Evaluation of Factors Affecting Emergence of Winter Wheat Planted with Seed‐Banded Nitrogen Fertilizers

Abstract

AbstractNitrogen use efficiency by cereal crops may be increased by the placement of fertilizer with the seed; however, high N concentrations often cause injury and reduce both germination and emergence. Two studies were conducted under controlled greenhouse conditions to evaluate factors affecting emergence of winter wheat (Triticum aestivum L.) planted with seed‐banded N fertilizers. Soil from the Ap horizon of a Palouse silt loam (fine‐silty, mixed, mesic Pachic Ultic Haploxeroll) was used in both studies. Two N materials (ammonium nitrate and urea) were banded with the winter wheat seed (‘Stephens’) at N rates of 0, 11, 22, 33, 44, 55, and 66 kg ha−1, and placed in soils at soil matric potentials of −0.15, −0.25, and −0.35 MPa. The tolerance of five winter wheat cultivars ‘Daws’, ‘Hill 81’, ‘Nugaines’, ‘Peck’, and Stephens to sulfur‐coated urea (SCU) materials SCU‐10, SCU‐20, and SCU‐30 was evaluated in a separate study. Nitrogen rates of 0, 50, 100, and 150 kg ha−1 were used at a soil matric potential of −0.20 MPa. In the first study significant N source × water potential (P < 0.0003) and water potential × N rate (P < 0.0001) interactions were observed. In the second study, significant N source × N rate × cultivar (P < 0.0001), N source × N rate (P < 0.0001), and N source × cultivar (P < 0.0001) interactions were found. The N source, N application rate, soil‐water potential, and winter wheat cultivar main effects were all significant for winter wheat emergence. Ammonium nitrate reduced winter wheat emergence 5 to 26% less than urea when comparable quantities of N were placed with the seed. Winter wheat emergence decreased as soil‐water potential decreased (became more negative). These studies demonstrated how the evaluated factors are interrelated with regard to winter wheat emergence. Consequently, guidelines routinely used for seed‐banded N fertilization that only consider N application rate should be modified to also consider N source and soil moisture.