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Design, Development and Performance 
evaluation of a manually operated multi 
row weeder for SRI rice in Sri Lanka 
P.D. K...
Introduction 
• Rice is the staple food for nearly a half of the 
world’s population 
• Rice production is to be increased...
•System of Rice Intensification (SRI) is a 
technology which was revamped recently for 
increasing the productivity of irr...
Barriers for increasing the farmer adoption of the 
SRI 
•Labour consuming activities like, 
marking the rows before trans...
•Presently, 
single row cono-weeder 
double row cono-weeder 
separate markers - manually operated 
manually operated 
•Yet...
•Most of the SRI farmers in Sri Lanka are 
holding small sized lands and involving the family 
labour in farming. 
•In ord...
Methodology 
Designing the weeder
•The most salient features of this design are, 
 arrangement of wheels 
 the frame with adjustable ground clearance 
(to...
•After completing one set of rows, operator has 
to lift the device with the frame and move into 
another set of rows. 
•H...
•The first trail of the prototype was carried out in 
the experimental paddy field of Rajarata University. 
•eight plots w...
•Before testing the machine in the field, 
 conditions of field and soil 
 type and characters of soil (soil moisture on...
Nursery 
Manual marking Manual transplanting
•First, second, and the third weeding were made 
between 8 -10, 18-20, 28-30 days after date 
of transplanting. 
•At each ...
Following equations were used 
Weeding Efficiency 
WE = (N1-N2)/N1 x 100 
N1 is the number of weeds before weeding 
N2 is ...
Effective Field capacity 
CE- hah-1 = (s.w)/10 
s - the traveling speed (kmh-1) 
w - is the width of work (m) 
(Hunt, 1995...
Results 
Device characteristics 
Total length of the device =125 cm 
Total width of the device =100 cm 
Total height of th...
•After the first trail, numbers of practical 
problems were recognized, 
 higher weight which created problems in handlin...
Modifications -01 
•The machine was modified in order to reduce the 
weight and obtained the optimum dimensions 
•In this ...
•The performance of the new design was evaluated 
as previous design and followings are the results. 
Calculations: 
Theor...
•Although it achieved a satisfactory field capacity, 
the damaged paddy plant percentage was still the 
same. 
•Reducing t...
Modifications -02 
•To address the problems encountered in the fist 
modifications, it was decided to reduce the number 
o...
•The performances of this three- row weeder 
were evaluated compared to the single row cono-weeeder, 
double row cono-weed...
Weeding with 
single row cono 
weeder 
Weeding with double 
row cono weeder 
Weeding with 
three 
row weeder
Results 
Device characteristics 
Total length of the device = 105 cm 
Total width of the device = 70 cm 
Total height of t...
Table 01: Comparison of weeders for the efficiency 
Weeding 
Weeds 
method 
destroying 
% 
Damaged 
paddy 
plant % 
Work 
...
Modifications -03 
•Although, the three row weeder has been 
modified up to a satisfactory level, it was realized 
that th...
•Therefore, the handle was modified and three 
floaters were attached in front of each 
weeding wheel to improve the weedi...
Results 
Device characteristics 
Total length of the device = 55 cm 
Total width of the device = 60 cm 
Total height of th...
Table 02: Performances of the three row weeder against sex 
Male Female 
Theoretical field capacity 0.043 ha/hr 0.043 ha/h...
Conclusions 
•The final version of the multi row weeder (Three row 
weeder) has shown the highest field capacity (0.034 
h...
Acknowledgement 
• This is one of the outcome of the on going 
collaborative research program between 
Oxfam in Sri Lanka ...
