Sugarcane responses to irrigation and nitrogen in semiarid south Texas
Water and N are often limiting factors for sugarcane (Saccharum spp.) production. This study was conducted to determine the effect of different levels of water availability on sugarcane growth, yield, and responses to N application, and also to evaluate the effectiveness of alternative N application methods. Three irrigation levels (20% below crop evapotranspiration [ETc], full ETc replacement, and 20% above ETc), four N application rates (0, 60, 120, and 180 kg N ha–1), and three fertilizer application methods (through-the-drip, sidedress, and knifed into the middle of the plant stool or ‘stool splitter’) were evaluated on sugarcane for four successive crops. Increasing water application in this study resulted in increased growth but no significant differences in cane or sugar yields. Water use efficiency therefore increased as water application declined, averaging 8.4 Mg cane mL–1 of water, including both rainfall and irrigation. Nitrogen application through the drip system resulted in linear increases in cane yield every year up to the highest rate applied of 180 kg N ha–1, averaging 74 kg per kg N applied in the plant through second ratoon crops, and 192 kg per kg N applied in the third ratoon crop. Over the 4 yr this study was conducted, N application through the drip system produced yields which were not significantly different from the sidedress application, while the ‘stool splitter’ application method was consistently the most inefficient N fertilizer application method. This work shows that maximum cane and sugar yields can be obtained, and responses to rate of N application are not reduced at less than optimum soil moisture conditions.