Effect of Excessive Calcium Applications on Growth and Postharvest Performance of Bedding-plant Impatiens

ABSTRACT

Application of excessive amounts of calcium (Ca) during the production cycle improves the quality and postharvest life of several florist crops. Most bedding plants are fertigated with Ca at 100 to 200 mg L^{? 1}throughout the production cycle, but we do not know the effects of higher Ca concentrations. The objective was to evaluate the effect of application of excessive Ca (≥ 280 mg L^?1) supplied during the production cycle on the growth, development, and subsequent postharvest performance of bedding-plant impatiens (Impatiens wallerana Hook. f. ‘Super Elfin White’) under simulated retail conditions. Calcium was applied at 120, 200, 280, 360, and 440 mg L^?1 during each fertigation during the growing cycle. The total nitrogen (N) concentration was 150 mg L^?1, and the nitrate (NO₃ ^?)-N to ammonium (NH₄ ⁺)-N ratio was 1:1. Application of excessive Ca began 30 d after sowing (22 d after germination) and continued until 60 d after sowing. From day 60 to day 65 only deionized water, as a leach, was applied. From day 65 to day 90, plants were held under shade cloth and irrigated with tap water. Excessive Ca applied during the production cycle decreased shoot dry weight, shoot fresh weight, leaf number, and shoot tissue K concentration at the end of the production cycle. Excessive Ca applied during the production cycle also decreased shoot dry weight, leaf number, and shoot tissue potassium (K) concentration at the end of the postharvest period. Plant height, plant diameter, number of open flowers, and number of unopened flower buds at the end of the production cycle and at the end of the postharvest period were not affected by the amount of Ca applied during the production cycle. It was concluded that excessive Ca applied to bedding-plant impatiens during the production cycle did not benefit plant performance during either the production cycle or the postharvest period.     

Effects of Nitrogen Source on Growth and Development of Strawberry Plants

ABSTRACT

An experiment was conducted to study the effects of nitrate (NO₃ ^?) and ammonium (NH₄ ⁺) ratios in nutrient solutions on the growth and production of fruits, runners, and daughter plants of strawberry Fragaria x ananassa Duch., grown in a hydroponic system. Five treatments were applied, consisting of different proportions of NH₄ ⁺ and NO₃ ^? in the nutrient solution. The NH₄ ⁺:NO₃ ^? ratios were: T0 = 0:4, T1 = 1:3, T2 = 2:2, T3 = 3:1, and T4 = 4:0, at a constant nitrogen (N) concentration of 4 mol m^?3. Growth and morphogenesis were characterized by monitoring leaf-area increase, number of flowers and fruits per plant, and number of daughter plants of first and second generations. Nitrogen and carbon (C) content were measured at the end of the experiment in the organs of both mother and daughter plants. None of the variables related to the growth of the mother plant was affected by the treatments. However, the number of fruits increased with the proportion of NH₄ ⁺ in the nutrient solution. The number of daughter plants produced was affected only at high NH₄ ⁺ proportions, and their size (dry matter per daughter plant) and fertility (number of second-generation plants per first-generation plants) were reduced. The N or C content of the plants was not significantly affected by the treatments, but the C/N ratio in the crowns of mother plants was higher in treatments with 25% and 50% NH₄ ⁺ in the nutrient solution.     

Fruit Yield of Tomato Cultivated on Media with Bicarbonate and Nitrate/Ammonium as the Nitrogen Source

