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3. SOIL • Rainfall - Rain causes washing off of nutrients and reduces their availability. • Soil pH - Low pH causes the soil to release certain nutrients making their content too high and poisonous to plants. High pH causes certain nutrients to be tightly bonded by the soil, making them unavailable as plant nutrients. 3.2.2 Types and functions of nutrients Nutrients are grouped into two types: • Macro nutrients - these are nutrients potato plants require in large quantities. Macro nutrients are nitrogen, phosphorus, potassium, calcium and magnesium. • Micro nutrients - these are nutrients required in relatively small quantities. Some nutrients included in this group are boron, zinc, calcium, iron, etc. Even though they are only needed in small amounts, they are vital for supporting plant growth. Many micro nutrients are found in organic fertilizer. Common functions of macro nutrients are described below: A. Nitrogen (N) Function: • Stimulates plant growth and enlarges leaves and tubers. • A component of chlorophyll helping plants to absorb sunlight and produce carbohydrates. • Increases tuber protein content. Important points: • Required in larger quantities than any other elements. • N-containing compounds are very unstable and hence easily lost from soil through washing off, evaporation and organic/microbial activity. • Potato crops need N particularly during the vegetative growth, tuber initiation and tuber bulking stages. B. Phosphorus (P) Function: • Plays a part in chemical processes in plant growth. • Encourages root and tuber development. Important points: • P is very stable, but bonds tightly to soil particles making it quite insoluble in soil water and difficult for plants to absorb. • Very high P content can poison and kill plants. • Potato plants need P particularly during the vegetative growth and tuber initiation stages. C. Potassium (K) Function: • Stimulates leaf growth. • Stimulates tuber growth and enlarges tubers. • Plays a part in producing proteins. • Counteracts the effects of excessive application of P. • Increases resistance to disease. • Improves tuber quality, reduces sugar content and improves storability. 8 ALL ABOUT POTATOES
3. SOIL • Increases vitamin A content. Important points: • K is relatively easily soluble in water and hence washed off in the soil. • Excessive quantity of K can poison plants. • Potato plants need K during the vegetative growth and tuber initiation stages, and especially during the tuber maturation stage. D. Calcium (Ca) Function: • Proper cell division and elongation • Proper cell wall development • Nitrate uptake and metabolism • Enzyme activity • Starch metabolism Important point: • Calcium helps reduce soil pH. • Calcium does not easily leach from soils, but over time moves to deeper layers. Sub-soils are therefore often richer in Calcium. E. Magnesium (Mg) Function: • Essential for chlorophyll formation; Mg forms the central part of chlorophyll. • Carrier of phosphorus in the plant . • As enzyme activator and a constituent of many enzymes. • Sugar synthesis. • Starch translocation. • Plant oil and fat formation. • Nutrient uptake control. Important point: • Potato plants need Magnesium in the early sprout development and vegetative growth stages in order to produce green tissue. • Deficiency of Magnesium leads to leaf yellowing with brilliant colors. • Excess causes calcium deficiency. 3.2.3 Testing soil to determine fertilizer needs Fertilizer requirements depend on quantities of nutrients already available in the environment (soil, water and air) and to what extent plants require these nutrients. If quantities already available are lower than plants’ needs, then fertilizer is applied. Excessive application can damage plants and waste money, while applying too little can prevent plants from growing to their optimum size. It is possible to determine what nutrients are present in the soil by testing soil samples. These tests can be conducted in laboratories. Simple Soil Test Kits, available in several Asian countries for ready use in the field, can also provide farmers and extension workers good indications of available nutrients in soil and corresponding fertilizer management requirements. If so desired, soil testing should be done 2-3 weeks before planting potatoes. Soil nutrient content varies greatly from A HANDBOOK TO THE ECOLOGY AND INTEGRATED MANAGEMENT OF POTATO 9
Page 2 and 3: Authors Editors Contributors Transl
Page 4 and 5: HOW TO USE THIS MANUAL? HOW TO USE
Page 6 and 7: TABLE OF CONTENTS 5.4. Planting____
Page 8 and 9: TABLE OF CONTENTS vi ALL ABOUT POTA
Page 10 and 11: 1. INTRODUCTION Originally, IPM was
Page 12 and 13: 2. POTATO PLANT GROWTH AND DEVELOPM
Page 14 and 15: 3. SOIL • Observe the sediment: t
Page 18 and 19: 3. SOIL field to field and at diffe
Page 20 and 21: 3. SOIL • Prevention of erosion a
Page 22 and 23: 3. SOIL application of the various
Page 24 and 25: 3. SOIL 16 ALL ABOUT POTATOES
Page 26 and 27: 4. SEED PREPARATION AND PRODUCTION
Page 32 and 33: 5. CULTIVATION PRACTICES Table 8: D
Page 34 and 35: 5. CULTIVATION PRACTICES 5.5 Hillin
Page 36 and 37: 5. CULTIVATION PRACTICES • Mainta
Page 38 and 39: 6. INSECT ECOLOGY 6.3 Insect life c
Page 40 and 41: 6. INSECT ECOLOGY 6.5 Beneficial in
Page 42 and 43: 6. INSECT ECOLOGY How to use it: Sq
Page 44 and 45: 6. INSECT ECOLOGY water or may alre
Page 46 and 47: 6. INSECT ECOLOGY F. Pesticide haza
Page 48 and 49: 7. MAJOR POTATO PESTS • Balancing
Page 50 and 51: 7. MAJOR POTATO PESTS pest has many
Page 52 and 53: 7. MAJOR POTATO PESTS to eat them.
Page 54 and 55: 7. MAJOR POTATO PESTS Lifecycle The
Page 56 and 57: 7. MAJOR POTATO PESTS Cutworms in t
Page 58 and 59: 8. MAJOR NATURAL ENEMIES OF POTATO
Page 64 and 65: 9. DISEASE ECOLOGY • The environm
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9. DISEASE ECOLOGY 58 ALL ABOUT POT
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10. MAJOR POTATO DISEASES Managemen
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10. MAJOR POTATO DISEASES • Destr
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10. MAJOR POTATO DISEASES o In thei
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10. MAJOR POTATO DISEASES B.3. Usin
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10. MAJOR POTATO DISEASES Viral dis
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10. MAJOR POTATO DISEASES Managemen
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10. MAJOR POTATO DISEASES • Potas
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10. MAJOR POTATO DISEASES Potato vi
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11. WEED ECOLOGY You can manage wee
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12. HARVEST AND POST-HARVEST MANAGE
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12. HARVEST AND POST-HARVEST MANAGE
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GLOSSARY GLOSSARY Aphid Bacterial w
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