Figure 1 showing the research area of this study. The research was held throughout boro 2020 season at Maisherkandi, Mithamain upazila, underneath the district of Kishorganj. Rice crop was harvested by Zoomlion combine harvester

from 16 March to 10 May. During the research period of this study, around 18 locations rice fields were selected. The most of the locations soil condition was sandy loam and data was gathering from selected 18 locations rice fields.

The criteria of field performance include machine running speed, theoretical field capability, actual field capacity and field efficiency, work per hour and consumption of fuel. The field efficiency is the ratio between effective field capacity and theoretical field capacity. The theoretical and effective field capacity was calculated below formulas [11] [12].

Theoretical field capacity ( ha ⋅ h − 1 ) = Total area harvested ( ha ) Effective operation time ( h ) (1)

Effective field capacity ( ha ⋅ h − 1 ) = Total area harvested ( ha ) Total operation time ( h ) (2)

Field efficiency% = Effective field capacit Theoretical field capacity × 100 (3)

The fuel consumption of the combine harvester was determined by differentiate the amount of fuel in tank before harvesting operation and amount of fuel in tank after harvesting time. Time parameters were measured utilizing automated stopwatch and the actual time (spending actual harvesting time), turning time (time of turning and reversing the machine without cutting rice plant), and idle time (operator resting and machine maintenance time). The total time was calculated in h/ha which was obtained by summarizing the whole-time parameters then divided it by the total harvesting area. To get the average time, total utilized time was summarizing and then it was divided by the number of total farms. The forwarding speed of Zoomlion combine harvester was obtained by taking total time needed to harvest each row and the amount of area harvest at that particular time.

Technical specification of Zoomlion model combine harvesters is given in Table 1.

Field operation of Zoomlion combine harvester in haor areas is shown in Figure 2. Inlet operation of the combine started when the machine moves forward direction the separator separates the crop for harvesting, the reel picks up the standing or laying crops and moves them to the cutting device. The auger transmits the retracting fingers passing the crop to the inclination conveyor chain feeding the crop into the thresher. The cylinder and concave assembly play a crucial role in dividing most of the crop into seed, chaffers that fall directly onto the grain pan or a conveyor with in thresher. At this point, the cylinder

beater starts to strip the threshed material from cylinder and supports in further separation and directs the straw and remaining seed to the straw carrier. The straw carrier aggravates the material to remove any existing seed and un-threshed heads as the straw is moved backward from the machine to be discharged. A crop transfer conveyor gathers the material extracted from the straw and is delivered to the crop container at the front of the chaffer sieve. The combination of threshed grain with several chaffer and small debris drops from the concave sieve falls to an oscillating sieve and is clean by a fan and the oscillating sieve together. After cleaning, a horizontal auger and a lifting auger delivers the grain to the grain tank. The tailings are then transferred through the oscillating sieve to the rear outlet. The straw in the thresher is poured out off the field after threshing through the straw outlet. The threshed and clean grain is discharged by grain outlet pipe in the sack or grain tank at the sacking site.

Figure 3 showing the field data collection of Zoomlion combine harvester. A total of 18 fields data were collected according to plot size. The plot size of the field was measured with help of measuring tape. Each turning time and passing time was recorded using stopwatch. The events and time loss were calculated according to plot sizes.

Before and after harvesting, grain fallen data in 1 m² was collected in three places in each field. Moisture and weight of the grain were recorded and measured as a percentage of total yields in unit area.

The costs were divided into two categories in separate harvesting segments (both mechanized and manual methods) which are fixed cost, and variable cost.

The combine harvester’s operating costs were calculated using the equation below.

A C = F C + V C (1)

where,

AC = Yearly operational cost, Tk∙yr⁻¹

FC = Yearly fixed cost, Tk∙yr⁻¹

VC = Variable cost, Tk∙yr⁻¹

It is self-determining use of machine and assessed on the basis of the method of capital consumption (CC). A capital recovery factor (CRF) has been employed to incorporate gross depreciation and interest adjustments into a sequence of compound interest equivalent annual payments. The capital recovery factor can be described as the sum of equivalent (or uniform) payments to be obtained for n years, so that, if the rate of interest is the cumulative present value of many of these equal installments is currently equivalent to one taka. This payment is being used to calculate agricultural machinery capital use [13].

