Variation in nitrogen use efficiency among grain sorghum genotypes

Four grain sorghum genotypes, [Sorghum bicolor (L.) Moench], differing in morphology and grain yields were evaluated in the field and greenhouse. The objective was to identify and assess physiological and morphological parameters associated with the efficient use of nitrogen. The four entries; SC325-12, SC630-11E, 8BH6956, and 77CS1, were grown in a replicated field trial on an Acuff loam, (fine-loamy, mixed, thermic Aridic Paleustoll), divided into high N rate (180 kg/ha added N), and a low N rate (0 kg/ha added N). Line SC325-12 is a partially converted version of IS 2462. Line SC630-11E is a partially converted version of IS 1269C. Line 8BH6569 is a cross of SC326-^ x SC103-12. Line 77CS1 has been released by the Texas Agricultural Experiment Station as TX 2816.

Plant components were sampled throughout two consecutive growing seasons to determine genotype X nitrogen fertility effects on uptake, translocation, and deposition of N and dry matter. The greenhouse evaluation consisted of the same four entries grown hydroponically four plants per pot with five N rates set at 100, to 800 mg per pot. Plants were separated into roots and shoots after being allowed to grow until deficiencies were observed, approximately 40 days after germination.