ABSTRACT

This article presents the effects of nitrate/ammonium (NO₃ ^?/NH₄ ⁺), applied at different proportions to the root media with or without 5 mmol bicarbonate (HCO₃ ^?), on the yield and chemical composition of tomato fruit. Tomato plants were grown hydroponically (pH 6.9) in glasshouse conditions. The yield of fruit fresh matter from four clusters obtained from plants grown on the medium with NH₄ ⁺ was about 25% lower than from the plants grown on the medium containing NO₃ ^? as the nitrogen (N) source. Supplying NO₃ ^?/NH₄ ⁺ at a ratio of 4:1 increased the fruit yield by about 20% in comparison with the value recorded for NO₃ ^??plants. The enrichment of the medium with HCO₃ ^? stimulated the bearing, while the result depended on the ratio of NO₃ ^?/NH₄ ⁺. A combined treatment of HCO₃ ^? with NO₃ ^? or NH₄ ⁺ in the medium increased yields by about 28% and 11%, respectively, in comparison to plants cultivated without HCO₃ ^?. The application of NO₃ ^?/NH₄ ⁺ at ratios of 4:1 and 1:1 with HCO₃ ^? increased the respective yields by about 16% and 10% in comparison with plants grown without HCO₃ ^?. Modifications in the composition of the media affected the accumulation of organic solutions in the fruit. The NH₄ ⁺ nutrition effected a 20% decrease in the accumulation of reducing sugars in the fruit in comparison to the fruit of plants grown in media with NO₃ ^?. In the cultivation of plants in media with various NO₃ ^?/NH₄ ⁺ proportions the intermediate values of the reduced sugar concentrations were recorded in comparison with the values obtained for NO₃ ^??plants and NH₄ ⁺?plants. The enrichment of media with HCO₃ ^? increased the concentration of sugars in fruit from about 28% (for NO₃ ^??plants) to about 10% (for NH₄ ⁺?plants).

Malate and citrate are the main constituents of carboxylates in tomato fruit. The form of nitrogen applied to the medium did not significantly affect the concentration of carboxylates in fruit. Significant differences in carboxylate concentrations appeared in fruit grown on media enriched with HCO₃ ^? ions. In comparison with the cultivation without HCO₃ ^?, increases in the accumulation of carboxylates varied from about 22% to 30% depending on the form of the applied nitrogen. The concentration of amino acids in the fruit of plants grown with NH₄ ⁺ exceeded that in NO₃ ^??plants by about 55%. In the plants grown on media of modified NO₃ ^?/NH₄ ⁺ proportions, the concentration of amino acids in fruits were positively correlated with the level of NH₄ ⁺ in the medium. The enrichment of media with HCO₃ ^? stimulated a further increase in amino acid concentration in fruit by about 9% in NO₃ ^? plants and about 21% in NH₄ ⁺ plants compared with the respective control (without HCO₃ ^?).     

Supplements of Nickel Affect Yield,Quality, and Nitrogen Metabolism When Urea or Nitrate is the Sole Nitrogen Source for Cucumber

ABSTRACT

Influences of nickel (Ni) concentrations in the nutrient solution on yield, quality, and nitrogen (N) metabolism of cucumber plants (Cucumis sativus cv ‘RS189’ and ‘Vikima’) were evaluated when plants were grown either with urea or nitrate as the sole N source. The cucumber plants were treated with two N sources, urea and nitrate as sodium nitrate (NaNO₃) at 200 mg L^?1, and three concentrations of Ni as nickel sulfate (NiSO₄·6H₂O; 0, 0.5, and 1 mg L^?1). Treatments were arranged in a randomized block design with six replicates. The highest concentration of Ni in the leaves (1.2 mg kg^?1 Dwt) was observed in the urea-fed plants at 1 mg L^?1 Ni concentration. Additions of Ni up to 0.5 mg L^?1 had no effect on the fruit Ni concentration in the both urea and nitrate-fed plants. Yield significantly (p < 0.05) increased with the Ni supplements from 0 to 0.5 mg L^?1 (10 and 15% in ‘RS189’ and ‘Vikima’, respectively), but decreased when 1 mg L^?1 Ni applied to the solutions in urea-fed plants. Nitrate-fed plants had a higher percentage of total soluble solids compare to those urea-fed plants. Nitrate concentrations of the fruits in urea-fed plants in both cultivars were reduced by approximately 50% compared to those nitrate-fed plants. The reduction of nitrate concentration in the fruits became more pronounced as the Ni concentration increased in the solution. The rate of photosynthesis (Pn) increased with the increase of the Ni concentration in the solution with urea-fed plants. Both N concentration and nitrate reductase (NR) activity of young leaves were higher in urea-fed plants at 0.5 mg l^?1 Ni concentration. Ni supplements enhanced the growth and yield of urea-fed plants by increasing Pn, N concentration and NR activity. It can be concluded that Ni supplements (0.5 mg l^?1) improve yield, quality, and NR activity in urea-fed cucumber plants.     

