IPI-NFS International Workshop Colombo, Sri Lanka 1-2 December, 2003 Importance of Potash Fertilizers for Sustainable Production of Plantation and Food Crops in Sri Lanka Edited by: V.V. Nossov IPI Coordinator India, Sri Lanka and Bangladesh IPC, Post Box 486, Moscow 119034, Russia Tel.: +7-095-258-61-81 Fax: +7-095-258-61-91 E-mail: [email protected] J.D.H. Wijewardena Regional Agricultural Research & Development Centre Department of Agriculture, Ministry of Agriculture, Livestock, Lands & Irrigation of Sri Lanka Bombuwela, Sri Lanka Tel./Fax: +94-34-22-816-73 E-mail: [email protected] National Fertilizer Secretariat Ministry of Agriculture, Livestock, Lands & Irrigation of Sri Lanka 80/5, Govijana Mandiraya, Rajamalwatta Avenue Battaramulla, Sri Lanka International Potash Institute P.O. Box 569 CH-8810 Horgen Switzerland © All rights held by: International Potash Institute P.O. Box 569 CH-8810 Horgen Switzerland Tel.: +41-43-810-49-22 Fax: +41-43-810-49-25 E-mail: [email protected] Web: www.ipipotash.org 2005 Printing: Lake House Printers & Publishers Ltd, Colombo, Sri Lanka 2 CONTENTS Foreword......................................................................................................................... 5 Chapter I: POTASSIUM STATUS IN SOILS OF SRI LANKA.............................. 7 Potassium status of tea growing soils in Sri Lanka......................................................... 9 A.K.N. Zoysa and G.P. Gunaratne Potassium status of coconut growing soils in Sri Lanka............................................... 19 N.A. Tennakoon Potassium status of rubber growing soils in Sri Lanka................................................. 29 Lalani Samarappuli Potassium status of rice growing soils in Sri Lanka ..................................................... 35 W.M.A.D.B. Wickramasinghe, A.R. Dassanayake and D.N. Sirisena Potassium status of Other Field Crops growing soils in Sri Lanka............................... 43 P. Weerasinghe Chapter II: POTASSIUM NUTRITION MANAGEMENT OF PLANTATION AND INDUSTRIAL CROPS ..................................................................................... 53 Importance of balanced fertilization to meet the nutrient demand of industrial and plantation crops............................................................................................................. 55 A. Krauss Current status of fertilizer use to plantation crops in Sri Lanka.................................... 69 D.R. Wijayatilleke Potassium fertilization of tea ........................................................................................ 77 A.K.N. Zoysa and G.P. Gunaratne Potassium fertilization of rubber................................................................................... 87 Lalani Samarappuli Potassium fertilization of sugarcane in Sri Lanka ........................................................ 99 M.W.N. Dharmawardene, S.A. Ranjith and W.L. Bodhinayake 3 Chapter III: POTASSIUM NUTRITION MANAGEMENT OF FOOD CROPS .................................................................................................................................... 117 Importance of balanced fertilization to meet world food challenges.......................... 119 A. Krauss Current status of fertilizer use to food crops in Sri Lanka .......................................... 135 D.R. Wijayatilleke Potassium fertilization of paddy in Sri Lanka............................................................. 143 W.M.J. Bandara, W.M.A.D.B. Wickramasinghe and D.N. Sirisena Potassium fertilization of Other Field Crops in Sri Lanka.......................................... 161 D.M. Jinadasa and K.J. Perera Potassium fertilization of fruit crops in Sri Lanka...................................................... 173 J.M.P.B. Jayasundara 4 Foreword Sri Lanka has favourable climatic conditions suitable for growing of a wide diversity of crops. During the recent yeas the country has experienced considerable changes, resulting in the open economy and the involvement of the private sector into the economic activities. Concern of a global food production to feed the growing population of the world requires increased efforts to develop new expedients for the future. Free world trade has opened new opportunities for producers in Sri Lanka to enter global markets. Undoubtedly, to send high quality production to the world market, appropriate attention should be paid to the balanced application of fertilizers. In this respect, potash fertilizers play a vital role in crop production. Healthy agricultural production of high quality could be achieved when potash fertilizers are applied in adequate rates and in balance with other nutrients. In general, Sri Lankan agriculture shows relatively balanced use