Differences In Soil Nutrient Status Research Articles

Effects of Camellia oleifera clone selection on soil nutrient and microbial community structure

AbstractCamellia oleifera Abel. is an important woody oil plant that could solve the disparity between the supply and demand of edible oil in China. Although numerous excellent clones have been developed and introduced to enhance production, the interactions between high yield clones and soil ecosystem sustainability remains poorly understood. The high‐yielding period of a C. oleifera plant is approximately 100 yr; therefore, appropriate clone selection is crucial. We evaluated the differences between four major clones based on soil nutrient and microbial community structure, following cultivation for 10 yr to infer the influence of clone selection on soil sustainable utilization. The results showed significant differences in soil nutrient status and rhizosphere microorganism populations among clones. The bacterial communities in the XL1 plots had the highest species richness. According to the results, clone XL1 was found to be suitable for sustainable cultivation considering the high organic matter concentration and microbial diversity in the soil where it was cultivated. Although clone XL210 exhibited high yields and good economic benefits, it had a risk of inadequate production capacity in later periods, meaning that fertilization rates would have to be increased, and some annual plants with rich rhizosphere flora would need to be integrated in the farms to enhance microbial diversity in the soil to decelerate soil fertility decline.

Difference in soil bacterial community composition depends on forest type rather than nitrogen and phosphorus additions in tropical montane rainforests

Rapid increase of nitrogen (N) deposition could alter nutrient availability, leading to changes in soil microbial processes and ecosystem carbon and nutrient cycling. However, the effects of N deposition on soil microbes remain elusive in the tropical rainforests in Asia. Here, we conducted a 3-year N addition experiment with four treatments (0, 20, 50, and 100 kg N ha−1 year−1) in a primary and secondary tropical montane forest in Hainan Island, China, to explore the effects of elevated N availability on soil microbial community composition. We also conducted a phosphorus (P) treatment (50 kg P ha−1 year−1) and a N + P treatment (50 kg N ha−1 year−1 + 50 kg P ha−1 year−1) to examine potential P limitation driven by N deposition in highly weathered tropical soils, using a bar-coded pyrosequencing technique. The composition of soil bacterial communities differed dramatically between the primary and secondary forests, but not significant dissimilarity among the fertilization treatments. The community composition, phylogenetic diversity and phylotype richness were significantly correlated with soil pH, total organic C (TOC), and total N (TN), respectively. There were significant differences between the primary and secondary forest in pH, TOC, and TN, but not among the fertilization treatments. These results suggest that differences in soil nutrient status between the primary and secondary forests due to different successional stages rather than chronic N fertilization may be the major factor affecting soil bacterial composition in the tropical montane rainforests.

Foliar trait contrasts between African forest and savanna trees: genetic versus environmental effects.

Variations in leaf mass per unit area (Ma) and foliar concentrations of N, P, C, K, Mg and Ca were determined for 365 trees growing in 23 plots along a West African precipitation gradient ranging from 0.29 to 1.62m a-1. Contrary to previous studies, no marked increase in Ma with declining precipitation was observed, but savanna tree foliar [N] tended to be higher at the drier sites (mass basis). Generally, Ma was slightly higher and [N] slightly lower for forest vs savanna trees with most of this difference attributable to differences in soil chemistry. No systematic variations in [P], [Mg] and [Ca] with precipitation or between trees of forest vs savanna stands were observed. We did, however, find a marked increase in foliar [K] of savanna trees as precipitation declined, with savanna trees also having a significantly lower [K] than those of nearby forest. These differences were not related to differences in soil nutrient status and were accompanied by systematic changes in [C] of opposite sign. We suggest an important but as yet unidentified role for K in the adaption of savanna species to periods of limited water availability; with foliar [K] being also an important factor differentiating tree species adapted to forest vs savanna soils within the 'zone of transition' of Western Africa.

