Fertilizer requirements for maintenance of a perennial ryegrass (Lolium perenne L.)/white clover (Trifolium repens L.) pasture growing on a humus iron podzol in N.E. Scotland

Ryegrass/white clover pastures were reseeded on heather moor in north-cast Scotland in 1978/79. By 1981, despite moderate fertilizer applications, the pastures had deteriorated and dry matter (DM) production was low. After preliminary soil and herbage analysis an omission trial was carried out in 1982/83 at two sites (A and B) to identify the factors which limited production.
At site A depressions in growth occurred in the absence of N, P and K. Perennial ryegrass was severely N deficient with concentrations in leaves of less than 22 g N kg⁻¹ in spring and summer even after application of 120 kg N ha⁻¹ annually. Rates of nitrogen fixation were high in spring but rapidly declined in June and July as the soil moisture tension increased. Application of N fertilizer also reduced the N₂ fixation rate. Deficiencies of F and K occurred despite apparently high levels of extractable F in the soil. Uptake of these nutrients was inhibited in the dry soil during the summer. White clover was more susceptible to drought than perennial ryegrass, probably because it rooted at a shallower depth.
Growth at site B was limited by acidity and lack of N and K. The soil pH was 4 8 (s.d. = 0middot;75) at 1-5 cm depth. Application of 2 5 t lime ha⁻¹ in spring 1982 had not altered the pH by autumn 1983.
It was concluded that methods of incorporating lime into the soil, together with ways of increasing the rates of N₂ fixation by white clover and transfer to grass, should be investigated further. Regular small applications of N and K may be necessary to sustain DM production at the level required by the farming system.     

Plant interference and chemical toxins in upland pastures

Supernatants derived from desiccated plant material gathered from Agrostis/Festuca vegetation had an inhibitory effect on the germination and early development of seedlings of Trifolium repens cv. S184. Two compounds, o -hydroxyphenylpropionic acid and benzoic acid, were identified chromatographically and their structures confirmed by mass spectrometry. Commercial preparations of the two compounds were effective inhibitors at a concentration of 10⁻² and 10⁻³ m respectively when T. repens was used as the phytometer species. Benzoic acid lost its inhibitory effect when the pH of the two solutions was adjusted to pH 5·5. The roots of seedlings of white clover were severely distorted by o -hydroxyphenylpropionic add at 10⁻³ m . It is likely that phenolic acids, produced from the surface trash created by slot seeding procedures, interfere with the establishment of white clover in upland pastures.     

The herbage intake and performance of set-stocked suckler cows and calves

Groups of eight Hereford × Friesian cows and their South Devon cross calves were set stocked over a 24-week grazing season at 3·23 (low), 3·21 (medium) or 4·24 (high) cows ha^-1 together with their calves. For the first 8 weeks only two-thirds of the total area was grazed. Increasing the stocking rate from low to medium reduced daily milk yield and cow and calf liveweight gains by 1·2, 0·24 and 0·29 kg d^-1 respectively, and from medium to high by 1·2, 0·24 and 0·23 kg d^-1. The main sward factor influencing faecal output and herbage intake was the quantity of organic matter on the pastures but the digestibility of the herbage selected also exerted a significant effect on the intake of cows. Major depressions in the herbage intake of cows occurred once the average sward height fell below 7 cm. Output of calf live weight was 628, 658 and 743 kg ha^-1 for the 3 stocking rates from low to high, and for cows 246, 179 and 30 kg ha^-1. It was concluded that decisions on pasture management should be taken in relation to the cow rather than the calf on set-stocked swards.     

