Potassium Improves Yield and Quality of Tomato in the Red & Lateritic Soils of West Bengal with Low Inherent Fertility

The importance of tomato as a vegetable crop is reflected in its large scale cultivation in the world. Tomato is grown in about 4 million hectares over 160 different countries, biggest producer being China with 25 million tonnes of production. India produces about 7.5 million tonnes of tomato from around 450 thousand hectares. Current average world yield stands at 27 tonnes/ha, while current average productivity in India is 17 t/ha.

Values in parenthesis are productivity in tonnes/ha at corresponding year

Tomatoes can be produced across a wide range of soil as long as drainage and physical soil structure is good. The plant produces a fibrous root mass, which can exploit the subsoil given the absence of cultivation pans. Most of the root mass is normally concentrated in the cultivated zone of top 60cm and 70% of the root volume is in the top 20cm of top soil. Optimum soil pH is between 6.0-6.5 but it can grow between 5.0 to 7.5 pH.

Tomato require good nutrition. Soil test based fertilizer application is essential to ensure nutrients don't limit fruit yield and quality. Nitrogen and potassium are fundamental to achieve high marketable yield while phosphorus is essential for early growth and root development. Correct form of nitrogen is critical where the ammonium form can restrict growth and adversely affect quality. The importance of potassium in ensuring normal growth and production of quality fruits is well recognized. Tomatoes have a relatively high potassium requirement compared to nitrogen with over 300 kg/ha of potassium typically being utilized. Potassium is needed throughout the season and is a major component of fruit at around 250 mg K per 100g of fruit, a very high concentration compared to phosphorus at 25-40 mg/100g of fruit. There is usually 2.6 to 3.6 kg of K taken into the plant for every tonne of tomato harvested and the demand is highest during fruit balking. Potassium also has an important role to ensure quality by determining sugar levels, as well as ripening and storage characteristics. An inadequate supply of potassium leads to uneven ripening, blotchy ripening, high levels of internal white tissue, yellow shoulder, decreased lycopene, irregular shape and hollow fruits. Deficiency of potassium in tomato plants causes leaves to turn dark brown, yellowish to white necrotic dots develop near the leaf margins of the older leaves, which merge into brown necrotic areas around the leaf margins.


Potassium deficiency symptoms in tomato plant

Seeing the need to improve farmers awareness on adequate and balanced NPK application, PPIC-India Programme conducted a farmer’s field trial in collaboration with Department of Horticulture of the Institute of Agriculture, West Bengal, in the sub-humid lateritic belt of Birbhum district, West Bengal. Considering the role of potassium in yield and quality of tomato, the effect of different levels of potassium on yield and quality of tomato, cv. S-120 were explored in a soil where the inherent potassium content is low. The available N, P₂O₅ and K₂O content of the soil was 90.7 kg/ha, 201.6 kg/ha and 122 kg/ha, respectively. Treatments were designed keeping the soil test based N (150 kg/ha) and P (80 kg/ha) recommendation constant, while varying the levels of K from 110 to 190 kg/ha. Experimental data clearly shows significant improvement in yield and yield attributing factors of tomato at higher level of potassium application.