Ammonia Transport in a Temperate Grassland: I. Seasonal Transport in Relation to Soil Fertility and Crop Management
1996
Harper, Lowry A. | Bussink, D Wim | van der Meer, Hugo G. | Corré, Wim J.
An understanding of N cycling in agricultural systems is necessary to optimize N-use efficiency and reduce N losses to the environment. The objectives of this research were to evaluate N cycling in a highly fertilized grassland in a humid temperate climate and to observe the effects of N surplus and deficit on NH₃ absorption-desorption by the grass. Soil, plant, and weather measurementws ere taken concurrently and soil-plant-atmosphere N transport were determined. After N application, soil inorganic N decreased rapidly to background levels, due to possible microbial immobilization and plant N demand. Much of the immobilized N was remobilized during the growth period, but at insufficient rates to avoid N stress by the crop, as shown by absorption of NH₃. During spring, 45% of the plant N was derived from applied fertilizer, with the balance obtained from mineralized organic N (49%) and absorption of NH₃ (6%). During summer, fertilizer accounted for 60% of accumulated grass N and NH₃ absorption accounted for 11% of N not derived from fertilizer (4% of the total N), with the balance coming from mineralized organic N. Soil water content and wind speed were the dominant factors influencing the crop NH₃ compensation point (CP). The daily NH₃ CP was variable, but the average seasonal NH₃ CP was about 14 μg m⁻³. Contribution from the USDA-ARS, NMI, AB-DLO, and the Dep. of Plant Ecology and Evolutionary Biology of the Univ. of Utrecht.
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