The field trial took place in Mithapukur upazila, situated in the Rangpur District. This area is positioned between 25˚26' and 25˚41' north latitudes and between 89˚06' and 89˚27' east longitudes, as depicted in Figure 1. The crop’s condition, including parameters such as plant height, plant-to-plant distance, plant density, number of hills per square meter, and hill-to-hill distance, along with overall crop density, was assessed using established procedures. Additionally, the soil composition was identified as clay in both cases.

The BRRI whole feed combine harvester, specifically the BRRI WCH2021 model, was chosen and deployed for the paddy harvesting operation at the experimental site. This harvester is produced by the Bangladesh Rice Research Institute (BRRI), an institution working under the Ministry of Agriculture, Government of Bangladesh, as part of the SFMRA project to develop domestically appropriate whole-feed combine harvesters. The efficiency and performance of the harvester were evaluated through the actual cutting of paddy in the field. For a visual representation, refer to Figure 2, and for detailed technical specifications, consult Table 1.

Three plots were carefully chosen to assess the operational parameters of the harvester, including operational speed, field capacity (measured in hectares per hour), fuel consumption, and grain losses attributed to the combine harvester. The plot sizes were determined using a measuring tape. Additionally, three smaller areas, each measuring 1 meter by 1 meter, were randomly selected within the plot to evaluate shattering loss. Following harvesting, three 1-meter by 1-meter plots were randomly designated, and any scattered spikes within those areas were collected. It is worth noting that all tasks related to paddy harvesting, from the actual harvesting to the subsequent cleaning processes, were seamlessly executed in a single pass of the combine, as depicted in Figure 2.

Various indicators were pinpointed to assess the technical performance of the BRRI comprehensively combine harvesters during the paddy harvesting process. These indicators encompassed the following key aspects: 1) operational time, 2) labor needed for harvesting, 3) fuel consumption, 4) field capacity, 5) working speed, 6) effective harvesting time, 7) grain yield, and 8) grain losses. Each of these metrics played a crucial role in evaluating the overall efficiency and effectiveness of the combine harvester in the context of paddy harvesting operations.

Several key parameters were considered during the paddy harvesting operation to assess the field capacity. These included measuring the plot’s area, the machine’s forward speed, the cutting width, and the time to harvest the designated area. These metrics provided valuable insights into the harvester’s efficiency and productivity in the context of paddy harvesting.

The forward speed was quantified by dividing the distance covered by the time the machine took to traverse that distance. This procedure was replicated six times within each plot to ascertain the average forward speed. The calculation for determining the forward speed of the combine harvester was based on the equation proposed by Hunt [18] . This method provided a reliable means of evaluating the harvester’s operational efficiency in the field.

Forward speed,

S = 3.6 D t (1)

where,

S = Forward speed (km/h)

D = Distance (m), and

t = Time (sec).

The criteria for evaluating field performance encompass parameters such as machine running speed, theoretical field capability, actual field capacity, field efficiency, work per hour, and fuel consumption. Field efficiency, a significant metric, is the ratio between effective and theoretical field capacity [19] . Theoretically and effectively, field capacity is calculated using the formulas outlined below. These metrics provide a comprehensive understanding of the machine’s performance and productivity in the field.

Theoretical field capacity (ha/h),

F C T h e o = A E (2)

where,

E = Effective operation time (h) and

A = Area of land reaping at the specified time (ha).

The effective field capacity quantifies the average rate at which the harvester covers the field, considering the total time spent on the operation. It is calculated by dividing the area covered by the total time taken. Determining effective field capacity involves meticulous measurement and consideration of all time-related elements throughout the harvesting process, as outlined by Hunt [18] . This metric provides a practical assessment of the harvester’s real-world performance in the field.

Effective field capacity (ha/h),

F C E f f = A T (3)

where,

T = total time for reaping operation (h) and

A = area of land reaping at the specified time.

Fieldefficiency ( % ) = Effectivefieldcapacity Theoreticalfieldcapacity × 100 (4)

Fuel consumption was determined after harvesting. Before starting the harvesting operation, the fuel tank of the combine harvester was filled up. At the end of the harvesting operation, the required fuel to fill the tank was determined by using a measuring flask. The following equation determined fuel consumption per unit area [18] .

Fuel consumption (l/ha),

F = F a A (5)

where, Fa = Fuel used during operation (l) and

A = Area of operation (ha).

