August 2010

IPNI-IPI-NBSS & LUP Workshop on "Review and Refinement of Fertilizer K Recommendations in Vertisols", 24-25 August 2010, Nagpur, India.

In recent years, it has become apparent that potassium (K) fertilizer recommendations are rather generalized when it comes to inclusion of vertisols. Vertisols, with high clay content, need a much higher K status to meet plant requirements, as compared to light textures soils.

The majority of vertisols in India are found in Maharashtra, Madhya Pradesh, Andhra Pradesh, Karnataka, Tamil Nadu, Gujarat, Rajasthan and Chhattisgarh (see soil map of India). Crops grown are predominantly rainfed and include sorghum, soybean, cotton, maize, groundnut, chickpea, sugarcane, and citrus, among others.

Within this context, the International Plant Nutrition Institute (IPNI), International Potash Institute (IPI), and the National Bureau of Soil Survey and Land Use Planning (NBSS & LUP) of the Indian Council of Agriculture Research (ICAR) organized a one and a half-day workshop to assess the requirement for changing K fertilizer recommendations in vertisols.

Around forty scientists from universities in the vertisol regions, ICAR and state officials were invited to discuss this issue with the aim to re-align fertilizer recommendations to maximize farmers’ income and maintain soil fertility. Twelve papers were presented including coverage of the special mineralogy of vertisols, K requirements of crops grown, typical responses to K applied, and suitability of the recommendations with regard to the actual responses reported over many years.

After lively and frank discussions, it was unanimously agreed that the present threshold for K fertilizer recommendations in vertisols (55 ppm as the limit that only below K is given) needs to be significantly increased, even doubled to 250 kg ha^-1 (approx. 120 ppm). Further steps are needed to be taken at universities working on vertisols to refine and conclude this recommendation. Dr. Dipak Sarkar, Director of NBSS & LUP summarized the workshop.

Dr. Harmandeep Singh, Deputy Director IPNI, organized the workshop and also edits its proceedings, which will be available later this year.