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The continuing degradation of United States surface waters by excessive nutrient loads has motivated the establishment of
nutrient criteria for streams, lakes, and estuaries as a means to protect aquatic resources. Nutrient criteria have been established
based on ecoregional differences, recognizing that geographic variation in climate, topography, geology, and land use require
use of different criteria values for different regions of the continental United States. Several studies have demonstrated
that land-cover composition also strongly influences nutrient concentrations and yields. We examined the relative importance
of ecoregions and watershed land-cover composition in explaining variability in nitrogen (N) and phosphorus (P) concentrations
by re-analyzing the National Eutrophication Survey (NES) data reported by Omernik (1977). The variance of N concentrations
among land-cover composition classes within ecoregions was six times larger than the variance among ecoregions. For P concentrations,
land-cover composition within ecoregions accounted for three times more variance than ecoregions themselves. Variance across
ecoregions was only weakly significant after accounting for variance in land-cover composition within ecoregions. The results
suggest that the relationship between land-cover composition and nutrient concentrations in aquatic systems should also be
used to help guide establishment of nutrient criteria. 相似文献
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Jing Fan Jing-Yuan Wang Xiao-Fei Hu Fu-Sheng Chen 《Urban Forestry & Urban Greening》2014,13(3):576-585
Urban forest remnants are a useful tool to study forest response to global change with urbanization. Soil nutrient status in urban forests has not been well understood, especially under the pressure of rapid urbanization in developing countries. In this study, ion-exchange resin bags and a modified Hedley P fractionation procedure were used to measure seasonal dynamics of soil N forms (ammonium and nitrate) and P fractions (available, labile, slow, occlude and weathered mineral P) under urban forest remnants across a successional sequence and non-forest land in the city of Nanchang, Southern China. Results showed that soil N availability varied with season and vegetation community (P < 0.05). Soil P fractions showed minimal seasonal variation except available P, while their averages generally increased with forest development from non-forest land to coniferous forest to conifer-broadleaf mixed forest to evergreen broad-leaved forest. The ratios of fresh soil N forms to P fractions generally decreased with forest development, while N forms absorbed by resins to P fractions generally increased from non-forest land to coniferous forest, then decreased from conifer-broadleaf mixed forest to evergreen broad-leaved forest. It is suggested that urban older forest remnants could easily move to N saturation status and soil P enrichment, causing urban water pollution due to the accumulative effect of elevated atmospheric N deposition and exogenous P input with urbanization. 相似文献
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以"苏州青"为试验材料,采用室内盆栽砂培方法,营养液按霍格兰配方进行配置,研究氮、磷、钾失调对其生长的影响.结果表明:不同养分处理对"苏州青"青菜的出苗、株高、根长、叶片数、叶长、叶宽等形态指标及地上部和根系鲜重均有不同程度的影响,缺磷和缺钾会明显降低"苏州青"的出苗率,氮过剩对出苗的抑制作用最为明显.除缺氮促使植株根系伸长外,缺氮、缺磷和氮过剩处理均使"苏州青"各形态指标数值有所降低.磷过剩、钾过剩及养分完全处理的地上部鲜重显著高于缺氮、缺磷、缺钾和氮过剩.氮过剩、磷过剩、钾过剩及完全处理地下部鲜重显著高于缺氯、缺磷、缺钾处理,氮过剩、磷过剩、钾过剩、完全处理之间根系鲜重差别不显著,缺氮、缺磷、缺钾处理之间的根系鲜重差别也未达到显著水平. 相似文献
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A romaine-type lettuce (Lactuca sativa L.) was cultivated during three successive crop seasons in an agricultural land near the Wastewater Treatment Plant (WWTP) of Alcázar de San Juan. Four fertilization treatments were compared, including: two different organic fertilizer treatments consisting of (i) air-dried sewage sludge (SS), and (ii) municipal solid waste compost (MSWC), (iii) an inorganic treatment of commercial fertilizer (FER), and (iv) a control treatment in which no fertilizer was applied (CONT). The highest yield was observed in the SS treatment in all crop