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Title: CORN, WHEAT AND POTATO CROP RESIDUE DECOMPOSITION AND NITROGEN MINERALIZATION IN SANDY SOILS UNDER AN IRRIGATED POTATO ROTATION

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

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2001
Publication Date: 6/1/2002
Citation: ALVA, A.K., COLLINS, H.P., BOYDSTON, R.A. CORN, WHEAT AND POTATO CROP RESIDUE DECOMPOSITION AND NITROGEN MINERALIZATION IN SANDY SOILS UNDER AN IRRIGATED POTATO ROTATION. COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS, 33:2643-2651. 2002.

Interpretive Summary: Potato production in the Pacific Northwest (PNW) follows 3 to 4 year rotation with corn, wheat, or alfalfa. After harvesting the product of economic value, the crop residue is returned to the soil which will decompose and eventually produce plant available forms of nitrogen, i.e., nitrate and ammonium forms. The amount of this plant available forms of nitrogen released from any crop residue soon after harvest is of some concern because it can contribute to leaching losses. However, the amount released during the subsequent cropping period is available for plant uptake thus is to be considered towards the crop nitrogen requirements. This study showed that the total nitrogen in corn, wheat, and potato residues were 398, 378, and 121 kg/hectare. During the period between January through September, the measured quantity of nitrogen mineralization accounted 172, 128, and 72 kg/hectare, respectively, from the above crop residues. Nitrogen mineralized during January through May accounted for 50% of total N mineralized during January through September.

Technical Abstract: This study was conducted in the Pacific Northwest (PNW) on an irrigated sandy soil under a potato (Solanum tuberosum) rotation system, where potato was grown in three or four year rotations with either corn (Zea mays L.), or wheat (Triticum sativa L.). After the crop product of economical importance is harvested, the crop residue is incorporated in the soil. The decomposition of crop residue and mineralization of nitrogen (N) provides source of plant available N. An in-situ column incubation technique was used to determine the N mineralized during January through September 2000 from corn, wheat, and potato crop residues. Residues were separated from the soil, by sieving, to determine the amount of crop residues incorporated. The dry weight of the crop residue in January soil samples, taken at the top 30 cm depth, ranged from 8.4 for potato to 26.5 Mg/ha for corn, but decreased to 4.6 to 12.7 Mg/ha in March, respectively. Total N content in the crop residue was used to estimate potentially mineralizable N (PMN) at the time of sampling. The PMN in the top 30 cm depth soil were 398, 378, and 121 kg/ha for the corn, wheat, and potato crop residues, respectively, but decreased to 189, 114, and 68 kg/ha, respectively, in March samples. Cumulative N mineralized in the top 30 cm depth of soil during January through September was 172, 128, and 72 kg/ha for corn, wheat, and potato residues, respectively. Cumulative N mineralized during January through May accounted for 53 percent of the total N mineralized from January through September. The fate of the mineralized N early in the cropping season is uncertain, since this period represents minimal N uptake by crops.