Yield Of Plantations Research Articles

Population-specific climate sensitive top height curves and their applications to assisted migration

Growth and yield (G&Y) of forest plantations can be significantly impacted by maladaptation resulting from climate change, and assisted migration has been proposed to mitigate these impacts by restoring populations to their historic climates. However, genecology models currently used for guiding assisted migration do not account for impacts of climate change on cumulative growth and assume that responses of forest population to climate do not change with age. Using provenance trial data for interior lodgepole pine (Pinus contorta subsp. latifolia Douglas) and white spruce (Picea glauca (Moench) Voss) in western Canada, we integrated Universal Response Functions, representing the relationship of population performance with their provenance and site climates, into top height curves in a G&Y model (Growth and Yield Projection System, GYPSY) to develop population-specific climate sensitive top height curves for both species. These new models can estimate the impact of climate change on top height of local populations and populations from a range of provenances to help guide assisted migration. Our findings reveal that climate change is expected to have varying effects on forest productivity across the landscape, with some areas projected to experience a slight increase in productivity by the 2050s, while the remainder are projected to face a significant decline in productivity for both species. Adoption of assisted migration, however, with the optimal populations selected was projected to maintain and even improve productivity at the provincial scale. The findings of this study provide a novel approach to incorporating assisted migration approaches into forest management to mitigate the negative impacts of climate change.

Organic fertilizers in increase of hazelnut yield

Goal. To assess the effect of various organic fertilizers on the yield of hazelnut plantations in the conditions of the Southern Steppe of Ukraine.
 Methods. Field experiment, laboratory-analytical, comparative.
 Results. The influence of organic fertilizers of various origins was studied (cattle manure; chicken droppings; Biofertilizer No. 1 — sewage sludge (SW) of the biological treatment station (SBO) «Pivdenna» in Odesa + winter wheat straw + Microbacterium barkeri LP-1 (M. b.); Biofertilizer No. 2 — «Southern» SBO + sunflower seed husks + M. b.; «Pivdenna» SBO, Odesa) on the agrochemical parameters of ordinary medium-humus chernozem in the conditions of the Southern Steppe of Ukraine for the cultivation of hazelnuts. It is shown that in comparison with the control of 2021 and 2022, an increase in the content of easily hydrolyzed nitrogen, mobile forms of phosphorus and potassium, and organic matter is noted in all variants of the experiment.
 Conclusions. The use of organic fertilizers of various origins for the cultivation of hazelnuts in the conditions of the Southern Steppe of Ukraine helps to increase the content of the main agrochemical indicators of the soil — easily hydrolyzed nitrogen (91.0—98.0 mg/kg with 84.0 mg/kg — control), mobile phosphorus compounds (174.75—306.30 mg/kg at 138.75 mg/kg — control), potassium (112.00—166.90 mg/kg at 108.40 mg/kg — control) and organic matter (3.78—4.18% and 3.76% — control). The advantages of biofertilizers No. 1 and No. 2 based on sewage sludge with the use of vegetable fillers (winter wheat straw and sunflower seed husks) and the phosphate-mobilizing bacterium Microbacterium barkeri LP-1 are shown. Organic fertilizers contribute to the increase in the content of nutrients in the soil, the activation of the activity of eco-trophic groups of microorganisms, which leads to an increase in the biological activity of the soil and, accordingly, the yield of agricultural crops.

Are operational plantations meeting expectations? A large-scale assessment of realized versus anticipated yield in eastern Canada

Forest plantations play an increasingly important role in meeting global demand for wood. They usually have higher yield than naturally regenerated forests. Thus, plantations can support economically viable wood production, enable forest conservation elsewere, help mitigate climate change by contributing to carbon sequestration and increase forest resilience and resistance to biotic and abiotic stressors. If yield of plantations is not as high as anticipated, then their use could generate important sustainability issues. There are still major gaps in our understanding of the factors that influence yield, even with respect to black spruce, white spruce, and jack pine, three of the most commonly planted tree species in northeastern North America. Our objective was to evaluate the yield of forest plantations of these species over a 416 000 km2 region that was representative of northeastern North American forests. Contrary to our prediction, realized yield of operational plantations was consistently lower than anticipated. Site index and competition both played a significant role in determining the yield of plantations. In the context of uncertain realized yield of operational plantations, we emphasize the necessity of relying on adaptive management to determine harvest levels that are compatible with sustainable management objectives.

