Abstract:
Low country wet zone (LCWZ), the buffer zone of rice production in Sri Lanka is having lower
productivity about 3.2 t/ha. The paddy soil in LCWZ is typically acidic and may be one of the
reasons for poor productivity. Nutrient availability in the soil is limited by the low soil pH.
Amelioration of soil pH by dolomite application is common. However, dearth of information is
available on reducing fertilizer when applying dolomite in rice cultivation. A field experiment was
conducted to study the dolomite application to enhance productivity as well as to reduce fertilizer.
Rice variety Bw 367 was tested with five treatments T1= nitrogen, potassium and phosphorus
were applied based on the Department of Agriculture fertilizer recommendation (DOA), T2 =
DOA+ dolomite (2t/ha), T3 = 75% DOA + dolomite, T4 = dolomite only and T5 = no fertilizer in
complete randomized block design with three replicates in maha 22/23 and yala 2023 seasons.
Dolomite was applied in the first season only. One month prior to sowing, dolomite was applied.
Soil pH was measured in monthly intervals and available phosphorus (P) exchangeable potassium
(K) and magnesium (Mg) were measured after harvesting. The analysis of variance and mean
separation were performed for the experimental data using the SAS version 9.4. The soil pH of the
dolomite-treated plots was increased up to 6 during the experimental period which is favorable
for rice plant growth. In DOA+ dolomite and 75% DOA + dolomite treated plots, the P, K and Mg
contents were similar. However, the significantly highest K was recorded in DOA-treated plots.
Magnesium content was 159% and 129% respectively higher in DOA+ dolomite and 75% DOA +
dolomite treatments than in DOA treatment. In both seasons, significantly higher yield was
recorded in DOA+ dolomite treated plots and it was a 20% yield increment. In both seasons, yield
of DOA treated plots and 75% DOA treated plots recorded the similar yield. In conclusion, the coapplication
of dolomite with the recommended dose of inorganic fertilizers increases the
productivity in acidic rice fields and 25% of fertilizer can be reduced without compromising the
yield.
