Organic Amendment,Fertilizer, and Lime Effects on Bareroot Jeffrey Pine Outplanted on a Sierra Nevada Surface Mine

Abstract

Composted organic matter, controlled release fertilizer, and dolomitic lime soil amendments were evaluated for their effectiveness in facilitating the reforestation of an acidic, semiarid Sierra Nevada surface mine with bareroot Jeffrey pine (Pinus jeffreyi Grev. & Balf.). Single application rates were used for the organic matter (2.0 L) and lime (28 g) amendments while low and high rates (8 g and 16 g, respectively) of the chemical fertilizer, High N 22-4-6 + Minors, were employed. All amendments were administered at outplanting using the minisite application method. The organic and lime amendments suppressed seedling survival, more so with the former than the latter, but this result did not extend to the High N fertilizer. Growth was also suppressed by the organic and lime amendments, although there was some evidence that these responses were waning late in the study, while High N was exceedingly stimulatory, especially with the high application rate. Annual assessment of seedling nutrition during this three-year study revealed numerous High N and organic matter treatment influences. Among them, increases in foliar N, P, and K and reductions in Fe, Mn, Zn, and Al were prominent within the High N treatments, but particularly so at the high application rate. For the organic matter treatment, the above increases and decreases in elemental concentrations were again noted, although the nutritional responses to this treatment were generally more subdued and somewhat ephemeral in comparison with those to High N. Calculation of base cation/metallic element molar ratios revealed that the organic matter treatment had the highest Ca/Al, Ca/Mn, Mg/Al, Mg/Mn, K/Al, K/Mn, and K/Cu during the initial season, but exerted little influence on these ratios thereafter. The High N treatments produced the highest Ca/Cu and Mg/Cu in the first season, the highest Ca/Al, Mg/Al, K/Al, and K/Mn in the second, and the highest Ca/Al, Mg/Al, Mg/Mn, K/Al, and K/Mn in the third season, with the high application rate especially prominent. Seedling nutrition was, at best, minimally affected by liming, with perhaps its most notable influence that of counteracting the positive responses indicated above with regard to the organic amendment effects on molar ratios. Overall, these results indicate that in the reforestation of difficult sites such as eastern Sierra Nevada surface mines, the favorable responses to controlled release fertilization can not be duplicated using composted organic amendments, and furthermore, dolomitic lime applications by the method used here are likely to prove exceedingly detrimental to seedling establishment.     

The potential of alley cropping im improvement of cultivation systems in the high rainfall areas of Zambia II. Maize production

Theee trials to evaluat the potential of alley cropping in maize production on the low fertility, acidic soils in Northern Zambia are described. Leucaena leucocephala, Gliricidia sepium, Sesbania sesban, Albizia falcataria, Fleminga congesta, and Cassia spectabilis, were grown in alley crops with hybrid maize and soybean. All trials received recommended rates of P and K fertiliser; N fertiliser was applied at three rates as a subplot treatment. One trial received lime before establishment.Only in the limed trial was there a significant improvement in maize yields through alley cropping; when no N fertiliser was applied, incorporation of Leucaena leucocephala prunings resulted in an increase of up to 95% in yields, with a smaller improvement being produced by Flemingia congesta. There was a significant correlation between the quantity of prunings biomass applied and the proportional increase in maize yields over the control treatment. It is suggested that the lack of effect of most of the tree species on crop yields was due to low biomass production.An economic analysis showed that alley cropping with limed Leucaena was only profitable when fertiliser costs were high in relation to maize prices. However, lime is both expensive and difficult to obtain and transport for most small scale farmers in the region, and is therefore not a practical recommendation. It is suggested that future alley cropping research should focus on screening a wider range of tree species, including other species of Leucaena, for acid tolerance and higher biomass production.     