A new Soil Management System in Enhancing the Yield of Plantation Using IoT Technique and Machine Learning for Smart Pineapple Farming

The machine learning technique is studied to aid farmers in decision-making and analysing soil quality based on the nitrogen, phosphorus, and potassium NPK nutrients as the current soil in Malaysia experience degradation of soil organic that affect in production of the nutrient for the crops. The research aim is to study and analyse the Artificial Neural Network model in analysing the quality of soil based on the prediction of NPK level class, which the data collected from Smart Agri-Scan. Next objective is to evaluate the prediction and accuracy of the model. The ANN model is constructed in Neural Net Fitting App in MATLAB. A feedforward neural network is applied to the ANN model and trains it with two different training functions and a different number of neurons of hidden layers. The model with the smallest Mean Square Error is chosen for data analysis as it means the model has the best performance. From the prediction graph, the output of training and validation that corresponds to the prediction model is observed. The points of the output prediction close to the reference line are considered a good prediction model, which means it can analyse soil quality accurately. In future, the model might be able to do the analysis and decision directly at the monitoring platform based on the real-life prediction data.

Effects of maintaining higher water level on the yield of oil palm plantations planted on tropical peat soils.

Effects of maintaining higher water level on the yield of oil palm plantations planted on tropical peat soils.

Exogenous salicylic acid induces defense responses in tea plants against Toxoptera aurantii (Hemiptera: Aphididae).

Toxoptera aurantii is one of the most destructive pests, threatening the yield and quality of tea plantations. The salicylic acid (SA)-mediated signaling pathway is vital for the induction of plant defense responses; however, its role in tea plant resistance to T. aurantii remains unclear. Thus, this study used and electrical penetration graph and monitoring of population dynamics to evaluate the effects of exogenous SA application on T. aurantii feeding behavior and population growth in tea seedlings. Moreover, the effects of SA treatment on the activities of defense-related enzymes were analyzed. Probe counts and the duration of xylem sap ingestion were significantly higher in SA-treated plants than those in the control group. The total duration of passive phloem ingestion was significantly decreased in 0.5 mmol/l SA-treated plants, and the application of 0.5, 1, and 4 mmol/l SA significantly inhibited T. aurantii population growth. In addition, the activities of polyphenol oxidase, peroxidase, and superoxide dismutase were significantly increased in the 0.5 mmol/l SA-treated plants. Overall, this study demonstrates the capacity of exogenous SA to activate defense responses against T. aurantii. These results have crucial implications for understanding the mechanisms of enhanced resistance, thereby providing a sustainable approach for managing T. aurantii.

Evaluation of biomass production of CO-3 fodder grass under coconut and its effect on nut yield of intermediate zone coconut plantations in Sri Lanka

Six CO-3 fodder grass planting systems under coconut palms were evaluated for six years concerning biomass production and coconut yield. This study was carried out at Potthukulama (PRS) Research Station of the Coconut Research Institute, in the Low Country Dry Zone of the Northwestern province of Sri Lanka, where the soil series is Ambakele. According to the experiment results, the highest CO-3 biomass was produced when five CO-3 rows were planted between coconut rows and harvested in 30 days lopping interval. There was no significant effect of CO-3 planting densities and lopping intervals on the yield of coconut.

