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1.
Growth and nutritional status of young plants of Eucalyptus were assessed in a field trial, under different scenarios of harvest residue management and nutrient availability. Treatments were as follows: incorporation of harvest residues into the soil by harrowing (I); I with N fertiliser application (IF); I with leguminous, Lupinus luteus L., seeding (IL); removal of harvest residues (R); R with N fertiliser application (RF); R with leguminous seeding (RL); distribution of harvest residues on the soil surface (S); S with N fertiliser application (SF). Treatments were replicated four times in four blocks with a fully randomised design. Tree growth (height and diameter at breast height) was measured and understory biomass destructively recorded. Tree nutritional status was assessed by foliar analysis (N, Ca, Mg, P, K and leaf area). Significant differences in growth between I, R and S treatments were only detected at early stage. Intercropping with Lupinus decreased tree growth during the early phase, but after 5 years growth was similar to that measured in the I and R treatments. Application of fertiliser enhanced tree growth especially when harvest residues were retained on the soil surface. Combining incorporation of harvest residues with fertiliser application (IF) was the best option to increase tree growth, which was significantly greater than in the R and S. Initially, leaf N was positively affected by the leguminous (RL and IL), but, after the first fertiliser application (1 year after planting), greater N was observed in the IF, RF and SF, the difference decreasing gradually over the following years.  相似文献   

2.
Trees exposed to elevated CO2 partial pressure ([CO2]) generally show increased rates of photosynthesis and growth, but effects on leaf respiration are more variable. The causes of this variable response are unresolved. We grew 12-year-old sweetgum trees (Liquidambar styraciflua L.) in a Free-Air CO2 Enrichment (FACE) facility in ambient [CO2] (37/44 Pa daytime/nighttime) and elevated [CO2] (57/65 Pa daytime/nighttime) in native soil at Oak Ridge National Environmental Research Park. Nighttime respiration (R(N)) was measured on leaves in the upper and lower canopy in the second (1999) and third (2000) growing seasons of CO2 fumigation. Leaf respiration in the light (R(L)) was estimated by the technique of Brooks and Farquhar (1985) in the upper canopy during the third growing season. There were no significant short-term effects of elevated [CO2] on R(N) or long-term effects on R(N) or R(L), when expressed on an area, mass or nitrogen (N) basis. Upper-canopy leaves had 54% higher R(N) (area basis) than lower-canopy leaves, but this relationship was unaffected by CO2 growth treatment. In August 2000, R(L) was about 40% of R(N) in the upper canopy. Elevated [CO(2)] significantly increased the number of leaf mitochondria (62%), leaf mass per unit area (LMA; 9%), and leaf starch (31%) compared with leaves in ambient [CO(2)]. Upper-canopy leaves had a significantly higher number of mitochondria (73%), N (53%), LMA (38%), sugar (117%) and starch (23%) than lower-canopy leaves. Growth in elevated [CO2] did not affect the relationships (i.e., intercept and slope) between R(N) and the measured leaf characteristics. Although no factor explained more than 45% of the variation in R(N), leaf N and LMA were the best predictors for R(N). Therefore, the response of RN to CO2 treatment and canopy position was largely dependent on the magnitude of the effect of elevated [CO2] or canopy position on these characteristics. Because elevated [CO2] had little or no effect on N or LMA, there was no effect on R(N). Canopy position had large effects on these leaf characteristics, however, such that upper-canopy leaves exhibited higher R(N) than lower-canopy leaves. We conclude that elevated [CO2] does not directly impact leaf respiration in sweetgum and that barring changes in leaf nitrogen or leaf chemical composition, long-term effects of elevated [CO2] on respiration in this species will be minimal.  相似文献   