seasons. In the organic treatment plots there was an increase in macronutrients and organic matter in the soil. An accumulation of heavy metals in the soil was not observed but there was an increase in microbial population in the organic treatment plot, especially in the SS treatment plot. In plant tissue, the continued addition of fertilizers did not produce an accumulative effect of macro- and micronutrients. Low heavy metal content (Cr, Cd, Pb and Hg) was observed in all treatments and crop seasons. Microbiological content was more numerous in the first crop season in SS-treated plants, mainly in lettuce leaves but also in the soil. 相似文献
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Effect of different drip irrigation methods and fertilization on growth,physiology and water use of young apple tree 总被引:3,自引:0,他引:3
A pot experiment was conducted to investigate the effect of three drip irrigation methods (i.e. conventional drip irrigation (CDI), both sides of the root-zone irrigated with full watering, alternate drip irrigation (ADI), both sides of the root-zone irrigated alternatively with half of the full watering, and fixed drip irrigation (FDI), only one side of the root-zone irrigated with half of the full watering) on growth, physiology, root hydraulic conductance and water use of young apple tree under different nitrogen (N) or phosphorus (P) fertilization (i.e. CK (no fertilization), N1 (0.2 g N/kg), N2 (0.4 g N/kg), P1 (0.2 g P2O5/kg) and P2 (0.4 g P2O5/kg)). Results show that compared to CDI, ADI and FDI reduced mean root dry mass, daily transpiration, root hydraulic conductance (Kr), leaf photosynthesis rate, transpiration rate and stomatal conductance of young apple tree by 6.9 and 27.7, 29.3 and 45.0, 6.8 and 37.9, 2.5 and 4.8, 32.6 and 33.0, 22.1 and 22.3%, but increased leaf water use efficiency (WUE) by 31.3 and 29.8%, respectively when they saved irrigation water by 50%. Compared to the CK, N or P fertilization significantly increased Kr, and Kr was increased with the increased N or P fertilization level. There were parabolic correlations between Kr and root dry mass, daily transpiration and stomatal conductance. Our results indicate that ADI reduced transpiration rate significantly, but it did not reduce photosynthesis rate and Kr significantly, thus alternate drip irrigation improved WUE and the regulation ability of water balance in plants. 相似文献
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The spatiotemporal dynamics of rapid urban growth in the Nanjing metropolitan region of China 总被引:12,自引:1,他引:12
To better understand the spatio-temporal dynamics of the urban landscape of the Nanjing metropolitan region, China, we conducted
a series of spatial analyses using remotely sensed data of 1979, 1988, 1998, 2000 and 2003. The results showed that the urban
area as well as the growth rate increased significantly. Three urban growth types were distinguished: infilling, edge-expansion
and spontaneous growth. The pattern of urban growth can be described as a ‘diffusion–coalescence’ phase transition. Although
edge-expansion was the most common growth type, the spontaneous growth took a greater proportion in area and patch number
than the infilling growth at the early stage, but its dominance decreased as urbanization proceeded from the diffusion phase
to the coalescence phase. Hot-zones of urban growth and the distribution pattern of newly urbanized areas in different periods
were studied with a buffering analysis. More than 80% of the growth area occurred within a zone of 1.4 km wide outwards from
the pre-growth urban fringes. The spatial distribution of newly urbanized areas in each period showed a uniform negative exponential
decline relative to the distance from the edge of the urban patches. There existed an outward wave-like shifting of urban
growth hot-zones, but the distance-growth area curves varied at different stages of urban growth. While a double-peaked pattern
usually occurred in the diffusion phase, a single-peaked pattern was common in the coalescence phase. 相似文献