Four distinct types of losses were considered in the context of using a combine harvester. These include 1) shatter loss, 2) cutter bar loss, 3) cylinder loss, and 4) separating loss. In the experimental setup, specific procedures were employed to measure these mechanical harvesting losses meticulously. This systematic approach ensured a comprehensive evaluation of the efficiency and effectiveness of the combine harvester in minimizing these various losses during the harvesting process.

The harvesting area’s size and configuration significantly impact the harvester’s performance. In the case of BRRI combine harvesters, their field capacity is closely tied to the dimensions and layout of the land being harvested. Research results indicate that the harvester’s capacity increases as the size of the harvesting plot expands, mainly due to a reduction in the frequency of turning events. Elsoragaby, Yahya [20] have pointed out that the performance of combined harvesters is notably affected by a reduction in the size and alteration in the shape of the plot area. This observation aligns with the findings of Islam, Alam [21] , which suggest that irregularly shaped plots can significantly decrease the field performance of the combine harvester. Therefore, selecting the crop field based on the land’s size is essential to optimize the field performance of the combined harvester.

The field capacity of the BRRI combine harvester showed variation in the plot length, a phenomenon primarily influenced by the frequency of turning events. As the plot length increased, so did the field capacity of the combine harvester. Notably, the lowest field capacity was observed in plots with a length of 25.6 meters. These findings underscore the importance of having a plot length exceeding 38.6 meters for optimal operation of the BRRI combine harvester, particularly when equipped with a 1.5-meter cutting width, as it allows for reduced turning events and enhances overall efficiency during the harvesting process (Table 2).

To optimize efficiency and minimize turning events, it is recommended that the BRRI Combine harvester be operated in plots with a length exceeding 38.6 meters. Currently, rice fields are often fragmented due to shifts in ownership, and farmers may deliberately divide the land to facilitate better water management in rice cultivation. The effectiveness of harvesting operations is closely tied to plot size and length. Operators strategically maneuvered the farm machinery lengthwise to further mitigate the need for frequent turns, enhancing overall harvesting efficiency. This approach proves beneficial in managing fragmented rice fields and ensuring a smoother harvesting process.

The time lost during turning maneuvers decreases proportionally with increased plot size. In smaller plots, a higher frequency of turns is required, leading to more significant time loss. To operate the BRRI combine harvester at full capacity and minimize turning-related inefficiencies, selecting plot areas exceeding 1200 square meters is advisable, particularly when equipped with a 1.5-meter cutting width. Similarly, for the efficient operation of the BRRI whole-feed combine harvester, a plot size of over 800 square meters is recommended. These considerations are pivotal in ensuring optimal performance and productivity during harvesting.

The field productivity of the BRRI combine harvester is closely linked to the size of the land it operates on. The performance of the combine harvester demonstrated variation based on the size of the land. Specifically, field efficiency showed an upward trend with increased land size. The highest levels of field efficiency were observed in plots exceeding 1200 m². Conversely, plots with an area of 800 m² noted the lowest field efficiency. These findings highlight the significant impact that land size has on the operational efficiency of the BRRI combine harvester, emphasizing the importance of selecting appropriately sized plots for optimal performance.

The findings indicate that the operational speed of the combine harvester ranged from 3.36 to 4.50 km/h during the harvesting process. According to ASAE Standards (2009), large and medium-sized combine harvesters typically operate within a range of 3 to 6.5 km/h during harvesting. In the case of the mini combine harvester, the theoretical and actual field capacity were measured at 0.19 and 0.11 ha/h, respectively (Table 3). Conversely, for full-feed and head-feed combine harvesters, the theoretical and effective field capacities were determined to be 0.50 and 0.36 ha/h, respectively, as noted by Alizadeh and Allameh [8] . Muazu, Yahya [22] further emphasized that the lowest field capacity (0.67 ha/h) was associated with the highest loss time (1.54 h) during the paddy harvesting operation, resulting in a relatively lower actual field capacity (Table 4 and Table 5). Grain loss during harvesting and the efficiency of the harvester are shown in Figure 3 and Figure 4 respectively. While the harvesting capacity of the BRRI combine harvester may be considered relatively low, it stands out for its adaptability to both smaller and larger fields, which is a notable advantage.

Farmers were invited to provide feedback and comments on various pertinent issues. These comments have been compiled and are presented in a summarized form in Table 8. This compilation serves as a valuable resource for gaining insights and perspectives directly from the end-users, which can inform future decisions and improvements in the context of the discussed matters.

Observations about the overall condition of the crop and the land have been meticulously recorded and are succinctly summarized in Table 9. This compilation serves as a valuable reference for assessing the health and status of the crop and the land, providing essential data for further analysis and decision-making in agricultural practices.