Dynamic of nitrogen in the sugarcane plant and soil system

Dynamics of nitrogen in the sugarcane plant and soil system were studied in 1998 at Suphan Buri, Chiang Mai and Khon Kaen. Nitrogen transformation, movement and distribution in the soil system was examined using micro-plot experiments, at the Suphan Buri and Chiang Mai sites. Three types of fertilizer nitrogen and a control with no nitrogen were compared in a RCB design with four replications. Native nitrogen mineralization was found to be higher in Chiang Mai soil than for that in the Suphan Buri soil. The amount of nitrogen released from urea, ammonium sulfate and 15-15-15 (compound fertilizer) fertilizer sources were not significantly different at Suphan Buri. In Chiang Mai, however, the 15-15-15 fertilizer provided higher inorganic nitrogen levels than those of urea and ammonium sulfate. These levels of mineralized nitrogen also stayed in the soil system for a longer period than for those in the Suphan Buri soil, this being due to the lower soil moisture content. The dynamics of nitrogen in the sugarcane plant were examined, following the soil study described above. The experiments were conducted at Suphan Buri, Chiang Mai and Khon Kaen in 1998. Three methods of application of nitrogen fertilizer (ammonium sulphate) and a control with no nitrogen were compared in a RCB design with four replications. The nitrogen uptake and distribution in different parts of the plant were determined at five stages of growth. The fertilizer application was found to increase the nitrogen content in all the plant parts examined, but was most concentrate in the top part. Uptake of nitrogen reached its maximum at the 32nd leaf growth stage, and then subsequently declined. The characteristics of nitrogen uptake differed with location and method of fertilizer application. Cane yield was significantly increased with the increasing amounts of fertilizer applications since there was an increase in the number of millable stalks. There was no advantage of splitting or delaying nitrogen application over the three sites. Over supply of nitrogen created a detrimental effect on the cane juice quality, as shown by low CCS, brix and sucrose values.