西南桦和尾巨桉凋落叶分解及其与土壤性质的相关性

[目的]探讨南亚热带西南桦和尾巨桉人工纯林的凋落叶分解动态及其与土壤化学性质之间的相关关系.[方法]采用原位分解袋法研究凋落叶的分解过程.[结果]表明:西南桦、尾巨桉人工林凋落叶分解系数分别为0.96 a^-1和0.88 a^-1.在为期12个月的分解试验中,2种凋落叶有机C含量在整个分解过程中呈逐渐下降趋势;全K含量和C/N比在分解前期迅速下降,之后趋于平缓;全N含量和全P含量在整个分解过程中呈逐渐上升趋势;2种凋落叶N/P比则呈先升高后下降的趋势.无论是分解前期还是分解后期,凋落叶质量损失与N含量均呈显著正相关(前期R=0.877;后期R=0.855),与C/N均呈显著负相关(前期R=-0.735;后期R=-0.697).与尾巨桉林地土壤性质相比,西南桦凋落叶分解提高了林地0~10、10~20 cm土壤的有机C、全N、全P、全K、N/P,对2030 cm土壤有机C、全K、pH值、C/N、N/P则未产生显著影响.相关分析表明:凋落叶初始有机C含量与土壤有机C、全N、全P、全K、N/P显著相关;凋落叶初始全N含量与土壤全N、pH值、C/N显著相关.[结论]凋落叶的养分含量与土壤养分的关系紧密;与尾巨桉相比,西南桦凋落叶的养分含量明显较高,分解速率更快,释放到土壤中的养分也更多.     

Aboveground nutrient components of Eucalyptus camaldulensis and E. grandis in semiarid Brazil under the nature and the mycorrhizal inoculation conditions

A study was conducted to evaluate the aboveground biomass, nutrient content and the percentages of mycorrhizal colonization in Eucalyptus camaldulensis and Eucalyptus grandis plantations in the semiarid region (15° 09′ S 43° 49′ W) in the north of the State of Minas Gerais in Brazil. Results show that the total above-ground biomass (dry matter) was 33.6 Mg·ha⁻¹ for E. camaldulensis and 53.1 Mg·ha⁻¹ for E. grandis. The biomass of the stem wood, leaves, branches, and stem bark for E. camaldulensis accounted for 64.4%, 19.6%, 15.4%, and 0.6% of the total biomass, respectively (Table 2); meanwhile a similar partition of the total above-ground biomass was also found for E. grandis. The dry matter of leaves and branches of E. camaldulensis accounted for 35% of total biomass, and the contents of N, P, K, Ca, Mg, and S in leaves and branches accounted for 15.5%, 0.7%, 12.3%, 22.6%, 1.9%, and 1.4% of those in total above-ground biomass, respectively. In the trunk (bark and wood), nutrient accumulation in general was lower. Nutrient content of E. grandis presented little variation compared with that of E. camaldulensis. Wood localized in superior parts of trunk presented a higher concentration of P and bark contained significant amounts of nutrients, especially in E. grandis. This indicated that leaving vegetal waste is of importance on the site in reducing the loss of tree productivity in this semi-arid region. The two species showed mycotrophy.     

不同种植年限尾巨桉人工林叶片-凋落物-土壤碳氮磷化学计量特征

[目的]为了解雷州半岛尾巨桉速生人工林生态系统的C、N、P分配格局及化学计量特征。[方法]采用空间换时间的方法,选取雷州半岛4种不同林龄(1、3、5、7 a)的尾巨桉人工林为研究对象,对尾巨桉叶片、凋落物及土壤的C、N、P含量及化学计量特征进行测定分析。[结果]表明:C、N含量表现为叶片凋落物土壤,P含量表现为叶片土壤凋落物,且3个库间差异显著;土壤的C含量随林龄增加而增加,N、P含量差异不显著,土壤C∶N随林龄的增加而增加,说明土壤有机质分解速率逐渐下降;凋落物的C∶N为54. 07 92. 18 ( 25),表明尾巨桉林下凋落物分解速率较慢,N元素成为主要限制凋落物分解的元素,凋落物的C∶N随林龄的增加先增加后下降,凋落物分解速度先降低后升高;叶片的N∶P为10. 80 12. 98,说明中幼林龄尾巨桉受N限制较明显。相关性分析表明:凋落物养分元素含量受叶片限制,土壤养分含量受凋落物限制,表明生态系统内部C、N、P元素在植物、凋落物与土壤之间实现了运输和转换。[结论]雷州半岛尾巨桉中、幼林龄时期土壤有机质及凋落物分解速率较慢;随林龄的增加,土壤有机质、凋落物分解速率下降,N元素成为其主要分解限制性元素,林分生长受N限制明显。     

Efforts Toward Improving Maize Yields on Smallholder Farms in Uasin Gishu County,Kenya, through Site-specific,Soil-testing-based Fertiliser Recommendations: A Transdisciplinary Approach

