Surfactant and nutrient uptake in citrus

Abstract

The availability of essential nutrients in appropriate amount ensures the growth, productivity and quality for sustainable production of tree fruits including citrus. The essential mineral element below the critical level adversely affects growth and yield even other minerals are within optimum range. A balanced and continuous supply of the essential nutrients is a key for citrus growers to ensure profitability. Soil application is recommended for most of the macronutrients such as N, P and K, as these are required in large quantities. However, the soil application leads to nutrient losses through runoff, leaching and fixation. Therefore, the foliar application is considered as an attractive alternative to the soil application of essential nutrients. Particularly, the trace elements which are required in small quantity are preferably applied through the foliar sprays. Nutrients applied through the foliar spray are directly absorbed though leaves and have several positive attributes. Foliar application can reduce overall fertiliser application rate and energy use, improve nutrient uptake and reduce underground water pollution. The efficiency of foliar application of nutrients can further be enhanced with the addition of surfactants or adjuvant into the spray solution. Surfactants can be classified into various groups on the basis of their composition such as cationic, anionic, non-ionic, zwilterionic or ampholytic. The surfactants are widely used in foliar application of both macro- and micronutrients. This chapter reviews the available information about the use of surfactants in the foliar application of mineral elements in citrus with special reference to nitrogen (N), calcium (Ca), iron (Fe), zinc (Zn), boron (B) or copper (Cu).