Potassium for Sustainable Crop Production and Food Security
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IPI Proceedings The First National Potash Symposium Dar es Salaam, Tanzania, 28-29 July 2015 Potassium for Sustainable Crop Production and Food Security The First National Potash Symposium Dar es Salaam, Tanzania, 28-29 July 2015 Potassium for Sustainable Crop Production and Food Security Edited By: Mkangwa, C.Z., J.D.J. Mbogoni, G.J. Ley, and A.M. Msolla Sponsored by Organized by Ministry of Agriculture Food Security and Cooperatives Agricultural Research Institute Mlingano National Soil Service P.O. Box 5088, Tanga, Tanzania African Fertilizer and Agribusiness Partnership (AFAP) Amverton Towers, 1st Floor, Chole Road, Dar es Salaam, Tanzania. www.afap-partnership.org Correct citation: Mkangwa, C.Z., J.D.J. Mbogoni, G.J. Ley, and A.M. Msolla (eds.). 2015. Potassium for Sustainable Crop Production and Food Security: Proceedings of the First National Potash Symposium in Tanzania, 28-29 July 2015, Dar es Salaam, Tanzania. 190 p. International Potash Institute, Switzerland. 2020 © All rights held by International Potash Institute (IPI) Industriestrasse 31 CH-6300 Zug, Switzerland T +41 43 810 49 22 [email protected] www.ipipotash.org ISBN: 978-3-905887-27-3 DOI: 10.3235/978-3-905887-27-3 Printed in Israel Contents Page Foreword ............................................................................................................. 5 Keynote Papers 1. The status of exchangeable potassium in major soils of Tanzania .................. 7 2. Role of potassium in human nutrition ............................................................ 27 Potash Distribution in the Soils of Tanzania 3. Potassium status in some soils: the case of Northern, Central and Eastern zones of Tanzania .................................................................................. 40 4. Status of exchangeable potassium in soils of selected landscapes of the Southern Highlands in Tanzania ........................................................................ 48 5. Potassium status in the major agricultural soils of Lake and Western zones of Tanzania and its role in sustainable crop production and food security ........ 56 6. Variability of exchangeable potassium in soils of Tanzania: A soil fertility challenge for sustainable crop production ............................................ 73 Role of Potash for Sustainable Crop Productivity in Tanzania 7. Potassium deficiencies limit common bean (Phaseolus vulgaris L.) production in West Usambara, northern Tanzania ............................................. 90 8. Nutritional requirements of potassium for crop production: the case of sisal production in Tanzania ........................................................................ 106 9. Potential for response to potash application: the case of maize and rice production in Tanzania ..................................................................................... 115 10. The role of potash for sustainable crop production: The case of flue-cured tobacco ............................................................................................ 131 Trends of Potassium Levels in Soils of Tanzania 11. Trends of potassium levels in soils under sisal, maize, rice and cassava-based production systems in Tanzania ............................................... 138 Economics of Potassium Based Fertilizers for Sustainable Crop Production 12. The law of the minimum: Linking potash fertilizer utilization, farm level production productivity, and economic losses in Tanzania .................... 151 13. African Fertilizer and Agribusiness Partnership (AFAP) .......................... 169 Annexes Annex 1. Way forward/deliberations from the First National Potash Symposium ........................................................................................... 173 Annex 2. Opening statement ............................................................................ 175 Annex 3. Closing remarks ................................................................................ 181 Annex 4. List of participants ............................................................................ 