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1.
Summary

Two field experiments during 1996-98 at Bangalore, India studied the effect of soil moisture regimes (0.3, 0.6 and 0.9 IW:CPE ratios) irrigation water cumulative pan evaporation (IW:CPE) ratios and three levels of nitrogen application (0,100 and 200 kg ha–1). Another experiment investigated three irrigation levels (0.3, 0.6 and 0.9 IW:CPE ratios), two levels of nitrogen application (100 and 200 kg ha–1) and organic mulch (0 and 5 t ha–1) on oil content, herbage, oil yield and quality of geranium grown on alfisols. Soil moisture maintained at 0.6-0.9 IW:CPE ratios significantly increased both the herbage and oil yields of geranium. Application of 200 kg N ha–1 gave maximum herbage and oil yield compared with those obtained from 0 and 100 kg N ha–1. Organic mulch increased the oil yield of geranium. The concentration and quality of essential oil were not influenced either by soil moisture regime, N rates or organic mulch.  相似文献   

2.
In the warm and wet north Florida climate, growing Italian parsley (Petroselinum crispum [Mill.]) is gaining popularity with small producers as a short duration crop on sandy soil. Application of compost to agricultural land can benefit the low fertile sandy soils in Florida and subsequent crop production, while providing an outlet for recycling municipal solid wastes (MSW) and biosolids. A field study was laid out in a randomized complete block design with four replications to evaluate the effects of compost (75% MSW:25% biosolids) application in comparison to fertilizer, fertilizer + compost (50:50), and control treatments on: (a) parsley fresh weight (FW), (b) soil and plant tissue nutrient concentrations, and (c) soil bulk density and moisture retention in winter and spring seasons. Soil amended with fertilizer or compost + fertilizer doubled parsley FW from 15.02 Mg ha−1 in the non-amended control plot to 30.75 and 32.67 Mg ha−1 in soils that received fertilizer + compost or fertilizer alone, respectively. Significantly higher total soil carbon (C) levels of 2.16% and 1.95% and nitrogen (N) levels of 0.19% and 0.16% were recorded in compost and fertilizer + compost treatments, respectively. Addition of compost reduced soil bulk density significantly to 1.03 Mg m−3 and increased soil moisture retention in simulated drier conditions at 1500 kPa to 0.12 m3 m−3 in plots that received only compost at the end of winter growing season. Overall, addition of compost resulted in improvement of both physical and chemical properties as well as increased parsley yields.  相似文献   

3.
In conservation tillage systems based on legume mulches it is important to optimize N management strategies. The present study evaluated the effect of some winter legume cover crops converted into mulches on the following no-tillage tomato (Solanum Lycopersicum L.) yield, tomato nitrogen uptake, tomato use efficiency (NUE), soil nitrate and the apparent N remaining in the soil (ARNS) in a Mediterranean environment. Field experiments were carried out from 2002 to 2004 in a tomato crop transplanted into: four different types of mulches coming from winter cover crops [hairy vetch (Vicia villosa Roth.), subclover (Trifolium subterranem L.), snail medic (Medicago scutellata L. Miller), and Italian ryegrass (Lolium multiflorum Lam.)]; a conventional tilled soil (CT); and a no-tilled bare soil (NT). All treatments were fertilized with three different levels of nitrogen (N) fertilizer (0, 75, and 150 kg N ha−1). Cover crop above-ground biomass at cover crop suppression ranged from 4.0 to 6.7 t ha−1 of DM and accumulated from 54 to 189 kg N ha−1, hairy vetch showed the highest values followed by subclover, snail medic and ryegrass. The marketable tomato yield was higher in no-tilled legume mulched soil compared to no-tilled ryegrass mulched soil, CT, and NT (on average 84.8 vs 68.7 t ha−1 of FM, respectively) and it tended to rise with the increase of the N fertilization level. A similar trend was observed on tomato N uptake. Hairy vetch mulch released the highest amount of N during tomato cultivation followed by subclover, snail medic, and ryegrass (on average 141, 96, 90 and 33 kg N ha−1). The tomato NUE tended to decrease with the increase of the N fertilization rates, it ranged from 39 to 60% in no-tilled legume mulched soil and from −59 to 30% in no-tilled ryegrass mulched soil when compared to the CT. The soil NO3-N content and the ARNS was always higher in the soil mulched with legumes compared to the soil mulched with ryegrass and in NT and CT. This study shows that direct transplanting into mulches coming from winter legume cover crops could be useful for improving the yield and the N-uptake in a no-tillage tomato crop. Furthermore, considering the high N content in the upper soil layer and the remaining N content in the organic mulch residues after tomato harvesting, there is a large amount of N potentially available which could be immediately used by an autumn–winter cash crop.  相似文献   