This study evaluated the effects of site-specific, soil-testing-based fertiliser recommendations on maize yields using the transdisciplinary (TD) process. The TD process utilizes knowledge from science and practice. Farmers, extension officers, local financial institutions, and other practitioners collaborated with local scientists from the University of Eldoret in the process of financing, purchasing, and applying fertilisers in adequate amounts and composition. A total of 144 farmers participated in the study, which lasted for two seasons. The data sampling was based on a randomized 2?×?3?×?4?×?2 factorial complete block design, including the following factors: TD (non-participation vs participation in the TD process); ST (soil testing in the following categories: fertiliser application with no soil testing, fertiliser application following government recommendations, and application of site-specific, soil-testing-based fertiliser recommendations), and location (Kapyemit, Kipsomba, Ng’enyilel, and Ziwa). The “no soil testing” (ST₁) category refers to farmers’ own practices at an average fertilisation of about 60?kg?N?ha^?1 and 15?kg?P?ha^?1. The government recommendation (ST₂) calls for 75?kg?N?ha^?1, 25?kg?P?ha^?1, and 6?t?ha^?1 manure, and site-specific fertiliser recommendations (ST₃) were based on actual soil-testing results; generally, this resulted in the recommendation of 90?kg?N?ha^?1, 30?kg?P?ha^?1, 25 kg K ha^?1, 2?t?ha^?1 lime, and 1?t?ha^?1 manure. Highly significant effects were seen where farmers participated in the TD process (TD) for soil testing (ST). The farmers’ yields in Uasin Gishu County of 4.5?t?ha^?1 increased by approximately 1.5?t?ha^?1 based on site-specific, soil-testing fertilisation recommendations and by approximately 1.0?t?ha^?1 based on participation in the transdisciplinary process. However, as indicated by a significant interaction of the variables ST and TD—and while there is a significant main effect of participating in a TD process—the latter increase occurs only if site-specific, soil-testing-based recommendations can be used in the transdisciplinary process with farmers.     

巨桉(Eucalyptus grandis)植被和其相邻的山地雨林中土壤营养的评价

A study was conducted to evaluate the status of soil nutrients under E. grandis plantation in comparison with that in its adjacent submontane rain forest. Twenty sequare plots, with an area of 20 m×20 m for each, were established in both of E. grandis plantation and its adjacent sub-montane rain forest, independently. Soil samples were collected from each square plot, at five points (at the four corners and at the center) of each plot. The collected soil samples were mixed to make a composite and representative sample for each plot, independently. The analyses were done in a soil laboratory following appropriate methods. The analysis result indicated that there were no significance differences between E. grandis plantation and its adjacent sub-montane rain forest in the level of major soil nutrients (total N, available P, exchangeable K, Ca and Mg), pH and total carbon of soils (p < 0.05). There were significance differences between two sites of forest soils in percentage of clay particles, and exchangeable Na content. E. grandis plantation was found improving soil nutrients and total carbon as compared with that of its adjacent submontane rain forest.     

Mixed-species plantations of Acacia mangium and Eucalyptus grandis in Brazil: 2: Nitrogen accumulation in the stands and biological N2 fixation

The sustainability of plantation forests is closely dependent on soil nitrogen availability in short-rotation forests established on low-fertility soils. Planting an understorey of nitrogen-fixing trees might be an attractive option for maintaining the N fertility of soils. The development of mono-specific stands of Acacia mangium (100A:0E) and Eucalyptus grandis (0A:100E) was compared with mixed-species plantations, where A. mangium was planted in a mixture at a density of 50% of that of E. grandis (50A:100E). N₂ fixation by A. mangium was quantified in 100A:0E and 50A:100E at age 18 and 30 months by the ¹⁵N natural abundance method and in 50A:100E at age 30 months by the ¹⁵N dilution method. The consistency of results obtained by isotopic methods was checked against observations of nodulation, Specific Acetylene Reduction Activity (SARA), as well as the dynamics of N accumulation within both species. The different tree components (leaves, branches, stems, stumps, coarse roots, medium-sized roots and fine roots) were sampled on 5–10 trees per species for each age. Litter fall was assessed up to 30 months after planting and used to estimate fine root mortality. Higher N concentrations in A. mangium tree components than in E. grandis might be a result of N₂ fixation. However, no evidence of N transfer from A. mangium to E. grandis was found. SARA values were not significantly different in 100A:0E and 50A:100E but the biomass of nodules was 20–30 times higher in 100A:0E than in 50A:100E. At age 18 months, higher δ¹⁵N values found in A. mangium tree components than in E. grandis components prevented reliable estimations of the percentage of N derived from atmospheric fixation (%Ndfa). At age 30 months, %Ndfa estimated by natural abundance and by ¹⁵N dilution amounted to 10–20 and 60%, respectively. The amount of N derived from N₂ fixation in the standing biomass was estimated at 62 kg N ha⁻¹ in 100A:0E and 3 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 16 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The total amount of atmospheric N₂ fixed since planting (including fine root mortality and litter fall) was estimated at 66 kg N ha⁻¹ in 100A:0E and 7 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 31 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The most reliable estimation of N₂ fixation was likely to be achieved using the ¹⁵N dilution method and sampling the whole plant.     

