Growth Of Radiata Research Articles

Mycocentric fertilisation of ectomycorrhizae-inoculated Pinus radiata during containerised production alters root microbiome and growth outcomes

ABSTRACT During containerised production in forest nurseries, seedlings are often intensively fertilised to maximise seedling survival and growth. However, this practice can inadvertently harm the development of a robust root microbiome needed for plant resilience post-planting. In this controlled study using Pinus radiata, we combined reduced fertilisation and seedling inoculation with a diverse ectomycorrhizal (ECM) community as an alternative to intensive, industry-standard fertilisation. After 9 months, we investigated growth responses and changes to ECM and non-ECM root fungal communities. Reduced fertilisation improved the belowground growth and mycorrhizal root colonisation of inoculated seedlings. Isotopic nutrient tracing determined that, under moderate fertilisation, more photosynthetically fixed carbon was allocated belowground, and root-tip nitrogen (N) accumulation, a proxy for N uptake from the soil, also increased. Fertilisation level resulted in shifts in both ECM and non-ECM fungal community composition and substantial changes in the abundance of certain fungi. This study demonstrates that employing more-mycocentric fertilisation regimes may improve plantation nursery outcomes and that interactions between ECM and non-ECM fungi within inocula should be considered when studying the role of the soil microbiome in supporting P. radiata growth during containerised production.

From scraps to sprouts: Boosting Vigna radiata growth with kitchen waste-synthesized iron nanoparticles

The metal nanoparticles (MNPs) are tremendously being used as growth-promoting agents in agricultural crops. One such MNP is iron nanoparticle (FeNP) as iron is an essential growth element for plants. In the current study, a unique method is employed to recycle kitchen waste (KW) and employ it in the synthesis of FeNPs. Further, the growth-promoting activity of these particles was assessed on Vigna radiata (Mung bean). The FeNPs were prepared using KW extract containing crucial phytocompounds as identified using GC-MS analysis. The synthesized KW-FeNPs were ellipsoidal/spherical in shape (150–185 nm) and had -6.14 mV Z-potential. Nano-priming of the seeds at varying concentrations of FeNPs (50–150 ppm) was done before germination of the seeds along with spraying of FeNPs throughout the growth period of the plantlets. In vitro and in vivo growth parameters were evaluated after the 10th and 21st day respectively. The seedlings sprayed with 150 ppm KW-FeNPs showed a highly significant increase in SL (21.63 ± 2.66 cm), RL (7.21 ± 2.11), and seedling length (28.85 ± 2.41) when compared to the control. The lower values of the S/R ratio (3.40–4.49) and increased number of lateral roots were seen in seedlings treated with Kw-FeNPs. A significant (13.02 ± 0.12 mg/g of leaves) and highly significant (17.01 ± 0.82 mg/g of leaves) increase in chlorophyll content was observed in 100 and 150 ppm KW-FeNPs treated plantlets respectively. The synthesized NPs were able to stimulate seedling and plantlet growth even at lower concentrations. A dose-dependent increase in all the plant growth parameters was observed till 150 ppm KW-FeNPs treatment without any visible sign of oxidative stress. The present research work has successfully utilized kitchen waste in the synthesis of a metal-based nanofertilizer for sustainable agricultural practice.

Microbial Decolorization of Crystal Violet Dye by a Native Multi-Metal Tolerant <i>Aeromonas caviae</i> MT-1 Isolate from Dye-Contaminated Soil: Optimization and Phytotoxicity Study

