Revisiting seedrow nitrogen placement with barley and wheat

• Published in: Canadian journal of plant science 2008-11, Vol.88 (6), p.1073-1086
• Main Authors: Karamanos, R.E, Harapiak, J.T, Flore, N.A
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; application rate; application timing; barley; Biological and medical sciences; fertilizer application; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; grain yield; Hordeum vulgare; nitrate nitrogen; Nitrogen fertilization; nitrogen fertilizers; Nitrogen, phosphorus, potassium fertilizations; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; residual nitrate nitrogen; seedbeds; seedrow-applied nitrogen; seeds; soil organic matter; Soil science; soil texture; soil water; Soil-plant relationships. Soil fertility. Fertilization. Amendments; sowing; Triticum aestivum; Water and solute dynamics; wheat
• ISSN: 0008-4220; 1918-1833
• DOI: 10.4141/CJPS08085

The rates of nitrogen (N) that can be safely placed with the seed remains a frequent question of producers, especially as direct seeding continues to increase as a practice in western Canada. Guidelines have been in place since the mid-1990s; however, they address only "favourable conditions" and experimentation relating to their derivation has not been formally published. This study attempted to quantify "favourable conditions" as well as supplement existing guidelines with information under non-favourable or ideal conditions so that producers may assess the risk of applying N with the seed. To this end, the results from 32 experiments with CWRS wheat and 10 with barley conducted in early to mid-1990s were compiled. The experimental design included three seedbed utilization (SBU) rates (10, 20, and 40%) and five N rates (0, 20, 40, 60, and 80 kg N ha -1 ) with four replications. Grain yield, relative plant stands (calculated as a percentage of the unfertilized control) and days to maturity (DTM) were determined in all experiments. Three types of responses to seedrow N application occurred. Type A had no impact of fertilizer N rate on the yield of CWRS wheat at wide (40%) SBU, but grain yield decreased at narrower SBU (10 and 20%). Type B had no impact of fertilizer N rate on the yield of CWRS wheat at narrow (10%) SBU but grain yield increased at wide SBU (20 and 40%). Type C had grain yield increases due to fertilizer N independent of SBU. Type A was characterized by dry soil moisture conditions and relatively high residual NO 3 − -N levels, whereas Types B and C were characterized by normal and very moist soil conditions and low to medium residual NO 3 − -N levels. The results within each response type were modified by soil organic matter (SOM) and texture. Grain yield losses generally occurred when relative plants stands were below 85% of those of unfertilized plots. In addition, conditions that led to a decrease in relative plant stands and grain yield also resulted in delayed maturity. Accounting for all the above factors enabled us to expand current guidelines under normal conditions to a range of agroecological conditions. Key words: Guideline, texture, soil organic matter, residual NO 3 − -N, soil moisture