Response of two irrigated wheat (triticum aestivum I.) varieties to row spacing and nitrogen supply: Yield, yield components and N uptake

Field trials were conducted at Kadawa, Nigeria during 1989-90 and 1990-91 d ry seasons to study the response of two irrigated wheat varieties (Siete Ce rros and Florence Aurore 8193) to row-spacing and nitrogen supply in terms of yield, yield components and N uptake and distribution. Using the split p lot design two varieties (Siete Cerros and Florence Aurore 8193); three row spacings (10, 20 or 30 cm) and four N levels (0, 60, 120 or 180 kgN/ha) we re compared. The two varieties did not differ with respect to their grain a nd straw yields, N uptake and most of the yield components. However, var. S iete Cerros had more grains per spike (24% more) but smaller grain size (14 % smaller) and slightly shorter spikes than var. Florence Aurore. Row spaci ng did not influence grain and straw yields, grain weight, spikelets per sp ike and spike length but wider rows enhanced productive tillering and grain s per spike, albeit only slightly. N uptake was highest under 20 cm row-spa cing initially but later on the greatest N uptake occurred under the wider row (30-cm) in 1989-90 season. In 1990-91 season, however, N uptake was hig hest under the narrower rows. Increasing N supply level significantly incre ased grain and straw yields, productive tillers, spike length, spikelets pe r spike, grains per spike, grain weight and N uptake. Although N uptake inc reased up to the highest N supply level (180 kgN/ha), significant response was only up to 120 kg N/ha. N distribution to different plant parts was a f unction of both growth stage and N supply level. As the plant's growth cycl e advanced, the level of N distributed to the leaves and stem was on the de cline while that to the spikes increased. Generally, N uptake either declin ed or levelled off after the flowering stage. The most beneficial practice for wheat under the conditions of this study is to plant the crop at 20 cm row-spacing and give it a 120 kg N/ha fertiliser dressing. Yield increase r esulting from N supply was mainly associated with variations in spikelets p er spike and grains per spike.