4.
Field experiments were initiated in May 1999 and continued through 2002 to investigate the application of municipal solid waste (MSW) compost and fertilizers to lowbush blueberry (Vaccinium angustifolium Ait.) fields. Three sites were selected: Debert, N.S. (Truro sandy loam) and two sites near Musquodoboit, N.S. (both Rawdon gravely loamy sands). Treatments at each site were in a randomized complete block design with six treatments (control [no fertilizer], NK fertilizer, NPK fertilizer, and three rates of MSW compost) blocked four times. Compost treatments provided the equivalent of 100, 200 and 400 kg ha−1 of total N. The experimental objectives were to evaluate soil and plant response to the compost and to determine whether it could be used as an alternative to the traditional chemical fertilizers. Yield, soil fertility, and leaf and fruit nutrients were examined following the four years of treatment applications. The MSW compost had a significant effect on pH and soil extractable levels of P, K and Ca, and influenced N and K levels in leaf samples. Fruit yield and nutrient content, except for Mn, were not affected by the treatments. In general, the compost treatments provided equivalent amounts of plant essential nutrients without negatively influencing trace element absorption.  相似文献   

5.
 为探求黄瓜适宜的节水灌溉方式,以温室栽培的黄瓜自根苗和嫁接苗为试验材料,设定每次灌水150、300和450 m3 · hm-2的不同灌水量,研究灌水量对黄瓜根系分布、商品瓜产量和水分利用效率的影响。结果表明,与常规灌水量对照（每次450 m3 · hm-2）相比,适度减少灌水量,在多数情况下不会显著影响黄瓜根系生长、垂直分布与水分利用,每次150 m3· hm-2的灌水量对自根与嫁接黄瓜的产量无显著影响,水分利用效率显著提高。每次150 m3 · hm-2灌水量下,嫁接黄瓜的根系旺盛且粗壮,同时诱发了大量毛细根向土壤深层分布,使其产量显著高于自根黄瓜,因此在减量灌溉条件下,嫁接具有良好的促根节水丰产的效果。  相似文献   

6.
This study was carried out to maximize the fertilization efficiency of mixed organic fertilizer (OF) for organically managed onion (Allium cepa L.) production during the one growing season of 2005–2006. The organic fertilizer was made of organic materials like sesame oil cake, rice bran and molasses and minerals like illite and mountainous soil. Four organic topdressing treatments, which all followed the same basal fertilization with solid OF, consisted of solid OF without mulch (OF/OFnM), liquid organic fertilizer without mulch (OF/LOFnM), liquid organic fertilizer under mulch (OF/LOFuM) and liquid organic fertilizer over mulch (OF/LOFoM). Chemical fertilizer (CF) and no fertilizer (NF) were treated as controls. The solid organic fertilization base was 2.0 ton ha−1, and 4.57 ton ha−1 and was used for topdressing. The total amount of liquid organic fertilization was 133.2 ton ha−1, which was divided into 6 applications from February through March. The OF/LOFuM and OF/LOFoM topdressings did not reduce onion height, leaf number or bulb diameter as compared to chemical fertilizer, whereas no mulch treatments made onion growth significantly poorer. Onion top weight in CF was significantly higher than that in OF groups at the peak growth stage, while there was not much difference in bulb weight between the CF and OF/LOFoM treatment. Finally, the onion marketable yield was 45.9 ton ha−1 in the OF/LOFoM treatment, which exceeded that in the CF treatment by up to 1.9 ton. Furthermore, OF/LOFoM was the most effective among all the treatments in transferring the nutrients from sink to source. CF made the soil pH more acidic than OF did, and the electrical conductivity (EC) remained higher with CF than OF as well. While organic fertilizer helped to keep the NO3-N content stable throughout the growing season, the concentration rapidly oscillated up and down according to CF fertilization. Organic fertilizer increased population number of soil microorganisms like aerobes, actinomycetes in the field.  相似文献   

