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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Publications at this Location » Publication #169009
Title: CYCLING OF SOIL AMINO ACIDS UNDER A CORN AND A SOYBEAN ROTATION 1651

Author
item Martens, Dean

Submitted to: American Society of Agronomy Meetings
Publication Type: Proceedings
Publication Acceptance Date: 9/15/2005
Publication Date: 10/13/2004
Citation: Martens, D.A. 2004. Cycling of soil amino acids under a corn and a soybean rotation. In: Proceedings of the American Society of Agronomy Meetings, Science to Secure Food and the Environment, held jointly with the Canadian Soc. of Soil Science, October 31 - November 4, 2004, Seattle Washington, 2004 CDROM.

Interpretive Summary: Why are N fertilizer application rates reduced for corn following soybean when N removed as grain exceed estimates of soybean N fixed? Understanding the contribution of soybean to the rotation can result in better predictions for corn N needs. Soil samples (0-15 cm) were taken from 10 sites in a 16 ha central Iowa field (1996 till 1999) to measure soil organic N fractions each May and September from a long-term (since 1957) corn (150 kg N)-soybean (0 N) rotation. Soil N at the sites measured as amino acids (AA) and sugars (AS) was depleted following corn (315 kg N per ha) and enriched following soybean growth (340 kg N per ha). The relative proportion of each amino acid to the total AA concentration did not change with sampling times suggesting that enrichment or depletion of soil AAs was uniform. AA decrease following corn was noted until the September samplings following soybean, which suggested that soil AA enrichment occurred during the growth of the soybean plant. AA enrichment during the soybean phase was also related to soybean grain yield suggesting that conditions that support a vibrant plant also support N export to the soil. Strong relationships between AS and AA and corn yield were noted in the study and emphasize that mineralization of soil N must be taken into accounted for predicting fertilizer N needs.

Technical Abstract: Why are N fertilizer application rates reduced for corn following soybean when N removed as grain exceed estimates of soybean N fixed? Understanding the contribution of soybean to the rotation can result in better predictions for corn N needs. Soil samples (0-15 cm) were taken from 10 sites in a 16 ha central Iowa field (1996 till 1999) to measure soil organic N fractions each May and September from a long-term (since 1957) corn (150 kg N)-soybean (0 N) rotation. Soil N at the sites measured as amino acids (AA) and sugars (AS) was depleted following corn (315 kg N per ha) and enriched following soybean growth (340 kg N per ha). The relative proportion of each amino acid to the total AA concentration did not change with sampling times suggesting that enrichment or depletion of soil AAs was uniform. AA decrease following corn was noted until the September samplings following soybean, which suggested that soil AA enrichment occurred during the growth of the soybean plant. AA enrichment during the soybean phase was also related to soybean grain yield suggesting that conditions that support a vibrant plant also support N export to the soil. Strong relationships between AS and AA and corn yield were noted in the study and emphasize that mineralization of soil N must be taken into accounted for predicting fertilizer N needs.