Nitrogen mineralization during the growing season, 1: Contribution to the nitrogen supply of spring barley
1992
Linden, B. (Sveriges Lantbruksuniv., Uppsala (Sweden). Inst. foer Markvetenskap) | Lyngstad, I. | Sippola, J. | Soegaard, K. | Kjellerup, V.
Net nitrogen mineralization during the growing season was estimated during 1984-86 in two 3-year experiments in each of the countries Denmark, Finland, Norway and Sweden, using two methods based on field measurements: I. In cropped soil without N fertilization, using the formula: (Total N in crop at yellow ripeness) + (residual mineral N in 0-100 cm soil at yellow ripeness) - (mineral N in 0-100 cm soil in early spring). II. In covered, fallow plots (uncropped soil), without N fertilization: determination of the accumulation with time of mineral nitrogen in 0-100 cm soil. Spring barley was grown every year. The preceding crops were cereals. During the decade prior to the study, merely arable crops had been grown, and one of the soils had once been fertilized with manure. On average, the net nitrogen mineralization in cropped soil from early spring to yellow ripeness was 41 kg N ha-1, with a range from 26 to 71 kg. The mean was equivalent to 0.40 kg ha-1 day -1. On average, 69% of the total supply of plant-available soil nitrogen refers to N released during the growing season, the rest being the plant-utilized part of the amounts of mineral-N present in soil in early spring (18 kg N ha-1). Larger amounts of nitrogen were mineralized in uncropped soil, with larger annual variations, than in cropped soil. Annual deviations in cropped soil were ca. 10% of the 3-year site means. The results indicate that in practical agriculture crop uptake of soil N in small annual plots without N fertilization can be used to predict net N mineralization during the growing seasons of subsequent years.
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