A handbbok on Weed Control in Rice.pdf

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Controlled-droplet applicator A controlled-droplet applicator (CDA) produces uniform-sized droplets of spray. Weeds may be effectively controlled with as little as 18 liters water/ha. Droplet size is controlled within narrow limits by spinning discs inside the applicator. Controlled- droplet applicators are lightweight. They have a plastic spray head, a small motor that drives the rotating disc, a liquid reservoir, a handle, and a power supply (e.g., one to eight 1.5-volt dry- cell batteries). Models that use a manually operated air pump (Fig. 4.3) (e.g., Birky sprayer) have been intro- duced. This eliminates the cost of batteries for the first-generation CDA. Granular applicator Herbicides sold as granules are applied using granular applicators. Whatever its size, a granular applicator consists of a hopper to contain the granules, a metering device to control flow rate, and a distribution mechanism. Granu- lar herbicides that are soluble in water may not require the same uniformity of distribution as those that are not soluble in water. Granules are often applied by hand, especially in the tropics. Because broadcasting granules by hand is not precise, the quantity of herbicide used will be higher than with other application techniques. More uniform application can be achieved on small areas by shaking the granules from a container with a perforated lid. Hydraulic applicator (pressurized) Hydraulic applicators commonly consist of a tank, pump, and nozzle. Other components include an agitator, pressure gauge, pressure regulator, hose, and boom. The tank that holds the spray solution is made of a 56 Weed control handbook corrosion-resistant material, such as stainless steel, polyvinyl material, or fiber glass. The tank has a special lid through which it is filled. The lid contains a strainer to remove debris that might clog the nozzle. The pump drives the solution through the pressure chamber to the nozzle. The most widely used small hydraulic applicator is the lever-operated knapsack sprayer (Fig. 4.4). For a detailed discussion, see Pesticide application methods (Matthews 1979). 4.2 Top, a leverage-operated knapsack sprayer; bottom, a controlled-droplet applicator. Operation of the knapsack sprayer Herbicide and water are poured into the sprayer tank. The lever is moved up and down, causing the pump to draw spray liquid from the tank into a special chamber inside the tank called the pressure chamber. Air trapped in
4.3 Controlled-droplet applicators that use a manually operated air pump are available. 4.4 Simplified drawing of a lever-operated knapsack sprayer. the pressure chamber is compressed as the liquid is forced in. On one side of the pressure chamber is the hose, which is connected to the trigger handle, and the on-and-off switch known as the cutoff valve. Compressed air forces the liquid from the pressure chamber through the hose to the nozzle. The nozzle turns the liquid into droplets, which aid in uniform cover- age of the weed or soil. The faster the lever is moved, the higher the pressure becomes. High pressure makes the herbicide droplets smaller and increases the speed with which the solution comes out of the nozzle (flow rate). For herbicide spraying, where coarse spray droplets are desired, 5-6 lever strokes per minute are adequate. Selecting the nozzle The flow rate through a nozzle de- pends on the size of the nozzle opening and the spray pressure. Increasing the nozzle size (diameter of opening) and increasing the pressure will increase the flow rate. A pressure of 70-275 kPa (see Appendix A) is recommended for herbicide application. The best way to regulate the flow rate is to change nozzle tips and to increase or decrease walking speed. Herbicide use 57
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1991 P.O. Box 933, 1099 Manila, Phi
Page 3 and 4:
Foreword Farmers everywhere search
Page 5 and 6:
Contents FOREWORD PREFACE 1 S IGNIF
Page 7 and 8: Table 1.3. Weeds as secondary hosts
Page 9 and 10: horizontal leaves. Tall plants have
Page 11 and 12: Chapter 2 Rice weeds of worldwide i
Page 13 and 14: Lowland rice weeds ASTERACEAE (Comp
Page 15 and 16: Lowland rice weeds / CYPERACEAE (se
Page 17 and 18: Lowland rice weeds / CYPERACEAE (se
Page 19 and 20: Lowland rice weeds / ONAGRACEAE (ev
Page 21 and 22: Mature plant Inflorescence Seed, ma
Page 23 and 24: Lowland rice weeds/POACEAE (grass f
Page 25 and 26: Lowland rice weeds / POACEAE (grass
Page 27 and 28: Lowland rice weeds / PONTEDERIACEAE
Page 29 and 30: Upland rice weeds AIZOACEAE (carpet
Page 31 and 32: Upland rice weeds / ASTERACEAE (sun
Page 33 and 34: Upland rice weeds / CYPERACEAE (sed
Page 35 and 36: Upland rice weeds / POACEAE (grass
Page 41 and 42: Upland rice weeds / PORTULACACEAE (
Page 43 and 44: Deepwater weeds / CONVOLVULACEAE (m
Page 45 and 46: Wetland tillage is common in most t
Page 47 and 48: leaf size), with the resultant shad
Page 49 and 50: Economics of control The economic b
Page 51 and 52: Chapter 4 Principles of herbicide u
Page 53 and 54: Preemergence herbicide application
Page 55 and 56: and behavior in the crop environmen
Page 57: Table 4.1. Meanings of signal words
Page 61 and 62: amount after spraying is 8 liters,
Page 63 and 64: The decision to spray should be mad
Page 65 and 66: farmers, however, should wear cloth
Page 67 and 68: Table 5.1. Susceptibilitles a of im
Page 69 and 70: Propanil can be used at 3-4 kg ai/h
Page 71 and 72: Thiocarbamates Thiocarbamates are a
Page 73 and 74: Quinclorac. Quinclorac is a chino-
Page 75 and 76: Planting method Transplanting into
Page 77 and 78: Direct seeded on puddled soil In di
Page 79 and 80: Table 6.2. Herbicides suitable for
Page 81 and 82: 6.4 Rice growth stages when herbici
Page 83 and 84: Fertilizer Incorporating N and P fe
Page 85 and 86: Nurseries Seedling nurseries should
Page 87 and 88: Land preparation Leveling the puddl
Page 89 and 90: Land preparation Land preparation s
Page 91 and 92: Chapter 8 Weed control in upland ri
Page 93 and 94: Hand weeding The weed-free period r
Page 95 and 96: Chapter 9 Weed control in deepwater
Page 97 and 98: Hand weeding Hand weeding is the mo
Page 99 and 100: Chapter 10 Management of some diffi
Page 101 and 102: Wild rices The important wild rices
Page 103 and 104: Herbicides For effective control of
Page 105 and 106: IRRI-International Rice Research In
Page 107 and 108: B. Conversion table for granular fo
Page 109 and 110:
Index A Absorption of herbicide, 50
Page 111 and 112:
in deepwater and floating rice, 96
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