MSc

The study entitled “Effect of continuous application of rice husk ash (RHA) on
Inceptisols of Palakkad Eastern plains” was conducted during 2014 - 16 in the Department
of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara with the
objective of finding out the physical and chemical changes of soil resultant to continuous
application of RHA and its relationship with performance of coconut palms.
Vadavannur region under Inceptisol soil order of Palakkad Eastern plains stands out
as a location where RHA (the product obtained on partial oxidation of rice husk, from rice
mill, at a temperature around 250 to 400oC) is continuously being applied in the field for
three decades along with inorganic nutrients to the coconut palms at the rate of four to five
baskets/palm on volume basis. In this study, RHA samples were collected from the rice
mills and analyzed for its composition in terms of carbon, macro and micro nutrients and
the beneficial element silicon.
Further, representative surface soil samples were collected during August -
December 2015 from four RHA amended and non- amended locations of the Palakkad
Eastern plains (Vadavannur, Muthalamada, Thathamangalam and Mullakkalkolambu) and
its physico- chemical properties were determined. The index leaves (14th leaf) of coconut
palms were also collected from RHA amended and non-amended locations and biometric
characters (length of index leaf, total number of leaflets per index leaf, average length and
width of leaflets, number of bunches per palm and average yield) were recorded. Samples
of soil and plant were analyzed for different nutrients viz. C, N, P, K, Ca, Mg, Fe, Mn, Cu,
Zn, Na and Si.
Analysis of RHA revealed that its pH was alkaline (7.5-8.3). Cation exchange
capacity of the material ranged from 7.5 to 9.5 cmol(+) kg-1. Chemical constituents
included Si (35%), C (7%), N (0.18- 0.27%), P (0.39-0.57%), K (0.35-0.58%), Ca (0.08-
0.1%), Mg (0.09-0.2%) and micronutrients in trace amounts.
On comparison of the physical properties of soil in amended and non-amended
locations, the aggregate stability, infiltration rate, water holding capacity and porosity were
found to be positively influenced by RHA application. The content of total N, total and
available P and K and available Si of soils showed significant increase in amended regions.
Exchangeable cations and effective cation exchange capacity were also more in the RHA
amended regions. The content of total carbon and particulate organic carbon especially that
associated with micro-aggregates was high in the amended area as compared to the nonamended
area.
A significant difference in the biometric observations of index leaves (length of
index leaves and total number of leaflets per index leaf) of palms in amended location as
against non-amended locations was another noticeable feature. The palms under integrated
nutrient management along with RHA yielded more. The average yield per palm was
observed as 86 nuts/year. The content of major nutrients, Ca and Si in the index leaves was
also recorded high in the RHA amended palms.
The farmers of Vadavannur region resorted to RHA application only with an
objective to address the issue of environmental nuisance and menace, without attributing
any scientific rationale on its value as a soil amendment. The results of the present study
indicate the benefit of application of RHA in improving the physical and chemical
properties of soil. The alkaline pH of RHA establishes its suitability as an alternative liming
material for acid soils to improve the soil fertility and productivity. It is suggested that
further studies conducted under designed experimental stipulations for validation of RHA
would decipher more precise information on its suitability as a balanced material for soil
amendment.