7.
Summary

Essential oil of rosemary (Rosmarinus officinalis L.) possesses good olfactory properties and is suitable for use in perfumes, soaps and fragrances. Field experiments were conducted over 2 years (2003-2005) in an area experiencing a semi-arid tropical climate, to study the influence of two N levels (150 or 300 kg N ha–1 year–1) and three K levels (41.5, 83.0 or 124.5 kg K ha–1 year–1), or no fertiliser, on the growth, herbage and oil yields and nutrient uptake patterns of rosemary. The results showed that application of 300 kg N ha–1 year–1 produced higher herbage and oil yields in rosemary, compared with 150 or 0 kg N ha–1 year–1. The application of 83.0 kg K ha–1 year–1 produced maximum herbage and oil yields, compared with 0 or 41.5 kg K ha–1 year–1. Total N and K uptake levels were increased significantly by the application of N and K. Nitrogen uptake increased by 85.2% and 137.7%, and K by 80.9% and 123.9%, respectively, with the application of 150 or 300 kg N ha–1 compared to controls (no N). Similarly, N uptake increased by 96.1%, 130.2% and 113.6%, and K by 79%, 124.3% and 110.4%, respectively, with the application of 41.5, 83.0, or 124.5 kg K ha–1 compared to controls (no K). Oil content and oil composition were not influenced by nitrogen or potassium levels.  相似文献   

8.
In a field experiment in the 1988-89 season, fertilizer formulations of NH4NO3, Ca(NO3)2, NaNO3, NaKNO3, and KNO3 as N sources were applied at 84 and 168 kg N ha?1 to onion plots direct seeded in the fall. A second experiment in the 1990-91 season tested the same N sources, except KNO3, at rates of 168 and 224 kg ha?1. Application strategy involved both splitting the total amount of fertilizer over two periods of the growing season (October–December and January—April) and the application frequency. With medium and high application rates (168 and 224 kg ha?1), NH4NO3, NaNO3, and NaKNO3, increased high-value jumbo and large onions (premium marketable grade). Increased premium grades was due to increased bulb size and weight. Only NH4NO3 and Ca (NO3)2 increased total onion weight when N rate was increased from 84 to 168 kg ha?1. Less frequent applications of split amounts of 84 kg N ha?1 reduced marketable weight in the 1988–89 season, but doubling the rate to 168 kg ha?1 restored the higher yields. At 224 kg N ha?1 in the 1990–91 season, differences in onion grades were more pronounced among the different N sources, and NH4 NO3 was superior in producing jumbo and large size onions. High N rates (224 kg ha?1) and more frequent applications of split portions also increased the weight of jumbo onions. Split applications, providing 33% of the total N in the first 12 weeks of the growth period plus three applications of 22% each in the second 12 week period, increased bulb size and maximized yield of premium marketable grades. Effect of N rate on onion rot was dependent on split methods of applying the N during early and late growth periods. However, reduction in onion rot by the split application strategy was dependent on N source. Bulb decay was highest with NH4NO3 and least with Ca(NO3)2 and NaNO3.  相似文献   

9.
《Scientia Horticulturae》2003,98(2):113-119
Leafy vegetables accumulate higher amount of heavy metals like nickel (Ni) due to their more leafy vegetative growth. Therefore, a screenhouse experiment was conducted using an alkaline sandy loam soil equilibrated with graded levels of Ni (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250 and 300 mg kg−1 soil) to assess the Ni accumulation pattern and its influence on growth and micronutrient distribution in fenugreek plants. Green as well as the dry matter yields of fenugreek increased slightly up to 20 g Ni kg−1 soil but decreased significantly with the application ≥40 mg Ni kg−1 soil. Crops showed characteristic toxicity symptoms of interveinal chlorosis in pots receiving ≥40 mg Ni kg−1 soil. While the total content of Ni in the plant tissues increased consistently with increasing rates of applied Ni, the roots accumulated much higher amount of this element compared to the shoot. The content of Fe in plants showed an increase whereas that of Cu and Zn experienced a decrease with the rise in the applied Ni.  相似文献   