An evaluation of the conical approximation as a generic model for estimating stem volume, biomass and nutrient content in young Eucalyptus plantations

Accurately and non-destructively quantifying the volume, mass or nutrient content of tree components is fundamental for assessing the impact of site, treatment, and climate on biomass, carbon sequestration, and nutrient uptake of a growing plantation. Typically, this has involved the application of allometric equations utilising diameter and height, but for accurate results, these equations are often specific to species, site, and silvicultural treatment. In this study, we assessed the value of incorporating a third piece of information: the height of diameter measurement. We derived a more general volume equation, based on the conical approximation, using a diameter projected to the base of the tree. Common equations were developed which allowed an accurate estimate of stem volume, dry weight and nutrient content across two key plantation grown eucalypt species, Eucalyptus grandis W. Hill ex Maiden and Eucalyptus globulus (Labill.). The conical model was developed with plantation-grown E. grandis trees ranging from 0.28 to 15.85 m in height (1.05 g to 80.3 kg stem wood dry weight), and E. globulus trees ranging from 0.10 to 34.4 m in height (stem wood dry weight from 0.48 g to 652 kg), grown under a range of contrasting cultural treatments, including spacing (E. grandis), site (E. globulus) and fertilization (nitrogen and phosphorus) for both species. With log transformed data the conical function (V_con) was closely related to stem sectional volume over bark and stem weight (R² = 0.996 and 0.990, respectively) for both E. grandis and E. globulus, and the same regressions can be applied to both species. Back transformed data compared with the original data yielded modelling efficiencies of 0.99 and 0.97, respectively. Relationships between V_con and bark dry weight differed for the two species, reflecting differing bark characteristics. Young trees with juvenile foliage had a different form of relationship to older trees with intermediate or adult foliage, the change of slope corresponding to heights about 1.5 m for E. grandis and age 1 year for E. globulus. The V_con model proved to be robust, and unlike conventional models, does not need additional parameters for estimating biomass under different cultural treatments. More than 99% of the statistical variance of the logarithm of biomass was accounted for in the model. V_con captures most of the change in stem taper associated with cultural treatments and some of the change in stem form that occurs after the crown base has lifted appreciably. Fertilization increased N and P concentrations in stem wood and bark, and regressions to estimate N and P contents (the products of biomass and concentration) were dependent on treatment. For instance, there was a large growth response to N fertilization in E. globulus corresponding with a change (P < 0.05) in the intercept of the regression to estimate N content.     

Phosphorus,nitrogen and potassium nutrition on Calonectria leaf blight in eucalypt plants

Calonectria pteridis causes Calonectria leaf blight (CLB), and consequently severe defoliation in eucalypt plantations, which results in losses in wood volume. To reduce the negative impacts of this disease in eucalypt, this study aimed to assess the application of different doses and combinations of the macronutrients N, P and K on the percentage of symptomatic leaf area (SLA) and defoliation induced by the pathogen. Cuttings of a clone of Eucalyptus grandis were transplanted to pots containing soil that received different dose combinations of N, P and K, according to an incomplete factorial design. At 200 days after transplanting, leaf samples were analysed for N, P and K contents, and then, the plants were inoculated. Forty‐five days post‐inoculation, SLA and percentage of defoliation were quantified. Potassium doses above 75 mg/dm³ of soil significantly reduced SLA and defoliation. The influence of N and P on defoliation was dependent on K doses, but both reduced symptomatic leaf area. The best control of the disease, expressed by decreased defoliation and symptomatic leaf area, was achieved with leaf content of N, P and K of 9.8, 0.8 and 10.4 g per kg leaf, respectively, obtained with doses of 55, 82.5 and 143 mg/dm³of soil, respectively. Therefore, N, P and K nutrition can be a component of an integrated management programme for the control of CLB in eucalypts.     