Slot-seeding investigations

Red clover cv. Hungaropoly was slot-seeded into a perennial ryegrass-dominant sward in April 1979. Glyphosate and paraquat were applied separately as bandsprays each at two doses and at two band widths. Control plots were either slot-seeded without a herbicide bandspray or received ±150 kg N ha⁻¹ a⁻¹. Red clover establishment was assessed and amounts of dry matter (DM) and total N accumulated were measured at two harvests in 1979 and three harvests in 1980. Bandspraying increased seedling vigour and development and resulted in the eventual replacement of 1 t grass DM ha⁻¹ by an equivalent amount of red clover. Of the treatment variables investigated, bandspray width had the greatest influence on red clover establishment and productivity. The slot-seeded area, meaned for all treatments, produced a total of 6.40 and 13.16 t DM ha⁻¹ in 1979 and 1980. This was estimated to be equivalent to the all-grass sward receiving 112 kg N ha⁻¹ a⁻¹ during the second year of the experiment or 238 kg N ha⁻¹ over the 2 years when measured in terms of N yield. Slot-seeding overcomes several of the problems associated with conventional establishment of red clover.     

Agronomic performance and nutritive value of common and alternative grass and legume species in the Peruvian highlands

The agronomic performance and nutritive value of twelve annual and perennial grasses and legumes were analysed in order to define alternatives to local forages for dry-season feeding of ruminants in the Peruvian Andes. There were twelve species and two fertilizer treatments (no fertilizer and a N;P;K fertilizer mainly applied at sowing) in an experiment with a randomized complete block design with three replicates at each of two sites. Plant height, soil cover by forage and weed species, frost damage, dry matter (DM) yield and nutritive value of herbage were evaluated in 2005 and 2006. Among the annual species, Hordeum vulgare L. cv. UNA 80 and × Triticosecale Wittm. had the highest DM yields when fertilized (8226 and 6934 kg ha⁻¹ respectively). Without fertilizer the alternative cultivars had similar DM yields to that of the local forages. Cultivars of Avena sativa L. had lower concentrations of neutral-detergent fibre (NDF) (557 g kg⁻¹ DM) and higher concentrations of predicted net energy for lactation (5·86 MJ kg⁻¹ DM) than the other annual grass species (625 g kg⁻¹ DM and 5·01 MJ kg⁻¹ DM respectively), while the legumes were superior in concentrations of crude protein (277 g kg⁻¹ DM) and NDF (362 g kg⁻¹ DM). Considering the low agronomic performance of the perennial forages, a mixture of fertilized annual grasses and legumes appears the most appropriate approach to meeting the demand for forage of high nutritive value in the Peruvian highlands.     

Seed availability and gap size influence seedling emergence of dandelion (Taraxacum officinale) in grasslands

Dandelion ( Taraxacum officinale agg.) seedlings colonize gaps in agricultural grassland and give rise to weedy pastures. It was investigated how this colonization is affected by seed availability and gap size. Flowering, seed production and spontaneous seedling emergence in artificial gaps were recorded at seven grassland sites. Fifteen to 126 flowers m⁻² (2·2–18·6 thousands of seeds m⁻²) were produced at particular sites in May 2005. Seed availability explained 0·91 of the between-site variation in seedling abundance. Seedling populations represented c. 0·03 of the seed produced at these sites. Shading, pH, soil nutrients and soil texture did not affect seedling emergence. In 2006, seed was sown at one site in small (33 cm²) and large (400 cm²) gaps on eight occassions during the growing season. Time to germination was on average 10 d shorter and 0·20 more of the seed germinated in small than large gaps, and both varied significantly with date of sowing. Germination was not limited by low temperature. Predation of seeds may have decreased the density of established seedlings. Patches of dandelions in sparse or weakly disturbed grassland are unlikely to disappear spontaneously and repeated cutting during spring flowering is recommended as an effective means of management.     