3.
Ginkgo (Ginkgo biloba L.) is a traditional economic tree species in China, and often cultivated in agroforestry systems. The objective of the study was to examine the effects of different Ginkgo and crop species combinations on soil fertility. We established two Ginkgo and crop species systems: Ginkgo + wheat + soybean (G+W+S), Ginkgo + rape + soybean (G+R+S), and one Ginkgo + mulberry (G+M) system, one pure mulberry plantation (M), and one crop systems of rape + soybean (R+S) in the field. Soil chemical properties and enzymes activities were measured 4 years after planting. These soil chemical properties and enzyme activities were used as soil fertility indicators (FI). Soil fertility of the five planting systems was finally evaluated by using improved Analytic Hierarchy Process (AHP). The result showed that soil chemical properties (including pH, organic matter, total N, hydrolysable N, available P and K, total K) and soil enzyme activities (including catalase, sucrase, urease, dehydrogenase, phosphatase, polyphenol oxidase and protease) in the five planting systems were significantly different from each other (P = 0.0237). The above parameters were also different at different soil depths. The concentration of total N, P, organic matter, available P and K of soil decreased significantly with soil depth (P = 0.0146), however, pH increased. The concentrations of organic matter, total N, hydrolysable N, available P and K of soil under rape + soybean (R+S) was lowest among the five planting systems. The activities of sucrase, urease, dehydrogenase, phosphatase and protease decreased with soil depth, however, the activity of catalase and polyphenol oxidase increased. Except for catalase, the activities of these enzymes in the R+S system were the lowest among the five planting systems. The integrated evaluation of soil fertility showed that soil fertility indicators (FI) were significantly different, and the FI values for the five systems followed order: G+M (0.847) > G+W+S (0.446) > M (0.399) > G+R+S (0.343) > R+S (0.211). These results indicated that adoption of a Ginkgo-crop combination could lead to increased long-term sustainability of soil fertility by improving levels of soil organic matter, pH, available nutrient and soil enzyme activity.  相似文献   

4.
Forest nitrogen (N) fertilization induces changes in the soil and soil microorganisms that could hypothetically affect the long-term productivity of the soil. The tree growth response following a normal (i.e. 150 kg N ha?1) single shoot N fertilization has a duration of 7–10 yrs. The aim of this study was to investigate whether any residual effects on tree growth persist, which could be attributed to previous N fertilization. The study included six Pinus sylvestris L. and three Picea abies (L.) Karst. experimental sites, sampled for growth parameters 14–28 yrs after the last fertilization. Residual growth effects were on average small, and not statistically significant. Negative residual growth effects of varying duration could be discerned, especially at low-fertility P. sylvestris sites. However, there was an overall tendency for growth to increase in the long term after N fertilization. The main conclusion is that operational forest N fertilization with a normal N dose should not be regarded as a threat to long-term forest production.  相似文献   

5.
Analysis of reflectance can be used to estimate foliar concentrations of photosynthetic pigments, thus providing information on the physiological status of green plants. We compared several methods of reflectance analysis for the capacity to differentiate among effects of fertilization treatments across different irradiances on seedlings of Engelmann spruce (Picea engelmanii Parry ex Engelm.). Seedlings were grown in two light treatments (0 and 60% shade) and three nitrogen (N) treatments (10, 25 and 100 mg N l-1) for one growing season, after which foliar reflectance of the needles was measured. Five indices were tested: R550 (% reflectance at 550 nm); red edge position; the ratio R698:R760; the structure independent pigment index (SIPI); and the photochemical reflectance index (PRI). Both the light and nutrient treatments significantly affected foliar chlorophyll a and b and carotenoid concentrations. Among the indices tested, R550, red edge position and R698:R760 ratio were related to chlorophyll concentration, and were significantly affected by both light and N treatments. Both SIPI and PRI were related to chlorophyll and carotenoid concentrations. Among these relationships, PRI was affected by both treatments, whereas SIPI was sensitive to N treatment but not to light treatment. All five indices were weakly but significantly correlated with growth as measured by dry weight.  相似文献   

