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NUTRIENT CYCLING & UPTAKE

Organic Amendment History and Crop Rotation Effects on Soil Nitrogen Mineralization Potential and Soil Nitrogen Supply in a Potato Cropping System

^a Agriculture and Agri-Food Canada, Potato Research Centre, P.O. Box 20280, Fredericton, NB, Canada E3B 4Z7
^b Dep. of Environmental Sci., Nova Scotia Agricultural College, P.O. Box 550, 21 Cox Rd., Truro, NS, Canada B2N 5E3
^c Agriculture and Agri-Food Canada, Brandon Research Centre, Grand Valley Rd., Brandon, MB, Canada R7A 5Y3
^d Dep. of Plant, Soil and Environmental Sci., 114 Deering Hall, Univ. of Maine, Orono, ME USA 04469

^* Corresponding author (ZebarthB{at}agr.gc.ca).

Crop management practices influence readily and potentially available N in soil. In this study, we evaluated the effects of organic amendment history and crop rotation on potentially mineralizable N (N₀), mineralizable N pools, and field estimates of soil N supply in potato (Solanum tuberosum L.) production, and evaluated a suite of N availability measures to detect changes in these parameters. Preplant soil samples (top 15-cm) were collected from the potato year of a rotation trial in Maine during 2004 and 2005. Treatments included three crop rotations, with and without a history of organic amendment [solid beef (Bos taurus) manure] application: PB, potato-barley (Hordeum vulgare L.); PSPB, potato-soybean [Glycine max (L.) Merr.]-potato-barley; and PSBA/T, potato-soybean-barley-alfalfa (Medicago sativa L.)/timothy (Phleum pratense L.). The N₀ and mineralizable N pools were determined by aerobic incubation at 25°C and periodic leaching for 24 wk with a fixed-k approach. On average, historically amended soil had 35% higher values of N₀, and an 8% higher proportion of mineralizable N partitioned to the stable mineralizable N pool, compared with nonamended soil. Lower values of N₀, mineralizable N pools and some measures of N availability were measured in PSBA/T compared with PB and PSPB rotations. All tested measures of N availability detected management-induced changes in N₀ and mineralizable N pools. The preplant nitrate, UV absorbance of 0.01 M NaHCO₃ extract at 205 nm and particulate organic matter (POM)-N were the best predictors of field-based indices of soil N supply (r² = 0.50 to 0.73). Management-induced changes in the size and quality of mineralizable N should be considered in developing best N management programs through organic amendment application and crop rotations.

Abbreviations: ISNT, Illinois Soil Nitrogen Test for amino sugar-N • k, mineralization rate coefficient • KCl-NH₄, extractable NH₄–N with 2 M KCl at the 0- to 30-cm soil depth before planting • KCl-NO₃, extractable NO₃–N with 2 M KCl at the 0- to 30-cm soil depth before planting • MBC, microbial biomass carbon by chloroform fumigation extraction method • NaHCO₃–205, ultraviolet absorbance of 0.01 M NaHCO₃ extract at 205 nm • NaHCO₃–260, ultraviolet absorbance of 0.01 M NaHCO₃ extract at 260 nm • N₀, potentially mineralizable N (Pool II + Pool III) • PB, potato-barley rotation • PNU_0N, total plant N uptake measured at vine desiccation with no fertilizer N application • POM, particulate organic matter • PSBP, potato-soybean-barley-alfalfa rotation • PSBA/T, potato-soybean-barley-alfalfa + timothy rotation • SMN_h, soil mineral N at 0- to 30-cm soil depth measured at harvest

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Received for publication February 12, 2008.