Nitrogen management and wheat genotype performance in a planting system on narrow raised beds

Wheat (<i>Triticum aestivum</i> L.) grain production in the Central Highlands of Mexico occurs under rainfed conditions. Traditionally this crop has been planted by conventional means in solid stands combined with heavy tillage and lack of ground cover. These practices have been leading to soil erosion in the sloping lands, frequent drought stress, and water logging after occasional heavy rainstorms in the low lands. To ameliorate those constrains, farmers have started to replace the traditional planting system by the planting system on narrow raised beds. However, information on N management and varieties is needed. This 5-yr study was conducted from 1999 to 2003 to test a set of eight wheat genotypes using a raised-bed system to evaluate their performance as affected by N fertilizer management. Three N rates (40, 70 and 100 kg N ha ⁻¹) were applied at planting, at the end of tillering-early jointing, and split at planting and at the end of tillering-early jointing. Treatments included an unfertilized check plot. Results indicated that the optimum N fertilizer rate for wheat grain production varies from 0 to 40 kg N ha ⁻¹) depending upon the variety. Nitrogen timing practices had no effect on grain yield but on N use efficiency (NUE). The split application of 40 kg N ha ⁻¹ increased the NUE. Higher N rates reduced the NUE irrespective of the N timing practice. According to the differential performance among varieties, this study showed that the planting system on narrow raised beds is a variety-specific technology. The relative grain yield, stability, and NUE, indicated that Tlaxcala F2000, Nahuatl F2000 and Romoga F96 are the most adequate varieties for the planting system on narrow raised beds in the Central Highlands of Mexico.