6.
LIM  M. T.; COUSENS  J. E. 《Forestry》1986,59(1):17-27
The fall of fine litter was 4.5 tonnes ha–1 y–1,(78% needles) returning to the ground 36.6 kg N, 2.2 kg P, 7.6kg K, 12.1 kg Ca and 2.0 kg Mg. Nutrient input in rainfall (880mm in 1978) was 2.6 kg N, 0.4 kg P, 4.3 kg K, 7.6 kg Ca and1.4 kg Mg. Throughfall was 534 mm. The method of Miller, Cooperand Miller (1976) was used to estimate aerosol contributions,leaching and absorption. Retranslocation estimates were 59.6kg N ha–1 y–1 (55% of Requirement), 8.5 kg P (64%R), 42.0 kg K (56% R) and 1.2 kg Mg (14% R). Retranslocationwas unchanged, but uptake increased with added N % P and decreasedwith added sawdust and glucose. Other typical effects of nutrientamendment were observed: with added N % P growth increased,current tissues had higher concentrations of N and P and litterfalldecreased in the first year but was heavier in the second year:with added sawdust and glucose, growth declined but concentrationsof N and P remained substantially the same.  相似文献   

7.
The presented paper analyses the relations between four features of geomorphology, i.e. aspect, slope, elevation and type of terrain, and tree layer diversity of forest ecosystems. The forest stand diversity is quantified by nine species diversity indices (N0, R1, R2, H, N1, N2, E1, E3, E5). The data used in this study come from the regional forest inventory of the Forest School Enterprise, Technical University Zvolen, Slovakia. Within this inventory, 26 permanent tracts were established in the systematic grid of 2×2 km, whereby a total of 120 sample plots were created on which 1,728 trees were measured. Analyses showed that species diversity is closely related only to elevation. However, the relationships of the individual species diversity indices to elevation are loose since the correlation coefficients do not exceed values of 0.30–0.40. The second part of this work presents spatial interpolation of species diversity degrees on a regional level using geostatistical methods. For this regionalisation, we used an indicator kriging. The final kriging map was found to be a suitable tool for the interpretation of tree species diversity over the investigated area.  相似文献   

8.
ABSTRACT

Litter decomposition plays a critical role in both nutrient cycling and the interspecific relationships between tree species. In this study, leaf litter from Robinia pseudoacacia was mixed with litter from 10 other species, this mixture was then ground and incubated in soil. The soil indexes (i.e., quantity of microbes, activities of enzymes, and chemical properties) were analyzed to study the effects of litter decomposition on soil properties and the interaction between the litters. If mixed separately with Larix principis-rupprechtii or Betula platyphylla, R. pseudoacacia litter exerted synergistic effects on the activities of most enzymes. The mixed litters of R. pseudoacacia and Pinus sylvestris var. mongolica or Ulmus pumila exerted synergistic effects on the soil available P. With regard to the soil properties as a whole, the mixed litters of R. pseudoacacia and B. platyphylla, Pinus tabulaeformis, P. sylvestris var. mongolica, or L. principis-rupprechtii exerted synergistic effects on soil during their decomposition. However, the mixed litters of R. pseudoacacia and Populus simonii, Quercus liaotungensis, U. pumila, or Caragana microphylla did not. This indicated that R. pseudoacacia mixed with the litter of other needle-leaf tree species benefits the development and regeneration of soil and thus can be used for sustainable forest management.  相似文献   

9.
Seedling growth response of two tropical tree species (Schima superba and Cryptocarya concinna) to simulated N deposition was studied during a period of 11 months. One-year-old seedlings were grown in forest soil treated with N as NH4NO3 at Control–no N addition, N5–5, N10–10, N15–15, and N30–30 g N m−2 year−1. The objective was to examine the effects of N addition on seedling growth and compare this effect between the two tropical tree species of different species-N-requirement. Results showed that both species responded significantly to N addition and exhibited positive effect to lower rate of N addition and negative effect to higher rate of N addition on growth parameters (height and stem base diameter, biomass production, and net photosynthetic rate). The highest values were observed in the N10 plots for S. superba and in the N15 plots for C. concinna, but the lowest values were observed in the N30 plots for both species. However, the reduction in the N30 plots was more pronounced for S. superba than for C. concinna relative to the control plots. Our findings suggest that response of seedling growth of tropical tree species to atmospheric N deposition may vary depending on rate of N deposition and species-N-requirement.  相似文献   