Bioenergy crops monitoring using Sentinel-2 and UAV-derived imagery

Purpose. Establishing the regularities for the monitoring of the bioenergy crop conditions using Sentinel-2 and UAV-derived imagery. Methods. A field experiment was carried out in an experimental field of the Institute of Bioenergy Crops and Sugar Beet National Academy of Agrarian Sciences of Ukraine (50.023194, 30.173895), located in a zone of unstable soil moisture in the Right Bank Forest Steppe, in 2022−2023. Results. Among the studied traditional crops, sugar sorghum, sugar beet, and fodder beet are interesting crops from the standpoint of biomass for energy, as they can produce 110 t/ha, 120 t/ha, and 135 t/ha of biomass, respectively, or 20 t/ha, 26 t/ha, and 24 t/ha of dry matter, respectively. The yield of energy crops can be predicted with an acceptable level of accuracy using many known vegetation indices. However, the relationships between vegetation indices and crop yield are not consistent at every stage of plant growth and development, leading to low accuracy in yield estimation. The combination of vegetation indices related to the structural characteristics of the canopy and chlorophyll content in the aboveground biomass can improve the accuracy of yield estimation. Moreover, combining vegetation indices related to canopy structure, chlorophyll content, and stress indices as input to yield prediction models may provide even higher correlations for yield prediction. Conclusions. Usually, plantations of miscanthus and switchgrass are fertilised annually, while willow and poplar are fertilised every 3–4 years, after each harvesting. Therefore, the nutrient provision of tree species may not be sufficient. It was found that the content of total nitrogen in the soil of bioenergy plantations highly correlates with NDVI. To use NDVI for bioenergy crop prediction, an algorithm for determining the level of plant nutrients should be developed. It was found that at the end of the growing season (September or early October), the use of vegetation indices allows for the accurate estimation of the size and condition of bioenergy plantations since most crops in this period are already harvested. Sentinel-2-derived imagery is useful for monitoring bioenergy crop plantations as it provides images with a resolution of 10 m at 3–5-day revisiting time. We investigated NDVI on a total area of Miscanthus × gigantheus plantations of 2.9 ha. The satellite-derived data accumulated and aggregated by the OneSoil application as of August 20 and September 19 resulted in NDVI values of 0.80 and 0.70, respectively, while the NDVI obtained with UAV imagery was 0.82 and 0.77, respectively. Consequently, the satellite can provide quite acceptable NDVI data for use in the monitoring of bioenergy plantation yield at the national level.

Morphological Characteristics and Chlorophyll Content of Dominant Weed Leaves After Peatland Fires in Oil Palm Plantation Areas

The weeds are high adaptability plants after peatland fires. The response of the dominant weeds growing after the fire is an important factor in weed control efforts to increase the yield of oil palm plantations on post-fire peatlands. The present study was conducted at the Kurao oil palm plantation, Lubuk Basung, West Sumatra, Indonesia. The weeds were collected by using the Quadrat method with random placement of 20 plots in post-fire and unburnt locations. The leaf morphological characteristics were determined by the descriptive method. While the chlorophyll content of leaves was measured by using calorimetry in the spectrophotometer. A total of 25 species and 17 families of weeds were collected in the present study. The Peperomia pellucida is the most dominant species collected with an important value index of 36.41% and follows by Ageratum conyzoides with an important value index of 28.99%. In the present study, we confirmed the differences in all aspects of the morphological characteristics of Peperomia pellucida leaves between post-fire and unburnt locations. Meanwhile, in Ageratum conyzoides leaves only show differences in several aspects. Furthermore, there were differences in the chlorophyll content of Peperomia pellucida, while Ageratum conyzoides did not show any differences in chlorophyll content.

Analysis of modern technologies for growing cherry varieties in temperate climates

The research relevance is predefined by the need to optimise fruit crop cultivation systems considering weather conditions. The research aims to test the grafting technology of intensive sweet cherry plantations on small and medium-sized rootstocks. The leading method in achieving the research goal was a field experiment. The main results of this study are as follows: the leading technologies for increasing the yield of sweet cherry varieties depending on the impact of environmental stress factors are presented; the use of clone rootstock technology in sweet cherry plantations in temperate climates is substantiated. According to a set of indicators of productivity formation, the yield of plantations of different designs was predicted. Namely, the scheme of variety-rootstock combinations of intercalary placement, its length, and parameters of the growth complex for plants were revealed; indicators of physiological activity, growth, productivity, fruit quality, and economic efficiency in intensive sweet cherry plantations were determined. It has been established that the application of this technology will increase yields and improve the quality parameters of sweet cherry fruits by developing varieties with compact crowns, which will allow to compact the plantations. It has been analysed that climatic conditions are the main factor in the process of harvest formation. A list of stress factors of temperate climate that affect the yield of sweet cherries has been identified. It is proved that the introduction of clonal rootstock technology is the most effective for growing intensive plantations of sweet cherries in a temperate climate. Practically, the research aims to determine and test a set of elements of physiological indicators of the potential yield of sweet cherry plantations of different designs, to introduce them into production and use them in further breeding

Study on the effects of stand density management of Chinese fir plantation in Northern China.

