• Effects Of Migratory Geese On Nitrogen Availability And Primary Productivity In Subarctic Barley Fields

      Pugin, Jennifer Adrienne; Sparrow, Stephen (1996)
      Agricultural areas are important for migratory geese, providing easy access to high energy foods. Geese affect agricultural production by removing biomass and by depositing fecal nutrients. This study used $\sp{15}$N as a tracer to examine the quantitative effects of fecal nitrogen contributions on agricultural production.<p> During winter 1994-95, 12-week lab incubations were conducted to determine net nitrogen and carbon mineralization potentials in soils amended with barley straw, grain, and goose feces. The greatest rates of nitrogen mineralization occurred in the soil amended with goose feces. Carbon mineralization occurred at the greatest rate in the soil amended with grain.<p> In comparison to barley grain and straw, goose feces provided the greatest amount of available nitrogen to the soil and to subsequent crops, and consequently higher barley yields (59 and 62% increase, respectively). However, supplementary fertilizer is still necessary for farmers to obtain maximum barley yields. <p>
    • Fate of fertilizer nitrogen in a subarctic agricultural soil

      Knight, Charles Winsett; Sparrow, Stephen D. (1988)
      A nitrogen balance approach was taken to determine the fate of fertilizer nitrogen in a subarctic agricultural soil. Urea and calcium nitrate fertilizers were compared in a three-year spring barley recrop field study. Methods of N application included incorporating the N fertilizer into the soil during spring tillage versus broadcasting it on the soil surface after planting. $\sp{15}$N labeled urea was applied on one-meter square subplots within the main fertilizer plots. Nitrogen transformations and movement were monitored with ammonia volatilization traps, suction cup lysimeters, deep soil cores, plant tissue samples, and grain samples. Environmental data including precipitation, soil temperatures and soil moisture tensions were collected. Fertilizer N loss by ammonia volatilization was negligible, amounting to only a few grams N/ha/day. Rate of urea hydrolysis was rapid in the cool soil and was not considered to be a limiting factor affecting N availability to the crop. There appeared to be a little nitrate leaching during the growing season, but some may have occurred between cropping seasons. Only 16 percent of the fertilizer N could not be detected when the crop was physiologically mature, and that loss was accredited mostly to denitrification. Fertilizer N use efficiency, determined by the Difference Method, was 73 and 60 percent for calcium nitrate and urea, respectively. When the crop was physiologically mature, average fertilizer N recovery rates determined by the Isotope Dilution Method were: 40 percent in the plants, 43 percent immobilized in the soil, 1 percent available in the soil, and 16 percent unrecovered. Barley yields were not significantly affected by N source, but plants took up more N where nitrate had been applied. Position of N placement had little effect on either N loss or barley yield, but the surface application of N resulted in delayed barley maturity when spring rains were deficient.
    • Soil Fertility And Corn And Soybean Yield And Quality In A Six-Year Nitrogen And Phosphorus Fertilization Experiment

      Anthony, Peter M.; Sparrow, Stephen; Malzer, Gary; David, Valentine,; Zhang, Mingcho (2012)
      Optimum management of nitrogen (N) and phosphorus (P) fertilizers for corn [Zea mays L.] and soybean [Glycine max (L.) Merr.] production requires quantitative understanding of multiple soil processes and crop responses, including supply and immobilization of N and P by soil, the response of yield and quality to nutrient availability, and the relationships and interactions between N and P cycling, crop response, and other soil physical and chemical variables. We conducted a six-year experiment on two 16-ha fields on glacial-till soils in south-central Minnesota. In each year of a corn--soybean rotation, we measured soil physical and chemical parameters and grain yield and quality at a 0.014-ha resolution within each field. These observations coincided with placement of a randomized complete block, split plot design of N and P fertilizer treatments. Spatial patterns of mineralizable N were consistent over time. Mineralizable N was highly correlated to soil nitrate at a well-drained site, but not at a poorly-drained site. Increases in available soil P per kg of net P addition were significantly related to soil pH. Within fields, spatial patterns of soybean yields were highly correlated across years, and we observed consistent relationships between yield and soil variables. Overall, soybean yield related positively to soil P and Zn and negatively to pH at all site-years. Quadratic-plateau regression models of soybean yield in relation to soil P and Zn indicate that in high pH soils at these sites, yield is optimized when soil P and Zn levels are higher than current recommendations. Corn yields responded significantly to N rate and N rate by P rate interaction in all site-years. Whole-field economic optimum N rate differed significantly by site-year and by P treatment at some site-years. Site-specific P fertilization should account for spatial variation in soil P buffering capacity. Nitrogen mineralization and NxP nutrient interactions should be accounted for in agronomic management decisions for corn production. The consistent influence of soil pH on nutrient cycling and crop response indicates the potential benefit to amelioration of high pH in calcareous glacial-till soils. Results highlight the significance of spatial variability in nutrient cycling to crop management.