Response of Sugarcane Ratoons to the Residual Effects of Urea-N Applied To Plant Cane and Ratoons

This study is based on two previously conducted experiments that were carried out to conserve urea-N. The first was planted October 2005, established for the first and second ratoon during seasons 2007 to 2009; and the second was planted in June 2006 and established for the first ratoon during the season 2007/2009. The treatments of the basic experiments were 357.1 and 535.7 kg urea /ha. Conserving treatments were splitting the dose of urea versus the full dose and burying the urea versus unburied urea treatments. Results of the basic experiments showed no significant differences between any of the used treatments.
The current study consisted of one treatment to all experimental units of the basic experiments. These treatments were application of 238.1 kg urea/ha for June planted cane basic experiment in the second ratoon (season 2009/2010). For both basic experiments, June and October plantings, no urea application in the third ratoon (seasons 2009/2010 and 2010/2011), and application of the normal rate of urea (usually given to the commercial cane fields i.e. 476.2 kg urea/ha) in the forth ratoons (seasons 010/2011 and 2011/2012). The objective of the current study was to investigate the response of the sugarcane crop to the residual N effect of previously conserved treatments of urea in the basic experiments after plant cane, first and second ratoons. The results of the current study revealed that there were no significant differences in cane yield, yield components of the ratoon crops for the residual N effects of previous conserved urea-N treatments of the basic experiments. However, yield and yield components of no urea treatments showed very low values possibly due to effects of N deficiency on the sugarcane crop. Moreover, application of half the normal commercial crop urea rate, i.e. 238.1 kg /ha, gave moderate yield and yield components. Finally, in application of the common commercial urea rate, i.e. 476.2 kg/ha, the sugarcane crop attained satisfactory yields and yield components. The quality parameters, namely brix, pol and ERS percentages of cane, were not affected with treatments. The current study confirmed the reported low residual effects of N fertilizers on subsequent crops even if it contained a conserving practice such as burying the urea or splitting the rate. It is thus recommended that at every growing season the sugarcane crop should receive the adequate rate of N fertilizer.