The aim of this study was to clarify the mechanism by which thinning alters stand structure and affects forest productivity by characterizing changes in stand quantitative maturity age, stand diameter distribution, structural heterogeneity, and forest productivity of Chinese fir plantations at different thinning times and intensities. Our findings provide insights into how the density of stands could be modified to enhance the yield and timber quality of Chinese fir plantations. The significance of differences in individual tree volume, stand volume, and timber merchantable volume was determined using one-way analysis of variance and post hoc Duncan tests. The stand quantitative maturity age was obtained using the Richards equation. The quantitative relationship between stand structure and productivity was determined using a generalized linear mixed model. We found that (1) the quantitative maturity age of Chinese fir plantations increased with thinning intensity, and the quantitative maturity age was much greater under commercial thinning than under pre-commercial thinning. (2) Individual tree volume and the proportion of medium-sized and large-sized timber merchantable volume increased with stand thinning intensity. Thinning promoted increases in stand diameter. pre-commercially thinned stands were dominated by medium-diameter trees when the quantitative maturity age was reached, whereas commercially thinned stands were dominated by large-diameter trees. The living trees volume will decrease immediately after thinning, and then it will gradually increase with the age of the stand. When the stand volume included both living trees volume and thinned volume, thinned stands increased stand volume compared with unthinned stands. In pre-commercial thinning stands, the greater the intensity of thinning, the greater the increase in stand volume, and the opposite was true for commercial thinning. (3) Thinning also reduced heterogeneity in stand structure, which was lower after commercial thinning than after pre-commercial thinning. The productivity of pre-commercially thinned stands increased with thinning intensity, whereas that of commercially thinned stands decreased with thinning intensity. (4) The structural heterogeneity of pre-commercially and commercially thinned stands was negatively and positively correlated with forest productivity, respectively. In the Chinese fir plantations in the hilly terrain of the northern Chinese fir production area, when pre-commercial thinning was performed in the ninth year to a residual density of 1750 trees per hectare, the stand quantitative maturity age was reached in year 30, medium-sized timber accounted for 75.2% of all trees, and the stand volume was 667.9 m3 per hectare. This thinning strategy is favorable for producing medium-sized Chinese fir timber. When commercial thinning was performed in year 23, the optimal residual density was 400 trees per hectare. When the stand quantitative maturity age was reached in year 31, large-sized timber accounted for 76.6% of all trees, and the stand volume was 574.5 m3 per hectare. This thinning strategy is favorable for producing large-sized Chinese fir timber.

Effect of physiographic type and harvesting age on biomass yield, chemical composition, and carbon sequestration of mangrove plantations for biofuel feedstock production

Many coastal communities of SE-Asia, including Thailand have managed mangrove forests for charcoal production. However, understanding and managing the harvesting age of mangrove plantations in different ecotypes is limited for sustainable biofuel production. Therefore, the objectives of this research were to determine the effect of physiographic type and harvesting age on the biomass yield, chemical composition, CO2 adsorption of aboveground mangrove biomass. The data were collected during 2018–2019 from two geographical types including the riverine and basin mangrove plantations in Samut-Songkhram, Thailand. The experimental plots were selected at different ages (5, 10, and 15 years). The riverine mangrove forest had higher dry aboveground woody biomass, calorific value, and CO2 adsorption than did the basin mangrove forest. For both mangrove ecotypes, there were no significant differences in chemical elements. Extending harvesting age from 5 to 15 years tended to increase the woody biomass yield and quality, and CO2 adsorption of mangrove forests. With increasing harvesting age, the dry aboveground woody biomass, calorific value, and CO2 adsorption of mangroves increased 34.4–283.9 t ha−1, 3841.1- 3924.9 kcal kg−1, and 55.6–453.4 t CO2 ha−1, respectively, but ash and N content decreased 4.8–3.4% and 0.2–0.1%, respectively. Compared with other ages, extending harvest until 15 years yielded the highest potential biomass for biofuel feedstock production and carbon sequestration in both mangrove ecotypes.

PENGARUH PENGETAHUAN ZAKAT,TINGKAT PENDAPATAN, TINGKAT KEIMANAN, KEPERCAYAAN TERHADAP MOTIVASI PETANI SAWIT DALAM MEMBAYAR ZAKAT HASIL PERKEBUNAN (STUDI KASUS PETANI DI KABUPATEN BENGKALIS-RIAU)

The purpose of this study was to determine the effect of knowledge of zakat, income level, level of faith, trust in the motivation of oil palm farmers in paying zakat from plantation yields (Case Study of Farmers in Bengkalis-Riau Regency). This research was conducted in Bengkalis Regency. This research uses the Structure Equation Model (SEM) Smart Pls by analyzing the facts that have occurred. In this study, primary data were collected using a questionnaire with the Slovin sampling method totaling 99. Respondents in this study were oil palm farmers in Bengkalis Regency. This study produced interesting findings, including knowledge of zakat has a significant effect on motivation to pay zakat, income level has a significant effect on motivation to pay zakat
 