Growth,Nutrition, and Photosynthetic Response of Black Walnut to Varying Nitrogen Sources and Rates

ABSTRACT

Black walnut (Juglans nigra L.) half-sib 1+0 seedlings were exponentially fertilized with ammonium (NH₄ ⁺) as ammonium sulfate [(NH₄)₂SO₄], nitrate (NO₃ ^?) as sodium nitrate (NaNO₃), or a mixed nitrogen (N) source as ammonium nitrate (NH₄NO₃) at the rate of 0, 800, or 1600 mg N plant^?1 and grown for three months. One month following the final fertilization, N concentration, growth, and photosynthetic characteristics were assessed. Compared with unfertilized seedlings, N addition increased plant component N content, chlorophyll content, and photosynthetic gas exchange. Net photosynthesis ranged from 2.45 to 4.84 μmol m^?2 s^?1 for lower leaves but varied from 5.95 to 9.06 μmol m^?2 s^?1 for upper leaves. Plants responded more favorably to NH₄NO₃ than sole NH₄ ⁺ or NO₃ ^? fertilizers. These results suggest that N fertilization can be used to promote net photosynthesis as well as increase N storage in black walnut seedlings. The NH₄NO₃ appears to be the preferred N source to promote black walnut growth and physiology.     

Effects of Nitrogen Form and Concentration on Yield and Quality of Cucumbers Grown on Rockwool During Spring and Winter in Southern Greece

The influence of nitrogen concentration and the ratio of NO₃ to NH₄ on the marketable yield and fruit quality characteristics of cucumbers (Cucumis sativus L. cv. Palmera) grown on rockwool during spring and winter in southern Greece were studied. Nitrogen (N) was supplied at three N concentrations and four ratios of NO₃ to NH₄. During the spring, increasing total nitrogen or NH₄ concentration within the nutrient solution significantly decreased the mean total yield and fruit size. However, during the winter, the yield and number of fruits per plant were not affected by N concentration, but were reduced by increasing NH₄:NO₃ ratio. Fruits that were produced under low N concentrations were lighter in color, but only the color of the apical tissues of the fruit was affected by the NH₄:NO₃ ratio. Flesh firmness of the fruit was not affected by N source or concentration, except for the apical tissue, the firmness of which declined with increasing N concentration. On the basis of the present results, for highest yield and fruit quality during both the spring and winter seasons of southern Greece, 100 ppm N applied solely in the form of NO₃ is indicated.     

Can Nitrogen Source and Nitrification Inhibitors Affect In-Season Nitrogen Supply?

ABSTRACT

This study sought to identify whether piggery effluent-derived nitrogen sources can be formulated with urea and nitrification inhibitors to better synchronize nitrogen (N) supply with crop demand than conventional urea fertilizer alone. A 288 pot pasture growth and leaching growth accelerator trial (5 pasture cuts) was completed with a factorial treatment structure of three N sources (2.63 g N [kg soil]^?1 applied as 100% urea-N, 8% struvite-N + 92% urea-N, and 8% piggery pond sludge-N + 92% urea-N), five rates of three nitrification inhibitors (including 3,4-Dimethylpyrazole phosphate, DMPP; limonene+ethanol; and dicyandiamide, DCD), and matrix encapsulated forms of these inhibitors. Applying a combination of piggery sludge with urea increased N uptake during the first 4 weeks of plant growth (by 65%), though total N uptake throughout the trial (22 weeks) did not differ across the N-sources. The microbial community of the soil to which the sludge was added was significantly different from the un-amended soil at the conclusion of the trial. All inhibitor formulations significantly decreased leaching losses of mineral-N relative to the control (by 14 to 61%). The use of DMPP decreased initial nutrient uptake, deferring uptake until later in the experiment. Inhibitor addition resulted in microbial community effects that persisted throughout the trial. The study demonstrated that a piggery-derived N-source and a nitrification inhibitor can be used to manipulate plant N uptake to occur later or earlier in a growing period with equal cumulative uptake, achieving an 11% increase in residual N store, and decreased N leaching losses.     

肥液浓度对不同形态氮素在土壤中运移转化特性的影响

为揭示肥液(尿素)浓度影响下土壤湿润体中不同形态氮素的运移转化规律,选取黏壤土和砂壤土作为肥液入渗试验供试土壤,量化分析肥液浓度对土壤累积入渗量和不同形态氮素在分布和再分布过程中运移转化特性的影响.结果表明:相同入渗时间内土壤累积入渗量随肥液浓度的增大而增加,Kostiakov公式的入渗系数与肥液浓度呈现线性关系,建立...     

