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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Starter Nitrogen Fertilizer on Nitrogen Fixation of Soybeans in the Northern Great Plains

Authors
item Osborne, Shannon
item Riedell, Walter

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 12, 2004
Publication Date: March 2, 2004
Citation: OSBORNE, S.L., RIEDELL, W.E. EFFECT OF STARTER NITROGEN FERTILIZER ON NITROGEN FIXATION OF SOYBEANS IN THE NORTHERN GREAT PLAINS. MEETING PROCEEDINGS. 2004.

Interpretive Summary: Environmental conditions at the time soybeans are planted in the northern Great Plains are such that nitrogen fixation may not occur immediately; therefore additions of nitrogen as starter fertilizer may increase initial growth of soybeans and possibly increase yield and quality. The objective of this study was to evaluate the response of soybeans to low rates of nitrogen applied at planting. A field experiment was established within a two-year corn/soybean rotation. Treatments included no-till, conventional tillage and starter fertilizer. Nitrogen fertilizer was applied as either ammonium nitrate or urea each at rates of 0, 7, 14, and 21 lb/ac. Tillage only affected biomass production for the beginning bloom sampling dates for 2001 and 2002. Biomass production significantly increased with increasing nitrogen rate for all growth stages and years except for the beginning maturity sampling in 2002. The beginning bloom 2000 sampling date was the only sampling date with a significant difference in biomass due to nitrogen source, with urea producing greater biomass compared to ammonium nitrate. Plant ureide concentration was significantly higher for urea compared to ammonium nitrate for the beginning bloom sampling date for 2000 and 2002 with no response in 2001, possibly due to differences in planting dates. Tillage significantly affected ureide concentration at the beginning maturity growth stage 2001 and 2002, with the no-till treatments resulting in a higher ureide concentration compared to conventional tillage. Relative ureide content decreased with increasing nitrogen rate for the beginning bloom sampling date in all years. In contrast biomass production increased with nitrogen application. This decrease in nitrogen fixation was not present for the beginning maturity sampling date but the significant increase in biomass production was still present, possibly indicating the potential benefits of applying nitrogen fertilizer at planting in unfavorable environmental conditions.

Technical Abstract: Environmental conditions at the time soybeans (Glycine max (L.) Merrill) are planted in the northern Great Plains are such that nitrogen (N) fixation may not occur immediately, therefore additions of N as starter fertilizer may increase initial growth of soybeans and possibly increase yield and quality. The objective of this study was to evaluate the response of soybeans to low rates of N applied at planting. 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, 8, 16, and 24 kg N ha-1. Tillage treatments only affected biomass production for the R1 sampling dates for 2001 and 2002. Biomass production significantly increased with increasing N rate for all growth stages and years except for the R7 sampling in 2002. The R1 2000 sampling date was the only sampling date with a significant difference in biomass due to N source, with UR producing greater biomass compared to AN. Plant ureide concentration was significantly higher for UR compared to AN for the R1 sampling date for 2000 and 2002 with no response in 2001, possibly due to differences in planting dates. Tillage significantly affected ureide concentration at the R7 growth stage 2001 and 2002, with the NT treatments resulting in a higher ureide concentration compared to CT. Relative ureide content decreased with increasing N rate for the R1 sampling date in all years. In contrast biomass production increased with N application. This decrease in N fixation was not present for the R7 sampling date but the significant increase in biomass production was still present, possibly indicating the potential benefits of applying N fertilizer at planting in unfavorable environmental conditions.

Last Modified: 12/17/2014