In the recent past, one of the main environmental issues is the contamination of textile dye wastes. The toxicity of dyes poses adverse effects on the flora and fauna of the ecosystem. The present study aimed to isolate bacteria that decolourize crystal violet dye, optimization of various environmental factors for effective decolourization, and phytotoxicity analysis. Out of 13 isolated bacteria, a single isolate was able to grow at 250 mg/L crystal violet dye concentration in a synthetic medium and identified as Aeromonas caviae MT-1 strain (accession number; LC720408) using morphological, biochemical and molecular analyses. Presumably, this is the first report of crystal violet dye decolourization by a native Aeromonas caviae isolate. In this study, after a 72-hour incubation period, a maximum of 98.0% dye decolourization was observed at neutral pH and 35°C with 5% v/v bacterial culture under static culture conditions. Dye decolourization was inhibited to a significant degree by the rising of its concentration. UV-Vis spectra analysis of samples before and after decolourization showed the possible degradation of crystal violet dye by A. caviae. The strain MT-1 was also tolerant to toxic heavy metals like arsenic, lead, and chromium. Phytotoxicity tests revealed that decolourized dye products inhibited Vigna radiata growth less than the un-decolourized dye solution. The findings revealed that a native multi-metal tolerant A. caviae MT-1 isolate could decolourize crystal violet dye rapidly, and possibly have the ability for extensive treatment of dyecontaminated waste.

Reduced growth of Pinus radiata in the presence of the Australian native Allocasuarina nana via direct allelopathy and inhibition of the pine-supporting mycorrhizal community

The establishment and productivity of new forest plantations can be significantly impacted by the presence of native vegetation. In a study site in New South Wales, Australia, the growth of a Pinus radiata plantation has been virtually halted in areas dominated by the native shrub Allocasuarina nana, effects that persist for decades even after its physical removal. To determine the mechanism by which A. nana impedes P. radiata growth, we compared the fungal soil community and metabolomic profile of soils in patches rich in A. nana with adjacent healthy P. radiata patches and the transition zone between them. This data was complemented by a pot experiment to assess P. radiata growth in soils from the different vegetation areas with and without a viable soil community or the addition of A. nana roots or exudates. Together, the data demonstrates that these A. nana soils are likely inhibitory to P. radiata growth through a dual mechanism: impacting the growth of the pine directly through root associated metabolites and indirectly through the inhibition of the fungal community supporting P. radiata health, including ectomycorrhizal fungi.

Plant growth promoting activities and effect of fermented panchagavya isolate Klebsiella sp. PG-64 on Vigna radiata.

A natural bacterial isolate from fermented panchagavya named as PG-64, exhibits multiple plant growth-promoting traits. This Gram-negative bacteria was identified as Klebsiella sp. PG-64 by 16S rRNA gene sequencing. The Klebsiella sp. PG-64 has shown production of indole acetic acid (106.0µg/ml), gibberellic acid (20.0µg/ml), ammonia (7.12µmol/ml), exopolysaccharide (2.04% w/v) and phosphate solubilization (106.0µg/ml). It produced 437µg/ml IAA with 0.75% (w/v) L-tryptophan supplementation and was increased to 575µg/ml in a laboratory-scale fermenter. The PG-64 has shown tolerance to abiotic stress conditions like pH (5.0-12.0), temperature (28-46°C), salt (0.5-10.0% w/v NaCl) and osmotic resistance (1-10% w/v PEG-6000). The PG-64 also produced 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (0.3ng α-ketobutyrate/mg protein/h) indicating its potential for drought tolerance. Owing to its diverse properties, the effect of Klebsiella sp. PG-64 on Vigna radiata (Mung bean) was examined. The seeds treated with PG-64 culture showed 92% germination with a good seedling vigour index (202). In the pot study, Vigna radiata growth showed 2.23, 1.55, 2.00, 1.65, 1.73, 1.88, 5.00, 5.00, 1.57 times increase in primary root length, dry root weight, root hair numbers, leaf width, leaf numbers, leaf area, fruits number, flower number and chlorophyll content, respectively after 75days. The application of Klebsiella sp. PG-64 culture resulted in substantial growth enhancement of Vigna radiata. The Klebsiella sp. PG-64 has multiple plant growth-promoting properties along with capabilities to tolerate abiotic stresses, making it a promising liquid biofertilizer contender for various crops.

