1. Coverage (Covered area)

Coverage (Covered area) will be used for certain farm work ability of certain period, which is a seasonal period of for a crop.

Coverage is simply obtained by following process.

CA = DC * AWD  / N            Eq. 3-1

CAS = DC * AWD / M / N                 Eq. 3-2

CAS = EFC * ANWH / N            Eq. 3-3

CAW = CA

where,

symbol	term	unit
CA	Coverage (Covered area)	ha
CAS	Coverage of one set	ha
DC	Daily capacity	ha/d
AWD	Available work days	d
EFC	Effective field capacity	ha/h
ANWH	Available net working hour	h
M *	Number of machine set	-
N *	Number of operation times	-

* : normally M and N = 1

 

Example: Next table and See fm-311.xls and fm-33.xls.

Table 311. Example of Covered Area

Item		Effective Field Capacity	Daily Capacity				Available work days				No. operation	Covered area
Work Name	Implement		Work hour	Net Work rate	Net Work	Daily Capacity	Operation Period	Days of work period	Rate of available work day	Available work days
	symbol	EFC	Dt	NWR	Dn	DC	WP	DWP	ADR	AWD	N	CAS
	unit	ha/h	h/d	%	h/d	ha/d	date	d	%	d	-	ha
Tillage	Rotary 1.8m	0.266	10.0	72	7.2	1.92	Apr.1-May 20	50	74	37.0	1	71.0
Harrowing	Paddy harrow	1.132	10.5	70	7.4	8.32	May.1-May 20	20	73	14.6	2	60.7
Trans-planting	Rice transplanter 2-row	0.036	10.5	67	7.0	0.26	May.1-May 20	20	73	14.6	1	3.7
Herbicide	Knapsack power sprayer	1.800	11.0	80	8.8	15.84	July 1-July 5	5	60	3.0	1	47.5
Harvest	Head-feeding combine	0.052	8.5	65	5.5	0.29	Sep.25-Nov.10	47	65	30.6	1	8.8

 

Exercise. 3-1, 3-2

 



Fig. 3 Flow chart to obtain coverage

 

Available work days means actual days available to work.

Freezing temperatures, precipitation, excessive deficient soil moistures, and other weather related factors may limit field machines operations. As weather variability is great, any prediction of the number of future working days can only be made probabilistically.

The number of working days in any time period is a function of: climatic region, slope of soil surface, soil type, drainage characteristics, operation to be performed, and traction devices.

 

AWD = DWP * ADR                 Eq. 3-4

Where,

symbol	term	unit
AWD	Available work days	d
DWP	Days of work period	d
ADR	Rate of available work days	%

Table 32. Example of Available work days

Work Name	Implement	Effective Field Capacity	Net Work hours	Daily Capacity	Working period	Days of work period	Rate of avail- able work day	Avail-able work days
		EFC	Dn	DC	WP	DWP	ADR	AWD
		ha/h	h/d	ha/d	date to date	d	%	d
Tillage	Bottom plow 14"x2	0.224	7.2	1.61	Apr.1- May 20	50	74	37.0
Tillage	Rotary 1.8m	0.266	7.2	1.92	Apr.1- May 20	50	74	37.0
Harrowing	Paddy harrow 20	1.132	7.4	8.32	May.1- May 20	20	73	14.6
Trans-planting	Rice trans-planter 2-row	0.036	7.0	0.26	May.1- May 20	20	73	14.6

Exercise. 3-3

 

1. Available net working hour

ANWH = AWD * Dn                       Eq. 3-5

Where,

symbol	term	unit
ANWH	Available net working hour	h
AWD	Available work days	d
Dn	Net working hours	h/d

        3-3. Rate of Available Work Days

In the work period, machines are not available for use due to the precipitation and periodical machine maintenance etc. Therefore, these unavailable days are deducted from total work days of the period.

The weather condition and its suitability to out side work can be get in the weather chart for agriculture which was gathered by meteorological agency.

Table 33a shows the rate of monthly available work day based on the data of “available work days at outside”.

Table 33a. The Rate of Monthly Available Days for Machinery Work with Judging from Weather (%)

Month Area Place		Jan.	Feb.	Mar.	April	May	June	July	Aug.	Sept.	Oct.	Nov.	Dec.
Hokkaido	Sapporo	0	0	0	73	73	70	71	69	75	61	57	0
Kanto	Kumagaya	90	88	84	75	73	62	71	82	67	74	87	94
Okinawa	Naha	77	75	77	68	60	52	74	65	73	74	82	77

rainfall less than 10mm/d

See fm-33a.xls (for upland work see ASAE-D497)

Exercise. 3-4

 

1. Coverage of combined work

See 5-1-6. Coverage of plural farm works

 

1. Machinery capacity from Coverage

How to obtain the optimal machinery capacity, when farm scale or coverage of farm system is given?

DC = CA * N / AWD                 Eq. 3-6

EFC = DC / Dn                          Eq. 3-7

TFC = EFC / EF * 100              Eq. 3-8

Where,

symbol	term	unit	tillage 1	tillage 2
TFC	Theoretical Field Capacity	ha/h	0.315	0.360
EF	Field Efficiency	%	71.0	74.0
EFC	Effective Field Capacity	ha/h	0.224	0.266
Dn	Net working hours	h/d	7.2	7.2
DC	Daily Capacity	ha/d	1.61	1.92
AWD	Available work days	d	37	37
N	No. of operation	-	1	1
CA	Coverage	ha	59.6	71.0

Example: Obtaining EFC, TFC from Coverage in above case.

Exercise. 3-5, 3-6

2. Selection of machine

From equation 2-9,

W = (TFC / V) * 10                   Eq. 3-9

Table 352 Example: Obtaining machine width from TFC

symbol	term	unit	Example
	Work name		Tillage 1	Tillage 2
	Implement		Bottom plow	Rotary
TFC	Theoretical Field Capacity	ha/h	0.315	0.360
V	Speed	km/h	4.5	2.0
W	Width	m	0.7	1.8

See fm-351.xls

Exercise. 3-7

 

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2004/5/30