 
 Keywords Zakat Knowledge, Income Level, Faith Level, Trust, Motivation

Kontribusi Subsektor Perkebunan Dalam Mendukung Pertumbuhan Ekonomi Masyarakat di Sumatera Utara

Economic Growth Is The Thing That Gets The Most Attention, Because One Of The People's Welfare Is Achieved If The Economic Growth Is Good. One Of The Economic Growth Comes From The Plantation Subsector. The Plantation Sub-Sector Is Of Concern To The Government Because Its Production Can Increase The Country's Foreign Exchange, And Also Has A Great Opportunity To Increase Exports. This Study Used Qualitative Research Methods. This Study Aims To Review How The Plantation Subsector Contributes To Supporting Economic Growth, Especially In The North Sumatra Region. The Results Of This Study Indicate That The Plantation Subsector Has A Large Contribution To Economic Growth In The North Sumatra Region, It Can Be Seen That The Area Of ​​Land Is Getting Wider And The Plantation Yields Are Increasing From Year To Year, Both From Oil Palm Plantations Which Are The Most Superior Commodities, Rubber, Coffee And Tobacco . Rubber, Coffee, Cocoa And Tobacco Are Very Important Commodities From The Plantations Of North Sumatra At This Time. Apart From That, Germany Is Also Very Well Known For Its Deli Tobacco Plantations, Which Originate From North Sumatra.
 Keywords: Contribution, Plantation, Growth, Economy

Effect of lime application on soil respiration is modulated by understory vegetation in subtropical Eucalyptus L’Hér. plantations

ObjectiveLime application and understory plant clearance are two common forest management methods employed to increase forest productivity in subtropical regions. However, the effect of these two management methods, or their combined application, on soil respiration in forest plantation settings is still not fully understood.MethodsHere, a field experiment was conducted to determine how lime application, understory clearance, and their combined application, would impact total soil respiration (Rs), autotrophic respiration (Ra), and heterotrophic respiration (Rh) in a Chinese subtropical Eucalyptus plantation. Changes in soil microclimate and microbial community (PLFAs), as well as Eucalyptus fine root biomass were also assessed.ResultsLime application stimulated Rh, but decreased Ra of understory vegetation (primarily Dicranopteris dichotoma), thus consequently inhibiting Rs. Understory clearance also reduced Rs, primarily due to reductions in soil PLFAs and associated Rh, and Ra of understory vegetation. Since the increase in Rh induced by lime application was greater than the decrease in Rh caused by understory clearance, the combined application of lime application and understory clearance decreased Rs primarily by reducing understory root respiration.ConclusionOur observations suggest that understory plants can modulate the effect of lime application on Rs, highlighting the important role of understory vegetation in regulating soil carbon cycling in subtropical Eucalyptus plantations. We concluded that the potential interactive effects should be considered in developing management practices that optimize the yield and sustainability of subtropical plantations.

Monitoring Thosea sinensis Walker in Tea Plantations Based on UAV Multi-Spectral Image

Thosea sinensis Walker (TSW) rapidly spreads and severely damages the tea plants. Therefore, finding a reliable operational method for identifying the TSW-damaged areas via remote sensing has been a focus of a research community. Such methods also enable us to calculate the precise application of pesticides and prevent the subsequent spread of the pests. In this work, based on the unmanned aerial vehicle (UAV) platform, five band images of multispectral red-edge camera were obtained and used for monitoring the TSW in tea plantations. By combining the minimum redundancy maximum relevance (mRMR) with the selected spectral features, a comprehensive spectral selection strategy was proposed. Then, based on the selected spectral features, three classic machine learning algorithms, including random forest (RF), support vector machine (SVM), and k-nearest neighbors (KNN) were used to construct the pest monitoring model and were evaluated and compared. The results showed that the strategy proposed in this work obtained ideal monitoring accuracy by only using the combination of a few optimized features (2 or 4). In order to differentiate the healthy and TSW-damaged areas (2-class model), the monitoring accuracies of all the three models were computed, which were above 96%. The RF model used the least number of features, including only SAVI and Bandred. In order to further discriminate the pest incidence levels (3-class model), the monitoring accuracies of all the three models were computed, which were above 80%, among which the RF algorithm based on SAVI, Bandred, VARI_green, and Bandred_edge features achieve the highest accuracy (OAA of 87%, and Kappa of 0.79). Considering the computational cost and model accuracy, this work recommends the RF model based on a few optimal feature combinations to monitor and distinguish the severity of TSW in tea plantations. According to the UAV remote sensing mapping results, the TSW infestation exhibited an aggregated distribution pattern. The spatial information of occurrence and severity can offer effective guidance for precise control of the pest. In addition, the relevant methods provide a reference for monitoring other leaf-eating pests, effectively improving the management level of plant protection in tea plantations, and guaranting the yield and quality of tea plantations.