Physiological and NPK Studies for Developing Agrotechniques for SRHD Energy Plantations in the North-Western Himalayas

The study was undertaken to develop agrotechniques for raising short-rotation, high-density (SRHD) energy plantations as a renewable energy source by using planting densities of 10,000 and 14,000 plants/ha. Under Species × Spacing × Fertilizers (N:P:K), the effect of fertilizers was more evident on plant height than on stem diameter. The species as Grevillea robusta, Bauhinia variegata, and Eucalyptus showed the most statistically significant vertical and radial growth in both of the spacings. The N:P:K::50:25:25 kg/ha produced statistically significant growth. The photosynthesis rate, as recorded, showed that Salix tetrasperma had high rates of CO₂ assimilation but poor aerial growth.

The photosynthetic rate under varying fertilizer treatments remained unchanged, but the biomass improved significantly. In G. robusta, excellent aerial growth was observed despite a low rate of photosynthesis (even at low water potential). The dry weight of Eucalyptus was recorded (60 and 233 t/ha; spacing 1 m × 1 m and 1 m × 0.71 m) after 3 yr. After 10 yr, the highest dry weight was recorded again in Eucalyptus at 1,471.44 t/ha. The lowest moisture content (36–38%) was recorded in Morus alba, while the highest moisture content was recorded in Eucalyptus (66–70%). In all tested species, G. robusta (26%) showed the maximum calorific value.     

A comparative assessment on regeneration status of indigenous woody plants in Eucalyptus grandis plantation and adjacent natural forest

Diversity, density and species composition of naturally regenerated woody plants under Eucalyptus grandis plantation and the adjacent natural forest were investigated and compared. Twenty plots, with an area of 20 m × 20 m for each, were established in both of E. grandis plantation and adjacent natural forest, independently. In each plot, species name, abundance, diameter and height were recorded. Numbers of seedling were collected in five sub-plots (4 m²) within each major plot. A total of 46 species in the plantation, and 52 species in the natural forest, which belongs to 36 families were recorded. The diversity of species (H′) is 2.19 in the plantation and 2.74 in the natural forest. The density of understory woody plant was 3842 stems/ha in the plantation and 4122 stems/ha in the natural forest. The densities of seedlings in the natural forest and the plantation were 8101 stems/ha and 4151 stems/ha, respectively. High similarity of woody species composition was found between the natural forest and the plantation. The E. grandis plantation was found favoring the regeneration and growth of Millitia ferruginia and Coffea arabica in a much better way than other underneath woody species.     

Responses of Acer saccharum canopy trees and saplings to P, K and lime additions under high N deposition

Heavy atmospheric nitrogen (N) deposition has been associated with altered nutrient cycling, and even N saturation, in forest ecosystems previously thought to be N-limited. This observation has prompted application to such forests of non-N mineral nutrients as a mitigation measure. We examined leaf gas-exchange, leaf chemistry and leaf and shoot morphological responses of Acer saccharum Marsh. saplings and mature trees to experimental additions of non-nitrogenous mineral nutrients (dolomitic lime, phosphorus + potassium (P + K) and lime plus P + K) over 2 years in the Haliburton region of central Ontario, which receives some of the largest annual N inputs in North America. Nutrients were adsorbed in the mineral soil and taken up by A. saccharum trees within 1 year of fertilizer application; however, contrary to expectation, liming had no effect on soil P availability. Saplings and canopy trees showed significant responses to both P + K fertilization and liming, including increased foliar nutrient concentration, leaf size and shoot extension growth; however, no treatment effects on leaf gas-exchange parameters were detected. Increases in shoot extension preceded increases in diameter growth in saplings and canopy trees. Vector analysis of shoot extension growth and nutrient content was consistent with sufficiency of N but marked limitation of P, with co-limitation by calcium (Ca) in saplings and by Ca, Mg and K in canopy trees.     

