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 dry seasons to study the response of two irrigated wheat varieties (Siete Cerros and Florence Aurore 8193) to row-spacing and nitrogen supply in terms of yield, yield components and N uptake and distribution. Using the split plot 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) were compared. The two varieties did not differ with respect to their grain and straw yields, N uptake and most of the yield components. However, var. Siete Cerros had more grains per spike (24% more) but smaller grain size (14% smaller) and slightly shorter spikes than var. Florence Aurore. Row spacing did not influence grain and straw yields, grain weight, spikelets per spike and spike length but wider rows enhanced productive tillering and grains per spike, albeit only slightly. N uptake was highest under 20 cm row-spacing 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 highest under the narrower rows. Increasing N supply level significantly increased grain and straw yields, productive tillers, spike length, spikelets per spike, grains per spike, grain weight and N uptake. Although N uptake increased 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 function of both growth stage and N supply level. As the plant's growth cycle advanced, the level of N distributed to the leaves and stem was on the decline while that to the spikes increased. Generally, N uptake either declined 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 resulting from N supply was mainly associated with variations in spikelets per spike and grains per spike.