Water stress during different sugarcane growth periods on yield and response to N fertilization

Sugarcane is a high biomass crop that requires large quantities of water for maximum production. Substantial input of N is also typically required. Previous research has shown the dramatic impact of extended reduced water availability on sugarcane production and responses to N fertilization. If water availability is limiting, then the question becomes: are there certain periods during sugarcane growth when water can be more effectively utilized by the crop? A five-year field study was conducted to determine the effects of water stress during four different six-week periods during the grand growth stage of sugarcane on growth, quality, and responses to N fertilization. Reductions in cane yield and sugar content were most frequent and severe when water stress occurred during the period which had the highest total evapotranspiration (ET) and the least amount of rainfall as a percentage of ET. Water stress during other six-week periods had a much lesser affect on sugarcane yield and quality. Lack of cane and sugar yield response to water stress during the earliest growth period may have been a result of much lower ET during this period, and may also indicate that the crop was taking advantage of moisture stored in the soil profile from off-season rainfall. Sugarcane responses to N fertilization were similar to those observed in other studies, and were not significantly affected by moisture stress during any of the different six-week periods. Cane yield and quality for the different six-week stress period treatments relative to the unstressed check were regressed against relative moisture availability as a function of crop ET during that period. The resulting equations predicted, during the 16 May to 30 June, and 1 July to 15 August periods, cane yield reductions of 8.3% and 15%, and sugar yield reductions of 11.7% and 19.1%, respectively, if no rainfall or irrigation water were received. Complete withholding of water during a six-week period was predicted to result in an average reduction in sucrose content of 4.7% for all periods. Sugarcane showed the capability to compensate for limited stresses on the order of those imposed in this study. (C) 2000 Elsevier Science B.V. All rights reserved.