Forage availability from a temperate pasture managed with intensive rotational grazing

Successful integration of rotational grazing into livestock production systems requires estimates of pasture growth rates for feed budgeting of daily animal intake. By matching livestock nutrient demand with forage availability, over-feeding of supplements can be minimized, which reduces feed costs and the need lo manage surplus nutrients, A three-year grazing study was carried out on a Kentucky bluegrass ( Poa pratensis L.)-dominant pasture to estimate the daily quantity of herbage available to cattle in an intensive, rotational grazing system. Herbage production, species composition, and forage quality were determined in each of the six grazing cycles in a year, from April until September. The average length of a grazing cycle was 28·6 d, with 2·7 d for duration of grazing on a paddock. Pre-grazing and post-grazing sward heights, measured with a plate meter, were 14 and 7 cm, and the corresponding herbage masses were 1955 and 775 kg DM ha⁻¹ respectively. Under adequate soil moisture during 1989, herbage available for daily intake was 53 kg ha⁻¹ from April until mid- August, declining to approximately 32 kg ha⁻¹ d⁻¹ by the end of September. Distribution of this herbage was fairly uniform until the end of August. However, a dry summer in 1991 reduced herbage availability to 15 kg ha⁻¹ d⁻¹. Bluegrass and white clover ( Trifolium repens L.) formed 70% of the herbage yield during the period April–June. Later in the season, dead matter and other species increased, reducing the contribution of bluegrass and clover to approximately 60% of total dry matter. While these pastures have the potential to provide significant amounts of forage for 5–6 months in a year, additional on-farm forage reserves are needed during periods of water stress.     

修剪物与茶多酚对茶树矿质吸收及根系有机酸分泌的影响

探究茶树修剪物水溶性成分及茶多酚对茶树生长的影响与作用机制。水培茶苗,于15、35、55、75、95 d收集根系分泌物,通过阴、阳离子树脂纯化、减压浓缩后,利用高效液相色谱（HPLC）测定分泌物中有机酸主要组成与含量。同时测定茶苗干物质量、茶多酚及矿质元素含量等指标。研究表明,茶多酚会抑制茶树对Ca、Mg、Fe、Mn、Zn的吸收,抑制生长,同时诱导茶树根系分泌苹果酸、柠檬酸;适量修剪物水溶物能够补充矿质营养,提高茶树K、Ca、Fe、Mn、Zn、Al的吸收,促进生长,但同时也会诱导草酸、苹果酸、柠檬酸和琥珀酸的分泌,降低收集液pH值,而收集液pH值变化与有机酸分泌量变化显著相关,结果提示茶树修剪物水溶性成分可能是导致土壤酸化的机理之一。     

Lime and major nutrient fertilizers required to establish a perennial ryegrass/white clover pasture on a non-calcareous gley in the Scottish uplands

A field experiment with mixed swards of perennial ryegrass and while clover carded out in 1982–83 using small cut plots is described. With perennial ryegrass, lime slightly decreased annual dry matter (DM) production in 1982 (the sowing year) but increased it in 1983 (the first harvest year) by about 1 t ha^-1. Applications of N and P produced small increases in DM in 1982 and greater increases in 1983. In the latter season annual DM production varied from an average of 3·5 to about 10 t ha^-1 with 0 or 480 kg N ha^-1 applied in three equal-sized dressings throughout the growing season. Application of 40 kg P ha^-1 in 1982 increased DM production by about 2·5 t ha^-1 in 1983 but higher rates had little effect. Fifteen mg extractable P kg^-1 soil seemed sufficient to support levels of production normally expected from ryegrass pastures in upland Scotland, Applications of K did not affect DM production. N increased tiller weight and sward height of ryegrass; lime and P tended to increase tiller weight but this effect was not statistically significant. Leaf appearance and tiller number were not affected by treatments.
The white clover content of the pasture was decreased 10-fold by application of N and increased by lime and P (1·45 and 1·46-fold. respectively). The DM response to P was most apparent in limed soil and was also affected by the siting of the plots in the experimental area. Effects of lime and P on growth of white clover were to increase the number of stolon growing points and root nodule numbers per unit area.
The results emphasize the importance of lime and P fertilizer for establishment and growth of pasture in this soil and the differences between white clover and ryegrass in their responses to these.     