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以叶芥菜‘雪里蕻’和‘包包青菜’为材料, 研究4个氮肥水平(10.3、100、200和300 kg·hm - 2 ) 和2个硫肥水平(0和50 kg·hm- 2 ) 对植株生长和营养品质的影响。结果表明, 随氮肥量增加,两品种的株高、地上部鲜质量、产量、叶绿素、β - 胡萝卜素、游离氨基酸、地上部氮含量、地上部硫含量均显著提高, 雪里蕻的硝酸盐含量也显著提高, 两品种的干物质和可溶性总糖含量则降低。较低施氮量(小于100 kg·hm- 2 ) 对可溶性蛋白质含量有明显影响。在不施硫处理(供应KCl) 中, 氮肥对包包青菜硝酸盐含量没有显著影响; 而在施硫处理(供应K2SO4 ) 中, 增加氮肥量显著增加其硝酸盐含量。增施硫肥, 雪里蕻可溶性蛋白质和包包青菜硝酸盐均显著提高, 两品种地上部硫含量显著提高, 而对其它指标没有明显影响。 相似文献
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Salinity and porosity of composted sewage sludge (CSS) were studied to evaluate their effect on vegetable seedlings, specifically on vegetable seedling performance and toxicity threshold of soluble salts. For the evaluation, CSS was mixed with different proportions of leached CSS to control the salinity. Soluble salt content of 1.45% or higher in growth media inhibited the growth of cucumber, tomato, and pepper seedlings, while that of 1.1% was relatively safe. Different porosities of CSS media were prepared by mixing CSS (<10 mm) with ground CSS (<1 mm) in different proportions (CSS and ground CSS were leached beforehand to prevent salt stress). The vegetable seedlings grew well in CSS media without showing symptoms of growth inhibition if the total porosity ranged from 66% to 81% and the water holding porosity ranged from 48% to 59%. However, the best seedling performances were achieved with the coarser media with high total porosities. The study indicated that when salt content was appropriate, CSS can be used alone as a vegetable seedling growth medium without the need for grinding or blending with other materials. 相似文献
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杂交茎瘤芥需肥规律研究 总被引:3,自引:3,他引:0
用分期取样、化验分析、模型拟合的方法,研究了杂交茎瘤芥干物质积累过程以及生长过程中对氮、磷、钾三大元素的吸收规律.结果表明,杂交茎瘤芥干物质积累和对氮、磷、钾的吸收均符合Logistic生长曲线.以茎瘤芥对养分的吸收规律为依据,研究其需肥特性,结果表明,杂交茎瘤芥目标产量若为3 500kg/667 m2,需纯氯33.56 kg、磷(p2O5)7.63 kg、钾(K2O)25.47 kg,其比例为1:0.23:0.76. 相似文献
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The effects of the NH4:NO3 ratio in replenishment solution on Rosa L. flower yield and the impact of NH4 substitution by urea on plant performance and on solution EC and pH have not been studied previously in closed (no leaching) hydroponic systems. A greenhouse experiment with six NH4:NO3:urea ratios (0:100:0, 12:88:0, 25:75:0, 50:50:0, 100:0:0 and 0:50:50) and two harvest cycles (winter and spring) was carried out to investigate these relationships. In winter, total and >40 cm cut flower yields were maximal in treatment 25:75:0. At lower NH4 percentages (12.5:87.5:0 and 0:100:0), growth container solution pH varied between 7.8 and 8.5, reducing P, Ca and Mn concentration in leaves and increasing dry matter allocated to them. At higher NH4 percentages, Ca uptake was inhibited, solution pH reached 3, and %P in leaves increased. Consequently, reducing sugars concentration in leaves increased and sucrose and starch concentrations decreased. A stepwise regression analysis indicated that the optimal NH4:NO3 ratio in feed solution is 40:60, with resulting solution pH of 5.9 in the growth container. In spring the maximum yield was obtained in treatment 0:50:50 and it exceeded the winter yield despite a higher solution EC (4.3 dS m−1 vs. 3.5 dS m−1 at harvest). The beneficial effect of urea (0:50:50 vs. 50:50:0) stemmed from the relatively lower NH4 concentration in solution, that alleviated the NH4–Ca uptake competition, and higher pH. The slope of the straight line relating [H+ efflux rate] to [NH4+ uptake rate] in treatments 25:75:0, 50:50:0 and 100:0:0 was 0.44 mol H+/mol NH4. In all other treatments the proton efflux was negligible. 相似文献
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One-year-old scale bulblets of Lilium longiflorum Thunb. ‘Nellie White’ (Easter lily) were grown under a combination of six constant day/night temperature regimes and five N–P–K nutrient treatments under short days for 107 d (growing period 1 or GP-1) to compare the effects on growth and development and bulb production. Results during GP-1 were as follows: failure of bulblets to produce a shoot (“no-shows”) was found at high temperatures (30/26 and 26/22 °C) and not influenced by the nutrient treatments. Flower bud abortion was observed in the minus-N, minus-P, and