Sustaining soil health cannot be divorced from sustainable crop production. Organic, or natural, farming is being promoted as a good sustainable agriculture practice. One aspect of organic farming that could significantly enhance and sustain soil health, soil quality, and crop productivity is the use of high-quality soil conditioners or organic amendments produced from agro-wastes. Thus, the objective of this study was to characterize the chemical and biological properties of selected agro-wastes with potential for use as organic amendments in sustaining soil health. Standard procedures were used to produce and characterize the soil conditioners, namely fermented plant juice (FPJ), fermented fruit juice (FFJ), palm kernel shell (PKS) biochar, and kitchen waste (KW) compost. The fermented juices (FPJ and FFJ), PKS biochar, and KW compost exhibited chemical and biological properties with good potential as soil conditioners or organic amendments to sustain soil health. The fermented juices contained important microbes that can solubilize P and K in soil for crop use. The high pH and C content of the biochar and compost and the high cation exchange capacity of the biochar are good indicators of the potential of these materials to sustain soil health in terms of the liming effect of acid soils, nutrient and water retention, nutrient reserves, and a suitable habitat for microbial life. Moreover, the organic amendments contain reasonable amounts of macro- and micro-nutrients, which could be released to increase soil fertility. Despite these potential benefits, field application of these organic amendments is necessary to evaluate their effects on soil health and crop production in both the short and long term.

Sustainable urban development is a major issue in developing countries, namely in environmental and social aspects. Urban forests have the potential to address these issues. Thus, it is not surprising that urban forest research is slowly gaining traction in these regions. However, there have been limited urban forest research reviews focusing on developing countries, especially tropical countries in the global south. Research reviews are vital in identifying the distribution of research themes, hence revealing research gaps and needs. Therefore, this review paper aims to provide a deep insight into the development of urban forest research in Malaysia in the past 20 years. The core purpose of this review is to analyze the distribution of research themes in Malaysia, thus identifying research gaps and needs in developing countries. A total of 43 articles were selected for this review, using the PRISMA framework. The distribution of research articles showed a continuous increase over time, especially for the past five years (2016 to 2021). The reviewed articles were categorized according to five emerging research themes in urban forestry. More than 41% of the reviewed articles fell under Theme 1 (the physicality of urban forests), with the majority being on biodiversity (n = 10). Theme 5 (the governance of urban forest) had the lowest research output (n = 3). Urban forestry research is slowly gaining prominence globally including the global south; however, there are obvious preferences in research focus, causing some research questions to be neglected. These research gaps are especially evident in four areas—soil science, ecophysiology, valuation (economics), and environmental justice. These research gaps should be addressed by the scientific community to ensure a thorough and complete research growth pertaining to urban forestry.

Inappropriate drainage and agricultural development on tropical peatland may lead to an increase in methane (CH₄) emission, thus expediting the rate of global warming and climate change. It was hypothesized that water table fluctuation affects CH₄ emission in pineapple cultivation on tropical peat soils. The objectives of this study were to: (i) quantify CH₄ emission from a tropical peat soil cultivated with pineapple and (ii) determine the effects of water table depth on CH₄ emission from a peat soil under simulated water table fluctuation. Soil CH₄ emissions from an open field pineapple cultivation system and field lysimeters were determined using the closed chamber method. High-density polyethylene field lysimeters were set up to simulate the natural condition of cultivated drained peat soils under different water table fluctuations. The soil CH₄ flux was measured at five time intervals to obtain a 24 h CH₄ emission in the dry and wet seasons during low- and high-water tables. Soil CH₄ emissions from open field pineapple cultivation were significantly lower compared with field lysimeters under simulated water table fluctuation. Soil CH₄ emissions throughout the dry and wet seasons irrespective of water table fluctuation were not affected by soil temperature but emissions were influenced by the balance between methanogenic and methanotrophic microorganisms controlling CH₄ production and consumption, CH₄ transportation through molecular diffusion via peat pore spaces, and non-microbial CH₄ production in peat soils. Findings from the study suggest that water table fluctuation at the soil–water interface relatively controls the soil CH₄ emission from lysimeters under simulated low- and high-water table fluctuation. The findings of this study provide an understanding of the effects of water table fluctuation on CH₄ emission in a tropical peatland cultivated with pineapple.

Sandy-textured soil infertility poses a problem for sustainable crop cultivation. This problem is usually dealt with by the addition of chemical fertilizers, which are expensive and can cause serious environmental issues if not managed well. A better alternative to improve and manage sandy soil infertility is the use of organic amendments produced from agro-wastes. This two (2)-year field study was conducted in a sandy-textured soil grown with black pepper to evaluate mainly the effects of chemical fertilizer, fermented plant and fruit juices, compost, and biochar on soil properties and morpho-physiological characteristics and yield of black pepper. Generally, the results indicated that the combination of fermented fruit juice, compost, and biochar was comparable to and in some cases better than chemical fertilizer in terms of soil physical, chemical, and biological properties as well as crop performance. These findings were even more pronounced in the second year of measurements. There were strong positive relationships between soil N and pepper leaf chlorophyll content and between soil microbes and soil respiration. The findings showed that these soil amendments produced from agro-wastes are a good alternative to the use of chemical fertilizers on sandy soils to improve soil fertility and productivity and the yield of black pepper sustainably.

Commercial plantations of Eucalyptus species have been established in Malaysia, especially during the past 10 years, with the aim of sustaining the supply of wood and timber products for industrial use in Malaysia. As part of an assessment of fungal diseases affecting Eucalyptus species in four regions in Malaysia, including Kelantan, Pahang, Sabah, and Selangor, stem canker disease was discovered to be a widespread disease infecting Eucalyptus species in Malaysia. This study aimed to identify the fungus-causing stem canker disease, test its pathogenicity in Eucalyptus, and determine the mating type of isolates from the infected trees. The fungi were identified based on morphology and through comparisons of DNA sequence data from the ITS, β-tubulin 2 gene, and TEF-1α gene regions. Phylogenetic analyses showed that the causal agent of the stem canker was Chrysoporthe cubensis infecting Eucalyptus plantations in Pahang and Chrysoporthe deuterocubensis infecting Eucalyptus plantations in Kelantan, Sabah, and Selangor. We believe this is the first report of Chrysoporthe cubensis-infected Eucalyptus in Malaysia and Southeast Asia, while Chrysoporthe deuterocubensis is the first-reported species infecting Eucalyptus pellita in Malaysia. Moreover, the fact that the mating-type MAT1-1 and MAT1-2 genes and the pheromone genes ppg1, ppg2, pre1, and pre2 were identified in all isolates indicates that Chrysoporthe cubensis and Chrysoporthe deuterocubensis are homothallic mating systems. Pathogenicity was tested on a 3-year-old standing tree, 1-year-old seedling, and detached healthy leaves, which were re-isolated for fulfilling Koch’s postulates. In pathogenicity trials, both Chrysoporthe cubensis and Chrysoporthe deuterocubensis gave rise to lesions on wounded Eucalyptus. Both Chrysoporthe spp. were equally pathogenic to Eucalyptus urograndis and Eucalyptus pellita and should be regarded as a biosecurity concern in Malaysia’s forest plantation industry.