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1.
Imbalanced application of nitrogen (N) and phosphorus (P) fertilizers can result in reduced crop yield, low nutrient use efficiency, and high loss of nutrients and soil nitrate nitrogen (NO3--N) accumulation decreases when N is applied with P and/or manure; however, the effect of applications of N with P and/or manure on root growth and distribution in the soil profile is not fully understood. The aim of this study was to investigate the combined effects of different N and P fertilizer application rates with or without manure on maize (Zea mays L.) yield, N uptake, root growth, apparent N surplus, Olsen-P concentration, and mineral N (Nmin) accumulation in a fluvo-aquic calcareous soil from a long-term (28-year) experiment. The experiment comprised twelve combinations of chemical N and P fertilizers, either with or without chicken manure, as treatments in four replicates. The yield of maize grain was 82% higher, the N uptake 100% higher, and the Nmin accumulation 39% lower in the treatments with combined N and P in comparison to N fertilizer only. The maize root length density in the 30--60 cm layer was three times greater in the treatments with N and P fertilizers than with N fertilizer only. Manure addition increased maize yield by 50% and N uptake by 43%, and reduced Nmin (mostly NO3--N) accumulation in the soil by 46%. The long-term application of manure and P fertilizer resulted in significant increases in soil Olsen-P concentration when no N fertilizer was applied. Manure application reduced the apparent N surplus for all treatments. These results suggest that combined N and P fertilizer applications could enhance maize grain yield and nutrient uptake via stimulating root growth, leading to reduced accumulation of potentially leachable NO3--N in soil, and manure application was a practical way to improve degraded soils in China and the rest of the world.  相似文献   

2.
Subsoil acidity restricts root growth and reduces crop yields in many parts of the world. More than half of the fertilizer nitrogen(N) applied in crop production is currently lost to the environment. This study aimed to investigate the effect of gypsum application on the efficiency of N fertilizer in no-till corn(Zea mays L.) production in southern Brazil. A field experiment examined the effects of surface-applied gypsum(0, 5, 10, and 15 Mg ha~(-1)) and top-dressed ammonium nitrate(NH_4NO_3)(60, 120, and 180 kg N ha~(-1)) on corn root length, N uptake, and grain yield. A greenhouse experiment was conducted using undisturbed soil columns collected from the field experiment site to evaluate NO_3-N leaching, N uptake, and root length with surface-applied gypsum(0 and 10 Mg ha~(-1)) and top-dressed NH_4NO_3(0 and 180 kg N ha~(-1)). Amelioration of subsoil acidity due to gypsum application increased corn root growth,N uptake, grain yield, and N use efficiency. Applying gypsum to the soil surface increased corn grain yield by 19%–38% and partial factor productivity of N(PFPN) by 27%–38%, depending on the N application rate. Results of the undisturbed soil column greenhouse experiment showed that improvement of N use efficiency by gypsum application was due to the higher N uptake from NO_3-N in the subsoil as a result of increased corn root length. Our results suggest that ameliorating subsoil acidity with gypsum in a no-till corn system could increase N use efficiency, improve grain yield, and reduce environmental risks due to NO_3-N leaching.  相似文献   

3.
Evaluation of nitrogen (N) dynamic in soil using regression equations is important for proper determination of N fertilization. A 3-year field experiment was conducted to (1) develop the best-fitted regression model relating corn grain and stover yield to soil residual ammonium (NH4)-N and nitrate (NO3)-N for corn yield prediction and (2) evaluate how such a model can be beneficial to the health of ecosystem by predicting the appropriate rates of N fertilization for corn production. Soil NH4-N and NO3-N were determined at corn harvest at the depths of 0–30 and 30–60 cm. Nitrogen fertilizer rates and soil mineral N accounted for a maximum of 93% variation in corn grain yield. Soil mineral N enhanced corn yield more than N fertilizer. Totals of 63.1 and 14.1 kg/ha of soil residual NO3-N and NH4-N were found in the 0- to 60-cm depth, indicating the importance of performing soil N tests.  相似文献   

4.
Abstract

White Rose potato plants were transplanted to nutrient solutions provided vith nine treatments of Ca(NO3)2 ranging from 0 to 64 mmoles per liter. Eighteen days later, symptoms of N‐deficiency ranging from very severe to none vere observed. The plants at this time were harvested, and leaves were sampled, oven dried, ground, and then analysed for K, Na, Ca, Mg, NO3‐N, and acetic acid soluble H2PO2‐P.