水耕年限对麦季土壤水—氮动态与小麦产量的影响

为揭示水耕年限对小麦生产的影响,在江汉平原选取了3种水耕年限（2年、18年、>100年）稻—麦轮作农田,采集了小麦各生育期的土壤样品与成熟期的小麦植株样品,测定了土壤水分、硝态氮含量、铵态氮含量和小麦产量等指标,分析了土壤剖面水—氮动态分布与积累特征,及其对小麦产量的影响程度与机制。结果表明：（1）随水耕年限延长,土壤水分和氮素含量显著增加。水耕2年、18年和100年农田的0—100 cm深度剖面平均体积含水量分别为0.36,0.39,0.42 cm³/cm³。硝态氮和铵态氮在0—20 cm土层富集,水耕2年、18年和100年农田0—20 cm土层硝态氮含量分别为12.26,12.74,14.88 mg/kg,铵态氮含量分别为6.01,8.33,11.69 mg/kg。（2）小麦产量随着水耕年限的增加而降低,水耕2年、18年和100年农田小麦产量分别为4 068,3 080,2 469 kg/hm²,主要表现为降低小麦的有效穗数和单株穗粒数。（3）长年耕作稻田形成的犁底层造成耕作层土壤水分滞留,进而导致小麦产量降低,而氮素含量差异未显著影响小麦产量,需要通过改善农田排水状况以降低长水耕年限农田的小麦渍害风险。     

Spatiotemporal Heterogeneity of Soil Available Nitrogen During Crop Growth Stages on Mollisol Slopes of Northeast China

Spatiotemporal heterogeneity of soil available nitrogen (AN) (sum of NO₃⁻–N and NH₄⁺–N) is the essential basis for soil management and highly correlates to crop yield. Both geostatistical and traditional analyses were used to describe the spatiotemporal distribution of AN in the 0–20‐cm soil depth on typical Mollisol slopes (S1 and S2) in Northeast China. The concentration of NO₃⁻–N dynamics at slope positions was typically opposite to NH₄⁺–N. The peak values of AN typically moved from the summit of the slope to the bottom from spring to autumn and were mainly influenced by the content of NO₃⁻–N (S1, 7·9–18·9 mg kg⁻¹; S2, 1·2–103·6 mg kg⁻¹), both of NO₃⁻–N (S1, 3·9–8·3 mg kg⁻¹; S2, 2·2–28·0 mg kg⁻¹) and NH₄⁺–N (S1, 21·4–30·5 mg kg⁻¹; S2, 2·1–23·3 mg kg⁻¹), and NH₄⁺–N (S1, 10·5–28·9 mg kg⁻¹; S2, 5·0–39·0 mg kg⁻¹) in the seedling stage, vegetative growth stage, and reproductive growth stage, respectively. The spatial autocorrelation of AN was strong and was mainly influenced by structural factors during crop growth stages. This was mainly determined by soil erosion–deposition (SED) and soil temperature–moisture (STM) in the seedling stage; this was also mainly influenced by SED, STM, crop type, and crop growth in the vegetative growth stage and by early STM and early SED in the reproductive growth stage. Generally, the content of AN, NO₃⁻–N, and NH₄⁺–N on the whole slope was mainly determined by the early SED and local fertilizer application, while their spatiotemporal heterogeneity, especially the evenness, was mainly changed by SED, STM, crop growth, and crop types on the slope scale. In order to increase more crop yields, additional N fertilizer application on both the summit and the bottom during the vegetative growth stage and conservation tillage systems or additional soil amendments on the back slopes was necessary. Copyright © 2016 John Wiley & Sons, Ltd.     

滴施不同铵硝比例氮肥对马铃薯生长的影响

在盆栽试验条件下,以滴灌施肥方式探讨滴施不同铵硝比例氮肥对马铃薯生长、产量和品质的影响。研究结果表明:在本试验条件下,滴施不同铵硝比例氮肥对马铃薯植株生物量的积累差异不显著;滴施铵态氮肥有利于提高马铃薯块茎中N的浓度,而滴施硝态氮肥有利于提高马铃薯块茎中Ca的浓度;滴施不同铵硝比例氮肥处理马铃薯的淀粉含量、干物质含量、灰分含量等均差异不显著,块茎产量也差异不显著,但马铃薯商品薯比例以滴施铵硝比例为50/50氮肥处理的最高,达到92.01%。     