Alleviation of Cr(VI) Toxicity and Improve Phytostabilization Potential of Vigna radiata Using a Novel Cr(VI) Reducing Multi-Stress-Tolerant Plant Growth Promoting Rhizobacterial Strain Bacillus flexus M2

Chromium (Cr) is a toxic heavy metal discharged into the environment through various anthropogenic sources, which affects soil properties and fertility. Hence, an effective soil restoration strategy is the need of the hour. In this study, a potent Cr(VI)-reducing strain M2 was isolated from the rhizosphere of Zea mays L. grown in leather industrial effluent contaminated sites and identified as Bacillus flexus through 16S rDNA sequencing. Strain M2 exhibited strong tolerance to multi-stresses such as temperature (up to 45 °C), pH (up to 9.0), Sodium chloride (NaCl) (up to 7%) and PEG 6000 (up to 50%) and showed strong Cr(VI) reduction with the presence of multi-stresses. The interaction of Cr(VI) with strain M2 was elucidated through various instrumentation analyses. Fourier Transform Infra-red (FTIR) Spectroscopy analysis confirmed that Cr(VI) exposures induce significant changes in the cell-surface functional groups. Raman spectrum and Transmission Electron Microscopy–Energy Dispersive X-ray spectroscopy (TEM-EDX) analysis confirmed the bio-reduction of Cr(VI) to Cr(III) and their intracellular localization as Cr(III). Further, strain M2 produced a significant quantity of Indole acetic acid (IAA), ammonia, and exopolysaccharide (EPS) and showed positive results for various plant-growth-promoting activities with the presence of Cr(VI). In greenhouse experiments, the strain M2 inoculation progressively increased the plant growth parameters and stabilized the antioxidant system of Vigna radiata under Cr stress. However, Cr(VI) exposure decreased the growth parameters and increased the level of proline content, Hydrogen peroxide (H2O2) accumulation, and antioxidant enzymes expression in V. radiata. Interestingly, strain M2 inoculation significantly reduced the accumulation of Cr in root and shoot of V. radiata when compared to the uninoculated Cr(VI) treatment. Hence, this study confirms that rhizobacterial inoculation markedly reduced the negative impact of Cr toxicity and improved V. radiata growth even in harsh environments by stabilizing the mobility of Cr in the rhizosphere.

Nitrogen isotope enrichment predicts growth response of Pinus radiata in New Zealand to nitrogen fertiliser addition

The fertiliser growth response of planted forests can vary due to differences in site-specific factors like climate and soil fertility. We identified when forest stands responded to a standard, single application of nitrogen (N) fertiliser and employed a machine learning random forest model to test the use of natural abundance stable isotopic N (δ15N) to predict site response. Pinus radiata growth response was calculated as the change in periodic annual increment of basal area (PAI BA) from replicated control and treatment (~ 200 kg N ha−1) plots within trials across New Zealand. Variables in the analysis were climate, silviculture, soil, and foliage chemical properties, including natural abundance δ15N values as integrators of historical patterns in N cycling. Our Random Forest model explained 78% of the variation in growth with tree age and the δ15N enrichment factor (δ15Nfoliage − δ15Nsoil) showing more than 50% relative importance to the model. Tree growth rates generally decreased with more negative δ15N enrichment factors. Growth response to N fertiliser was highly variable. If a response was going to occur, it was most likely within 1–3 years after fertiliser addition. The Random Forest model predicts that younger stands (< 15 years old) with the freedom to grow and sites with more negative δ15N isotopic enrichment factors will exhibit the biggest growth response to N fertiliser. Supporting the challenge of forest nutrient management, these findings provide a novel decision-support tool to guide the intensification of nutrient additions.

Flexible Bi2MoO6/N-doped carbon nanofiber membrane enables tetracycline photocatalysis for environmentally safe growth of Vigna radiata

Photocatalysis technology has attracted great attention in the field of wastewater purification for plantation purposes. In the present work, we report the preparation, characterization, and application of flexible γ/γ′ -Bi2MoO6/N-doped carbon (Bi2MoO6/N-C) nanofiber membranes in tetracycline (TC) treatment and Vigna radiata growth. The phytotoxicity of degraded intermediates in treated water was evaluated for seed germination and growth of Vigna radiata. The as-prepared flexible Bi2MoO6/N-C homojunction nanofiber membrane, composed of subunits of γ-Bi2MoO6 nanoparticles and γ′ -Bi2MoO6 nanorods, showed strong visible-light harvesting capability, and good photogenerated electron-hole separation, which displayed the better photocatalytic efficacy in the TC treatment, in terms of degradation rate (97%, 60 min), and recyclability (4 cycles). Further, the germination and growth of Vigna radiata seeds were used to check the phytotoxicity level of the photocatalyst itself (0–10,000 mg/L), the treated and untreated TC solution. Phytotoxicity studies were undertaken via growing Vigna radiata in this Bi2MoO6/N-C photocatalyst solution and treated TC solution. The results demonstrated that Vigna radiata thrived in photocatalyst solution even at a high concentration of 10,000 mg/L and TC solution treated by the photocatalyst. Our work could afford an effective multifunctional photocatalyst for improving water quality for irrigation and plantation purposes.