10.
华南地区蔬菜钾肥推荐施肥技术体系建立   总被引：3，自引：0，他引：3  
在华南地区不同地点、不同肥力水平的菜园上进行叶菜类、瓜类、豆类3 类主要蔬菜的钾肥
田间试验,并对138 个试验点的3 类蔬菜相对产量与土壤有效钾含量、土壤有效钾含量与施钾量的关系
进行相关分析,建立回归方程,以此分别建立适用于瓜类、豆类、叶菜类的土壤有效钾养分丰缺指标和各
等级土壤的推荐施钾肥指标。结果表明：蔬菜相对产量为＜ 75%、75%～95%、＞ 95% 的各肥力等级土
壤有效钾丰缺指标,苦瓜分别为＜ 50 mg·kg-1、50～240 mg·kg-1、＞ 240 mg·kg-1;豇豆分别为＜ 45
mg·kg-1、45～195 mg·kg-1、＞ 195 mg·kg-1;叶菜分别为＜ 20 mg·kg-1、20～140 mg·kg-1、＞ 140
mg·kg-1。各有效钾等级对应的施钾量,苦瓜分别为15.0 kg·（667m2）-1、7.5～15.0 kg·（667m2）-1、＜ 7.5
kg·（667m2）-1; 豇豆分别为12.5 kg·（667m2）-1、7.0～12.5 kg·（667m2）-1、＜ 7.0 kg·（667m2）-1;
叶菜分别为9.5 kg·（667m2）-1、5.5～9.5 kg·（667m2）-1 、＜ 5.5 kg·（667m2）-1 。  相似文献   

11.
ABSTRACT

Ericoid mycorrhizal fungi (EMF) form symbiotic relationships with roots of blueberry plants providing increased access to nutrients from fertilizers and soil. In August of 2001, we sampled 55 fields in Oregon to assess the mycorrhizal status of blueberry plants under production conditions and to determine whether any relationships exist between field characteristics, root distribution, soil characteristics and level of colonization by mycorrhizal fungi. Variation in measured soil characteristics, root type, root distribution and mycorrhizal colonization occurred with cultivar, field age, bed type, rate of nitrogen fertilization, irrigation type, and mulch. Root biomass was lower in the upper 15 cm of soil compared to 15-30 cm depth. Distribution of roots between the two sampled depths varied significantly with field age, nitrogen fertilization rate, and the time of 50% harvest for the different cultivars sampled. Root length was generally greatest in the upper 15 cm of the soil than at the 15-30 cm depth. Root colonization by ericoid mycorrhizal fungi (EMF) ranged from 0.5 to 44% of total root length with higher colonization generally occurring in the upper 15 cm of the soil where the majority of smaller, finer roots were found. Colonization generally increased with increasing plant age. In young plants the highest levels of colonization were found in roots from the upper 15 cm of soil while in older plants the highest levels of colonization were found in roots at the 15-30 cm depth. Colonization of roots by EMF in the upper 15 cm of the soil tended to decrease with increasing N fertilization rate, while root colonization at the 15-30 cm depth was unaffected by rate of N fertilization. Roots on cultivars that fruited early in the season tended to have higher levels of colonization than cultivars that fruited later in the growing season. Root biomass and root length were negatively correlated with soil pH and available Ca in soil, while root colonization by EMF was negatively correlated with ammonium levels in the soil. Differences in soil characteristics, root type and distribution, and mycorrhizal colonization found in this study need to be investigated in terms of production efficiency of blueberry in Oregon.  相似文献   

12.
Oil cake, widely used as an organic source of nutrients in horticultural production in South Korea, is a by-product when oil is extracted from various oilseeds. Split applications of oil cake were supplied to evaluate their effects on tree growth and fruit production in organic, non-astringent persimmon (Diospyros × kaki Thunb.) trees in 2009 and in 2010. Treatments included a single annual application of oil cake at 150 kg N ha?1 in April (single application), two applications in April and July (105 and 45 kg N ha?1, respectively; two-split application), or three applications in April, June, and August (60, 45, and 45 kg N ha?1, respectively; three-split application), as well as zero application of oil cake (control). All applications of oil cake significantly increased the amount of ground-cover vegetation compared to the control. The single and two-split applications increased soil organic matter (OM), K2O, CaO, and MgO concentrations, and cation exchange capacity to a soil depth of 0–30 cm in 2010. Oil cake applications increased soil porosity in 2010, as well as overall chlorophyll (SPAD values) and macronutrient concentrations in leaves in 2009 and 2010. Single and two-split applications stimulated water-sprout development, reduced the light intensity inside the tree canopy, and increased fruit drop. Fruit yield was higher in the two-split [24.7 metric tonnes (MT) ha?1] and three-split application trees (25.0 MT ha?1) compared to zero application control trees (19.8 MT ha?1) and single application trees (21.0 MT ha?1) in 2010. A single application resulted in soft fruit and slow skin colouration during maturation. Total soluble solids contents were higher in the control and three-split application trees in both years. The three-split application in 2010 increased the estimated production income by approx. 21% compared to the zero application, and by approx. 33% compared to a single application of oil cake.  相似文献   

