ISHS Acta Horticulturae 446: VI International Symposium on Vaccinium Culture
INFLUENCE OF SOIL IRON AND AEROBIC STATUS ON PHOSPHORUS AVAILABILITY IN CRANBERRY (VACCINIUM MACROCARPON AIT.) SOILS |
| Authors: | J.R. Davenport, M.T. Pitts, W. Provance, C. DeMoranville |
| Abstract:
Recent changes in cranberry agriculture warranted a reassessment of soil phosphorus (P) dynamics. Plant tissue often tests deficient for P even though soil tests indicate adequate P content. Three soils - peat, sand and layered peat/sand - were evaluated in the laboratory for sorption/desorption patterns and soil test effectiveness. Each soil type was incubated with triple superphosphate fertilizer (0–44-0) at six rates: 0, 12, 23, 35, 27, or 58 kg P/ha. Phosphorus sorption and desorption was examined under aerobic, anaerobic and transitional conditions to simulate the annual moisture patterns on a cranberry bed. Sand soils readily released P, however only 22% was available. Phosphorus fertilizers should be added to these soils in small doses throughout the growing season. Very low P additions in peat soils were tightly sorped. Approximately 30% became immediately plant available. One half of the sorped P will eventually be released. However, as the peat soils dry, P release declined. Fertilizer should not be applied until these soils reach seasonal dry conditions. Low additions of P to layered soils were also tightly sorped. Only 33% of the sorped P will eventually be released. Fertilizer should not be applied until this soil has reached seasonal dryness. Currently the industry standard for soil P extraction is the Bray I method. Comparison of this with other soil P and soil Fe extraction methods showed that the Bray I is as good or better than any other method. However, when soil Fe levels, as determined by citrate-dithionate extraction, are higher than 200 ppm the soil test P values are not meaningful. Due to the difficulty in evaluating available soil P, tissue testing appears to be a better method for evaluating crop nutritional status. | |
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