The rotary weeder cum fertilizer drill is mounted on Mahindra Yuvraj 215 mini tractor (15 hp). It was designed and developed at the Department of Farm Machinery and Power Engineering, College of Agricultural Engineering and Technology, Junagadh Agricultural University, Junagadh. Overall dimensions of the machine length × width × height of the machine was 1050 × 1460 × 1240 mm. The three major components of the developed machine are main frame, weeding system and fertilizer application system. Width of coverage of implement was designed for 1.2 m row crops. An amount of ₹ 41000 were spent for development of the machine.

Performance evaluation of developed machine was conducted through the two field experiments in the castor crop. First experiment was done after the 30 DAS and second experiment was done after the 45 DAS by using standard procedure (ISI, 1993). Experiments were conducted in field by varying forward speed ranged 1.8-2.0 km/h, 2.5-2.7 km/h and 3.0-3.2 km/h (Venkat et al. 2020). Calibration of the machine was conducted at laboratory condition and at field conditions to estimate the deviation in fertilizer delivery rates. The performance of the machinery was found to be satisfactory in lab and field conditions. At the time of peak weeding stages for weeding and fertilizer application 10 manual labour are required per one day (8 hours) in manual methods, by using rotary weeder cum fertilizer drill inter-culturing and fertilizer operations are completed by using 1 manual labour up to 5.1 hours of time only.

Cost of operation of the developed machine was estimated assuming that rotary weeder cum fertilizer drill is attached to a mini tractor. It was assumed that weeding and fertilizing operations performed two times in castor, pigeon pea and cotton crops i.e. 30 and 45 DAS after sowing of the seeds. Annual use of tractor and the implement was considered as 1000 and 320 h, respectively. Total cost of operation of the machine was computed on per hour basis considering both fixed and variable costs. Fixed cost includes depreciation and interest on capital assets, insurance, taxes and housing. The expenditure on fuel, lubrication, repair and maintenance and operator were added to the variable cost. It was converted into area basis by multiplying it with the effective field capacity of the machine and expressed in rupees per hectare. The development or production cost of rotary weedercum-fertilizer drill was the sum of cost of materials used and cost of labor used for fabrication works. Production cost was considered as purchase cost in this study. Break-even point (BEP), area wise as well as time wise and payback period was calculated as per standard cost estimation methods (ISI, 1979).

It is the average usage of farm machinery or any machine annually. It depends upon how many working days are available for a particular operation with the machine in a year. Annual utility of mini tractor and the machine was considered as 1000 and 320 hours respectively.

Depreciation is the largest component of machine total costs. It measures the amount, by which the value of a machine decreases on-time passage, whether a machine is used or not (Hunt, 2001). By using above the formulae cost estimations of mini tractor and rotary weeder cum fertilizer drill were estimated.

Breakeven analysis, also called a point of no profitloss is performed to assess the duration of work at a given price that is necessary to meet out all the costs or expenditures. The breakeven point is the intersection of the lines at which the line of total cost and the line of custom hiring cost intersect each other. If the breakeven point value is less than the annual utility time of machinery then the farmer benefitted by owning a machine. If the breakeven point value is found more than the annual utility time of machinery then owning machinery can lead to a loss for the farmer, at that time going for custom hiring is the better option for him.

It is the time taken for an investment to return its original cost through annual cash revenues generated. The payback period was calculated from the following formula. Generally, it is expressed in years for farm machinery.  Payback period =⋯⋯⋯ Average net annual benifit 

Where, Average net annual benefit, ₹ = (CHC – TOP) × Annual utility

CHC = Custom hiring charge, ₹/h = (25 per cent over total cost of operation ₹/h)

TOP = Total operating cost, ₹/h

Life and annual utility and of tractor were considered as 10 years and 1000 hours per year respectively. Fixed cost and variable costs of a tractor were calculated as 46.5 ₹/h and 168.3 ₹/h. The operating cost of the tractor obtained was 214.8 ₹/h.

Life and annual utility of machine were taken as 10 years and 320 hours per year respectively. Fixed cost and variable costs of the machine was calculated as 23.83 ₹/h and 6.41 ₹/h. Operating cost of the machine obtained was 30.24 ₹/h.

Total fixed cost is the summation of fixed costs of tractor and machinery which is obtained as 54,125.6 ₹/year. The total variable cost of the combination was calculated as 174.71 ₹/h. The total operating cost of tractor and machinery combined was calculated as 245.04 ₹/h. But in existing manual methods it requires 1900 ₹/ha for completion of weeding and fertilizer applications, with that of mini tractor drawn rotary weeder cum fertilizer drill it requires 1250 ₹/ha to complete the weeding and fertilizer operations in hectare land. By adopting this machinery farmers can save 650 ₹/ha over one hectare of land.

Break-even point was determined by plotting the total cost (annual operating cost) and custom hiring cost against the usage of the machine. The location of the intersecting point made by the two cost lines gives the number of hours of work required for break-even. Below picture “y = 174.71x + 54126” is the line of the total operating cost and “y = 373 x” is the line of total custom hiring cost (existed manual cost). In both, the lines “x” indicates the number of operating hours of machinery. From the below graphical representation breakeven point of the machine was calculated as 273 hours per year.

Fixed, variable and operating costs of tractor, machinery and combine are presented in the following table. The cost of existed method of cultivation is also presented in the following table.