Weeds are diverse in habitats throughout the world. In landscape management, weed is of major concern because they compete for growth factors with landscape plant of interest. Modern management relies on the importance of synthetic chemicals to control weeds as unwanted plants to reduce the weed management cost. The use of herbicides is not an appropriate tool for controlling development of some weeds but can create negative effects to the environment. Managing the natural and landscape resources are not only designing for good views and environment merely, but need to sustain all of living environment through consideration. Therefore, this study was aimed to explore Melaleuca cajuputi, heath forest species as potential natural herbicides agent in sustainable landscape management. Three assessments were conducted to determine their effectiveness towards suppressing weeds without degrading the environmental quality index. Assessment of allelochemical compounds in M. cajuputi demonstrated that these species have allelopathic potential as a natural herbicide.

Kerangas or heath forests are found on podzolised siliceous sands (spodosols), where gradually decomposing organic matter occurs on the soil’s surface. Changes in the extent of podzol development, soil consistency, and poor nutrient contents signify the unique properties of sandy soil in the heath forest at Rantau Abang, Terengganu, Malaysia. Unfortunately, the sandy soil’s chemical and physical properties are in critical condition due to human activities such as cutting and burning, impacting the sustainability of this ecosystem and its ground cover of shrubs, sparse grass and sedge. Therefore, it is crucial to study the properties of sandy soils in heath forests before their extinction. This analyzed the physical and chemical attributes of heath forest sandy soils regarding heavy metal toxicity, pH, concentrations of carbon, nitrogen, available phosphorus, cation exchange capacity (CEC), allelochemical compounds, total phenolic content in the soil, soil colour, and soil texture. The solid was found to be nutrient-deprived due to its extreme acidity and toxicity. The results showed that allelochemical matters were higher in plants but not in the soil attributes and the water bodies, along with a highly active response in young plant tissues due to their sources of phenolic content. Remarkably, the overall phenolic content was observed to be considerably high in the semi-mature phase of vegetation.

Rhizophora apiculata and Acrostichum aureum are a common mangrove species in Malaysia. Allelochemical interaction of the mangrove species was speculated to play an important role in dominance in the harsh mangrove environment. This study assessed the quantitative and qualitative determination for total phenolic content and individual phenolic compounds as allelochemical content for R. apiculata and A. aureum leaves as a potential allelopathic substance. The second objective is to investigate the allelopathic effect towards weed germination and growth through in vitro model system. Two types of maceration extraction comprising water extraction and sequential alkaline extract were used for allelochemical screening analysis. Both extractions were separated by ethyl acetate. Acrostichum aureum had the highest total phenolic content (1129.52 µg GAE/g DW) in comparison with R. apiculata. Meanwhile, the quantitative analysis by HPLC, revealed that different extraction detected different individual phenolic acid, Caffeic acid detected in both mangrove species in sequential alkaline extraction by A. aureum. The allelopathic effect of Chloris barbata for A. aureum extract indicated that during pre-emergent development, the suppression of weed growth was higher compared to post-emergent. Therefore, A. aureum may work as an allelochemical producer and can contribute to the establishment of pure colonies of A. aureum in the mangrove ecosystem.