SOILS
A precise knowledge of soil is of great value in managing forests and plantation for increasing productivity, as it helps in correlating site conditions with regeneration, growth, distribution and successful establishment of commercial plantation; however S. album has no barrier for the type of soil texture or structure. It adapts well to different climatic and soil conditions. It is commonly said, “While other tree species requires soil with good nutrients for its growth and establishment, Sandalwood trees grows well even though soil is not fertile”.
Occurrence in different soil type
Red ferruginous loam is the most common soil on which sandal tree occurs, the underlying rock often is metamorphic and is chiefly geneiss. In India S.album occur in different type of soils; like laterite, sandy loam, geniss quartz, black clayey soils.
The soils should be moderately deep with good drainage with good physical properties, mostly acidic to neutral, with soil pH 6.5 to 8.5
In Indonesia, trees grows well in well-drained soil and adapt to rocky or stoney soils with low fertility. In Australia, ORIA (Ord River Irrigation Area) soil is described as black cotton soil texture of Kanunurra clay derived from recent river alluvia with an alkaline pH of 7.8 These soils are dark brown self-mulching plastic clays. They have poor drainage when wet. In Sri Lanka, it occurs in different type of soil ranging from lateritic to sandy loam and clay.
Mei Qi-wen et al (2011) during their studies on the influence of rhizosphere pH value of the host on growth of Indian sandalwood found, that the root length and shoot height are significantly higher at pH 5.5 The tree grows best in the weak acidic condition. However, they also feel, there is no evidence to prove for the optimum rizospheric pH for sandalwood tree, but there could be some veiled association between the host parasitic relationships. Their study was based on change of sub-localisation of acid phosphate (ACP) during the haustorial development.
Influence of soil on growth and heartwood formation
In a study carried out by Jain et al., (1988) on soil properties and their relationship to the growth of sandal in three areas, it was observed that lime status, water holding capacity, pore space, volume expansion on wetting, exchangeable calcium and magnesium and available potash, exert positive influence on the increment in girth and height. It was observed that specimens obtained from trees on relatively poor rocky gravely soils had higher oil content than those of specimens from fertile soils. It is believed that the best growth of sandal can be seen when it is growing in fertile soil and in association with xerophytic conditions and suitable host.
Soil in relation to incidence of spike disease of sandal
The spike disease of sandal has been studied from various angles and due attention has also been given to understand the role of soil on the incidence of spike disease.
Comparison of data of the soils from healthy and spiked areas showed that under spiked threes they were calcareous and had lower quantities of available nutrients, especially phosphorus, whereas those having healthy sandal plants were all non-calcareous and had higher amount of available nutrients. Hence, it was viewed that calcareous nature and low amount of available nutrients in the soil may serve as predisposing factors for the onset of the disease (Khan and Yadav, 1962).
The nature and properties of soil as such may not directly influence the incidence of spike disease. However, in combination with other ecological and edaphic factors, it could serve as a predisposing factor for the onset of the disease.