Role of plant growth-promoting rhizobacterial consortium in improving the Vigna radiata growth and alleviation of aluminum and drought stresses.

Aluminum (Al) is a major constraint for plant growth by inducing inhibition of root elongation in acid soils around the world. Besides, drought is another major abiotic stress that adversely affects growth and productivity of agricultural crops. The plant growth-promoting (PGP) rhizobacterial strains are useful choice to decrease these stressful effects and is now extensively in practice. However, the use of bacterial inoculation has not been attempted for the mitigation of Al stress in plants growing at high Al levels under drought stress. Therefore, in the present study, Al- and drought-tolerant bacterial strains were isolated from Lactuca sativa and Beta vulgaris rhizospheric soils. Among the bacterial isolates, two strains, CAM12 and CAH6, were selected based on their ability to tolerate high levels of Al (8 mM) and drought (15% PEG-6000, w/v) stresses. The bacterial strains CAM12 and CAH6 were identified as Bacillus megaterium and Pantoea agglomerans, respectively, by 16S rRNA gene sequence homology. Moreover, both strains showed multiple PGP traits even in the presence of abiotic stresses. In the pot experiments, inoculation of the strains CAM12 and CAH6 as individually or as included in a consortium improved the Vigna radiata growth under abiotic stress conditions and reduced Al uptake in plants. However, the most effective treatment was seen with bacterial consortium that allowed the plants to tolerate abiotic stress effectively and achieved better growth. These results indicate that bacterial consortium could be used as a bio-inoculant for enhancing V. radiata growth in soil with high Al levels subjected to drought conditions.

Edaphic properties related with changes in diversity and composition of fungal communities associated with Pinus radiata

Effective symbiosis with ectomycorrhizal (ECM) fungi is important for the successful growth and establishment of Pinus radiata. However, the structure of ECM communities varies across soil (edaphic) and environmental conditions, and thus affects the potential range of symbiotic associations. To improve our understanding of these factors, we characterised the range of ECM fungi present across six sites varying in edaphic properties. We also assessed ECM fungi in root tips of P. radiata planted two years earlier at these sites to assess the extent in overlap between root and soil ECM communities. The structure of the ECM community varied substantially with site. Across all sites, correlations were identified between soil pH and metrics describing ECM community structure in both soil and root samples, indicating soil pH was contributing to the differences in the fungal communities between sites. Mineralisable nitrogen, soil carbon, and phosphorus content also varied with site, but were not significantly related to descriptors of the ECM communities. Root tips and surrounding soils shared some taxa but were inhabited by diverse communities of fungi, and a number of ECM P. radiata associations unique to New Zealand were identified. It is possible that the establishment of linkages between metrics could provide an opportunity to begin predicting the response of ECM populations to site modification, and potentially increase the growth of radiata pine and improve forest health through enhanced resilience to disturbance.

Efficiency of the formulated plant-growth promoting Pseudomonas fluorescens MC46 inoculant on triclocarban treatment in soil and its effect on Vigna radiata growth and soil enzyme activities