Herbivory and habitat association of tree seedlings in lowland evergreen rainforest on white-sand and terra-firme in the upper Rio Negro

Background: It has been proposed that the interaction between herbivory and soil nutrient availability drives habitat association of tree species in Peruvian Amazonia. Nevertheless, there is no empirical evidence that this interaction holds across other Amazonian regions. Aims: We address this knowledge gap by testing whether the interaction between herbivory and soil nutrient contributes to habitat association of tree species in white-sand and terra-firme forests in the upper Rio Negro, Brazil. Methods: We conducted a reciprocal transplanting field experiment in which we controlled for the presence of herbivores. We tested for differences in tree-seedling growth and herbivory among seven white-sand and seven terra-firme habitat-specialist species. Additionally, we assessed whether tree seedlings differed in their functional traits. Results: We found no empirical evidence that an interaction between herbivory and soil nutrients shapes habitat association in white-sand and terra-firme forests of the upper Rio Negro. Tree seedlings showed higher mortality when growing in their non-typical habitat. Growth and herbivory were similar regardless of the presence or absence of herbivore protection and type of soil. Conclusions: We suggest that the overall differences in soil nutrient status between white-sand and terra-firme forests in the upper Rio Negro are insufficient to trigger an interaction between herbivory and soil nutrient availability.

Allelopathy and soil nutrient status in tree-crop Agric system in Arid region

The leaf extract of Aonla and Ber showed allelopathc influence over the test crops- Cluster Bean, Moth Bean, Brinjal and Mustard. Cluster Bean and Moth Bean showed significant reduction in germination and seedling growth characters treated with aqueous leaf extract of Karonda. While Brinjal and Mustard recorded a significant increase in these characters following use of leaf extract of Karonda as compared to control. Significant differences in soil nutrient status with respect to N, P, K, Ca, Mg, Mn and Fe content between tree-crop agric system and sole cropping were recorded while non-significant differences were obtained in zinc content among different treatments during initiation and termination of experiment. The nutrient status was recorded to be more in the soils under tree-crop agric system as compared to the soils under sole cropping. A decreasing trend in the nutrient status was observed with increasing depth of soil profile.

Influence of site and rate of low-volume aerial phosphite spray on lesion development ofPhytophthora�cinnamomiand phosphite persistence inLambertia�inermisvar.inermisandBanksia grandis

The influence of site on effectiveness of low-volume spray of phosphite for the control of Phytophthora cinnamomi was compared between sites differing in soil nutrient status. The sites ranged from infertile deep grey sands to a red loam in the Esperance Plains bioregion, and infertile gravelly sand of the Havel site-vegetation type P to a red loam of Havel site-vegetation typeQin the northern Jarrah Forest bioregion. Following low-volume spray of 0, 24 or 48 kg phosphite/ha, phosphite effectiveness was determined from assessment of rate of colonisation and inhibition of stem colonisation by P. cinnamomi, and stem phosphite concentration in challenge inoculation stems of Lambertia inermis var. inermis in Esperance Plains bioregion sites and Banksia grandis in Jarrah Forest bioregion sites. Phosphite effectiveness was mainly influenced by plant species rather than site. Phosphite spray significantly controlled P. cinnamomi colonisation in B. grandis, but not in L. inermis var. inermis. Site had no consistent influence on the effect of phosphite on P. cinnamomi despite large differences in soil nutrient status between sites. Differences between sites and site ranking changed with inoculation time and rate of phosphite spray, and duplicate sites differed significantly from each other. Site, rate of phosphite spray, time after spray and plant species significantly affected stem phosphite concentrations. In both Esperance Plains bioregion and Jarrah Forest bioregion sites, stem phosphite concentrations were greatest in fertile loam sites and least in infertile sand or gravelly sand sites. Stem phosphite concentrations increased with rate of phosphite spray with concentrations in stems receiving 48 kg phosphite/ha being 1.2 to 3-times-greater than that in stem sprayed with 24 kg phosphite/ha. Six months after low-volume spray, phosphite concentrations in L. inermis var. inermis stems had declined for all sites and spray rates to only 4–17% of original concentrations. Decline of phosphite concentrations in B. grandis stems was slower than that for L. inermis var. inermis stems. The results indicate that effectiveness of phosphite against P. cinnamomi infection in different communities will depend more on plant species composition than soil nutrient status. Differences in phosphite effectiveness between plant species may be related to differences in phosphite concentration thresholds yet to be quantified, above which tissue concentrations must be achieved before inhibition of P. cinnamomi colonisation occurs. In rapid colonisation/phosphite low-responsive species such as L. inermis var. inermis, the threshold may be greater than that required for a response in a rapid colonisation/phosphite high-response species such as B. grandis. These results demonstrate the need to determine thresholds for individual plant species and in different environments.