13.
Soils in central Florida citrus production region are very sandy, hence are vulnerable to leaching of soluble nutrients and chemicals. The objective of this study was to develop nitrogen (N) and irrigation best management practices for citrus in sandy soils to maintain optimal crop yield and quality, and to minimize N leaching below the rootzone. A replicated plot experiment was conducted in a highly productive 20+ year-old ‘Hamlin’ orange [Citrus sinensis (L.) Osbeck] trees on ‘Cleopatra mandarin’ [(Citrus reticulata Blanco)] rootstock grove located on a well drained Tavares fine sand (hyperthermic, uncoated, Typic Quartzipsamments) in Highland County, FL. Nitrogen rates (112–280 kg ha−1 year−1) were applied as fertigation (FRT), water soluble granular (WSG), a combination of 50% FRT and 50% WSG, and controlled release fertilizer (CRF). Tensiometers were used to monitor the soil moisture content at various depths in the soil profile as basis to optimize irrigation scheduling. Fruit yield and quality and nutritional status of the trees were reported in a companion paper. Soil solution was sampled at 60, 120, and 240 cm depths under the tree canopy using suction lysimeters. Concentrations of NO3-N in the soil solution at 240 cm deep, which is an indicator of NO3-N leaching below the tree rootzone, generally remained below the maximum contaminant limit (MCL) for drinking water quality (10 mg L−1) in most samples across all N sources and rates, but for few exceptions. Total N in the fruit was strongly correlated with fruit load, thus, at a given N rate N removal by the fruit was lower during years of low fruit yield as compared to that during the years of high fruit yield. Furthermore, there was a strong linear relation between N and K in the fruit. This supports the need to maintain 1:1 ratio between the rates of N and K applications. In a high fruit production condition, the N in the fruit accounted for about 45% of the total N input on an annual basis. Fifteen percent of the total N input at 280 kg N ha−1 year−1 was not accounted for in the citrus N budget, which could be due to leaching loss. This estimate of potential leaching was very close to that predicted by LEACHM simulation model. The improved N and irrigation management practices developed in this study contributed to an improved N uptake efficiency and a reduction in N losses.  相似文献   

14.
Sweet cherry (Prunus avium L.) is a fruit of increasing economic importance though it is less significant than other stone fruit species such as peach. Cherry has received little attention concerning nitrogen (N) uptake and dynamics in mature trees. The aim of this work was to determine N uptake and partitioning as influenced by the timing of fertilizer application in 7-year-old sweet cherry trees cultivated in a cold region (Los Antiguos, Santa Cruz, Argentina; 71°38′ W, 46°32′ S). Nitrogen (95 kg ha−1) was applied as ammonium nitrate to a soil with ‘Bing’ sweet cherry trees grafted onto Prunusmahaleb rootstocks. Fertilization was split into two equal applications per treatment, involving either the commercial fertilizer ammonium nitrate or the same fertilizer labelled with 15N isotope (10% atom.). Treatments consisted of one early spring (full bloom, October 2005) or one summer (late January 2006, 15 days after harvest) application of 15N ammonium nitrate to three replicate trees. Fruit were harvested in early January and leaves were collected at both full canopy and leaf fall. All trees were excavated in winter (August, 2006). Trees were partitioned into their components: trunk, branches (current-season shoots, 1-year-old and over-1-year-old branches), buds of the same age, small roots (less than 1 mm thick), large roots, leaves (sampled in February and April), and fruit (collected at harvest). Those components were dried and analysed for total N and 15N content. Total N per tree and N content derived from the fertilizer did not differ between treatments. Summer postharvest 15N application partitioned not only to structural components (trunk and roots) but also to buds and leaves. Uptake efficiency was significantly (p = 0.0113) higher in the spring than in the summer application (65.7% vs. 37.44%). Nevertheless, 52.5% of N applied in spring was lost due to harvest and summer pruning. This emphasizes the importance of the postharvest N fertilization which increases N accumulation in both reserve organs and buds though, according to our data, it is less efficiently used. The extent of nitrogen uptake, efficiency of use and partitioning in the following growing seasons are still open questions that deserve further research.  相似文献   

