Effect of Nitrogen Levels on Nitrogen Uptake and Nitrogen Use Efficiency of Sugarcane Varities.

EFFECT OF NITROGEN LEVELS ON NITROGEN UPTAKE AND NITROGEN USE EFFICIENCY OF SUGARCANE VARITIES SIREESHA.AMBATI Regional Agricultural Research Station, Anakapalle, Andhra Pradesh, India. Sugarcane being a very exhaustive crop removes about 205 kg of N for yielding 100t/ha and for suataining productivity nitrogen is should be replenished through chemical fertilizers every year. The objective in nitrogen fertilization of sugarcane is to supply this nutrient in an amount adequate for maximum cane and sugar yield. There is increasing interest in improving the nitrogen use efficiency of cultivated crops, due to the high cost of synthetic N fertilizer. Earlier studies indicated that there was differences in nitrogen use efficiency between sugarcane varieties, which could be exploited to improve N fertilization. Therefore an experiment was conducted to study the differential response of promising pre release genotypes to nitrogen fertilization. A field experiment was conducted with five levels of nitrogen (Control (0% Recommended Dose of Nitrogen), 75% RDN, 100% RDN,125%RDN and 150% RDN) applied in two splits at 45 and 90 days after planting using four varieties (two early 2001A63 ; 2000A56 and two mid late 98A163; 96A3) with three replications in factorial RBD. Recommended dose of phosphorus and potassium were applied as basal. Whole plant samples were collected for calculating nitrogen use efficiency at grand growth stage. The crop was harvested at maturity. The data was collected and treated with statistical method. Cane yield and Sugar yield were increased with increase in level of Nitrogen. 2001A63 recorded significantly higher yield at 100% RDN level ( 81.5t/ha), which was on par with 125%(84.1t/ha) and 150% (86.8 t/ha).Varieties 98A163 and 2000A56 recorded significantly higher yield 85.8t/ha and 76.75t/ha respectively at 125% RDN level, which was on par with 150% (86.2t/ha and 81.8t/ha).96A3 recorded significantly higher yield at 150% RDN (77.7t/ha). Apart from the influence on cane yield nitrogen also plays important role in influencing the juice quality. Data on sugar cane juice quality parameters revealed that there was a decrease in juice sucrose(%) with increase in levels of nitrogen application. Variety 98A163 recorded highest sucrose (%) followed by 2001A63, 2000A56 and 96A3. In all the varieties tested highest sucrose (%) was observed at 100% recommended dose of nitrogen application. Nitrogen use efficiency (%) was high at 100% recommended dose of N for the varieties2001 A 63 (37.05%) and 98 A 163(38.83%).However 96 A 3 recorded higher use efficiency at 150% RDN and 2000A56 at 125% RDN. The amount of cane (kg) produced with increase in kg of nitrogen applied was varied with the variety (Table.2). Early variety 2001A63 (0.29t/ha/kg. of N) and mid late variety 98A163(0.30 t/ha/ kg. of N) reported to be with high nitrogen use efficiency in terms of kg of cane produced per kg of nitrogen applied. Correlation co-efficients were also calculated for cane and sugar yield with the levels of nitrogen applied. There was a significant and positive correlation was observed with cane yield (0.9894), sugar yield (0.9850). The increase in cane yield with increase in nitrogen application in sugarcane was due to the increase in yield attributing characters of sugarcane like no. of milliable canes, no. of inter nodes, length of internodes etc,.(Jaypaul et al.,2000) The decrease in juice quality with an increase in nitrogen was observed due to the hydration and succulence of plant tissue. Uptake of high amounts of nitrogen results in continued consumption of carbohydrates in manufacturing body building materials even late in the growing period. This prolonged growth naturally leaves less amount of food manufactured by the plant for accumulation as sugars.(Asokan et al.,2005).The differential yields of sugarcane varieties with nitrogen application was due to the specific internal nitrogen requirement of sugarcane varieties for maximum yields. (Stanford and Ayres,1964).