Soil enrichment by Acacia mellifera subsp. detinens on nutrient poor sandy soil in a semi-arid southern African savanna

The study was conducted in a semi-arid savanna of South Africa, dominated by an almost pure stand of Acacia mellifera subsp. detinens (Black Thorn). Due to its invasive habits and suppression of the herbaceous layer, this woody species is viewed by land owners as a serious threat. Clearing of all A. mellifera trees in order to restore the production potential of the herbaceous layer is thus a well-established practice. In view of possible beneficial effects of A. mellifera, a study was undertaken with the objective of quantifying differences in soil nutrient status under A. mellifera canopies (canopied subhabitat) in comparison to the open areas (uncanopied subhabitat). The results of the study confirmed the existence of differences in the soil nutrient status between the various subhabitats, which occurred in a specific spatial gradient from the stem base of the plants towards the open, uncanopied areas. These differences were statistically significant ( p < 0.05 ) for total N, % organic matter and Ca, with the highest values recorded in the area surrounding the stem base. Though statistically non-significant ( p > 0.05 ) the P and K contents, and to a lesser extent Mg, were also higher under the tree canopies, while pH was lower. No differences ( p > 0.05 ) were established for Na. Some notable differences to similar studies in other areas were established, of which the reduction of soil pH is an example. The practical significance of these results in terms of land management practices is discussed, which will invariably necessitate a change in attitude of land owners in their approach to the management of A. mellifera.

The Performance and Nutrient Use Efficiency of Two Contrasting Systems of Organic Milk Production

ABSTRACT During a four year study, two contrasting systems of organic milk production were studied to determine differences in soil nutrient status, crop production, milk output and quality, efficiency of feed conversion and the effect on animal performance. The key aim of the first system was to increase the levels of both self-sufficiency and sustainability of the system by establishing a balanced crop rotation and minimizing the imports of nutrients. The second system was based on increasing the output and flexibility of the system by establishing a forage-only cropping strategy and importing purchased concentrate feeds into the system. The results showed that increasing the level of self sufficiency led to an improved nutrient input/output balance and improved efficiency of milk production from forage but not an increased efficiency of total feed utilization. This type of system is dependent on the production of high-energy forage to meet the cow's nutrient requirement and avoid problems of reduced milk persistency during early lactation, lower milk quality and reduced fertility. In the system based on purchased concentrate feeds, higher levels of both crop energy and milk output were recorded without any adverse effects on milk persistency during lactation. The flexibility of the system ensured that any potential deficiency or imbalance in the availability and quality of the forages produced within the system was avoided by the import of concentrate feeds. However, the reliance on purchased rather than home-grown concentrate feed reduced the sustainability of the system and also led to both a lower efficiency of forage utilization and reduced milk output from forage.