10.
Despite the promotion of prunings as sources of nitrogen for crops, lack of synchronization between N mineralization from prunings and plant uptake remains a major limitation to the impact of prunings on crop yields. A laboratory and a field experiment were therefore carried out to determine the mineralization patterns of selected prunings and assess the potential that exists to improve synchrony by mixing prunings of different quality. The laboratory incubation experiment was conducted for 84 days to determine the C and N release patterns of prunings of different quality and the manipulation of the C and N mineralization trends by mixing prunings of different quality. High quality prunings were considered to be those with high CO2 evolution rates and mineralize N rapidly. The % C and % N released in 84 days were highest for the high quality prunings of Tithonia diversifolia (70% and 30% respectively) and least for the low quality prunings of Flemingia macrophylla (25% and –5% respectively). The medium quality prunings of Acacia angustissima and Calliandra calothyrsus had similar proportions of released C and N (about 40% C and 10% N). Different mixtures of T. diversifolia with other species showed contrasting influence on C release and N mineralization. Most mixtures released less C than that predicted, but in contrast most mixtures released N at a rate either matching or above the predicted. The % N released was strongly correlated with the polyphenol protein binding capacity (r2 = 0.53) and also with the % C released (r2 = 0.62). The field experiment was done for two cropping seasons to determine the effects of the prunings of these species and their mixtures on maize grain yield. The prunings were added at 5 t ha–1 and incorporated into the top 15 cm by hand hoeing in the first season and their residual effects were monitored in the second season. Medium and low quality prunings produced significantly (p < 0.05) higher maize grain yields in the first season ranging between 2.4 t ha–1 and 3.4 t ha–1 compared with T. diversifolia which produced 1.7 t ha–1. This suggested better synchrony in N release and uptake by maize with medium and low quality prunings compared with high quality prunings. The only mixture that indicated improved synchrony was the mixture of T. diversifolia and C. calothyrsus. This study showed that mixing prunings of different quality produce different patterns of N mineralization, some of which were unexpected and had a potential for improving N synchrony.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

11.
The effects of soil animals on soil nitrogen （N） mineralization and its availability were studied by investigating soil animal groups and their amounts of macro-faunas sorted by hand, and middle and microfaunas distinguished with Tullgren and Baermann methods under three Pinus sylvestris var. mongolica Litv. plantations in Zhanggutai sandy land, China. In addition, soil N mineralization rate was also measured with PVC closed-top tube in situ incubation method. The soil animals collected during growing season belonged to 13 orders, 5 groups, 4 phyla, whose average density was 86 249.17 individuals-m^-2. There were significant differences in soil animal species, densities, diversities and evenness among three plantations. Permanent grazing resulted in decrease of soil animal species and diversity. The average ammonification, nitrification and mineralization rates were 0.48 g：m^-2·a^-1, 3.68 g·m^-2·a^-1 and 4.16 g·m^-2·a^-1, respectively. The ammonification rate in near-mature forest was higher than that in middle-age forests, while the order of nitrification and net mineralization rates was： middle-age forest without grazing 〈 middle-age forest with grazing 〈 near-mature forest with grazing （P〈0.05）. Soil N mineralization rate increased with soil animal amounts, but no significant relationship with diversity. The contribution of soil animals to N mineralization was different for different ecosystems due to influences of complex factors including grazing, soil characteristics, the quality and amount of litter on N mineralization.  相似文献   