For bioaugmentation-based treatment of triclocarban (TCC), an emerging soil pollutant that is recalcitrant to biodegradation and phytotransformation, efficient TCC-degrading bacteria with an effective soil-delivering means are required. This work developed the formulated bacterial inoculant, and successfully demonstrated its TCC removal and detoxification performance in pot soil experiment with Vigna radiata plants. The soil bacterium Pseudomonas fluorescens MC46 was isolated as TCC-degrading, plant-growth promoting bacterium. The characterizations were conducted in vitro revealing that it could utilize TCC as a sole carbon source, and at a wide and higher concentration range from 1.6–31.6mgkg−1 than those previously reported, while the detoxification was assessed by cytogenotoxicity and phytotoxicity tests. The developed sawdust-based inoculant formula combined with molasses (5% w/w), and either PEG or CMC-starch blend (1% w/w) could maintain a 20-week shelf-life inoculant stability in terms of cell viability, and TCC-degrading activity. Bioaugmentation of the formulated inoculants into TCC-contaminated soil efficiently removed TCC up to 74–76% of the initial concentration, mitigated toxicity, restored plant growth and health, and enhanced soil enzyme activities. This work is the first to demonstrate potential application of the formulated plant-growth promoting bacterial inoculant for the treatment and detoxification of a persistent TCC contaminated in soil.

Vigna radiata var. GM4 Plant Growth Enhancement and Root Colonization by a Multi-Metal-Resistant Plant Growth-Promoting Bacterium Enterobacter sp. C1D in Cr(VI)-Amended Soils

Contamination of agricultural soils by heavy metals has become a major concern due to their toxic effects on plant growth, symbiosis and consequently the yields of crops. In the present study, to enhance plant growth in Cr(VI)-amended soils, novel metal-resistant plant growth-promoting bacteria (PGPB) were isolated from a soil contaminated with industrial waste effluent. One of the bacterial isolates, identified as Enterobacter sp. C1D by 16S rRNA gene sequencing, was found to be multi-metal resistant in nature with excellent plant growth-promoting (PGP) traits. Mung bean (Vigna radiata var. GM4) inoculation with Enterobacter sp. C1D significantly (P < 0.01) increased root and shoot length, shoot and root weight, and chlorophyll content in a range of Cr(VI) treatments. Plant tolerance towards Cr(VI) measured as effective concentration showed higher values with Enterobacter sp. C1D-treated plants compared to un-inoculated plants. Root colonization study was also carried out using green fluorescence protein-labeled Enterobacter sp. C1D under a hydroponic system. Confocal laser scanning microscopy of the plant roots showed heavy bacterial loads on the surface of the plant root specifically at the root tip and the point of root hair/lateral root formation. The results of PGP traits showed that elevated indole acetic acid levels and 1-aminocyclopropane-1-carboxylate deaminase activity enabled Enterobacter sp. C1D to enhance V. radiata growth in Cr(VI)-amended soils, whereby it significantly increased plant tolerance towards elevated Cr(VI) concentrations.

Redox biotransformation of arsenic along with plant growth promotion by multi-metal resistance Pseudomonas sp. MX6

Remediation of toxic metal-polluted sites by microorganisms is an environment-friendly remediation technique. Multi-metal-resistant bacteria were isolated from a wastewater treatment plant showing resistance against As(III), As(V), Cr, Co, Cu, Cd, Hg, Ni, Pb, Se and Zn. Maximum resistance against all metals was shown by the bacterial isolate MX-6 (As 20mM, Cd 30mM, Cr 5.0mM, Co 25mM, Cu 25mM, Ni 20mM, Zn 30mM, Pb 15mM, Se 20mM and Hg 2.5mM), which was identified as Pseudomonas sp. through 16S rDNA sequencing. Pseudomonas sp. MX-6 reduced 506μM As(V) and also oxidized 160μM As(III). The genes for As, Cd, Se and Zn resistance in Pseudomonas sp. MX-6 were found to be plasmid borne, as indicated by transformation. Pseudomonas sp. MX-6 produced 49.37μg·mL−1 IAA and was also positive for HCN production and phosphate solubilisation. The bacterial isolate also supported Vigna radiata growth, both in the absence and presence of the aforementioned metals. Such bacteria can be used as biofertilizers to reclaim the polluted lands and to enhance crop production in metal-contaminated soils.