Big-leaf mahogany ( Swietenia macrophylla) seedling survival and growth across a topographic gradient in southeast Pará, Brazil

Adult populations of big-leaf mahogany ( Swietenia macrophylla) occur in aggregations along seasonal streams in transitional evergreen forests of southeast Pará, Brazil. To test whether variable seedling survival and growth across topography may underlie this observed distribution pattern, we planted nursery-grown seedlings in the forest understory and in artificial gaps at opposite ends of a slope gradient where mahogany occurs (low-ground hydromorphic soils) and does not occur (high-ground dystrophic soils). At both positions seedling survival and growth were significantly greater through 42 months in gaps than in adjacent forest understories, though mean understory survival exceeded that in gaps through the first growing season. Mean seedling growth in gaps on low ground was significantly greater than growth in gaps on high ground. Under nursery conditions (well watered, 70% full sun light), growth of seedlings planted in soils from low ground was significantly higher than that of seedlings planted in soils from high ground, indicating that differences in soil nutrient status, particularly Ca and Mg, may account for results in the outplanting experiment. Ca+Mg nutrient supplement accelerated growth rates of nursery seedlings planted in high-ground soils relative to growth rates of seedlings planted in low-ground soils, nullifying significant differences between controls. Soil differentiation across topographic relief with consequent gradients in soil nutrient status complements canopy disturbance regimes (increased light levels) in shaping adult distribution patterns and population structures. This implies that recruitment success under natural and artificial regeneration management practices may vary as a function of both gap size and soil fertility.

The effect of long-term mowing and ungulate exclusion on grass species composition and soil nutrient status on the Athi-Kapiti plains, central Kenya

The long-term (>30 years) impacts of mowing (for hay-making) and ungulate exclusion, on natural, unfertilised rangelands were investigated. Changes in grass species composition and soil nutrient status were measured The study site, situated on the Athi-Kapiti plains of central Kenya, comprised of an ungulate exclusion camp, subjected to an annual mow, and an adjacent control plot, exposed to herbivory from cattle and game. Significant changes were noted in four of the seventeen grass species. Relative percentages of Pennisetum mezianum and P. stramineum increased significantly within the mowed/exclusion plot, while those of Microchloa kunthii and Sporobolus iocladus showed a significant drop. No significant differences were noted in relative frequency of grass species designated as 'decreasers', or in basal cover index. Analysis of soils inside the mowed/exclusion plot showed significantly higher soil pH, and soil Ca levels, but significantly lower plant available soil P and inorganic N, when compared to the control plot. The long-term treatment of mowing/herbivore exclusion, has resulted in severe depletion of plant available soil P and inorganic soil N. Results suggest that differences in species composition can be primarily attributed to the lower defoliation levels, and shading effects inside the exclusion plot, while differences in soil nutrient status can be attributed primarily to the export of nutrients with bailed hay, and to the absence of the stimulating effect that large herbivores have on nutrient recycling. Results are consistent with the hypothesis that herbivory plays an important role in maintaining P recycling in plant available forms, particularly for soils where P may be limiting.

Application of a nutrient cycling model (NuCM) to a northern mixed hardwood and a southern coniferous forest.

The nutrient cycling model, NuCM, which incorporates state-of-the-art understanding of the biogeochemical and transport processes controlling nutrient cycles, simulates vegetation growth, litterfall and decay, soil biogeochemical processes, and movement of water. Output of the model includes the available nutrients in soil strata and vegetation pools and the fluxes between pools on a weekly, monthly or annual basis. Solution and adsorbed concentrations in the various soil layers can be plotted versus time. The model has been used to simulate effects of acidic deposition on nutrient status at two sites: Huntington Forest, New York and Smokies Tower, Tennessee. Model results show only minor changes in nutrient status at the sites over the next 65 years at current rates of acidic deposition. The results also show only small differences in soil nutrient status between two alternative scenarios for reduction of SO(x) emissions. Neither "threshold effects" nor abrupt changes in nutrient pool sizes occurred in either of the simulations.

Relations Between Mineral Nutrient Availability and Fine Root Biomass in Two Costa Rican Tropical Wet Forests: A Hypothesis

Relations Between Mineral Nutrient Availability and Fine Root Biomass in Two Costa Rican Tropical Wet Forests: A Hypothesis