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 fo r maximum production. Substantial input of N is also typically required. Pr evious research has shown the dramatic impact of extended reduced water ava ilability on sugarcane production and responses to N fertilization. If wate r availability is limiting, then the question becomes: are there certain pe riods during sugarcane growth when water can be more effectively utilized b y 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 gro wth 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 ev apotranspiration (ET) and the least amount of rainfall as a percentage of E T. Water stress during other six-week periods had a much lesser affect on s ugarcane 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 low er ET during this period, and may also indicate that the crop was taking ad vantage of moisture stored in the soil profile from off-season rainfall. Su garcane responses to N fertilization were similar to those observed in othe r studies, and were not significantly affected by moisture stress during an y of the different six-week periods. Cane yield and quality for the differe nt six-week stress period treatments relative to the unstressed check were regressed against relative moisture availability as a function of crop ET d uring 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 ra infall or irrigation water were received. Complete withholding of water dur ing a six-week period was predicted to result in an average reduction in su crose content of 4.7% for all periods. Sugarcane showed the capability to c ompensate for limited stresses on the order of those imposed in this study. (C) 2000 Elsevier Science B.V. All rights reserved.