Grass height as an indicator for supplementary feeding of continuously stocked dairy cows

Three groups of cows were continuously stocked on pasture and offered supplementary concentrates according to the herbage height measured weekly with a grass disc. Concentrates were offered when the mean herbage height fell below 9 cm for treatment A, 7 cm for treatment B and 5 cm for treatment C at a rate of 1 kg d^-1 for each 0·2-cm decline below these threshold levels. If the herbage height declined by more than 1·2 cm (8 kg concentrates d^-1) hay was offered in addition ad libitum. The stocking rates for all three treatments were 5·2, 3·2 and 3·2 cows ha^-1 for three successive 8-week periods. For treatments A, B and C the mean concentrate DM intakes were 3·2, 1·2 and 1·2 kg d^-1 (treatment A also received 0·2 kg hay DM d^-1), and the mean daily milk yields were 17·2, 16·2 and 15·2 kg respectively. The increasing level of supplementary feeding from treatment C to A also resulted in an increase in liveweight and body condition score change, and a reduction in milk fat.     

Interaction between water-soluble carbohydrate reserves and defoliation severity on the regrowth of perennial ryegrass (Lolium perenne L.)-dominant swards

A field-study was undertaken in Hamilton, New Zealand to determine if there was an interaction between water-soluble carbohydrate (WSC) reserve content and defoliation severity on the regrowth of perennial ryegrass-dominant swards during winter. Perennial ryegrass plants with either low or high WSC content were obtained by varying the defoliation frequency. At the third defoliation at the one-leaf stage and at the first defoliation at the three-leaf stage (harvest H₁), swards were mown with a rotary lawnmower to residual stubble heights of 20, 40 or 60 mm. All swards were then allowed to regrow to the three-leaf stage before again defoliating to their treatment residual stubble heights (H₂). Frequently defoliated plants contained proportionately between 0·37 and 0·48 less WSC in the stubble after defoliation, depending on the severity of defoliation. There was no interaction between WSC content and defoliation severity for herbage regrowth between harvests H₁ and H₂. Herbage regrowth was lower from swards containing low WSC plants compared with high WSC plants (2279 vs. 2007 kg DM ha⁻¹). Furthermore, swards defoliated to 20 or 40 mm had greater herbage regrowth compared with those defoliated to 60 mm (2266, 2249 and 1914 kg DM ha⁻¹ for swards defoliated to residual stubble heights of 20, 40 and 60 mm, respectively). Regrowth of perennial ryegrass was positively correlated with post-defoliation stubble WSC content within defoliation severity treatment, implying that WSC contributed to the defoliation frequency-derived difference in herbage yield. However, the effect of defoliation severity on herbage regrowth was not associated with post-defoliation stubble WSC content.     

