J . agric . Engng Res . (1996) 65 , 143 – 149

Improvement of Planosol Solum : Part 5 , Soil Bin Experiments with a Three-stage Subsoil Mixing Plough

K . Araya ; * M . Kudoh ; * D . Zhao ; † F . Liu ; † H . Jia †

* Environmental Science Laboratory , Senshu University , Bibai , Hokkaido 079 – 01 , Japan

† Hejiang Agricultural Research Institute , Jiamusi , Heilongjiang , P . R . of China

( Recei y ed 2 January 1 9 9 6 ; accepted in re y ised form 1 5 May 1 9 9 6 )

A drop-down type plough (two-stage subsoil mixing plough) was ef fective for the one-to-one mixing of the second (Aw) and third (B) horizons to improve the planosol solum in China leaving the first (Ap) horizon undisturbed . However , this machine had the following disadvantages : (1) it produced large soil clods , (2) it had a large draught requirement , (3) it required a furrow following system , (4) it has poor frame strength , and (5) it was necessary to remove the first plough body to facilitate opening of the first furrow . Basic soil bin tests were conducted in Japan to develop a three-stage subsoil mixing plough to solve these problems using half-size model ploughs . The results showed that the draught requirement and clod size , could be reduced by using three plough bodies ; one for the Ap , one for the Aw and one for the B horizons . A slatted mouldboard should be used to minimize draught rather than a plate mouldboard . The optimum working widths of the second and third plough bodies were 150 mm , which minimized draught but resulted in a wider working width than the nominal value . ÷ 1996 Silsoe Research Institute

Notation

F x horizontal force , draught , N M x mixing rate [(no mixing) 0 < M x < 1

(perfect mixing)] T Aw 5 B transfer rate [(no transfer) 0 < T Aw 5 B <

1 (perfect transfer)] b operational cutting width , mm h operational depth , mm w soil moisture , %d . b .

1 . Introduction

In the field tests made by Zhao et al . 1 and in the soil investigations of Araya , 2 the improvement of planosol

solum was achieved by mixing the Aw and B horizons in a one-to-one ratio below the surface leaving the Ap horizon undisturbed . In previous papers , 3–7 ploughs which mixed Aw and B horizons in a one-to-one ratio leaving the Ap horizons undisturbed , have been developed after soil bin tests and fields tests in pseudogley soil in Japan . The ploughs , which showed good performance , were the roll-in and drop-down types . The two kinds of prototype ploughs were sent to China , and actual field tests were conducted in a planosol solum field . The results showed that the drop-down type plough (the two-stage subsoil mixing plough) in Fig . 1 and Fig . 2 a was found to be ef fective for mixing of the Aw and B horizons of the planosol solum . 7 However , new problems were encountered , as follows .

(1) Large clods of the Aw and B horizons were produced when the Aw (200 – 400 mm) and B (400 – 600 mm) horizons were tilled using the drop-down (first) plough body as shown in Fig . 1 and Fig . 2 a . Unfortunately , the Ap horizon crumbled between the large soil clods and reached the lower layers , such that the amount of Ap horizon decreased .

(2) The large clods of the Aw and B horizons were sometimes moved into the Ap horizon and inversion of the Ap horizon by the second mouldboard plough body in Fig . 2 a did not work well .

(3) The draught of the plough 7 in Fig . 1 was 65 kN . Tractors , which can produce such a traction force , are not widely used in China and hence the draught should be decreased to less than 50 kN so that the plough can be drawn by 110 kW tractors (Russian TE150 or John Deere 4450) which are fairly common .

(4) The tractors used in China are larger than those in Japan and hence ploughing could not be operated with a furrow following system where one of the tractor tyres runs in the ploughed furrow because the tyre width is too large . The plough traction system

143 0021-8634 / 96 / 100143 1 07 $25 . 00 / 0 ÷ 1996 Silsoe Research Institute

K . A R A Y A E T A L . 144

Fig . 1 . Two - stage subsoil mixing plough

(a)

2nd 1st 50°

460

460

2nd

1st

200

200

200

30°

400

240

Ap

Aw

B

b

(b)

3rd 2nd 1st

230

120

3rd2nd

1st

30°

30°

100

100

100

Ap

Aw

B

45

Plate

650

Slat

Fig . 2 . Schematic drawings of the two - and three - stage subsoil mixing ploughs . ( a ) Two - stage subsoil mixing plough ( prototype ) . The actual prototype dimensions are gi y en ; ( b ) Three - stage subsoil mixing plough ( half - scale model ) . The

actual model dimensions are gi y en

should therefore be a land drawing system where the entire tractor tyre is not in the ploughed furrow .