Cost 
• Cost for first five row weeder= 12,000.00LKR 
• Cost for last three row weeder = 5,000.00 LKR
1411 - Design, Development and Performance: Evaluation of a Manually Operated Multi-row Weeder for SRI Rice in Sri Lanka
1411 - Design, Development and Performance: Evaluation of a Manually Operated Multi-row Weeder for SRI Rice in Sri Lanka
1411 - Design, Development and Performance: Evaluation of a Manually Operated Multi-row Weeder for SRI Rice in Sri Lanka
1411 - Design, Development and Performance: Evaluation of a Manually Operated Multi-row Weeder for SRI Rice in Sri Lanka
1411 - Design, Development and Performance: Evaluation of a Manually Operated Multi-row Weeder for SRI Rice in Sri Lanka
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1411 - Design, Development and Performance: Evaluation of a Manually Operated Multi-row Weeder for SRI Rice in Sri Lanka

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Presentation at the Workshop on Crop Production Equipment for the System of Rice Intensification (SRI)
Authors: P.D. Kahandage and G.A.S. Ginigaddara: Rajarata, University of Sri Lanka
Title: Design, Development and Performance Evaluation of a Manually Operated Multi-row Weeder for SRI Rice in Sri Lanka
Date: November 1, 2014
Venue: ACISAI, Asian Institute of Technology, Thailand, weeders

Published in: Technology
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1411 - Design, Development and Performance: Evaluation of a Manually Operated Multi-row Weeder for SRI Rice in Sri Lanka

  1. 1. Design, Development and Performance evaluation of a manually operated multi row weeder for SRI rice in Sri Lanka P.D. Kahandage and G.A.S. Ginigaddara Faculty of Agriculture, Rajarata University of Sri Lanka, Puliyankulama, Anuradhapuraand
  2. 2. Introduction • Rice is the staple food for nearly a half of the world’s population • Rice production is to be increased by another 50 % to fulfill the demand which will arise by 2025. • Increasing the productivity of existing lands • Improving the crop may give a satisfactory approach to increase the production
  3. 3. •System of Rice Intensification (SRI) is a technology which was revamped recently for increasing the productivity of irrigated rice while reducing the burden on environment. •Weed growth in wider gaps between and within rows of paddy has been recognized as one of the major obstacles faced by rice farmers.
  4. 4. Barriers for increasing the farmer adoption of the SRI •Labour consuming activities like, marking the rows before transplanting transplanting Weeding (highly affect to the yield) •Mechanization of weeding in SRI fields might be a good solution for the labour consuming nature of weeding in SRI.
  5. 5. •Presently, single row cono-weeder double row cono-weeder separate markers - manually operated manually operated •Yet there is no a two-in-one machine developed for the marking and the weeding in SRI fields. •The ability of using the same machine for several purposes with slight adjustments is convenient and economical investment for the SRI farmers.
  6. 6. •Most of the SRI farmers in Sri Lanka are holding small sized lands and involving the family labour in farming. •In order to suit for these conditions, a dual purpose machine was designed, developed and tested in SRI fields.
  7. 7. Methodology Designing the weeder
  8. 8. •The most salient features of this design are,  arrangement of wheels  the frame with adjustable ground clearance (to reduce damages to the plants) adjustable operating handle to provide a (convenient operation) easily detachable marker. •In this design, five weeding wheels are arranged in such a way that paddy plants do not get crashed in between two weeding wheels. •The operator has to push and pull the device
  9. 9. •After completing one set of rows, operator has to lift the device with the frame and move into another set of rows. •Here, the convenient directions for force applying have been considered.
  10. 10. •The first trail of the prototype was carried out in the experimental paddy field of Rajarata University. •eight plots with 50 m2 area •two rice seedlings in one hole with 20 cm x 20 cm spacing.
  11. 11. •Before testing the machine in the field,  conditions of field and soil  type and characters of soil (soil moisture on dry basis, depth of standing water, bulk density (g/cm3), cone index, cone apex angle and base diameter)  conditions of weeds (types, weed number, average height of each weed type, number of leaves)  conditions of operator (age, height, weight, skills and wage per head)
  12. 12. Nursery Manual marking Manual transplanting
  13. 13. •First, second, and the third weeding were made between 8 -10, 18-20, 28-30 days after date of transplanting. •At each and every weeding of the plots,  weeding efficiency  damaged plant percentage  actual and theoretical field capacities  suitable traveling speed of the machines during operation was measured.
  14. 14. Following equations were used Weeding Efficiency WE = (N1-N2)/N1 x 100 N1 is the number of weeds before weeding N2 is the number of weeds after weeding (Remesan et al., 2007) Damaged Plant Percentage DP = (Pt/Pd) x 100 Pt is the number of total plants in 1m2 Pd is the number of damage plants in 1m2.
  15. 15. Effective Field capacity CE- hah-1 = (s.w)/10 s - the traveling speed (kmh-1) w - is the width of work (m) (Hunt, 1995): Field efficiency FE-% = (Te/Tt) x 100 Te - the useful working time (h) Tt - the total working time (h) (Hunt, 1995): Work capacity WC- hha-1 =WC = 1/ CE (Hunt, 1995):
  16. 16. Results Device characteristics Total length of the device =125 cm Total width of the device =100 cm Total height of the device =147 cm Maximum height between frame and ground =45 cm Minimum height between frame and ground =24 cm Total weight =30 kg Calculations: Theoretical Field Capacity = 0.0064 ha/h Actual Field Capacity = 0.0048 ha/h Field Efficiency = 75% Weed Destroying Percentage = 87% Damaged paddy plant percentage = 21%
  17. 17. •After the first trail, numbers of practical problems were recognized,  higher weight which created problems in handling  lower field capacities  high damaged plant percentages •It was also realized that, length of the machine, 125 cm makes difficulties for the operator to control the machine in the rice rows and it increases the damaged plants percentage. •Similarly higher weight of the machine has caused to reduce the field capacity.