C C = ( P − S ) C R F + S × i (2)

C R F = i ( i + 1 ) n ( 1 + i ) n − 1 (3)

where,

CC = capital of consumption

P = combine harvester’s purchase price (Tk)

S = salvage value (Tk)

CRF = recovery factor of capital

i = interest on investment (%)

n = machine life (yr)

These variable costs are applied to combine harvester usage and assessed on the basis of the continuity formula [13].

V C = A C [ ( R & M ) × P + L ] (4)

where,

A = area coverage yearly (ha)

C = effective field capacity (ha∙hr⁻¹)

R & M = repair and maintenance cost (%)

L = labor wage (Tk∙hr⁻¹)

The break-even point (BEP) is the stage where there is no benefit or loss. The farm enterprise’s overall costs should be the same as total profits. Continuous investigation of farm machine operating costs is necessary. The fixed costs of the farm ought to be met by the profits: the greater the fixed costs, the longer it will take for the enterprise to hit break-even and turn a profit. Therefore, holding the fixed costs down to a minimum level is important. The equation below was used to estimate the machine’s BEP.

B E P = F C C R − V C (5)

where,

BEP = break-even point (ha∙yr⁻¹)

FC = fixed cost of machine (Tk∙yr⁻¹)

VC = variable cost of machine (Tk∙ha⁻¹)

CR = rate of custom hire (Tk∙ha⁻¹)

The per unit area rent charge normally depends on the cost of the machine, useable fuel, labor cost, transportation costs, yearly use and benefit.

The rental charge of the combine harvester was calculated based on the following assumptions:

• The combine harvester’s purchase price was taken as Tk 2,000,000.

• Government aid accounts for 70 percent of the machine price in haor region.

• The investment interest rate for banks is taken 12 percent.

• Rice harvester’s repair and maintenance cost is taken as 5 percent of its purchase price.

• The combine harvester’s life is taken to be 8 years.

• Take fuel price as Tk 70 L⁻¹.

• Labor charge is taken as Tk 900 Day⁻¹.

• Manual harvesting and threshing costs were taken as Tk 16,500 ha⁻¹.

Comments on the performance of combine harvester were recorded from the users and operators throughout by structured questionnaire. The comments were validated through KII (Key Informant Interviews).

We used MS-Excel 2013 software to analyze the data and then visualized the results in tabulated and graphical formation.

Figure 4 has shown that turning event decreases with increase the plot length. Combine harvester should be operated in plot length of more than 30 m to reduce turning events. In the current land tenure system, the rice fields are mostly fragmented due to changes in ownership. Farmers themselves also artificially fragmented the land for good water management in rice cultivation. Harvesting efficiency depended on the plot size and plot length [3]. He suggested the operator to operate the farm machine in lengthwise to reduce the turning events.

Figure 5 shows the time loss in turning decreases with increase the plot size. Smaller sizes of plot required more turning events which increase the time loss turning. Plot areas should be selected more than 800 m² to operate Zoomlion combine harvester having the cutting width of 2.0 m in full capacity as well as minimize the turning loss. The recommended plot should be more than 500 m² to operate head feed combine harvester in an efficient manner.

The combine harvester’s harvest capability relied on the size of the field. Figure 6 shows the combine harvester field capability in reference to the land area. The harvesting capacity increased when the field size was increased. Combine harvester worked at full capacity for the larger sizes of land due to less turning events. The size of the land should be at least 800 m² to operate the combine harvester having a cutting width of 2 m at full capacity. The benefit of large area makes to help the combine better field capacity. [13] studied the land sizes in haor areas and observed that most of the lands are bigger in size. Crop field should be selected based on the size of the land to get the highest field performance of combine harvester.

Figure 7 demonstrates the combine harvester’s field productivity with regards to the land area size. Combine harvester field performance varied with land size. The field efficiency increases with the increase in land size. The highest field efficiency was observed the land sizes of more than 2000 m². Field efficiency showed the lowest in the field sizes of 800 m². Hence, field sizes of less than 800 m² should be avoided for the Zoomlion combine harvester.

