Saturday, 15 July 2006
152-10

Potassium Availability, Distribution and Categorization of Various Soil Types Under Different Rainfed Production Systems of India.

Cherukumalli Srinivasarao, Central Research Institute for Dryland Agriculture, Santoshnagar, Saidabad Post, Hyderabad, Andhra Pradesh, AK 500 059, India

Potassium Availability, Distribution and Categorization of Various Soil Types Under Diverse Rainfed Production Systems of India* Ch.Srinivasarao1, KPR.Vittal1, KN.Tiwari2 and H. Magen3

1 Central Research Institute for Dryland Agriculture, Santoshnagar, Hyderabad, 500059, Andhra Pradesh, India, 2 Potash and Phosphate Institute of Canada, India programme, Gurgaon, 122 016, Haryana, India.3 International Potash Institute, P.O. Box 569, CH-8810 Horgen, Switzerland,

Potassium fertilization is not practiced in rainfed agriculture in India assuming that Indian soils are rich in potassium and corps do not need external K supply. However, under continuous cropping in rainfed regions, huge crop K removals are reported up to 150-200 kg ha-1 depending upon amount and distribution of rainfall and biomass production. These crop removals essentially deplete soil K reserves if cropping continues further for longer period. Therefore, present study was undertaken to evaluate the soil K reserves under diverse rainfed production systems (Rainfed rice, groundnut, soybean, cotton, rabi sorghum, pearl millet, finger millet and maize) and to categorize rainfed soils based on different soil K fractions. Depth-wise sampling was done from 21 locations across different soil types under eight production systems and various fractions of soil K were assessed. In general total K was higher in Inceptisols (1.60-2.28%) followed by Aridisols (1.45-1.84%), Vertisols and Vertic sub-groups (0.24-1.72%) and Alfisols and Oxisols (0.30-1.86%). However, wide variation in total K was observed within each group of soils. Nonexchangeable K reserves also showed similar trend as that of total K in most of the profiles. Many of Inceptisls showed substantial amounts of nonexchangeable K while some of the Vertisols (Akola) and Alfisols (Bangalore) showed exceptionally low. Contrary to nonexchangeable K reserves, Vertisols showed higher exchangeable K than Inceptisols and Alfisols/Oxisols. Nonexchageable K showed significant positive correlation with total K in Inceptisols and Vertisols while it was non-significant in Alfisols/Oxisosls. However, it has significant positive correlation with exchangeable K in all the soil types indicating the dynamic equilibrium between two soil K fractions. Nonexchangeable K reserves were also involved along with exchangeable K in categorizing soils for evolving strategies to manage soil K fertility in rainfed agriculture in India.

* Contribution of Chief Scientists in soil sampling at 21 AICRPDA centres is gratefully acknowledged.


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