The effect of nitrogen fertilization and foliar application of fertilizers on yield and energy efficiency of giant miscanthus plantations

Purpose. To improve the technology of caring for giant miscanthus plantations and establish the features of its productivity formation with the use of different types of fertilizers, starting from the second year of crop vegetation.
 Methods. The research was carried out in the years 2020–2021 in the Bila Tserkva Experimental and Breeding Station of the Institute of Bioenergy Crops and Sugar Beet of the National Academy of Agrarian Sciences of Ukraine, which is located in the zone of unstable moisture of the Right Bank Forest Steppe of Ukraine. The design of the experiment included application of mineral fertilizers [ammonium nitrate + ammonium sulfate (N24 + S6 kg/ha a.i.), ammonium nitrate (N24 kg/ha a.i.)] in a row zone in spring, foliar application of humates (Vermisol, 8.0 l/ha, Humifield BP-18, 0.4 l/ha) and complex fertilizer with amino acids (Quantum Aminomax, 0.5 l/ha). Mineral fertilizers were applied before the emergence of miscanthus sprouts; foliar application of fertilizers was carried out in the 5-leaf stage and the second time after two weeks.
 Results. Giant miscanthus plants in second year of vegetation formed from 18 to 37 shoots with an average weight of 76.3 to 111.0 g, with the maximum weight of one plant reaching 4091 g. In the next year of research, the number of stems per plant and their average weight increased by 1.5–2 times, and the maximum weight of one plant was 7016 g. Biomass yield of giant miscanthus in the third year of vegetation was 31.0–74.6 t/ha, the estimated yield of solid biofuel was 19.2–41.6 t/ha and energy 315.5–683.2 GJ/ha.
 Conclusions. Application of mineral fertilizers (ammonium nitrate + ammonium sulfate, ammonium nitrate) in spring contributed to significant increase in the indicators of raw biomass yield, solid biofuel output, and energy yield per hectare. Foliar application of Humifield BP-18 has a significant positive effect on the productivity of giant miscanthus. The best indicators of crop productivity were obtained in treatments combining spring fertilization with ammonium nitrate and ammonium sulfate (N24 + S6) followed by two-time foliar application of humates (Vermisol, 8.0 l/ha, Humifield BP-18, 0.4 l/ha) and complex fertilizer with amino acids Quantum Aminomax, 0.5 l/ha.

Potential effects of soil chemical and biological properties on wood volume in Eucalyptus urophylla × Eucalyptus grandis hybrid plantations and their responses to different intensity applications of inorganic fertilizer.

Long-term and high-intensity application of inorganic fertilizer leads to a strong variation of soil characteristics. The changes in soil chemical and biological properties can significantly affect the yield of Eucalyptus plantation. However, the mechanism of soil chemical properties affecting wood volume mediated by biological factors is not clear. The purpose of this study was to identify which soil properties were affected by different fertilization intensities and to disentangle the dominant factors affecting Eucalyptus volume. After clear felling evergreen broad-leaved forest, a Eucalyptus plantation was established that was coppiced every 5 years and fertilized every year. Within this plantation, areas with different treatments were established. These treatments were a 5-year growth period (low); two times 5-year growth period (medium); and three times 5-year growth period (high). In each treatment area and in a nearby evergreen broad-leaved forest (EBLF Control), five sample plots per treatment were set up. Various biological and chemistry analyses (18 in total) were related to determining the most important path and index for optimizing Eucalyptus plantation. The analysis of variance of enzyme activity and microbial biomass showed that the soil biological characteristics decreased over 10 years of plantation, and the enzyme activity was close to the state of EBLF control in medium, while the microbial biomass failed to return to its original state during continuous planting. Redundancy analysis results show that there was a strong correlation in chemical indicators and biological characteristics. Partial least square structural equation model showed that total phosphorus, nitrate nitrogen, urease, catalase, and microbial biomass nitrogen and phosphorus were the most influential soil biochemical factors, and the indirect effect of chemical properties on volume was achieved by microorganisms through enzyme activity. Continuous planting and large-scale application of inorganic fertilizer would lead to a decrease in plantation yield and fertilizer utilization efficiency and would affect the microbial biomass and enzyme activity by destroying the stability of soil chemical properties.