Shoot and fibrous root growth increased with nitrate supply to an optimum, and then decreased with increased nitrate supply, suggesting nitrate toxicity due to the high nitrate supply of the nutrient solution. The nitrate content of the tissues increased with increased nitrate supply. Toxicity due to excess nitrate was associated with a very high nitrate content of the leaf tissues.

The critical NO3‐N concentration at a 10% reduction in vegetative growth due to N‐deficiency is about 2000 ppm (0.2%) on a dry basis for the petioles and about 300 ppm (0.03%) for the blades of recently matured leaves.  相似文献   

5.
A field experiment was conducted to determine the effects of long-term applications of fertilizers and manure (1982 to 2003) and short-term irrigation level (2002 and 2003) on accumulation of nitrate nitrogen (NO3-N) in soil at Zhangye Oasis, China. The treatments included manure (M) and no manure (M0) as main plots; check (Ck), nitrogen (N), nitrogen + phosphorus (NP), and nitrogen + phosphorus + potassium (NPK) as subplots; and two amounts of irrigation (I1 and I2) as subsubplots. The application of N alone resulted in large NO3-N accumulation in soil, accounting for 6% of the applied N, and the lowest crop N recovery. Application of manure resulted in increased NO3-N in the soil profile compared to treatment with no manure, and the MN treatment resulted in the greatest amount of NO3-N in soil. Nitrogen applied with P and/or K reduced the amount of NO3-N in soil in both manure and no-manure treatments compared with N only. The unaccounted N was greatest (60%) in the N-alone treatment and lowest (30%) in the NPK treatment. When manure plus fertilizer were applied together, the unaccounted N ranged from 35%–42%. Based on results from only 2 years, greater amounts of irrigation (I2) caused greater leaching of NO3-N in the soil profile compared with I1, especially in treatments receiving manure. The implications of these findings are that these high amounts of accumulated NO3-N in surface and subsoil layers can be a potential threat to surface water, underground water, and air quality in the long run. This accumulated N in the soil profile can be used as a source of available N for future crops and should be recycled by using proper crop, soil, fertilizer, and water-management strategies/practices. The findings also suggest the need for further research to make an effective and efficient use of this accumulated NO3-N in the soil profile in order to save cost of N fertilizer application to future crops.  相似文献   

6.
针对于非点源污染机理模型在实际运用中的限制，将人工神经网络引入地下水非点源污染格局的模拟和预报中，建立了基于GIS的BP神经网络模型用以模拟分析农区浅层地下水NO-3-N含量及其空间分布特征。结果表明，以农田氮盈余、地下水埋深、30～60cm土层砂粒含量和土壤有机质4个因素为输入因子，以地下水NO-3-N为输出因子，通过网络训练以及观测点缓冲区半径的设定与调整，BP神经网络模型有效地模拟了山东省桓台县地下水NO-3-N含量及其空间分布特征，并且有较高的精度。该研究可为华北平原农区地下水质管理提供分析工具与决策依据，是对非点源污染机理模型的有益补充。  相似文献   