  18. 18. Modifications -01 •The machine was modified in order to reduce the weight and obtained the optimum dimensions •In this new design, the size of the frame was reduced and marker attachment was removed. FLOATER
  19. 19. •The performance of the new design was evaluated as previous design and followings are the results. Calculations: Theoretical Field Capacity = 0.038 ha/h Actual Field Capacity = 0.025 ha/h (12 mins for 50 m2) Field Efficiency = 65.78% Weed Destroying Percentage = 90 % Damaged paddy plant percentage = 16%
  20. 20. •Although it achieved a satisfactory field capacity, the damaged paddy plant percentage was still the same. •Reducing the dimensions and changing the shape had reduced the weight to 14.5 kg. •After this trial it was realized that, controlling the five weeding wheels simultaneously is still difficult in Sri Lankan field conditions due to poor land preparation, marking and transplanting.
  21. 21. Modifications -02 •To address the problems encountered in the fist modifications, it was decided to reduce the number of weeding wheels up to three and reconstruct the machine
  22. 22. •The performances of this three- row weeder were evaluated compared to the single row cono-weeeder, double row cono-weeder and manual weeding.
  23. 23. Weeding with single row cono weeder Weeding with double row cono weeder Weeding with three row weeder
  24. 24. Results Device characteristics Total length of the device = 105 cm Total width of the device = 70 cm Total height of the device = 90 cm Maximum height between frame and ground =40 cm Minimum height between frame and ground =28 cm Total weight = 12.5 kg
  25. 25. Table 01: Comparison of weeders for the efficiency Weeding Weeds method destroying % Damaged paddy plant % Work capacity, hr/ha Actual Field capacity (ha/hr) Field efficiency, % Single row cono- weeder 94.55 1.531 65.5 0.0153 76.72 Double row cono- weeder 91.82 3.053 38.5 0.026 65.07 Three row weeder 86 4.02 29.4 0.034 76.62 Manual weeding 98.06 1.042 130 0.0077
  26. 26. Modifications -03 •Although, the three row weeder has been modified up to a satisfactory level, it was realized that the weed destroying percentage should be further developed. •Because other manually operated weeders have achieved higher weed destroying percentages than three row weeder
  27. 27. •Therefore, the handle was modified and three floaters were attached in front of each weeding wheel to improve the weeding percentage •The total weight of the weeder was reduced up to 10.1 kg. •After these modifications, the performance of the weeder was evaluated with male operators and female operators separately.
  28. 28. Results Device characteristics Total length of the device = 55 cm Total width of the device = 60 cm Total height of the device = 90 cm Height between frame and ground = 25 cm Total weight = 10.1 kg
  29. 29. Table 02: Performances of the three row weeder against sex Male Female Theoretical field capacity 0.043 ha/hr 0.043 ha/hr Actual Field Capacity 0.034 ha/hr (9 mins for 50 m2) 0.028 ha/hr (11 mins for 50 m2) Field Efficiency 76.5% 65.1 % Weed Destroying 89 % 91% Percentage Damaged paddy plant percentage 3.5% 3.1%
  30. 30. Conclusions •The final version of the multi row weeder (Three row weeder) has shown the highest field capacity (0.034 ha/hr) amongst manually operated other weeders which are mostly been used in Sri Lanka. •The weed destroying percentage of three row weeder is still lower (Table 01) than other manually operated weeders. •Although the damaged paddy plant percentage of three row weeder is bit higher in three row weeder than other manually operated weeders, it can be used effectively to control weeds in SRI fields with less labour usage.
  31. 31. Acknowledgement • This is one of the outcome of the on going collaborative research program between Oxfam in Sri Lanka and Rajarata University in Sri Lanka • Financial assistance and other numerous assistances for developing and testing the machine was given by Oxfam –Australia in Sri Lanka is greatly acknowledged
  32. 32. Cost • Cost for first five row weeder= 12,000.00LKR • Cost for last three row weeder = 5,000.00 LKR

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