STARTER FERTILIZER EF~'ECTS ON SOYBEAN GRAIN YIELD AND QUALITY

Fertilizing soybeans (Glycine max (L.) Merrill) is not an entirely new concept; for a number of years, scientists have investigated the effect of nitrogen (N) fertilizer on yield and quality of soybeans. The objective of this research was to investigate the effect of starter fertilizer N rates and sources on soybean yield, protein, and oil content in the cool soils of the Northern Great Plains. A field experiment was established within a two-year corn (Zea mays L.) soybean rotation. Using a split-plot design with four replications. Whole plots were no-till (NT) and conventional tillage (CT) and the split plots were starter fertilizer (two sources x four rates) treatments. Nitrogen sources were either ammonium nitrate (AN) or urea (UR) each applied at 0,7.8, 15.7, and 23.5 kg N ha-l. Grain yields were higher for 2000 growing season compared to 2001 largely due to differences in rainfall. A yield reduction resulted from the 7.8 kg N hal rate during 2000. Maximum yield occurred at the 23.5 kg N hal AN treatment. Application of UR had no significant effect on grain yield regardless of N rate. The only yield difference for the 2001 season was between the tillage treatments. Similar to 2000 data the 7.8 kg N ha- l A