7.
氮肥形态及配比对菠菜生长和安全品质的影响   总被引：4，自引：1，他引：4  
【目的】铵态氮肥和硝态氮肥是蔬菜生长过程中经常施用的氮肥种类,氮肥形态及配比对蔬菜生长和安全品质有着重要影响。菠菜是一种叶菜类蔬菜,富含矿质元素、维生素C和维生素E。本文通过施用铵态氮和硝态氮肥,探究氮肥形态及其配比(NH+4-N/NO-3-N)对菠菜生长和安全品质的影响。【方法】采用水培试验,设置5种不同氮素形态配比(NH+4-N/NO-3-N比值分别为100∶0、75∶25、50∶50、25∶75和0∶100)的营养液,定期采集菠菜样品并测定菠菜的生物量、株高、根系长度、硝酸盐和亚硝酸盐、有机酸和氨基酸参数值。【结果】随着NH+4-N/NO-3-N比值从100∶0变化到0∶100,菠菜的生物量、株高、根系长度、硝酸盐和亚硝酸盐累积量以及有机酸含量均呈增加趋势,而氨基酸总量则明显下降;当NH+4-N/NO-3-N比值为0∶100时,菠菜茎叶生物量为6.2g/plant,株高和根系长度分别为16.3 cm和22.5 cm,分别是NH+4-N/NO-3-N比值为100∶0时的6倍、2.2倍和2.0倍,表明菠菜是一种喜硝酸盐氮的蔬菜;当NH+4-N/NO-3-N比值由0∶100变为25∶75时,即在氮肥组合中增加25%的铵态氮肥,此时的硝酸盐和亚硝酸盐含量分别由398.5 mg/kg、1.42 mg/kg降为249.1 mg/kg、0.98mg/kg,降幅为37.5%和8.0%,表明在菠菜生长过程中适当增施铵态氮肥可有效降低硝酸盐和亚硝酸盐在茎叶中的累积;当NH+4-N/NO-3-N比值从100∶0变化到0∶100,对6种有机酸(苹果酸、富马酸、琥珀酸、α-酮戊二酸、柠檬酸和丙酮酸)而言,增加幅度最大的是富马酸,约8.6倍,增加幅度最小的是柠檬酸,约2.5倍,苹果酸则在NH+4-N/NO-3-N=25∶75时达到最大值,为985.3 mg/L;随着NH+4-N比例的减少,菠菜茎叶中的氨基酸总量呈下降趋势,NH+4-N/NO-3-N比值为100∶0、75∶25、50∶50、25∶75和0∶100的氨基酸总量分别为21.80μmol/g、12.92μmol/g、9.20μmol/g、8.30μmol/g和7.50μmol/g,表明菠菜的营养价值降低,这一趋势与上述所研究的指标(株高、根系长度、硝酸盐和亚硝酸盐含量以及有机酸含量)有着明显的区别。【结论】菠菜是一种典型的喜硝态氮类蔬菜,施用硝态氮肥可明显提高菠菜产量,但过高的施用量可导致菠菜安全品质下降。适当增施铵态氮肥可降低硝酸盐和亚硝酸盐在菠菜体内的累积,并有效调节氨基酸和有机酸的代谢。因此,在菠菜种植过程,应该合理地搭配铵态氮肥和硝态氮肥,以便在保证安全性和营养价值的基础上获取最大的生物量。  相似文献   

8.
Abstract. In dairy farming systems the risk of nitrate leaching is increased by mixed rotations (pasture/arable) and the use of organic manure. We investigated the effect of four organic farming systems with different livestock densities and different types of organic manure on crop yields, nitrate leaching and N balance in an organic dairy/crop rotation (barley–grass-clover–grass-clover–barley/pea–winter wheat–fodder beet) from 1994 to 1998. Nitrate concentrations in soil water extracted by ceramic suction cups ranged from below 1 mg NO3-N l?1 in 1st year grass-clover to 20–50 mg NO3-N l?1 in the winter following barley/pea and winter wheat. Peaks of high nitrate concentrations were observed in 2nd year grass-clover, probably due to urination by grazing cattle. Nitrate leaching was affected by climatic conditions (drainage volume), livestock density and time since ploughing in of grass-clover. No difference in nitrate leaching was observed between the use of slurry alone and farmyard manure from deep litter housing in combination with slurry. Increasing the total-N input to the rotation by 40 kg N ha?1 year?1 (from 0.9 to 1.4 livestock units ha?1) only increased leaching by 6 kg NO3-N ha?1. Nitrate leaching was highest in the second winter (after winter wheat) following ploughing in of the grass-clover (61 kg NO3-N ha?1). Leaching losses were lowest in 1st year grass-clover (20 kg NO3-N ha?1). Averaged over the four years, nitrate concentration in drainage water was 57 mg l?1. Minimizing leaching losses requires improved utilization of organic N accumulated in grazed grass-clover pastures. The N balance for the crop rotation as a whole indicated that accumulation of N in soil organic matter in the fields of these systems was small.  相似文献   