12.
Hedged stock plants of four full-sib families [27-2 × 27-5, 27-3× 27-1, 27-2 × 27-1, and 27-6 × 27-1 (designated B, G, R, andW)] of loblolly pine (Pinus taeda L.) were fertilizeddailywith a complete nutrient solution containing N at either 10, 25, 40, 55, or 70mg·L–1. May (spring softwood), July(summersoftwood), and January (winter hardwood) terminal stem cuttings were taken fortissue analysis and rooting studies. Spring cuttings rooted in the highestpercentages (59.5%), followed by winter (40.5%), and summer (34.7%). Maximumrooting for spring (70.0%), summer (48.6%), and winter (55.6%) occurred withcuttings taken from hedges that received N at 55mg·L–1. Genetic differences among familieswere evident as families G and W rooted in greater percentages at lower appliedN rates and family B was the best rooting family at the highest applied N rate.When internal N levels were considered families G and W also rooted best at lowinternal N levels, while family B was the best rooting family at high internalNlevels. Neither total nonstructural carbohydrates (TNC) nor any of severalspecific carbohydrates were correlated with rooting and an optimal TNC : Nratiofor rooting was not found. Root counts generally increased with increases inapplied N. Root number was weakly correlated with TNC (R = 0.29, P 0.01) and several specific sugars, but was not correlated with internal N.Totalroot dry weight, total root length, and total root area responded similarly.  相似文献   

13.
The objective of this study was to quantify the effects of high nitrogen (N) inputs on N cycling in a 35–45-yr-old Scots pine (Pinus sylvestris L.) forest. Nitrogen was added annually (single doses) as NH4NO3 in doses of 0 (N0), 30 (N1) and 90 (N2) kg N ha?1 yr?1. The only N input to the N0 plots was atmospheric deposition of 10 kg N ha?1 yr?1. The N cycle in these plots was tight, with almost complete retention of the incoming N. In the N1 plots the N retention was 83% after 9 yrs of N addition. The trees were the major sink, but the soil also contributed to the N retention. In the N2 plots the N retention was 63%, being mainly accounted for by accumulation in the soil. The leaching of N from the N2 stands was as high as 35 kg N ha?1 yr?1. The N2 system was N saturated.  相似文献   

14.

Coppicing is a widely adopted management system for forest plantations; however, little information is available pertaining to responses to fertilizer application. Our objective was therefore to assess the effect of individual and conjunct omissions of N, P, K, Ca, Mg, B, and Cu on the growth of a highly productive Eucalyptus urophylla?×?E. grandis hybrid clone, managed for coppicing at the second rotation, in two soils of contrasting fertility in southeastern Brazil. Two commercial sites of approximately 7 years of age, one in an Arenosol and the other in a Ferralsol, were harvested and the experiments installed. At the Arenosol site, the yield from the fertilizer treatment in the coppice system (R2) was the same as determined for the first rotation (high forest; R1), at approximately 40 m3 ha?1 year?1 at 6 years old. In contrast, the yield from the fertilizer treatment in R2 at the Ferralsol site was 11% lower compared with R1. Despite some alterations in leaf nutrient concentrations, other than for K at the Arenosol site (where the K omission treatment reduced wood volume at 6 years by 21%), no yield reduction was found for any no-fertilizer treatments. Due to the widely distributed root system already established in coppiced plantations, ensuring a large volume of soil exploration, coppiced eucalypts only responded to K application. This is due to low soil K availability and the high K demand in eucalypt plantations.