HCO3−和灌溉方式对水稻铁吸收和利用的交互影响

【目的】膜下滴灌水稻是一项兼顾高产和节水潜力的水稻栽培技术。然而，在石灰性土壤上膜下滴灌水稻经常表现出缺铁(Fe)黄化症状。前期研究发现，在滴灌条件下HCO₃⁻对水稻Fe吸收的抑制强度弱于淹灌，但内在机制并不清楚。本文主要探讨HCO₃⁻对两种灌溉型水稻土壤DTPA-Fe浓度、水稻木质部伤流液pH值、Fe吸收和利用的影响。【方法】在两种灌溉水稻[淹灌(FI)和覆膜滴灌(DI-PFM)]处理下设四种灌溉水HCO₃⁻浓度处理(0，2，10和40 mmol/L HCO₃⁻，分别表示为BC-0，BC-2，BC-10和BC-40)。【结果】DI-PFM土壤DTPA-Fe含量显著低于FI。随着HCO₃⁻浓度增加，土壤pH增加，而土壤DTPA-Fe浓度呈降低趋势。水稻木质部伤流液pH值随灌溉水中HCO₃⁻浓度的增加而增加，FI处理水稻木质部汁液pH值显著高于DI-PFM。水稻叶片和根系质外体铁浓度均随HCO₃⁻浓度的上升表现为先减少后增加的趋势，在BC-40处理下最高。两种灌溉型水稻叶片活性铁浓度、共质体铁浓度、水稻生物量和全铁积累量均随HCO₃⁻浓度的上升而降低，但DI-PFM处理下这些参数的降幅小于FI。水稻根系和叶片中共质体Fe与质外体Fe浓度比值随HCO₃⁻浓度的增加而降低，FI处理水稻根系和叶片中共质体Fe与质外体Fe浓度比值大于DI-PFM。【结论】HCO₃⁻引起水稻木质部伤流液pH升高影响水稻铁吸收和利用，但HCO₃⁻并不是造成滴灌水稻缺铁的主要因子。石灰性土壤上滴灌水稻缺铁的主要原因可能仍是因为土壤铁有效性低引起的。     

Interactions between N supply and N uptake by perennial ryegrass, 15N recovery and soil pH for four acid Scottish soils

The effects of NH₄⁺−N, NO₃⁻-N or urea-N addition on N uptake by perennial ryegrass ( Lolium perenne ), ¹⁵N recovery and pH of four limed and unlimed soils were determined in a pot experiment over 10 weeks. The best form of N in terms of herbage N uptake and fertilizer recovery differed between the soils. Recovery of applied ¹⁵N in herbage was greatest for the soil with the lowest pH and highest organic matter content, and overall recovery in the soil–plant system was influenced more by soil type than by N form. There was always an apparent mineralization of soil N when perennial ryegrass was present. Soil pH changes ranged from +0·11 to −0·58 units for the unlimed soils and from +0·03 to −1·06 units for the limed soils. The use of NO₃⁻-N rather than NH₄⁺-N or urea-N avoided further acidification. Lime increased herbage N only from the soils with the lowest pH values. Although the acidifying effect of NH₄⁺-fertilizer was alleviated, liming may increase nitrification and possibly N loss via denitrification and/or leaching in the field.
The major influence of soil type on herbage N uptake, pH response to the treatments and fertilizer recoveries implies that liming and fertilizer N management decisions should consider soil characteristics, such as organic matter, clay contents and pH.     

Frequency of stocking rate adjustments required on contrasting upland perennial ryegrass pastures continuously grazed to a sward height criterion from May to July

The use of sward height as a criterion for determining the time and extent of stocking-rate changes on continuously grazed swards was investigated over a 2-year period (1985–86) in a sheep production experiment. Swards of three contrasting perennial ryegrass ( Lolium perenne L.) varieties were established with and without Aberystwyth S184 small-leaved white clover ( Trifolium repens L.) at an upland site (310–363 m) in mid-Wales. From spring (late April) until weaning (mid-July) the pastures were continuously stocked with Beulah Speckled Face ewes and Suffolk cross lambs. During this period sward heights of 4 ± 0.5 cm were obtained and maintained by regular adjustment of animal number on individual paddocks. Grass-only swards received 160 and 200 kg N ha⁻¹ and the grass clover swards were given 80 and 75 kg N ha⁻¹ in 1985 and 1986 respectively.
Differences were observed between the treatments in sward height profiles over the season necessitating contrasting adjustments to stocking rates. Mean stocking rate necessary on early flowering Aurora (22 6 ewes ha⁻¹) was respectively 27% and 17% higher than on late-flowering Aberystwyth S23 and Meltra (tetraploid) ryegrasses; mean stocking rate on grass-only swards was 19% higher than on the grass-clover pastures.
It is concluded that sward height is a useful criterion on which to make adjustments to stocking rates to compare the potential performance of contrasting swards, under continuous grazing. The infrequent adjustments required to maintain a constant sward height, especially on the late flowering diploid perennial ryegrass variety on which many upland pastures are based, suggest that the criterion of sward height could be successfully employed on farms as an aid to efficient grazing management.     