9.
Understanding the temporal distribution of NO3-N leaching losses from subsurface drained ‘tile’ fields as a function of climate and management practices can help develop strategies for its mitigation. A field study was conducted from 1999 through 2003 to investigate effects of the most vulnerable application of pig manure (fall application and chisel plow), safe application of pig manure (spring application and no-tillage) and common application of artificial nitrogen (UAN spring application and chisel plow) on NO3-N leaching losses to subsurface drainage water beneath corn (Zea mays L.)–soybean (Glycine max L.) rotation systems as a randomized complete block design. The N application rates averaged over five years ranged from 166 kg-N ha?1 for spring applied manure to 170 kg-N ha?1 for UAN and 172 kg-N ha?1 for fall applied manure. Tillage and nitrogen source effects on tile flow and NO3-N leaching losses were not significant (P?<?0.05). Fall applied manure with CP resulted in significantly greater corn grain yield (10.8 vs 10.4 Mg ha?1) compared with the spring manure-NT system. Corn plots with the spring applied manure-NT system gave relatively lower flow weighted NO3-N concentration of 13.2 mg l?1 in comparison to corn plots with fall manure-CP (21.6 mg l?1) and UAN-CP systems (15.9 mg l?1). Averaged across five years, about 60% of tile flow and NO3-N leaching losses exited the fields during March through May. Growing season precipitation and cycles of wet and dry years primarily controlled NO3-N leaching losses from tile drained fields. These results suggest that spring applied manure has potential to reduce NO3-N concentrations in subsurface drainage water and also strategies need to be developed to reduce early spring NO3-N leaching losses.  相似文献   

10.
Zeolite minerals may improve nitrogen availability to plants in soil and reduce losses to the environment. A study was conducted to determine the influence of clinoptilolite (CL) on nitrogen (N) mineralization from solid dairy manure (224 kg N ha?1) in a sandy soil. Clinoptilolite was added to soil at six rates (0 to 44.8 Mg CL ha?1), each sampled during 11 sampling dates over a year. Over time, nitrate (NO3)-N increased, ammonium (NH4)-N decreased, but total inorganic N increased. Clinoptilolite did not influence the nitrification rates of initial manure NH4-N or mineralization of organic N (ON) over time. It is possible that adsorption of manure-derived potassium (K) outcompeted the NH4-N for CL exchange sites. The ON concentration was constant up to 84 days and then decreased by approximately 18% over the remaining time of the study across all treatments. Clinoptilolite use in this sandy soil did not alter mineralization of N from dairy manure.  相似文献   

11.
Abstract

Early spring application of N to Iowa sandy, leachable soils results in reduced sweet corn yields and kernel protein content. Normally, split N applications are used to coincide with crop N demand. Our objectives were to determine if nitrapyrin, a nitrification inhibitor, applied with urea would provide high yields and kernel protein levels when applied at planting.

Nitrogen rate increased yield, ear leaf N concentration, and kernel protein content in 1976 and 1978, with the optimum rate dependent on the year and soil N residual. Urea, with or without nitrapyrin, significantly enhanced yield 13%, early leaf N concentration 17%, and kernel protein content 9% as compared with Ca(NO3)2 for both years. High leaching loss of NO3‐N occurred with the Ca(NO3)2 source as compared with urea alone. Kernel protein concentration correlated well with ear leaf N concentration (r = .74) and yield (r = .61). Ear leaf K content was not affected by N rate or source, but Ca(NO3)2 enhanced uptake of Ca and Mg as compared with the urea sources. Urea, with nitrapyrin, decreased leaf Mg content in 1978, but not in 1976, as compared with urea alone.  相似文献   

12.
The objective of this study was to test if the effects of different nitrogen forms on potato growth depend on the plant growth stage. Plants from different potato cultivars were treated with different forms of nitrogen before tuber initiation and after tuber formation. A nitrification inhibitor was used to prevent the transformation of ammonium (NH4+) to nitrate (NO3?). Plant growth, tuber formation, leaf area, leaf chlorophyll content, and tuber yield were assessed. The results obtained over 2 years indicate that plants treated with NO3-nitrogen (N) before or at tuber initiation produced more tubers per plant than those treated with NH4-N. However, plants treated with NH4-N develop tubers earlier. Additionally, after tuber formation, plants treated with NH4-N had better shoot growth than plants treated with NO3-N. A larger leaf area with higher leaf chlorophyll content resulted in greater dry matter accumulation and higher tuber yield at harvest for plants treated with NH4-N.  相似文献   