DBH and height show significant correlation with incoming solar radiation: a case study of a radiata pine (Pinus radiata D. Don) plantation in New South Wales, Australia

The aim of this study was to determine whether diameter at breast height (DBH, at 1.3 m) and total height of radiata pine (Pinus radiata D. Don) trees showed any significant relationships with microsite estimates of solar radiation. A total of 77 plots were established in two even-aged stands of radiata in Nundle State Forest, New South Wales, Australia. Within these plots, tree DBH and height measurements were recorded and their relationships with solar radiation evaluated. Airborne light detection and ranging (LiDAR) data were processed to generate a high resolution digital elevation model (DEM), and the DEM was used for calculating the incoming solar radiation. Overall, at both study sites, taller and larger trees were found on areas with lower solar radiation, possibly due to a lower loss in soil moisture. The findings of this study suggest that LiDAR-derived DEM estimates of solar radiation are significantly correlated with DBH and height variation, and therefore suitable for use as a sub-compartment stratification variable as well as for possible inclusion in fine-scale estimates of P. radiata growth and productivity.

Pinus pinaster and Pinus radiata survival, growth and form on 500–800 mm rainfall sites in southern NSW

SummaryPinus radiata (GF27- and Guadalupe-based intraspecific hybrids) and Pinus pinaster were trialled to examine the potential for commercial deployment on three lower-rainfall sites within the 500–800 mm rainfall zone of New South Wales. All three ex-pasture sites were considered to be dry for P. radiata; two lower-elevation sites to the west of Gundagai being more challenging than a high-elevation site near Bombala. Cuttings and seedlings of genetically improved P. pinaster and P. radiata and a Guadalupe × routine cross seedlot of P. radiata were planted at three stockings (625, 1250 and 1850 stems per hectare (sph)) and were assessed for survival, growth (diameter at breast height, height, volume), form (straightness, malformations, branch size, branch angle) and number of commercially acceptable trees per hectare up to age 8 years.Survival in P. pinaster didn’t decline after minor post-establishment mortality and was not affected by stocking or plant type. In contrast, survival in P. radiata continued to decline over time at 1250 and 1850 sph stockings at the two low-rainfall, low-elevation sites. Guadalupe-based seedlings had better survival than GF27 cuttings, but both present a high risk under dryland or drought conditions.Site and stocking affected growth of the two species differently. P. radiata grew larger than P. pinaster at all sites. The combination of survival and growth resulted in site volume production that increased with stocking and site quality for P. pinaster. P. radiata exhibited a similar pattern but with reduced volume production at higher stockings on the high-quality Bombala site due to poor survival.The form and branching of P. pinaster was better than that of P. radiata on all sites except the high-rainfall Oak Range. Form of P. pinaster cuttings was better than of seedlings. Form and branch size were improved by higher stockings and were worse on higher quality sites for both species. However, branch angle was better for P. radiata than for P. pinaster.P. pinaster was reasonably productive on the best performing of the low-rainfall, lower-elevation sites. Given periods of very low rainfall since the establishment of these trials, the productivity of 6–7 m3 ha–1 y–1 at age 8 years at stocking of 1250–1875 suggests that 12–15 m–3 ha–1 y–1 may be possible when mean annual increment (MAI) peaks at a later age. Although P. radiata growth rate was high, the poor survival and form of GF27, and to a lesser extent the Guadalupe cross, suggest it presents a high risk on these sites. Continued monitoring of the sites is therefore suggested. Further work could look at more drought-resistant taxa of P. radiata.

Factors influencing the growth of radiata pine plantations in Chile

We examined environmental factors affecting growth rates of Pinus radiata in Chile. The relationships between annual volume growth and soil, climate, canopy and stand factors were analysed using data from 48 permanent sample plots in P. radiata plantations in central Chile. Water availability (as affected by precipitation, soil water holding capacity and potential evapotranspiration) appeared to be the factor most limiting to leaf area and growth. Maximum growing season temperature also negatively affected growth. Sites with the highest productivities had the lowest annual water deficits. The most productive sites used water and light more efficiently. Growth per unit of potential evapotranspiration ranged from 0.5 to 1.6 kg of wood per m 3 of water and growth per unit of radiation ranged from 0.3 to 0.5 g of wood per MJ of photosynthetically active radiation for low and high productivity sites. The inclusion of simple climatic variables such as maximum temperature and precipitation into Chilean P. radiata growth and yield models should improve their performance.