  相似文献   

15.
Reduction in forage production (FP) under trees in the humid tropics is well known, but information on how different levels of nitrogen (N) fertilizer influence FP under trees is meager. The present study reports effects of four N fertilizer levels (0, 60, 80 and 120 kg ha−1 N) on net soil N mineralization rate (NMR) and soil moisture (SM), FP, shoot biomass/root biomass ratio (SB/RB), N concentration in SB, N uptake and nitrogen use efficiency (NUE) of three grasses [guinea (Panicum maximum Jacq.), para (Brachiaria mutica (Forssk) Stapf) and hybrid-napier (Pennisetum purpureum Schumach.)] under three canopy positions [under canopy (UC, representing high shade), between canopy (BC, representing low shade) and open] of coconut trees (Cocos nucifera L.) in a coconut based silvopastoral system in the humid tropical climate of South Andaman Island of India. The study was performed for two annual cycles (2005–2006 and 2006–2007). The hypotheses tested were: (1) FP would decline under tree shades, both in N fertilized as well as no N fertilized conditions, when SM was not growth limiting in the open. However, amount of decline in the FP would depend on grass species and intensity of shades i.e., higher was the shade greater would be the decline; (2) N fertilizer would increase FP under tree shades, but the increase depended on grass species, intensity of shades and amount of N applied. Amount of N applied, however, would not annul the shades effects when SM was not growth limiting in the open. The study revealed that the tree reduced light 59% under UC and 32% under BC positions, but the N fertilizer levels increased NMR by 11–51% under UC and 3–44% under BC positions compared to the open. SM did not differ across the canopy positions. Under all situations, FP of all grasses declined under UC (47–78%) and BC (18–32%) positions compared to the open; the decline was greater in Hybrid-napier than Guinea and Para grasses. Forage production of all grasses increased with N fertilizer increments under all canopy positions reaching 32 t ha−1 dry matters for hybrid-napier at 120 kg ha−1 N in the open. Both guinea and para grasses outyielded hybrid-napier grass under UC but not under BC or in the open. N concentration in the forage (SB) also increased as N fertilizer level increased. These observations support our hypotheses and suggest that forage production under coconut palms can be increased by the application of N fertilizer with both guinea and para grasses being more productive than hybrid-napier grass under the high shade. Where light conditions are better, hybrid-napier would produce more forage than the other species.  相似文献   

16.
Five new triterpene saponins, Ilexpublesnins N–R (1–5), along with seven known analogs were isolated from the root of Ilex pubescens. Their structures were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. Ilexpublesnin N (1) possessed a rare 20-hydroxyursolic acid scaffold from natural resource. These compounds were evaluated in vitro for their cytotoxic effects on human cancer cell lines HepG2, HLE, BEL7402, BEL7403, BEL7405, MCF-7, HeLa. Among them, only compounds 5 and 10 showed cytotoxic potentiality against BEl-7403 and HEL cell lines [inhibition (%): 35.38 and 45.12, respectively].  相似文献   

17.
退化红壤恢复过程中芒萁的N、P化学计量特征   总被引：1，自引：1，他引：0       下载免费PDF全文
[目的]探究生态恢复过程中严重退化红壤区林下芒萁的化学计量特征变化规律,为红壤水土流失区芒萁的恢复及水土保持提供科学依据。[方法]以福建长汀严重退化红壤区芒萁群落为对象,通过对比不同治理年限的芒萁和土壤的N、P含量及比值的关系,研究了生态系统恢复对芒萁化学计量特征的影响。[结果]表明:(1)治理后芒萁地上新鲜器官的N、P含量显著高于未治理的(羽叶N 8.11 g·kg~(-1)、P 0.297 g·kg~(-1);叶柄N 2.63 g·kg~(-1)、P0.103 g·kg~(-1)),但次生林下的芒萁的N、P含量仍高于各样地(羽叶N 12.41 g·kg~(-1)、P 0.497 g·kg~(-1);叶柄N4.32 g·kg~(-1)、P 0.211 g·kg~(-1);枯羽叶N 11.09 g·kg~(-1)、P 0.356 g·kg~(-1);枯叶柄N 3.83 g·kg~(-1)、P 0.163 g·kg~(-1);根茎N 5.330 g·kg~(-1)、P 0.348 g·kg~(-1));与未治理的对照相比,芒萁干枯器官的N∶P比呈现递减的趋势。(2)随着土壤养分的增加,芒萁地上和地下器官的N和P含量亦协同增加,并与土壤N∶P存在显著的相关关系;在所有群落中,芒萁新鲜羽叶的N∶P16。(3)芒萁羽叶N、P和N∶P比的内稳性指数均高于马尾松叶的内稳性指数,芒萁各器官对N、P元素具有较高的内稳性,与马尾松相比芒萁的养分含量更能反映土壤的养分状况。(4)芒萁枯羽叶与枯叶柄N、P含量与土壤N、P含量有显著的正相关(p0.05),芒萁枯死后器官的养分含量与土壤养分含量间的相关性更显著。[结论]在生态恢复过程中芒萁地上与地下器官N、P含量协同增加并与土壤N∶P存在显著的相关关系;在退化红壤区芒萁种群受到P的限制作用强于N的限制;干枯的芒萁器官可能是比新鲜的芒萁器官更好的土壤养分指示器。  相似文献   