15.
The aim of the study was to examine the effect of boron (B) fertilization on the vegetative and the reproductive responses of apple (Malus domestica Borkh.) trees grown at low soil B availability. The experiment was carried out in 2005 under a greenhouse on 5-year-old ‘Jonagold’ apple trees/M.9 EMLA planted singly in 50-L containers filled with a sandy loam soil with hot water-soluble B concentration of 0.32 mg kg−1. The trees were fertilized with B as foliar or soil application. Foliar B sprays were applied at the stage of pink bud, beginning of flowering, petal fall, and 10 days after flowering, at a solution concentration of 0.03%. Soil B fertilization was done at the bud break stage at a rate of 2 g per tree (27 mg B kg−1 soil). The trees untreated with B served as the control. The results showed that soil B fertilization improved root development and tree vigor. Leaves of trees supplied with B to the soil had higher B concentration and chlorophyll, net photosynthetic rate, stomatal conductance, and activity of catalase and glutathione reductase than those of the control plants. Boron fertilization, regardless of application mode, increased fruit yield; the efficiency of foliar B sprays was higher than soil B application. Apple fruits of trees fertilized with B to the soil were bigger, more colored, richer in B, and had higher soluble solids concentration, and titratable acidity compared to those of the control trees.  相似文献   

16.
The investigation was carried out to examine the performance of Azospirillum isolates on growth and N uptake of Gaillardia pulchella with two nitrogen levels. Azospirillum strain OAD-2 inoculation significantly increased plant height, number of leaves per plant, branches per plant and total dry mass accumulation in G. pulchella than other inoculations and/or uninoculated control. The application of 150 kg N ha−1 further enhanced the above plant growth parameters significantly over application of 112 kg N ha−1. The N uptake of G. pulchella was enhanced due to Azospirillum strain OAD-2 inoculation, which was further augmented in the presence of nitrogen. The combination of Azospirillum strain OAD-2 and 150 kg N ha−1 showed the highest N uptake at 120 DAT. Plant growth and yield parameters also increased when inoculated with the non-diazotrophic, but efficient IAA producing, Azospirillum strain OAD-57. From this investigation, it can be concluded that Azospirillum strains OAD-2 and OAD-11 can play an important role in the N nutrition of G. pulchella.  相似文献   

17.
Zucchini squash (Cucurbita pepo L.) is an economically important vegetable crop in Florida. Typically, it is intensively managed with high inputs of fertiliser and irrigation water. Our objectives were to evaluate the interaction between fertilisation rates and irrigation treatments, and to quantify nitrate leaching in a plastic mulched/drip irrigated zucchini squash production systems. Three studies were carried out. The first study evaluated different depth placement of drip and fertigation lines on plant growth and fruit yield. Treatments included SUR (both irrigation and fertigation drip lines placed on the surface); S&S (both lines buried 0.15 m deep); and SDI (irrigation line placed 0.15 m below the fertigation line on the surface). The second and third studies compared three different N-rates and different soil moisture sensor-based irrigation strategies. Nitrate-N leaching was monitored by zero tension drainage lysimeters and soil samples. N leaching increased when irrigation and N-rates increased, with values ranging from 2 to 45 kg ha−1 of N. Use of SDI increased yields by 16% compared to the S&S treatment, and reduced nitrate leaching by 93% while increasing the water use efficiency by 75% compared to a fixed 2-h irrigation event per day treatment. Application of N above the standard recommended rate of 145 kg ha−1 did not increase yield, although yields were reduced at the lowest N-rate. The use of soil moisture sensors for automatic irrigation control reduced irrigation application and minimized nitrogen leaching. In addition, combining the soil moisture controlled SDI system that had surface applied fertigation resulted in similar or higher yields, while reducing both water use and potential N leaching because of improved nutrient retention in the root zone.  相似文献   

