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Title: NITROGEN TRANSFORMATION FROM POTATO AND ROTATIONAL CROP RESIDUES

Author
item Alva, Ashok
item Collins, Harold
item Boydston, Rick

Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2002
Publication Date: 10/1/2002
Citation: ALVA, A.K., COLLINS, H.P., BOYDSTON, R.A. NITROGEN TRANSFORMATION FROM POTATO AND ROTATIONAL CROP RESIDUES. PROCEEDINGS 41ST WASHINGTON STATE POTATO CONFERENCE, P. 75-86. 2002.

Interpretive Summary: Columbia Basin region provides ideal conditions for production high yields of potato with premium processing qualities. This area is extremely dry, thus the production is highly dependent on irrigation. High termperature during the growing period and adequate soil moisture through irrigation provides ideal conditions for rapid breakdown of soil organic residues and transformation of organic nitrogen into plant available inorganic forms. The latter process is termed as "mineralization". Potatoes are grown in 3-4 year rotation with corn or wheat. The mineralization of residues from corn, wheat, and potato was investigated in a sandy soil in the Columbia Basin region with irrigation equivalent to that for potato production. During January through September, the mineralization of nitrogen from previous years' residues from corn, wheat, and potato accounted for 171, 129, and 72 lbs per acre, respectively. These quantities represented 48, 38, and 67 percent of total N in the corn, wheat, and potato crop residues, respectively, estimated for the top 12 inch depth soil in the beginning of the study period.

Technical Abstract: This study was conducted to determine the amount of nitrogen (N) from the crop residues and soil organic matter transformed into inorganic forms, i.e. ammonium and nitrate forms, during January through September 2000 in a sandy soil under irrigation. Corn, wheat, and potato residues were evaluated. The dry weight of corn, wheat, and potato residues sampled in the 0-12 inch depth soil in January 2000 (after the respective crops were harvested in the fall of 1999) were 11.8, 9.0, and 3.7 ton/acre, respectively. The total N content in the above residues were 355, 338, and 108 lbs/acre, respectively. By March 2000, the residue weights have decreased to 5.7, 3.4, and 2.1 ton/acre, respectively, along with the respective total N contents of 169, 102, and 61 lbs/acre. The residue weights further decreased to 1.1 - 1.7 ton/acre by September 2000 across all crop residues, with the total N content of 32 to 53 lbs/acre. The mineralized N, as both ammonium and nitrate forms, in the top 12 inch depth soil during January through September 2000 were 171, 129, and 72 lbs/acre from corn, wheat, and potato residue plots. The above values represented 48, 38, and 67 percentage of the total N in the respective crop residues measured in January 2000. This study demonstrated the transformation of N from potato residue was more rapid as compared to that from corn and wheat residues.