184 Foreword Over five decades, potassium (K) has been regarded as sufficient in most Tanzanian soils. This generalization has led to limited research with regards to soil K status, plant nutrition and to the development of fertilizer recommendations which include K in fertilizer formulations. Tanzania has K-blended fertilizer recommendations for just a few crops like sisal, tea and tobacco, with other crops depending on inherent K supply from the soil, which is gradually declining due to inadequate K supplies. In recent years, it has been recognized that K levels in some soils are lower than anticipated, and that K deficiency symptoms are now common in certain major crops like cassava, maize, and rice. With such observed deficiencies, it is not possible to provide fertilizer recommendations – that include K – with certainty. In response to declining potash levels in Tanzanian soils, the first Tanzania National Potash Symposium was held at the Protea Hotel Courtyard, Dar es Salaam, Tanzania from 28-29 July 2015. The Symposium’s objectives/themes were to: 1) obtain baseline information on K research in Tanzania; 2) synthesize available information; and 3) identify research gaps which will establish a K research agenda. These proceedings are an outcome of the Symposium, which was relevant and timely to address K fertilizer demand in Tanzania, and include the papers presented at the event. The main theme of the symposium was Potassium for Sustainable Crop Production, Food Security and Poverty Reduction. In this Symposium, two keynote and 11 research papers were presented. The research papers presented were divided into four sub-themes, namely: Sub-theme 1: Potash distribution in the soils of Tanzania Sub-theme 2: Role of potash for sustainable crop productivity in Tanzania Sub-theme 3: Trends of potassium levels in soils of Tanzania Sub-theme 4: Economics of K-based fertilizers for sustainable crop production A presentation was also made on K-based fertilizer formulation and packaging, but this paper was not made available for inclusion in this publication. The proceedings also include a chapter on the way forward, which provides recommendations for the K research agenda in Tanzania. The papers presented at the Symposium highlighted the extent of potash deficiency, which was not previously known and is among the major soil fertility constraints resulting in low crop yields. Over the years, research has concentrated 5 only on nitrogen and phosphorus-containing fertilizers which, in order to balance nutrient ratios, have resulted in the greater acceleration of potash uptake from soil reserves. The Tanzanian Department of Research and Development of the Ministry of Agriculture, Livestock and Fisheries is keen to ensure that a K research agenda is implemented for the benefit of local farmers. The Department of Research and Development will also include potash research in the priority areas. On behalf of the Department of Research and Development, I would like to acknowledge the African Fertilizer and Agribusiness Partnership, in collaboration with the Agricultural Research Institute-Mlingano, for organizing this wonderful symposium; as well as the International Potash Institute of Switzerland for providing the financial support needed to hold this symposium and produce these proceedings. I sincerely thank them all for their efforts, determination and commitments in this endeavour. Dr. Hussein Mansoor Ag. Director, Research and Development Ministry of Agriculture, Livestock and Fisheries 6 Keynote Papers 1. The status of exchangeable potassium in major soils of Tanzania Joseph D. Mbogoni Agricultural Research Institute Mlingano, P.O. Box 5088, Tanga, Tanzania Mobile: +255 685 493 600, E-mail: [email protected] Introduction Tanzania has a total area of 945,000 km2 and is the largest country in the East African Community. The area covered by inland lakes is 59,000 km2 (6% of the total area) and the remaining land covers 886,000 km2 (94% of total area). Over 100,000 km2 are devoted to reserves and national parks (NBS, 2012a). The physiography ranges from coastal plains along the Indian Ocean to the highest mountain in Africa, Mount Kilimanjaro (5,895 m). The occurrence of a wide range of climatic conditions with the potential to support substantial growth in agricultural production highlights this complex physiography. About 66% of the land area is planted with annual crops, while permanent or perennial crops occupy 15% and about 8% is planted with a mixture of annual and permanent crops. The remaining area (11%) is under fallow (FAO, 2004). Tanzania currently has a population of 45 million of which approximately 80% obtain their livelihood mainly from smallholder agriculture. Nationwide, maize is the crop of choice for an overwhelming majority of households. Other food crops are beans, paddy rice, groundnuts, sorghum and sweet potatoes, in that order, each engaging at least 500,000 farm families. Major cash crops are coffee, tea, sugarcane, wheat, barley, tobacco, sisal, cotton, sunflower, sesame and cashew (NBS, 2012b). Nationwide, a significant proportion of all crops are planted during the long rainy season. The area planted with cereal crops during the short rainy season is about a fifth of the area planted during the long rainy season (NBS, 2012a). Despite the dependency on agriculture for livelihood and economic development, fertilizers are only used on a small proportion