13.
’Shogoin’ turnip plants (Brassica rapa L.) were grown in sand culture under five nitrate:ammonium (NO3:NH4) ratios (N:N of 1:0, 3:1, 1:1, 1:3, 0:1). The leaves expressed symptoms of NH4 toxicity (reduced growth and curly leaves with dark‐green areas surrounding yellow spots) when NH4 was the dominant nitrogen (N) form. Increasing NO3 in the nutrient solution significantly (p<0.01) increased leaf and root fresh weight and dry weight. Leaf nutrient concentration and composition of all elements analyzed, except N and calcium (Ca), responded quadratically (p<0.01) to NO3:NH4 ratios, and the highest values were observed with the 1:0 [for molybdenum (Mo)], 3:1 ([or magnesium (Mg)], 1:1 [for boron (B), coper (Cu), iron (Fe), manganese (Mn ), and zinc (Zn)] or 1:3 [for phosphorus (P) and potassium (K)] treatments. Nitrogen and Ca leaf concentration responses were linear and highest at 0:1 and at 1:0, respectively. Cultural practices and fertilizer applications should maintain NO3 as the dominant N form in the root zone, and the continuous use of NH4‐ based or NH4‐releasing fertilizers is not recommended for the production of high yields of turnip greens.  相似文献   

14.

Background and Objectives  

Soil nitrate nitrogen (NO3 −-N) accumulation is related closely to NO3 − leaching, which is an important issue in groundwater pollution, especially in intensive agricultural areas with saline soils where volumes of water are used in irrigation to avoid salt accumulation in the root zone. However, in the saline environment in Hai River Basin, China, the importance of detailed research into NO3 −-N distribution in the root zone has not been adequately recognized. Considering the impacts of eco-environmental system N and crop production, the present study aimed at contributing to an understanding of the effects of N application rate on soil NO3 −-N distribution, NO3 −-N residue, N loss, and maize (Zea mays L.) yield in this region.  相似文献   

15.
The effects of months of the year and nitrogen (N) sources on salad rocket (Eruca sativa Mill.) yield, quality, and nitrate accumulation was investigated during the years 2002 and 2003. In both years, seeds were sown on the first day of April, May, June, July, August and September. Three different nitrogen sources were used: farmyard (cattle) manure (100 tonnes·ha?1), calcium nitrate [Ca(NO3)2]-15.5% N (150 kg N·ha?1) and ammonium sulfate [(NH4)2SO4)]-21% N (150 kg N·ha?1). Yield, leaf color, dry matter, vitamin C and total glucosinolate content and nitrate accumulation was assessed. Growing months affected all the assessed parameters significantly both years, with the exception of hue angle in 2003, whereas nitrogen source only influenced yield and nitrate accumulation in 2003. In both years the highest yield was obtained in April, but vitamin C and total glucosinolate contents were higher during summer months, and leaves were slightly darker colored. Chemical fertilizers increased the yield compared to farmyard manure; however, they also increased nitrate accumulation slightly, without any significant difference between them. Nitrate accumulation never exceeded 300 mg kg?1 fresh weight (FW), which is well below the acceptable daily intake of 3.7 mg nitrate per kg?1 bodyweight set by European Commission's Scientific Committee on Food.  相似文献   

16.
The objectives of this study were to determine the effects of fertilization system, nitrate (NO3)– nitrogen (N) distribution along soil profile, and their interaction on corn yield. The study was conducted at the experimental field of Institute of Field and Vegetable Crops in Novi Sad (Serbia) during 2001–2004. Corn monoculture included four fertilization variants: control (Ø), nitrogen–phosphorus–potassium (NPK) mineral fertilizers, mineral fertilizer + corn stalks (NPK + S), and mineral fertilizers + manure (NPK + M). The greatest yield was found in the variant NPK + M (9.25 t ha?1). Path coefficients showed that greatest direct positive effects on corn yield were exhibited by NO3-N levels at soil depths of 60–90 cm and 30–60 cm. The path analysis showed that winter precipitation (WP) had a direct negative effect on yield performance. However, the effect of the downward movement of NO3-N from the topsoil to deeper soil layers of WP on yield was positive.  相似文献   

17.
Environmental issues associated with intensive use of nitrogenous fertilizers have generated an interest in alternative management systems. An experiment was conducted to mitigate nitrate leaching from sandy soil using different waste materials such as charcoal, manure, sawdust, wood ash, and control (no amendment). Urea was applied at the rate of 300 kg nitrogen (N) ha?1. Nitrate was determined during six leaching events. During an incubation experiment, nitrate release was also determined in soil amended with charcoal at the rates of 0, 10, 20, and 40 t ha?1. Urea was applied at the rates of 0, 100, 200, 400, and 1000 ppm N. Results indicated that urea application increased nitrate (NO3) concentration in leachate. Soil amendments substantially reduced NO3 in leachates irrespective of the type of material used. Waste amendments differed for NO3 leaching as follows: charcoal < wood ash < sawdust < manure. Leaching of NO3 enhanced up to the fourth leaching event and thereafter reduced significantly. Nitrate retention in soil varied among material in the order of manure > charcoal > wood ash > sawdust. Nitrate accumulation occurred in the lower layer (25–50 cm) of soil column after the leaching process. Application of charcoal retained greater NO3 level as compared to control soil during an incubation. Enhanced urea applications also enhanced NO3 release. This experiment suggests that waste material can be viably recycled to mitigate NO3 concentration in water.  相似文献   