Effective concentration of phosphite in controlling Phytophthora cinnamomi following stem injection of Banksia species and Eucalyptus marginata

The effect of phosphite concentration on lesion development by Phytophthora cinnamomi in stems and roots of Banksia grandis and Eucalyptus marginata and in stems of Banksia coccinea was assessed during a 4.3 year period after stem injection of phosphite. Lesion length 6 weeks after inoculation was significantly less in roots of B. grandis trees that had been stem injected with three concentrations of phosphite (50, 100 and 200 g phosphite/l) at two rates (1 and 2 ml/cm of stem circumference) compared with the not‐injected control. With the exception of B. grandis trees injected with 50 g phosphite/l, lesion length for the high rate was not significantly different to the low rate. In roots of E. marginata, lesion development in response to phosphite was different to that in roots of B. grandis; lesion length in roots did not differ significantly between phosphite concentration and rate. Lesion length and girdling in stems of B. grandis and E. marginata was significantly less in those injected with phosphite than in not injected stems. One year after injection, callus tissue had contained lesions in stems injected with phosphite. By 4.3 years after injection of both hosts there was a steep significant negative linear relationship between phosphite concentration and either lesion length or girdling, with greatest lesion development in not injected stems and least in stems injected with 100 g phosphite/l. Recovery of P. cinnamomi from lesion margins 1 year after injection, was significantly less in trees injected with phosphite than in not injected trees. The amount of plant death reflected containment of lesion extension and girdling, and reduction of recovery of P. cinnamomi with phosphite concentration; 4.3 year after injection there was a steep significant negative linear relationship between phosphite concentration and percentage of plant death. In contrast to B. grandis and E. marginata, there was a U‐shaped non‐linear relationship between phosphite concentration and effectiveness of phosphite in controlling lesion extension and girdling in B. coccinea. Containment of lesion extension and girdling with time was greatest for B. coccinea stems injected with 25 g phosphite/l, least for stems not injected, and intermediate in stems injected with 50 and 100 g phosphite/l. As in B. grandis and E. marginata, containment of lesion extension and girdling in B. coccinea with phosphite concentration was reflected in the amount of plant death. The non‐linear response to phosphite of some plant species indicated that injected concentration for B. coccinea should not exceed 50 g phosphite/l, whereas injected concentrations of up to 100 g phosphite/l could be recommended for B. grandis. Longevity of action of phosphite for 4–5 years in native plant species after one injection makes phosphite injection a practical control option for the control of P. cinnamomi disease front extension and the protection of threatened flora. Research into the effect of factors affecting longevity of action of phosphite would facilitate optimization of timing of injection.     

Effect of silvicultural treatments on growth,fertility and capsule traits in seedling seed orchards of <Emphasis Type="Italic">Eucalyptus camaldulensis</Emphasis> and <Emphasis Type="Italic">E. tereticornis</Emphasis>

The effects of nutritional treatments and the flowering promoter Paclobutrazol™ on tree growth and fertility were studied in unpedigreed seedling seed orchards (SSOs) of Eucalyptus camaldulensis and E. tereticornis at two locations in southern India. At Pudukkottai, a semi-arid site in Tamil Nadu State, five treatments were applied: (1) untreated control, (2) nitrogen (two doses of urea at 217 g N/tree), (3) nitrogen plus phosphorus (two doses of 312 g single superphosphate), potassium (two doses of 83 g muriate of potash) and trace elements (two doses of 10 g sodium borate and 25 g zinc sulphate), (4) pollarding trees at 4 m height with application of N, P, K and trace elements, (5) drenching with the flowering promoter Paclobutrazol (0.25 ml active ingredient per cm of stem girth) along with N, P, K and trace elements. At Panampalli, a higher-rainfall site in Kerala State, only treatments 1, 2 and 3 were applied. Four replicates of treatment plots sized 18 m × 18 m, with 22–32 trees per plot were set up in each orchard in randomized complete block designs. Untreated plots of E. camaldulensis and E. tereticornis at Pudukkottai displayed 12 and 21% fertile trees, respectively, in the first year of monitoring, while at Panampally the percentage of fertile trees in untreated E. camaldulensis plots was higher at 72%, and that of E. tereticornis similar at 23%. Both species attained greater stem diameter at breast height at age 9 years at the higher-rainfall location but there was no significant impact of fertilizer application on 9-year diameter at either site. Diameter was reduced by pollarding and Paclobutrazol application at Pudukkottai. Only Paclobutrazol produced a significant increase in fertility in both species for four successive years, increasing the percentage of fertile trees to 59 and 71%, respectively, for E. camaldulensis and E. tereticornis 1 year after application. The number of capsules produced per tree also increased significantly with Paclobutrazol application, although the difference was comparatively less by the fourth year. The number of capsules per umbel did not differ significantly between locations, whereas the germination rate varied between treatments although no consistent trends were observed.     

