Amount Of Nitrogen Input Research Articles

Nitrogenase Activity in Intertidal Sediment Along the Tanzanian Coast, Western Indian Ocean

Nitrogenase activity was determined using the acetylene reduction assay in the littoral areas near Tanga, Dar es Salaam and Mafia with the aim of investigating its spatial and temporal distribution along the Tanzanian coastal line. Ethylene (C 2 H 4 ) production rates ranged from 0.07 - 13.5 nmol C 2 H 4 cm- 2 h- 1 in Tanga area, 0.30 - 5.43 nmol C 2 H 4 cm- 2 h- 1 in Dar es Salaam and from 0.10 - 6.25 nmol C 2 H 4 cm- 2 h- 1 in Mafia. Significantly higher rates of nitrogenase activity were measured during night-incubated samples compared to daytime incubated samples suggesting that the sediments were mostly composed of non-heterocystous diazotrophic organisms. However, there were no significant differences in rates of nitrogenase activity between the rainy and dry season and between the sandy and muddy beaches. Also, there were no significant differences in nitrogenase activity between the upper, mid and lower littoral zones, and between the three sampling locations, i.e. Tanga, Dar es Salaam and Mafia. A nitrogen fixation rate of 38 mmol N m- 2 y- 1 was estimated. We conclude that diazotrophs contribute a substantial amount of nitrogen input to the Tanzania coastal ecosystems. Keywords : Nitrogen fixation, Acetylene Reduction Assay, diazotrophs, intertidal sediment, Tanzania West Indian Ocean Journal of Marine Science Vol. 5 (2) 2006: pp. 133-140

Risk assessment of nitrate pollution in groundwater based on the environmental nitrogen-assimilation capacity of agricultural lands in Hokkaido

(pp. 17–24) A trial calculation was performed of the environmental nitrogen-assimilation capacity and the amount of nitrogen input based on various statistical data, which were compiled from each city, town and village in Hokkaido prefecture. The relationship between the excess quantity of nitrogen, after nitrogen input, and the environmental nitrogen-assimilation capacity and the nitrate-nitrogen concentration of the groundwater was considered. Environmental nitrogen-assimilation capacity = nitrogen output by the crops + acceptable level of residual nitrate in the soil profile.* *It is calculated by the amount of nitrate precipitation evapotranspiration ×10 mg L−1. 1. The average value of the environmental nitrogen-assimilation capacity in Hokkaido Prefecture was observed to be 183 kg ha−1. The maximum and minimum values of the environmental nitrogen-assimilation capacity were 308 kg ha−1 and 94 kg ha−1, respectively. When the average value of the environmental nitrogen-assimilation capacity with respect to main agricultural land use was compared across municipalities, it was largely in the following order · grassland (218 kg ha−1), upland (169 kg ha−1), and paddy land (157 kg ha−1). 2. The average value of the amount of nitrogen input in Hokkaido Prefecture was 185 kg ha−1. This value was largely in the following order · grassland (212 kg ha−1), upland (186 kg ha−1), and paddy land (151 kg ha−1). 3. The average value of the excess quantity of nitrogen, i.e., the difference between the nitrogen input and the environmental nitrogen-assimilation capacity, in Hokkaido Prefecture was 2 kg ha−1. This value was largely in the following order · upland (18 kg ha−1), paddy land (6 kg ha−1), and grassland (6 kg ha−1). 4. The average value of the nitrate-nitrogen concentration investigated in groundwater was 4.0 mg L−1 at a depth of 20 m or less. This value was largely in the following order · upland (6.5 mg L−1), grassland (2.5 mg L−1), and paddy land (2.4 mg L−1). 5. Significant positive correlation was obtained between the difference between the nitrogen input and the environmental nitrogen-assimilation capacity and nitrate-nitrogen concentration of groundwater. A case where the nitrate-nitrogen concentration of groundwater exceeded the environmental standards of water quality (10 mg L−1) was in one part of encountered municipality in Hokkaido Prefecture · in such a case, the nitrogen input exceeds the environmental nitrogen-assimilation capacity. 6. Based on these results, it was concluded that the environmental nitrogen-assimilation capacity is an effective guideline for nitrogen input in agricultural lands and helps in the prevention of nitrate pollution in groundwater derived from agricultural land.