滴灌点源施肥灌溉对土壤氮素分布影响的试验研究

利用室内试验,研究了点源施肥灌溉条件下硝态氮和铵态氮的分布规律。试验土壤为砂壤土,滴头流量的变化范围为0.6～7.8L/h、灌水量为6～15L、肥液(NH₄NO₃)浓度为100～700mg/L。销态氮在距滴头17.5cm范围内呈均匀分布,其浓度随肥液浓度的增加而增加;在湿润边界上硝态氮产生累积;肥液浓度是影响硝态氮分布的主要因子。在距滴头15cm范围内,滴头流量和灌水量对土壤中硝态氮分布的影响不明显,在此范围以外,随滴头流量的增大或灌水量的减小,硝态氮浓度增加。铵态氮浓度在滴头附近出现高锋值,肥液浓度越高,锋值越大,且施肥灌溉对铵态氮分布的影响范围较小,一般在距滴头10cm范围以内     

灌施连续与间歇入渗硝态氮运移与土壤含水量的关系

通过室内土壤灌施间歇入渗试验，研究了灌施条件下波涌灌溉土壤间歇入渗硝态氮的运移与分布特性，分析了硝态氮分布与土壤含水量的关系，并与灌施条件下土壤连续入渗进行了对比，为进一步研究施肥条件下波涌灌溉土壤间歇入渗溶质运移规律奠定了基础。     

滴灌施用不同氮肥对马铃薯生长的影响

本研究是在盆栽试验条件下,通过滴灌施肥系统施用四种不同氮肥,以了解不同氮肥对马铃薯生长及块茎产量、品质的影响。试验所选用的氮肥有:尿素、氯化铵、硫酸铵、硝酸铵。结果表明:在滴灌施肥条件下,尿素在促进马铃薯植株营养生长方面所起的作用优于其它3种氮肥;滴施4种不同氮肥影响马铃薯块茎对N、P、K、Ca、Mg等养分的吸收;硝酸铵在提高马铃薯块茎产量、降低还原糖含量方面效果明显。     

Effect of Clinoptilolite Addition to Soil on Wheat Yield and Nitrogen Uptake

Abstract

During the past years, appreciable amounts of zeolite‐rich tuff that contains more than 70% clinoptilolite (Cp) have been discovered in Greece. The present study evaluates the ability of natural Greek Cp to increase the efficiency of nitrogen (N) fertilizer uptake in wheat. A pot experiment with winter wheat was conducted in a Typic Xerorthent that was fertilized with ammonium sulfate and amended with 0 to 60 ton/ha of Cp. Clinoptilolite application resulted in an increase of the cation exchange capacity of the soil from 9.5 to 13.6 meq/100 g (i.e., 43%). Soil ammoniacal N was greater in the samples amended with Cp at the boot stage, as was NO₃‐N. Clinoptilolite addition increased total wheat yield (dry matter of hay plus seed) 52% (from 21.1 g/pot in the control to 32.0 g/pot) in the treatment with 60 ton/ha of Cp. The influence was greater for seed yield than hay yield. Clinoptiloite addition resulted in high increase in total N uptake, about 141% (from 156 mg/pot in the control to 376 mg/pot) in the treatment with the highest Cp rate. For hay, the increase was 133% (from 125 mg/pot to 291 mg/pot), whereas for seed it was 126% (from 31 mg/pot to 70 mg/pot) from control to the treatment with the highest Cp rate, resulting in a more efficient N fertilizer use. The optimum Cp addition rate was estimated as large as 15 ton/ha.     

Nitrogen rates in strawberry (Fragaria ananasa) nursery on growth and yield in the field

Strawberry (Fragaria ananassa cv. Aliso) plants were grown under three N‐rates in the nursery: 80, 320 and 640 kg N/ha, and then transplanted to the fruiting field. Plants from each nursery treatment were given 150, 300 and 450 kg N/ha. The fertilizer was given as ammonium sulfate in the nursery and as ammonium nitrate in the field, a part broadcasted before planting and the other part applied as top dressings. Biomass production, plantlets size distribution and N content were restricted by the lowest level of N given in the nursery. Plants grown at 320 kg N/ha in the nursery gave significantly earlier and higher total yields than those grown at the other rates. Fruit yields were not significantly influenced by the N‐application in the field. N fertilization in the early stages of strawberry plant development in the nursery is more important than later field application.