18.
Soil temperature is a very easily measured parameter that influences nutrient availability in vineyards. We monitored soil temperature and plant-available nitrogen (N) in a study evaluating the potential of legumes as an interrow cover crop to supply N to Concord grape (Vitis labruscana Baily). Nitrogen sources used were hairy vetch (Vicia villosa subsp. villosa L.) and yellow sweet clover [Melilotus officinalis (L.) Lam] as green manure sources and either blood meal (in a certified organic vineyard) or urea (in a conventional vineyard) as soluble sources. Plant-available N was measured both continuously using ion exchange membranes (PRSTM) and point in time by soil sampling at regular intervals; both were analyzed for nitrate (NO3) N and ammonium (NH4) N, although negligible concentrations of NH4-N were detected. PRS NO3-N concentration varied by treatments because of differences in the chemical composition of the N source. Soil NO3-N concentration reached a peak between 520 and 550 degree-days with no significant differences by treatment or site. These findings are similar to results from incubation and field mineralization studies of organic amendments and suggest that N availability from organic sources in vineyards can be predicted using a degree-day-type model.  相似文献   

19.
铵、硝营养对水稻叶细胞膜H+-ATPase和质子泵活性的影响   总被引：2，自引：1，他引：1  
用两相法分离铵态氮(NH4+-N)和硝态氮(NO3--N)培养的水稻苗期叶细胞膜,并测定了细胞膜H+-ATPase水解活性和质子泵活性,以期阐明铵、硝营养对水稻叶细胞膜H+-ATPase的影响。结果表明,叶细胞膜H+-ATPase活性最佳pH值均为6.2。 NO3--N培养的水稻叶细胞膜H+-ATPase的水解活性、Vmax和Km均显著高于NH4+-N培养的水稻叶;Western Blot分析结果看出,NO3--N培养的水稻叶细胞膜H+-ATPase酶浓度也高于NH4+-N培养的水稻叶,说明NO3--N培养的水稻叶中单位细胞膜上的H+-ATPase酶分子数量大于NH4+- N培养的水稻叶,这与细胞膜上H+-ATPase蛋白的表达量升高有关。此外,NO3--N培养的水稻叶质子泵初速度和膜囊体内外H+浓度梯度均高于NH4+- N培养。由于NO3-的跨膜运输是与细胞膜上H+-ATPase紧密联系的主动运输过程,NO3--N培养的水稻叶片细胞膜H+-ATPase活性和质子泵活性高可能与水稻叶细胞吸收大量NO3-有关。  相似文献   

20.
Nitrogen (N) by form of nutrition, ammonium (NH4+) or nitrate (NO3?), affects metabolic and physiological processes of plants. In general, a high proportion of N in NH4+ form results in poor growth. Nonetheless, a number of species exhibit optimum growth when high levels of NH4+ are provided. In the present study, lisianthus [Eustoma grandiflorum (Raf.) Shinn] was grown in rockwool cultures and irrigated with nutrient solutions containing 15 mM N with varying proportions of NH4+ and NO3?. The results showed that an increase in NH4+-N form increased plant height, number of flowers and leaves, leaf area, and shoot, stem, and leaf dry weight. The proportion of NH4+ also affected leaf concentration of phosphorus, potassium (K), calcium (Ca), and magnesium (Mg), although leaf N concentration was unaffected. Potassium leaf concentration was higher when a low proportion of NH4+ was supplemented in the nutrient solution; however, plants exhibited a decrease in leaf K concentration and a decrease in leaf Ca as the proportion of NH4+-N increased. Shoot dry weight was higher with low leaf K whereas high leaf Ca was associated with high shoot dry weight. Net photosynthesis rate was higher in plants irrigated with solutions containing 75% of total N in NH4+ form than in those irrigated with solutions of 0 or 25%. The results suggest that lisianthus can tolerate high levels of NH4+, probably associated with a higher assimilation of Ca.  相似文献   

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