Response of Pinus radiata D. Don to Boron Fertilization in a Glasshouse Study

Limited information is available on the effect of slow-release boron (B) fertilizer on Pinus radiata growth and physiological properties and soil microbiological activities. A 7-month-long pot experiment was carried out under glasshouse conditions to investigate the response of Pinus radiata to different rates (0.0222, 0.0446, 0.089, and 0.178 mg B g−1 soil), equivalent to 0, 4, 8 16, and 32 kg B ha−1 of ulexite, a slow-release B fertilizer. Hot 0.02 M calcium chloride (CaCl2)–extractable soil B, soil dehydrogenase activity, plant B concentration, growth, and photosynthesis were measured at the time of harvest. The B concentrations in the soil and plant organs (needles, stem, and roots) significantly increased with increasing rates of B fertilizer. The optimum B fertilizer rates of 4–8 kg B ha−1 produced the greatest plant growth and net photosynthetic rate. However, the B rates of 16 and 32 kg B ha−1 significantly reduced net photosynthetic rate, and the rate of 32 kg B ha−1 significantly reduced stem diameter growth when compared to the optimum B rates. Soil dehydrogenase activity, an indicator of soil microbiological activities, was significantly reduced by B application at the rates of 16 and 32 kg ha−1. This study confirms the narrow range between B deficiency and toxicity in a tree crop and stresses the need for selection of the optimum rate of B fertilizer application.

Plantation management induces long-term alterations to bacterial phytohormone production and activity in bulk soil

Phytohormone production and modification by soil bacteria has the potential to influence plant growth and performance. We studied the long term effects of nitrogenous fertilisation and weed control on the concentration of IAA equivalents and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity in bulk soil in a Pinus radiata plantation. IAA equivalent concentrations were increased by weed control and ACC deaminase activity was increased by weed control and fertilisation. Measurements of P. radiata growth were positively correlated with IAA equivalent concentrations. ACC deaminase activity was positively correlated with P. radiata growth only in the absence of fertilisation. These results suggest that plantation management can induce long term effects on soil bacterial phytohormone production and modification, which may influence plant growth.

Land evaluation for forestry: a study of the land requirements for growing Pinus radiata D. Don in the Basque Country, northern Spain

AbstractLand requirements for the growth of Pinus radiata D. Don were studied in 112 plots by comparing site index (SI) values with land characteristics. The SI at the reference age of 20 years ranged from 10.4 to 32.7 m. The growth of Radiata pine increased as soil rootable depth increased, with a mean depth of about 50 cm in plots with an SI higher than 29 m. The results show that soil physical properties had a major influence on growth rates with soils of a loamy texture resulting in higher rates than clay rich soils. Soil nitrogen and phosphorus availability had significant effects on growth on soils developed on non‐volcanic parent material whilst potassium availability was significant in soils on volcanic parent material. There were strong interactions among the land characteristics of each land unit so that the magnitude of the specific effect of a given variable was highly dependent on the values of the others. Results are discussed in relation to land use planning.

A model of the juvenile growth and survival of Pinus radiata D. Don; Adding the effects of initial seedling diameter and plant handling

Initial ground line diameter (GLD) of Pinus radiata D.Don and the care of treesduring transport to the field growing siteaffect subsequent tree growth and survival. Anexisting model of juvenile growth had notincluded these effects, and so a new model wascreated that represented their effects ongrowth, survival and uniformity. The new modelwas built with cohorts defined by each initialGLD class and with quality of tree stockhandling as an extra independent variable,using data from 17 experiments. Weibulldistributions representing the size classesdeveloping within each cohort enabled the modelto represent interchanges in dominance, andadded to the range of questions that could beanswered using the model. Reducing quality ofhandling and reducing initial GLD decreasedgrowth, survival, and crop uniformity. Changesin small GLDs were more important than changesin large ones. The final model represented theeffects of initial ground line diameter, treestock handling (careful, timely plantingcompared to rough, poorly scheduled planting),site quality, and site preparation on growth ofradiata pine in the central North Island of NewZealand in a way that allows managers toevaluate the impacts of seedling grading.