sugarcane responses to irrigation and nitrogen in subtropical iran

limited information is available on water and nitrogen (n) management of sugarcane (saccharum officinarum l.) in khuzestan, southwestern iran, where this crop is currently and extensively grown under heavy irrigation and n fertilization. therefore, a field experiment was conducted from september 2000 to march 2002 at the research department of karoon agro-industry in khuzestan to determine the effect of four irrigation [irrigation water/cumulative pan evaporation (iw/cpe) ratios of 0.6, 0.8, 1.0, and 1.2)] and four n (0, 86, 172, and 258 kg n ha-1) levels on sugarcane yield and water and n use efficiencies. the experiment was carried out as split-plot arranged in a randomized complete blocks design with four replications. pan evaporation data was recorded daily using class a open pan. increased water and n application increased both plant cane crop and sugar yields. the highest sugar yield was obtained under iw/cpe = 1.2 (29 irrigations) and with 172 kg n ha-1  with no significant difference with iw/cpe = 1.0 (25 irrigations) and 86 kg n ha-1, respectively. higher irrigation and n levels showed a small but not significant reduction in both juice sucrose and purity percentages. higher n levels significantly increased the n use efficiency (nue) for cane yield, but nue for sugar yield was highest at 86 kg n ha-1. water use efficiency (wue) increased with higher water application. thus pan evaporation data and n management can effectively meet both irrigation (iw/cpe = 1.0) and n requirements (86.0 kg ha-1) of sugarcane without any adverse effect on yields and environment and reduces production costs as well.