RESENSIES—REVIEWS

Results at harvesting are described of two comprehensive NPK fertilizer experiments with E. grandis on sites previously under wattle in the Natal Midlands. The experimental sites differ considerably in respect of physiography, climate, and soil. The difference in climate and soil are clearly evident from the respective analyses of soil samples from the sites, one soil of a dystrophic series belonging to the Griffin form, and the other a mesotrophic series of the Hutton form.

Except in one instance, nitrogen application showed no significant response, which is expected on these nitrogen-enriched soils of old wattle plantations. There is a tendency, which in one instance was significant, that nitrogen has a depressive effect on E. grandis, but this is ascribed to burning the transplants when the fertilizer is too concentrated and applied too close to the trees.

Superphosphate application on these sites gives highly profitable results, the additional net profit per ha being nearly R400 on the better site and at least R35 on the poorer site. The optimum application rate on the better site is not more than 130 g superphosphate (8,3% P) per tree, while the optimum rate on the poorer site might be as high as 260 g.

Significant responses to potash application are limited to mesotrophic soils and are of a curvilinear nature. This last phenomenon especially is difficult to explain, but is known to have occurred elsewhere.     

Impact of harvest residues,fertilisers and N-fixing plants on growth and nutritional status of young <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> plantations,under Mediterranean conditions

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.     

Water relations of Eucalyptus nitens × Eucalyptus grandis: is there interclonal variation in response to experimentally imposed water stress?

This study tested the hypothesis that water stress increases the hydraulic efficiency of Eucalyptus nitens × E. grandis saplings as a result of osmotic and elastic adjustments. Eucalyptus nitens × E. grandis clones (NH00, NH58, NH69 and NH70) were potted in coarse river sand supplemented with a slow-release fertiliser, drip-irrigated four times daily and exposed to full sunlight for eight months. Thereafter, irrigation was withheld twice for seven consecutive days from half of the saplings of each clone, with a seven-day recovery period (regular irrigation) in-between. Relative soil moisture content did not correlate with stomatal conductance (g_s) at pre-dawn and at midday. Leaves of plants subjected to the water-stress treatment wilted in 7 d, and the reduction in g_s was significant at midday with no significant differences between clones. Stomatal conductance and all traits derived from pressure-volume graphs (e.g. osmotic potential at full turgor) were constant in the control treatment. There were no clear patterns in osmotic and elastic adjustments in both treatments. Root hydraulic conductance was constant between treatments and clones. However, water stress reduced shoot hydraulic conductance and stem hydraulic conductivity with significant interclonal effects. Plant biomass, leaf area and leaf weight ratio were significantly lower in the water-stressed plants, but there were no differences between the clones. In conclusion, the water-stress treatment did not introduce significant differences in stomatal conductance and tissue-water relations of Eucalyptus nitens × E. grandis clones. Interclonal variation in water-stress response was found in shoot hydraulic traits, and clone NH58 may be more suitable for planting across sites prone to moderate water stress.     

云南松不同部位氮、磷、钾储量分配及异速生长研究

为更好进行云南松苗木培育,提升云南松苗木质量,通过对2年生云南松苗木生长性状及不同部位氮（N）、磷（P）、钾（K）储量进行统计以及相关性、异速生长分析,研究云南松氮、磷、钾储量。结果表明,云南松幼苗生长2年后,其地下部位氮、磷、钾分配大小依次为钾储量＞氮储量＞磷储量;氮、磷、钾在土壤中的分配比例为氮储量＞磷储量＞钾储量;地上部位氮、磷、钾储量占单株氮、磷、钾储量的比例为钾储量＞磷储量＞氮储量;磷和钾在地下部位的累积速率大于地上部位的累积速率。以期为云南松苗木培育提供理论参考,为实际生产提供一定理论依据。