Effects of Nitrogen Deposition on an Arid Grassland in the Colorado Plateau Cold Desert

Historically, ecosystems in the southwestern United States derived much of their nitrogen (N) from N-fixation in biological soil crusts. Today, these regions have highly reduced crust cover, and atmospheric deposition may be the dominant source of N. This study investigates the effects of increased nitrogen deposition on nitrogen uptake, photosynthesis, and growth of the two main forage grasses on the Colorado Plateau, galleta (Hilaria jamesii [Torr.] Benth.) and Indian ricegrass (Oryzopsis hymenoides, [Roemer J.S. Schultes] Ricker ex Piper). Plots were fertilized for 2 years with 0, 10, 20, and 40 kg nitrogen ha-1 annually, up to 43 the estimated current annual deposition rate, in 2 applications per year (spring and summer). Half-plots were fertilized with either (NH4)2SO4 in KCl solution or with KNO3 solution to determine possible differences in the effects of NH4+ and NO3 in this system. Neither grass increased leaf photosynthesis or tiller size due to supplemental N. Galleta also did not increase tiller density, while estimated live tiller density in Indian ricegrass increased up to 50% in the second year. Nitrogen applications accelerated the onset of water stress in both species presumably through stimulating ecosystem transpiration. Nitrogen form did not significantly affect any aspect of grass physiological performance or growth. However, leaf nitrogen in NH4+/-fertilized plants was significantly more isotopically enriched than in NO3-fertilized plants, suggesting that both species incorporated NH4-N only after it had been enriched by soil turnover. Seedlings of Russian Thistle (Salsola iberica, Sennen Pau), a noxious annual invasive weed on western rangelands, grew rapidly in the first summer on plots with 40 kg nitrogen ha-1 per annum, and more so on plots fertilized with NO3 than with NH4+. The study suggests that changes in the timing and amount of nitrogen input may alter community composition through facilitating the invasions of summer-active noxious weeds.

Effects of Nitrogen Deposition on an Arid Grassland in the Colorado Plateau Cold Desert

Abstract Historically, ecosystems in the southwestern United States derived much of their nitrogen (N) from N-fixation in biological soil crusts. Today, these regions have highly reduced crust cover, and atmospheric deposition may be the dominant source of N. This study investigates the effects of increased nitrogen deposition on nitrogen uptake, photosynthesis, and growth of the two main forage grasses on the Colorado Plateau, galleta ( Hilaria jamesii [Torr.] Benth.) and Indian ricegrass ( Oryzopsis hymenoides , [Roemer & J.S. Schultes] Ricker ex Piper). Plots were fertilized for 2 years with 0, 10, 20, and 40 kg nitrogen ha −1 annually, up to 4× the estimated current annual deposition rate, in 2 applications per year (spring and summer). Half-plots were fertilized with either (NH 4 ) 2 SO 4 in KCl solution or with KNO 3 solution to determine possible differences in the effects of NH 4 + and NO 3 − in this system. Neither grass increased leaf photosynthesis or tiller size due to supplemental N. Galleta also did not increase tiller density, while estimated live tiller density in Indian ricegrass increased up to 50% in the second year. Nitrogen applications accelerated the onset of water stress in both species presumably through stimulating ecosystem transpiration. Nitrogen form did not significantly affect any aspect of grass physiological performance or growth. However, leaf nitrogen in NH 4 + -fertilized plants was significantly more isotopically enriched than in NO 3 − -fertilized plants, suggesting that both species incorporated NH 4 -N only after it had been enriched by soil turnover. Seedlings of Russian Thistle ( Salsola iberica , Sennen & Pau), a noxious annual invasive weed on western rangelands, grew rapidly in the first summer on plots with 40 kg nitrogen ha −1 per annum, and more so on plots fertilized with NO 3 − than with NH 4 + . The study suggests that changes in the timing and amount of nitrogen input may alter community composition through facilitating the invasions of summer-active noxious weeds.