Abstract:
An experiment was conducted at the Agronomy farm, Eastern University, Sri Lanka to study the
effect of paddy husk ash as a source of potassium on the performance of cowpea ( Vigna
unguiculata) in sandy regosol. The treatments included recommended rate (75 kg/ha) of muriate
of potash (T1) and application of paddy husk ash at the rate of 1500 (T2), 2500 (T3), 3500 (T4) and
4500 (T5) kg/ha. This experiment was laid out in a Randomized Complete Block Design (RCBD)
with five treatments and four replications in sandy regosol. Before being carried out the research
work, potassium and phosphorous contents and the pH of the soil at the experimental site and
paddy husk ash used in this experiment were analyzed. The agronomic parameters such as plant
height, number of leaves, total biomass of plant and harvest index were recorded. Potassium
content of cowpea seeds were also analyzed after harvest of pods.
The present results revealed no significant differences in plant height and number of leaves
among treatments. Significant difference was observed in total biomass among treatments.
Application of paddy husk ash at the rate of 4500 kg/ha (T5) gave the highest biomass (0.068 kg/
plant) followed by T4. Treatments showed significant difference in weight of cowpea seeds per
plant. Application of paddy husk ash at the rate of 4500 kg/ha (T5) gave the highest seed weight
per plant (0.017 kg/plant) and muriate of potash at the rate of 75 kg/ha (T1) gave second highest
weight (0.016 kg/plant). Harvest index was higher in the treatment with recommended rate of
muriate of potash (T1)(28.2%) followed by treatment with the application of paddy husk ash at the
rate of 4500 kg/ ha (T5)(24.2%). Potassium (1.46 g) content in 100 g cowpea seeds was slightly
high in the treatment with recommended rate of muriate of potash (T1)than other treatments and
in T5, potassium content was 1.44 g. After the harvest of crop, the soil pH and potassium content
of soil increased with the increasing rate of application of paddy husk ash. The soil potassium
content after harvest was high in T5 (0.193 %) followed by T4 (0.191 %) and T1 (0.191 %). In this
study, the application of paddy husk ash at the rate of 4500 kg/ ha (T5) would be more suitable for
obtaining high yield and the paddy husk ash has the positive effect on cowpea cultivation as a
source of potassium fertilizer.