Root size estimates of red clover and alfalfa based on electrical capacitance and root diameter measurements

Electrical capacitance and root diameter techniques for estimating root dry weight were evaluated in one test with red clover plants grown on slant-boards in plant growth chambers for 37–77 d, and in six tests with alfalfa grown in the field for 55–165 d. Root dry weights of red clover were estimated satisfactorily with regression equations from both diameter ( R ²=90%) and capacitance ( R ²=76%) measurements. Root dry weights of alfalfa were estimated satisfactorily throughout the entire season from diameter values ( R ² from 51 to 92%). Alfalfa root weight was significantly ( P <0·25) related to capacitance values at the beginning and at the end of the season but not at mid-season. Electrical capacitance measurements were similar for intact root systems and roots severed 4 cm below the crown in separate experiments with red clover and with alfalfa. The root diameter technique provided an accurate, rapid and inexpensive method of estimating root size throughout the first season of growth. The root capacitance method provided satisfactory estimates of roots at certain times during the summer. Neither method would be useful if a large portion of the root was naturally severed.     

Salinity effects on the early development stages of Panicum coloratum: cultivar differences

The Argentinean semiarid Chaco region is climatically suitable for cattle raising and has an average annual rainfall of 550 mm, concentrated from November to February. There, large areas are affected by high salinity; thus, perennial forages suitable for this region must combine adequate salt and drought tolerance. Panicum coloratum is a C₄ perennial grass adapted over a wide range of soil and rainfall conditions, and the purpose of this study was to evaluate the response of two cultivars (Klein Verde and Bambatsi) to salinity. Under controlled conditions, 100 and 200 mmol l⁻¹ NaCl delayed germination and significantly reduced germination percentages and seedling survival in both cultivars. However, in the field, factors other than salinity (possibly drought) had a large impact on plant survival. In short-term experiments under controlled environmental conditions, the vegetative growth of cultivar Klein Verde was less affected by salinity than Bambatsi. The cumulative growth over one year in a saline plot was also higher in cultivar Klein Verde. This cultivar also had higher shoot K⁺/Na⁺ ratios under salinity, as a result of higher K⁺ concentrations, and accumulated more triglycerides in roots. These features have been associated with salt tolerance in other species.     

Mineral concentrations in herbage and soil in a Pinus radiata silvopastoral system in north-west Spain after sewage sludge and lime application

Silvopastoral systems in north-west Spain can reduce the risk of fires and promote multi-purpose forest land use. Fertilizer application is important for optimal pasture and tree production. The application rate of sewage sludge as a fertilizer is regulated and is based on its nutrient concentration, especially nitrogen. The aim of this study was to assess the effect of three consecutive years of application of different application rates of sewage sludge and inorganic fertilizer, with or without lime (2·5 t CaCO₃ ha⁻¹) on the ammonium, nitrate and exchangeable K, Ca and Mg contents in soil, and on the crude protein (CP), K, Ca and Mg concentrations in herbage in a silvopastoral system established under a 5-year-old Pinus radiata D. Don plantation with a density of 1667 trees ha⁻¹. The experiment was started in autumn 1997, when a pasture mixture was sown (25 kg ha⁻¹ Lolium perenne , 10 kg ha⁻¹ Dactylis glomerata and 4 kg ha⁻¹ Trifolium repens ). Changes in ammonium and nitrate content in the soil in response to liming and sewage sludge application reflected the initial pH of the soil. In general, liming increased the available Ca and Mg content in soil, and CP and Ca concentrations in herbage, but reduced exchangeable K content in the soil in the first year. Application of sewage sludge increased all of the measured nutrients in both soil and herbage.     