The influence of N fertilization on the growth and yield of strawberry plants has been studied by several workers. In some reports yields were increased when the rate of N applied was increased (1, 2, 3). In other studies no influence was found (4, 5, 6), or even a decrease in yield was reported as the rate of applied N was increased (7). While in some studies detrimental effects of N‐fertilizer on fruit yield were observed at 200–300 kg N/ha (8, 9), in other studies (6, 7) N applications up to 400 kg/ha did not affect yield. In Spain (3), adding up to 680 kg/ha caused an increase in fruit yield.

Even at relatively low applied‐N levels, up to 150 kg N/ha, strawberry response reports are not consistent. Some workers found that increasing N in this range caused an increase in fruit yield (8, 9, 3, 7, 10), while no effect was observed (4, 5, 6, 11) in several other studies. Most of the reported experiments with N‐fertilizer were carried out after plants were transplanted from the nursery to the field. To the best of our knowledge no attempt was made to evaluate the effect of fertilizer applied in the nursery.

The objective of this work was to evaluate the influence of different levels of N‐fertilizer, in both the nursery and the field, on strawberry plant development and composition, earliness, yield level and yield distribution.     

铜绿微囊藻对亚硝态氮的利用

通过室内培养,研究了不同亚硝态氮浓度对铜绿微囊藻（Microcystis aeruginosa）生长的影响和藻对亚硝态氮的利用,实验分析了水体中亚硝态氮、硝态氮和铵态氮浓度的变化,测定了铜绿微囊藻的生长曲线、藻细胞内亚硝态氮含量和藻亚硝酸氧化酶（NOR）。结果显示,在10mgNO^-2-N·L^-1的处理组中,培养基中亚硝态氮和硝态氮浓度同时减少,说明铜绿微囊藻可以同时利用亚硝态氮和硝态氮;在20和30mgNO^-2-N·L^-1的处理组中,随着藻的生长培养基中亚硝态氮的浓度减少,硝态氮浓度增加,而且电泳实验显示此培养条件下铜绿微囊藻能产生亚硝酸氧化酶,表明培养基中的亚硝态氮被亚硝酸氧化酶氧化为硝态氮。本实验也表明高浓度的亚硝态氮（大于10mgNO^-2-N·L^-1）能够抑制藻的生长。     

Nitrogen effect on yield and kernel protein content of sweet corn grown on sandy soils

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.     

Nitrogen transport in plants,with an emphasis on the regulation of fluxes to match plant demand

Physiological methods, especially the use of isotopes of N, have allowed for the detailed characterizations of the several putative transport systems for nitrate and ammonium in roots of higher plants. In the last decade, the cloning of genes that appear to encode both high- and low-affinity transporters represent major advances, as well as substantiating the inferences based on earlier physiological methods. Nevertheless, the unexpected plethora of genes that have been identified now presents even greater challenges, to resolve their individual functions and to attempt to place these functions in a whole plant/environmental context.     

紫色土区坡耕地玉米季地表径流及其氮素流失特征

研究川中丘陵紫色土区坡耕地玉米全生育期地表径流及其氮素流失特征,以期为坡耕地氮素流失预测和有效防控提供理论依据。采用人工模拟降雨与微小区(1 m×2 m)相结合的方法,降雨强度设置为1.0,1.5,2.0mm/min,分别在玉米苗期、拔节期、抽雄期和成熟期进行人工模拟降雨。结果表明:玉米全生育期地表径流量及其氮素流失量随降雨强度的增加而增加。不同降雨条件下,玉米全生育期地表径流总量表现为苗期显著高于其它生育期。玉米拔节期地表径流中氮素平均流失浓度高达16.36mg/L;地表径流中氮素平均流失量在玉米苗期最高,为10.24mg/m~2,而抽雄期仅为2.97mg/m~2。玉米苗期地表径流中铵态氮流失量最大,成熟期地表径流中硝态氮流失量最大,抽雄期硝态氮和铵态氮流失量均最小;玉米全生育期地表径流中硝态氮为氮素流失的主要形态,占总氮的77.98%~97.85%。玉米拔节期氮素流失浓度最高,而苗期为氮素输出负荷量最大,苗期和拔节期地表径流中氮素流失易造成地表水体富营养化,可通过控制基肥、追肥的施入量和增加地表覆盖度减少氮素流失。