of mineral fertilizers (nitrogen to potassium ratio is about 1:0.4). High share of potash in mineral fertilizers is a clear indication that crops, and especially plantation crops, are fed with balanced nutrients. At the same time, there is low total application of fertilizers for some crops, for instance, such plantation crops as coconut and rubber. This is a serious restrain to achieve higher yields and, hence, more earnings from export-oriented agriculture. The International Potash Institute (IPI) in cooperation with the National Fertilizer Secretariat (NFS), Ministry of Agriculture, Livestock, Lands & Irrigation of Sri Lanka, has conducted the International Workshop on “The Importance of Potash Fertilizers for Sustainable Production of Plantation and Food Crops in Sri Lanka” in Colombo on 1-2 December 2003. This workshop is a continuation of IPI activities in Sri Lanka since the year 1994, when the International Seminar on the “Integrated Crop Management in Tea: Towards Higher Productivity” has taken place in Colombo. This book summarizes the results of research activities on the status of soil potassium (Chapter I) and the response of major plantation and food crops to potash fertilizer application (Chapter II and III) in different agro-ecological zones of Sri Lanka. Updated fertilizer recommendations are given for the most important crops. Moreover, major directions of further research activities are indicated to improve the available potash fertilizer recommendation. In general, the main objective of this publication is to attract more attention to the important role of potash fertilizers in achieving of sustainable high yields and top quality of both plantation and food crops in Sri Lanka. V.V. Nossov IPI Coordinator India, Sri Lanka and Bangladesh 5 6 Chapter I POTASSIUM STATUS IN SOILS OF SRI LANKA 7 8 Potassium status of tea growing soils in Sri Lanka A.K.N. Zoysa and G.P. Gunaratne Tea Research Institute of Sri Lanka, Talawakelle, Sri Lanka Abstract Tea (Camellia sinensis L.) is grown on highly weathered Oxisols and Ultisols in Sri Lanka. The main features of tea growing soils are low nutrient availability, acidity and low organic carbon content and high erodability. Tea occupies an extent of 180,000 ha in Sri Lanka and spreads from low to high elevations categorized as: Low country (0-600 m), Mid country (600-1200 m) and Up country (>1200 m), which accounts for 42, 30 and 28% respectively. The soils of different agro- ecological regions suitable for tea growing in Sri Lanka fall in to three major soil groups. They are Red Yellow Podzolic soils, Reddish Brown Latasolic soils and Immature Brown Loam soils, of which the greatest extent is represented by Red Yellow Podzolic soils. Tea soils could be divided in to three groups according to mineralogy. Some soils in Mid country have considerable amounts of K-containing minerals, i.e. mica, interstratified mica/vermiculite and vermiculite. The K release patterns in a range of tea soils were studied using an indicator plant with exhaustive cropping to examine the relationship between various K forms. The content of total and exchangeable K in tea soils varies with the location. Both these forms of K are generally high in the Up country compared to the Low country. Potassium that is immediately available for plant nutrition is generally present in the soil solution and application of K fertilizer in tea plantations greatly influences K concentrations in the soil solution. In soils, containing low specifically absorbed or non-exchangeable K, the exchangeable K may play a dominant role in the K availability. The chemical equilibrium between non-exchangeable and exchangeable K forms is very complex and depends on the overall K status of soils. Therefore, differences could be observed in soil K levels in tea growing soils owing to differences in buffering characteristics of soils. It is worthwhile to consider the K dynamics in tea soils while recommending K fertilizer application for tea plantations on a discriminatory basis. Introduction Tea is one of major plantation crops grown in Sri Lanka and its contribution to the national economy is highly significant owing to its large share in the annual foreign exchange earnings to the country. Tea generally prefers acidic soil conditions and it 9 is well grown in the wet and intermediate zones of Sri Lanka. The total tea production in the country steadily increased in the last decade and the major contributor to this growth is the tea smallholder sector in the Low country that accounts 61% of the production. Tea production in the country recorded a peak production of 310 million kg in 2002 (CBSL, 2002). As the country’s annual tea production and the productivity are increasing, soil fertility and sustainability issues