Nitrogen management systems to optimize spring wheat under no-till: Effects on plant development

Abstract

Surface residues and standing stubble protect soil against erosion and mitigate against crop water deficits by conserving additional moisture. However, residues and stubble can also present a dilemma for producers practising no-till in terms of nitrogen (N) fertilizer management and row spacing. The objective of this research was to determine how row spacing, N management using urea and two rates of post-emergent herbicide (66 and 100% of recommended) affect spring wheat establishment and plant development. The study was conducted using a no-till system and a canola-springwheat cropping system at three locations over a 3-yr period. The N management and row spacing treatments were (1) 23-cm row spacing with fall banded N on 30 cm; (2) 23-cm row spacing with spring banded N on 30 cm; (3) 30-cm row spacing with the N side-banded; (4) 23-cm row spacing with the N side-banded; and (5) sweep on 23-cm spacing with seed and fertilizer scattered over a 20-cm width. Herbicide rates did not affect wheat development. Planting depth was greater for the sweep treatment, but only by 6 mm. Plant densities were at the low end of the optimal range of 200–250 plants m-2 for all treatments and were least for the 30 cm row spacing. Average frequencies for tillers T0, T1, T2 and T3 were 20, 81 61 and 10%, respectively. Fall and spring band treatments resulted in lower tiller frequencies than the sweep treatment, with intermediate levels for the side-band treatments. Tiller frequencies were identical between the 23-cm and 30-cm row spacings with N side-banded. Greater tiller frequencies for the sweep treatment likely resulted from the greater spread of seed, reducing inter-plant competition and closer proximity of the seed to fertilizer N. Spike density was not affected by N management. Expected spike density, calculated from tiller frequency and plant density data, was within 1% of the actual spikes recorded, when averaged over treatments. This means that tiller frequencies at the 5 to 5.5 leaf stage are a good predictor of expected spike density. Wider row spacings did not affect plant and tiller development but applying N fertilizer at time of seeding provided better spring wheat tiller development. Key words: Triticum aestivum L., nitrogen management, tiller development