better P, and also K availability if applied together. Broadcasting P on ratoon sugarcane is less desirable.

Irrigated areas

One way to ensure that nutrients are applied at the right time during various growth stages is by making use of fertigation where possible. This can lead to an improvement in water use efficiency and NUE. Fertigation is used to ensure that a balanced nutritional approach is followed for both macro- and micronutrients. Although micronutrients are needed in smaller quantities, they are just as important as macro-nutrients if soil levels are inadequate. These nutrients include boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu) and molybdenum (Mo).

  • B is necessary for the production of plant hormones and for the movement of plant sugars.
  • Zn is part of the enzyme system that regulates plant growth, the formation of chlorophyll, the transformation of carbohydrates and regulation of the consumption of sugar in the cane.
  • Mn is involved in photosynthesis and root growth.
  • Fe is essential for chlorophyll formation and function and is also critical for healthy vegetative growth. In green leaves, most of the Fe is localised in the chloroplast.
  • Cu has an influence on the chlorophyll content and is a catalyst in several oxidation processes.
  • Mo plays a specific role in catalysing the reduction of nitrate taken up by the plant to nitrite (Havlin et al., 2005).

Split applications of macro- and micronutrients can also be considered on more sandy soils where nutrient leaching and salinity issues are likely (Figure 2). Routinely testing your soils, optimising nutrient inputs, and focusing on what is actually needed can help increase your yields and profit in the long run.

Figure 1: Yield as influenced by additional nutrients added in a field experiment (adapted from Singh et al., 2008). α = 0,05.

Figure 2: An Omnia trial in the Eston area on sandy soil to determine the effects of split applications and additional nutrients on sugarcane growth and yield.

References
  • Singh, V.K., Shukla, A.K., Gill, M.S., Sharma, S.K., and Tiwari, K.N. 2008. Better Crops 2: 12-14.
  • Havlin, J.L., Beaton, J.D., Tisdale, S.L., and Nelson W.L. 2005. Soil fertility and fertilizers: An introduction to nutrient management. New Jersey: Pearson Education, Inc.
  • Fertilizing for high yield and quality sugarcane. 2013. International Potash Institute: Australia.