Long-term use of urea vs. anhydrous ammonia for N-fertilization of a Dark Brown loam: III. Soil microbial populations and activities

Non-Peer ReviewedThe influence of fertilizers on soil quality, including soil microbial well-being, has been frequently questioned by proponents of organic farming and Low Input Sustainable Agriculture (LISA). A 10-yr experiment, conducted on a Dark Brown loam at Scott, in which the influence of urea and and anhydrous ammonia at rates up to 180 kg N ha-1 on yields of cereals and oilseeds was examined, provided the basis for this study. In the tenth year we took soil samples at 2 depths (0 to 7.5-, 7.5 to 15-cm) at 3 times (3 days before, 6 days, and 26 days after fertilizer application) . We assessed the impact of these treatments on populations of filamentous fungi, yeasts, bacteria, actinomycetes, nitrifiers, and denitrifiers. The fertilizer effects were most pronounced 6 days after N application but were also apparent just prior to N application, confirming a residual treatment effect. Generally, the effects were greater in the second depth where the fertilizer was placed. There were no obvious effects on yeasts or denitrifiers. Generally bacterial and fungal populations were directly related to N rates and were increased more by anhydrous ammonia than by urea. In contrast, actinomycete populations were inversely related to rate of N and the population was lower for anhydrous ammonia than for urea. Nitrifiers responded positively to N rate near the depth of N placement with the response peaking at the 90 kg ha-1 rate. The pHCaCl2 of the check soil, which was already low (5.2) was further decreased to 4.2 by 180 kg N ha-1, the decrease being greater for the anhydrous ammonia source. We believe positive responses in microbial populations are due to the nutritive value of N and negative responses related to soil acidification

Quantitative Aspekte der Waldernaehrung in Forststandorten mit Bodenversauerung und anthropogener Immissionsbelastung - dargestellt am Beispiel des Westharzes

Available from TIB Hannover: RO 2404(65) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Long-term use of urea vs. anhydrous ammonia for N fertilization of a Dark Brown loam: I. Soil acidification and nutrient availability

Non-Peer ReviewedThe decline of indigenous soil fertility on the pra1r1es has necessitated higher nitrogen fertilizer inputs into cropping systems. Our objectives were to quantify the acidifying effects of urea and anhydrous ammonia nitrogen injected at 0.1 m depth annually at rates of 45, 90, and 180 kg ha-1 in a Dark Brown loam at Scott. Soil acidity increased with increasing rates of nitrogen fertilization and anhydrous ammonia was more acidifying than urea. After 9 years of anhydrous ammonia application at 180 kg ha-1, soil pHCaCl2 at injection depth had dropped to 4.2 compared to 5.2 in the unfertilized check treatment. This acidification was associated with a depletion of exchangeable base cations (1307 kg calcium ha-1, 307 kg magnesium ha-1) and a concomitant increase in exchangeable acidity in the top 0.3 m. The base depletion and the increase in exchangeable manganese were correlated with the amount of nitrate leached into 0. 3 to 1.5 m depth (r = 0.66 and 0.79***). The soil solution was more acidified 6 days after fertilizer injection than 3 days before and 26 days after injection. With increasing acidity, the solution concentration of potentially phytotoxic manganese increased from 0.2 to 29 mg l-1 and nutrient ratios changed significantly, e.g., the molar K/NH4-ratio decreased from 5.4 to 0.1. Our data suggest that large losses of nitrogen beyond rooting depth and to atmosphere take place where high rates of fertilizer nitrogen are used

Evaluation of EPIC Model of Soil NO3-N in Irrigated and Wheat-Maize Rotation Field on the Loess Plateau of China

International audienceEPIC model has been evaluated and used world wide, however there is still some disagreements on the simulation results of nitrogen cycle. Based on field experimental data, simulation results of soil NO3-N was evaluated and the parameter sensitivity for simulated NO3-N was analyzed in irrigated winter wheat / summer maize field on the Loess Plateau of China. Results showed 1) EPIC model estimated soil NO3-N content and its movement among different soil layers well, with the mean RRMSE value of 0.46, for irrigated winter wheat / summer maize cropping system in the semi-humid region of the Loess Plateau. 2) Simulation results of soil NO3-N was more sensitive to soil parameters, compared with crop parameters and meteorological parameters. 3)To improve the parameter value of BN2, HI, TB, WA, CNDS, BD and FC was better to the EPIC model to simulate soil NO3-N on the Loess Plateau of China

Absorção de cátions e ânions pelo capim-coastcross adubado com uréia e nitrato de amônio Cations and anions uptake by coastcross grass fertilized with urea and ammonium nitrate

Os processos fisiológicos das plantas são afetados pelo balanço de cátions e ânions absorvidos. O objetivo deste trabalho foi determinar a absorção de cátions e ânions quando plantas de capim-coastcross receberam doses elevadas de nitrogênio. O delineamento experimental foi o de blocos casualizados com quatro repetições, num esquema fatorial 2x5 - duas fontes de N: uréia e nitrato de amônio, e cinco doses de N: 0, 25, 50, 100, 200 kg ha-1 corte-1 . As doses de N foram aplicadas após cada corte num total de cinco cortes, durante a época das chuvas. A absorção de cátions e de ânions pelo capim-coastcross aumentou com o acréscimo das doses de N dos dois fertilizantes, sendo maior com o nitrato de amônio. Com doses crescentes de N, verificou-se entre os cátions maior absorção do K+, e do Cl- entre os ânions. Com exceção do N, a absorção do K+ foi superior à dos demais nutrientes, com redução no teor relativo de cálcio. Doses altas de N aplicadas em capim-coastcross, na forma de uréia ou de nitrato de amônio, favorecem a absorção de cátions e de ânions.<br>Physiologic processes of plants are affected by uptake of cations and anions. The aim of this work was to determine the uptake of cations and anions when plants of coastcross grass received high doses of nitrogen. The experimental design was a randomized block, in a 2x5 factorial arrangement - two N sources: urea and ammonium nitrate and five N rates: 0, 25, 50, 100, and 200 kg ha-1 cutting-1 - with four replications. Treatments were applied after each of five consecutive cutting in the rainy season. Uptake of cations and anions by coastcross grass increased with increasing of N rates with both fertilizers, but was higher with ammonium nitrate. Increasing rates of N caused higher K+ uptake in relation to other cations, and in Cl- among the anions. Except for N, K+ uptake was greater than that of other nutrients, with a reduction on the relative content of Ca2+. High doses of N as urea or ammonium nitrate applied on coastcross grass favor absorption of cations and anions