Planting density affects soil quality in the deep soils of pine plantations

Planting density is one of the important factors affecting soil properties, thereby directly impacting plantation yields. However, the effect of planting density on soil quality and productivity in plantation ecosystem mostly remain unknown. The present study aims to assess soil quality in four mature pine (Pinus kesiya) plantations with increasing planting densities i.e., 700 trees ha−1 (low planting density, LPD), 1080 trees ha−1 (moderate planting density, MPD), 1260 trees ha−1 (high planting density, HPD), and 2340 trees ha−1 (very high planting density, VHPD) respectively, up to 1 m soil depth. The soil samples collected at 0–20, 20–60, and 60–100 cm depth intervals were analyzed for a total of thirty-nine physical, chemical, and biological properties. The soil quality index (SQI) was calculated using linear scoring and weighted additive method. Total carbon, arbuscular mycorrhizal fungi (AMF) biomass, gram-positive bacteria biomass, soil moisture content, and β-glucosidase enzyme were selected as the important drivers of SQI. Total carbon, AMF, and moisture content had higher contribution to SQI. The results showed that increasing planting density adversely affected soil quality. SQI was higher in the surface (0–20 cm) soil layer, and it decreased with depth. Planting densities, soil depths, and their interaction had a significant effect on SQI. Increasing SQI promoted the stem biomass with a positive linear response. Therefore, maintaining a moderate to low planting density by thinning practices and selective logging could recover natural understory vegetation, acquire high timber yield, and sustain soil quality in pine plantations.

Effect of spacing on growth performance and leaf biomass yield of Moringa stenopetala tree plantations

Moringa stenopetala is a multipurpose tree distributed naturally in the lowland dry lands of the southern part of Ethiopia. The tree has vital nutritional, industrial, and medicinal applications and is thus good for large scale and/or commercial plantations. However, its cultivation is limited to traditional practices by small holder farmers for food, fodder, shade, windbreak and medicinal value around homesteads and on farmlands. The aim of this study was to determine the effect of plant spacing on plant growth parameters and leaf biomass production of M. stenopetala. The study was conducted in Arbaminch zuria woreda of Southern Nation Nationalities and Peoples Region (SNNPR). Three planting spacings (0.5 × 0.5 m; 1 × 1 m and 2 × 2 m) were arranged in a randomized complete block design (RCBD) and the treatments were replicated three times. Survival%, root-collar diameter (RCD), height and stem diameter of the trees in each plot were recorded at three monthly intervals from the 3rd to 15 months. Data for leaf biomass were collected at the age of 27, 32 and 48 months. The harvested leaves were then oven dried to determine the dry leaf biomass. Individual Moringa trees showed better growth performance at the wider spacing of 2 × 2 m. The mean RCD, plant height and stem diameter were 7.45 ± 0.20 cm, 1.69 ± 0.06 cm and 3.19 + 0.11 cm for the wider spacing, while 3.12 ± 0.16 cm, 1.02 ± 0.07 cm and 2.12 ± 0.14 cm for the narrow spacing at the age of 15 months. The wider spacing produced the largest quantity of dry leaf biomass per individual plant (119.28 ± 9.02, 143.85 ± 10.29 and 249.8 ± 24.220 g/tree, but the least quantity on hectare bases 298.20 ± 22.54, 359.62 ± 25.73 and 624.49± 60.59 kg/ha) while the narrow spacing produced the smallest quantity per individual plant (48.36 ± 5.10, 44.74 ± 3.19 and 88.15 ± 30.28 g/tree), but the largest quantity on hectare bases (1934.40 ± 203.89, 1789.56 ± 127.78 and 3526.01± 1211.2 kg/ha) at the first, second and third harvest, respectively. This indicates that an increase in the plant spacing led to higher dry leaf biomass production per tree due to better plant growth, but the lesser the leaf biomass yields per hectare due to the lower planting density. The performance of M. stenopetala is promising and hence it can be considered for large scale and commercial plantation .