18.
选择章古台地区三块典型樟子松(Pinussylvestrisvar.mongolica)人工固沙林为研究对象,采用实验室好氧培养法测定了不同土壤层次和在不同水分条件下的N矿化过程。结果表明:土壤0-60cm层N净矿化速率垂直变化范围为1.06–7.52mg·kg-1·month-1;土壤层次和含水量及其交互作用对土壤N净矿化速率的影响均达到差异显著(P<0.05);净矿化速率随着土壤层次的加深而明显下降,0-15cm层占总净矿化量的60.52%;半饱和与饱和含水量处理差异不显著,但均高于不加水处理。为此,在半干旱地区必须进一步加强开展调控生态系统N矿化、循环及其收支平衡影响因素的研究。图1表4参20。  相似文献   

19.
The effects of soil compaction and cultivation on soil mineral N dynamics were investigated through an 18-month, in situ N mineralisation experiment during the inter-rotation and early establishment period of a second rotation (2R) hoop pine (Araucaria cunninghamii Aiton ex A. Cunn) plantation in southeast Queensland, Australia. Treatments were 0, 1 and 16 passes of a fully laden forwarder (gross weight, 40.2 Mg) and cultivation by disc plough (zero cultivation and cultivation). Nitrate N was the dominant form of mineral N throughout the 18-month sampling period in both non-cultivated and cultivated soils, varying between 10 and 40 kg ha−1 whilst ammonium N remained <10 kg ha−1. Compaction had no significant effect on N mineralisation or nitrification. However, the remediation of the effects of compaction on soil through the use of the disc plough had significant impacts on N mineralisation, nitrification and N leaching. On a seasonal basis, the mean net N mineralisation increased from around 30 to 53 kg ha−1, nitrification from 28 to 43 kg ha−1 and nitrate N leaching from around 10 to 73 kg ha−1 following cultivation.  相似文献   

20.
The effects of applying N(urea, 46% N), P(phosphate, 12% P2O5) and K(potassium sulphate, 54% K2O) fertilizers on the growth performance and biomass yield of 8-month-old Archidendron clypearia seedlings were examined by L9 orthogonal array with 3 replicates in the nursery of Zengcheng Forest Farm of Guangzhou, Guangdong Province. The test seedlings were potted with the subsoil of total N 0.0484%, total P 0.1518% and total K 1.2629%, and fertilized at the 2nd and 6th months with the application rates of 0, 10 and 20 mg of N, 0, 20 and 50 mg of P and 0, 10 and 20 mg of K per seedling. The results showed that the diameter at ground level(DGL), the height and the oven-dried weight biomass of 8-month-old seedlings differed significantly at P=0.05. The combined application dose of 20 mg N, 20 mg P and 0 mg K per seedling resulted in the best seedling growth and biomass yield. N fertilizer was a significant factor in the growth of DGL and height of A. clypearia seedlings. P fertilizer had no significant effects on both DGL and height, while K fertilizer only affected DGL significantly. Analysis of the leaf and root stoichiometry suggested that N may be the most single limiting nutrient, A. clypearia seedlings used N more efficiently than they used P.  相似文献   

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