18.
《Scientia Horticulturae》2005,104(1):79-89
The seasonal effect of soil water availability on leaf gas exchange of plantain plants cv. Hartón growing on two different texture soils (loamy and clayey) were evaluated. Soil water deficits corresponded to 48, 24 and 4 days without precipitation. Daily measurements of leaf gas exchange and microclimatic conditions were carried out at 2 h intervals in a humid tropical environment south of Maracaibo Lake, Venezuela. The results show that cv. Hartón is sensitive to conditions of low water deficit on loamy and to a much greater degree on clayey soils. A marked reduction in leaf conductance (gs) was observed under severe as well as moderate deficit (below 50 mmol m−2 s−1) on clayey soils. Under low deficit gs increases to values between 60 and 100 mmol m−2 s−1. The same trend was observed in plants on loamy soils but higher gs for all conditions were obtained compared with plants on clayey soil. Stomatal closure produced a reduction of 85 and 55% of total assimilation (Atot) for severe and moderate deficit in plants on clayey soils, respectively. While plants on loamy soil exhibited a 65 and 35% reduction, respectively. Water use efficiency (WUE) consistently decreased as available soil water decreased on both soil types. Independently of soil water conditions, higher WUE were always obtained for loamy soils. This suggests that cv. Hartón does not have the ability to adjust the CO2 assimilation to transpiration ratio in order to optimize gas exchange. This evidences the importance of maintaining high conditions of available soil water in order to avoid lower assimilation rates that probably influence negatively on yield and fruit quality.  相似文献   

19.
To evaluate their salt tolerance, two-year-old potted honeysuckle plants were exposed to 50, 100, and 150 mM NaCl, respectively. The effects of salt stress on growth parameters, ion concentration, lipid peroxidation, and the enzymatic antioxidant system in honeysuckle were studied. Salt stress reduced biomass accumulation and root activity, and also induced oxidative stress, as indicated by elevated levels of O2·-, malondialdehyde content, and electrolytic leakage. Increased salinity resulted in a slight decline in the K+ concentration in different plant tissues, but a significant boost in Na+ levels, which were much higher in roots than in other tissues. The concentrations of Ca2+ and Mg2+ increased significantly in leaves, but remained unchanged in shoots and decreased slightly in roots. Higher levels of soluble sugars and proline were observed in the plants after 30 days of NaCl treatment, suggesting that compatible osmolytes had been synthesised to acclimatise to the salinity. Under the treatments, major antioxidant enzymes involved in the reactive oxygen species scavenging system, including superoxide dismutase, ascorbate peroxidase, catalase and peroxidase were activated. The increased activities of the antioxidant enzymes were significant and occurred in a time-dependent manner.  相似文献   

20.
We conducted two experiments to evaluate the impact of cultural treatments on growth and establishment of container-grown London planetrees (Platanus × acerifolia’ Bloodgood’). In both experiments, 48 trees grown in 100 l (#25) black plastic containers were assigned at random to one of three root-ball treatments prior to planting; no treatment (Control), outer 3 cm of roots removed around entire root-ball (Shave), or outer circling roots disentangled from the root-ball (Tease). In Experiment 1, half of the trees were fertilized with 400 g of controlled release fertilizer (15-9-12; N-P2O5-K2O) at planting and the remainder of the trees were not fertilized. In Experiment 2, half of the trees were mulched with an 8 cm deep × 2 m diameter ring of coarse ground pine bark at planting and the remainder of the trees were not mulched. In Experiment 1, fertilization at planting increased SPAD chlorophyll content on two of four measurement dates but did not affect cumulative height or caliper growth after two years. After two growing seasons, root-ball treatments (shaving or teasing) increased root growth outside the original root-ball compared to control trees. Both root-ball treatments also reduced circling roots. In Experiment 2, mulching at planting increased soil moisture and cumulative tree height and diameter growth. Shaving increased new root growth and both root-ball treatments improved root architecture and reduced circling roots. Overall, the study demonstrates that root-ball manipulations can stimulate new root growth and reduce circling roots. Mulch is a valuable aid to conserve soil moisture and increase tree growth. Fertilization at planting provided little benefit in this experiment, which may have been related to a high level of soil fertility at the site or nutrient loading of the trees from nursery culture prior to transplanting.  相似文献   

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