The effect of sward height on the liveweight gain of farmed yearling red deer (Cervus elaphus) stags

The effect of sward height on the liveweight gain of yearling farmed red deer stags grazing permanent upland pastures in the UK in two successive years is described. The swards received nitrogen fertilizer at a rate of 218 kg ha⁻¹. Red deer stag calves, which had been weaned in September and housed over winter on a hay and concentrate diet to gain on average 57 g d⁻¹ in year 1 and 75 gd⁻¹ in year 2, grazed at one of fourmean sward heights of 4, 6, 8 and 10cm from the beginning of June until September. Liveweight gains were recorded over a period of 15 weeks. All animals were slaughtered and carcass weights were recorded after the end of the grazing period. Liveweight gains and final live weights and carcass weights were significantly ( P <0·05) lower on the 4-cm sward than on the other swards, but there were no differences between the performance of animals on the 6-, 8- and 10-cm swards.     

The deposition of Caesium 137 on grassland at a site in SW England following the Chernobyl accident

Following the Chernobyl accident in April 1986 ¹³⁷Cs was detected in samples of grass collected at AGRI, North Wyke, Devon, UK. Samples of grass from permanent and reseeded swards under uniform management were taken on three occasions. The ¹³⁷Cs content of the samples was assessed as both Bq kg^-1 of sample and Bq m^-2, Samples taken from the same site in 1985 were used as a control group; these contained no measurable ¹³⁷Cs. The samples taken on 8 May 1986 had a ¹³⁷Cs content of approximately 30 Bq kg^-1; by 31 July 1986 the content had dropped to 1% of this value. The permanent pasture initially showed a higher level of ¹³⁷Cs than the reseeded sward. Analysis of soil cores from the sampling area showed a much higher level of ¹³⁷Cs than that found in the herbage. This was attributed to the atmospheric testing of nuclear devices in the early 1960s: the short-lived ¹³⁷Cs isotope was found in the 1986 herbage samples but not in the soil cores.     

闽中某县茶园土壤-茶树-茶汤中镉含量及健康风险评价研究

以闽中某县8个代表性茶园为研究对象,采集茶园土壤和茶树各器官样品,分析镉在茶园土壤-茶树中积累和分布规律,并探讨其受土壤理化性质的影响;同时测定茶汤中镉含量并算出茶叶中镉的溶出率,利用美国国家环保署（USEPA）推荐的健康风险评价模型进行人体致癌健康风险评价。结果表明,茶园土壤全镉含量均值为112.74βμg·kg^-1,是福建省土壤背景值的2.06倍,茶园土壤镉积累明显;茶园土壤有效镉含量均值为26.44βμg·kg^-1,镉活化率均值为24.86%,有效程度较高。土壤pH和有机质是影响土壤镉及其有效性的主要因素,土壤全磷和速效磷是影响镉活化率的主要因子;茶树主根和侧根与土壤全镉、有效镉和有机质呈显著正相关（P<0.05）,新叶镉含量与土壤有效镉和全磷呈显著正相关（P<0.05）。茶树各器官镉含量分布规律为：侧根（1β253.89βμg·kg^-1）>主根（382.20βμg·kg^-1）>主茎（167.25βμg·kg^-1）≈侧茎（154.65βμg·kg^-1）>老叶（30.60βμg·kg^-1）≈新叶（27.13βμg·kg^-1）,茶树根部镉富集系数显著大于其他器官（P<0.05）,新叶和老叶镉富集系数较低,镉大部分被根和茎固定,向叶的迁移能力较低。茶汤中镉含量均值为192.28βng·L^-1,远低于《生活饮用水卫生标准》中镉含量,茶叶中镉溶出率均值为15.29%;茶汤和茶叶中镉致癌健康年风险分别为6.33×10^-7和4.42×10^-6,比国际辐射防护委员会推荐的化学有害物最大可接受水平（5×10^-5）低约1~2个数量级,说明可以安全饮用。