Table 2 shows the field capacity and field efficiency of combine harvester. The operating speed of the combine harvester is 1.23 - 3.20 km∙hr⁻¹. [13] observed

the operating speed of Sifang and small combine harvester was 1.60 and 0.79 km∙hr⁻¹. The variation of operating speed was due to high horsepower and good trafficability of combine harvester. Crawler size was also bigger to developing sufficient traction than those of combine harvesters. The operational speed of the traditional and medium sized combine harvester would be within the recommended operating speed of 3 - 6.5 km∙hr⁻¹ for combine harvesting performance with a self-propelled combine by [14]. The forward speed of combine harvester in lengthwise operation was higher than the widthwise operation. Widthwise operation reduced the 35% speed than lengthwise operation. The theoretical and actual field capacity of Zoomlion combine harvester was 0.15 ha∙hr⁻¹. [14] considered 0.50 and 0.36 ha∙hr⁻¹, respectively, to be theoretical and effective field capacities of whole-crop and head-feed combinations. [15] recorded that paddy harvest would have the largest time on the field (1.54 h) and the lowest field capability (0.67 ha∙hr⁻¹) of all the activities supported by their study. Fuel consumption was found 32 L∙hr⁻¹. Fuel consumption varied depending on the field size, turning events, travelling distance, soil condition. Grain loss was observed as 1.6% - 1.9% respectively.

Figure 8 shows that the combine harvester spent 45% of the total harvesting time of operation. During the study it was found that 17% of the total turning time was spent with combine harvester. The others 38% time was spent in combine repairing, idle, work stop due to rain. Sifang and small combine harvester spent 45% and 56% time spent for harvesting rice in haor areas. [15] stated that, by using traditional combine, 66% of the total harvesting time was used to conduct the actual harvesting activities while turning and reversing time constituted 13% of the total harvesting operation. Turning time of combine harvester is lost factor operation which need to proper plan to make the turn without slower or additional gesture to the line up to the next row. Some nonproductive activities (turning time, adjustment time, etc.) are unavoidable; the goal is to minimize the sum of these nonproductive activities, as they may total as much as 40%. The time factor may be optimizing by using proper plan and supervision.

Materials handling is the overall man and machinery relationship in field and lab conditions. Materials handling including the combine harvester operation, feeding, cutting, threshing, cleaning, storage, protection, and material control.

Repair and maintenance rates are significant factor in assessing of a combine. The combine needed so little maintenance and repair mostly during entire harvest season.

Variable cost i.e. operational cost of combine was characterized as labor’s charge, cost of useable fuel and cost of repair (Figure 9). Operator’s charge indicated the largest share followed by fuel cost. Daily repairing cost was observed in minimum level.

Figure 10 illustrates the break-even chart for mechanized methods using the mini combine harvester. The break-even area of mechanized harvesting using mini combine harvester would be 20 hectare of rice land.

The skill of the operator is very important to run the combine harvester efficiently. The machine has the ability to run faster. The adjustments of the combine harvester need to be made according to type and variety of crop, moisture content of crop (soft or dry), time of harvest, field, density of crop and crop conditions (lodged/unlodged), etc. Improper adjustments cause damage to grains or machine. Operator has to take instant decision on the adjustment of different parts. The machine should be operated in lengthwise to reduce the turning events. Adjacent field should be selected to reduce plot to plot movement time. Sudden turn is strictly prohibited.

Mechanical fault of the combine harvester during harvesting operation was summarized and presented in Table 3.

Operators’ were asked to make comments on the following issues. The comments are summarized and given in Table 4.

Farmers were asked to express comments on the following issues. The comments are summarized and given in Table 5.

Overall observation on the crop and land condition was recorded and presented in Table 6.

• Larger harvesting machine like Zoomlion is not suitable in haor areas.

• During the operation, wet paddy creates heat in grain tank.

• Spare parts are not available in local markets.

• Repair and maintenance are not easy of this combine harvester due to its heavy weight.