minus-N–P–K treatments at high temperatures (30/26 or 26/22 °C), but not observed at any temperatures in the complete and minus-K treatments. The loss of bulb fresh weight in minus-N treated bulblets was less than in the other treatments resulting in less root and shoot growth in the minus-N treatment. At the intermediate temperatures where growth was highest, omission of N, P, K, or all three resulted in losses in stem bulb fresh weight, stem plus leaf fresh weight, number of flowers, and stem root fresh weight. Omission of N, P, or all three nutrients resulted in lowest basal root fresh weight. Bulb N and K concentrations were lowest in plants grown with complete nutrient solution at the two coldest temperature regimes (14/10 and 10/6 °C). Bulb P concentration was lowest at the three coldest (18/14, 14/10 and 10/6 °C) and the warmest (30/26 °C) temperature regimes. Stem length was shorter when P was omitted. Omission of any of the three nutrients resulted in lower concentrations of the other nutrients. The one exception was where low K did not affect N concentration. In the second phase of the experiment, plants grown at 18/14 °C and irrigated with the complete nutrient solution for 107 d (GP-1) were continued at this day/night temperature regime and five N–P–K nutrient treatments for another 89 d under long days (growing period 2 or GP-2). Results during GP-2 were as follows. Basal bulb yield was not impacted by omission of N, P, or K, or all three. Of all growth measurements, only stem plus leaf fresh weight was lower and only when all three nutrients (minus-N–P–K) were omitted. At the end of GP-2, basal bulb concentrations of N and P did not differ from the concentrations in bulbs at the beginning of GP-1; however, K concentration was lower at the end of GP-2. Omission of N or P further resulted in lower bulb K concentration, suggesting that a moderate supply of N, P, and K be applied during GP-2 since an additional year of bulb production is needed to produce forcing-sized bulbs. 相似文献
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Compost (CP) made from 70% ligno-cellulosic compounds and 30% sewage sludge was studied as a component of growing media in a 6-month Philodendron cultivation. CP's agronomic viability was evaluated via four plant-growth media containing 25–50–75–100% CP and white sphagnum peat (WP) in comparison to a commercial substrate with white and black peat. Plant nutrition conditions were investigated by determining macro- (TKN, P, K, Ca, Mg and micronutrients (Mn, Fe, Cu, Zn, Na) and heavy metals (Ni, Cd, Cr, Pb) in roots and shoot tissues. Data were compared by vector analysis against control. Even if no leaf injuries were visible after 6-months’ growth, a CP ratio of up to 50% caused growth depression of canopy tissues, as attested by the 37 and 36% reduction in total leaf dry weight and leaf area, respectively. Root growth decline was also notable at 25% CP, where 38% root dry weight reduction implied a significant increase (46%) in shoot–root dry weight ratio. The investigation on nutrient tissue content showed high accumulation of Ni, Fe, Cr, Zn, Cd, Mn, Mg and P in roots; Mg appeared related to K deficiency. Above-ground nutritional status showed a severe lack of P, Mg and Mn. Vector analysis suggests the sewage sludge CP in Philodendron pot cultivation produces many such effects like direct toxic action and antagonistic action, resulting in a general nutrient imbalance in plants. 相似文献
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研究了不同菌剂及不同菌剂浓度处理对高羊茅草坪剪草堆肥的催化腐熟效果。结果表明:接种菌剂A时,菌剂量与原料的比为0.2:1000,堆肥的感官变化和生物降解度最明显,堆肥的腐熟效果最好。接种菌剂B时,菌剂量与原料的比为0.4:1000,堆肥的温度变化和生物降解度最明显,堆肥的腐熟效果最好。接种菌剂C时,菌剂量与原料的比为0.025:1000,堆肥的感官变化和生物降解度最明显,堆肥的腐熟效果最好。在3种菌剂中,菌剂C的菌剂量与原料的比为0.025:1000时,堆肥的腐熟效果比菌剂A和菌剂B都好。 相似文献
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果梅完全花与不完全花氮磷钾质量分数比较分析 总被引:1,自引:0,他引:1
果梅不完全花的形成和营养水平关系密切。为研究果梅完全花与不完全花营养水平的差异,测定并分析了4个果梅品种完全花与不完全花不同发育时期的氮磷钾质量分数。结果表明,4个果梅品种完全花中氮元素的质量分数大于不完全花中氮的质量分数,但是磷元素质量分数要比不完全花磷的质量分数低。各品种钾元素质量分数变化比较复杂,在小蕾期完全花钾的质量分数大于不完全花,而在开花期完全花钾质量分数小于不完全花钾的质量分数。各品种完全花与不完全花中氮、磷、钾质量分数在不同时期的变化趋势不相同。试验结果为研究果梅雌蕊败育提供了一定的营养学数据,也为进一步探索雌蕊败育问题的解决方案打下了基础。 相似文献