(5) The plough frame should be strong enough to withstand the draught forces necessary to till the planosol solum .

(6) When the first furrow was opened , the first plough body in Fig . 2 a had to be removed and the second plough body operated alone , such that the furrow for the first plough body could be prepared . This furrow is subsequently covered by Ap horizon soil , tilled by the second plough body , on the next pass .

To solve problems (1) , (2) and (3) , the following three measures were adopted .

(1) To prevent the production of large clods , the Aw horizon (200 – 400 mm) and the B horizon (400 – 600 mm) were tilled using two dif ferent plough bodies (the second and third) as shown in Figs 2 b and Fig . 3 (hereafter , called the three-stage subsoil mixing plough) .

(2) The slatted mouldboard was used for the second and third plough bodies to decrease the soil – metal friction as shown in Fig . 3 .

(3) To decrease the draught , the working widths of the second (Aw) and the third (B) plough bodies were made smaller than the first (Ap) plough body width to decrease the draught , as shown in Fig . 2 b . Some of the soil will not be tilled , and soil mixing of the Aw and B horizons does not take place but lossening of this soil will be induced .

It was envisaged that the prototype plough , as shown in Fig . 2 b , would solve the disadvantages presented by (4) and (6) . The mouldboard plough body for the Ap horizon , which was at the rear of the two-stage subsoil mixing plough in Fig . 1 and Fig . 2 a ,

Fig . 3 . Half - scale model of three - stage subsoil mixing plough

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was used as the first plough body in the three-stage subsoil mixing plough , as shown in Fig . 2 b . In the two-stage subsoil mixing plough shown in Fig . 2 a , the plough body for the Ap horizon and the first drop- down plough body to till the Aw and B horizons were in dif ferent furrows but in the three-stage subsoil mixing plough in Fig . 2 b , these were set in the same furrow and the three plough bodies were in a line .

To confirm the ef fects of these above measures , basic soil bin tests were conducted in Japan with half-size model ploughs .

2 . Experimental details

2 . 1 . Apparatus and equipment for soil bin experiments

Laboratory plough tests were conducted in a move- able soil bin which is described in Part 1 . 3 The soil in the soil bin was pseudogley soil which is Japanese heavy clay . Soil moisture was controlled at about 22% , near the plastic limit . The mechanical properties of the pseudogley soil and planosol solum are given in Part 1 . 3

Three working widths , b , of the second and third plough bodies in Figs 2 b and Fig . 3 were used , namely , 230 mm , 150 mm and 115 mm . The working depth was 200 mm (Aw horizon of 100 mm and B horizon of 100 mm) . In this study , only the mixing of the Aw and B horizons is discussed as in the model plough tests made in the soil bin , the first mouldboard plough in Fig . 2 b to till the Ap horizon was not used . Two kinds of mouldboard , slat and plate mouldboards were prepared for the second and third plough bodies , respectively .

The height of the second plough body , 45 mm in Fig . 2 b , was determined in Part 3 5 as the optimum shape which caused breakage of the Aw horizon , then transferred the soil backwards and which required minimum draught . The height of the third plough body , 120 mm , was also determined as the optimum shape for tillage of the B horizon , with soil dropping down from the end of the mouldboard to give good mixing with a minimum draught requirement . 5 The inclined angle of the third plough body , 30 8 , was determined as being where the lower B horizon slice was compressed on the sloping mouldboard , causing slip between the B and Aw horizons , such that good random mixing was obtained when the soil dropped down . 5

In order to represent the two-stage subsoil by the full scale plough illustrated in Fig . 1 , tillage was also carried out by the third plough body alone , of the half-size model plough , by removing the second plough body in Fig . 3 .

Two to four experimental runs were made for each combination of parameters .

2 . 2 . Principle of mixing the Aw and B horizons

The process of mixing the Aw and B horizons using the three-stage subsoil mixing plough is shown sche- matically in Fig . 4 (full scale dimensions are given for the furrows) . Initially , the first mouldboard plough

(1)

(2)

(3)

(4)

(5)

(6)

Ap

0 460

200

400

600

Aw

B

Aw

B

Ap

Ap

ApAp

BAp

Ap

Ap

Ap

ApAp

B

Fig . 4 . Schematic diagram of mixing Aw and B horizons . Dimensions ( mm ) are for a full - scale furrow

K . A R A Y A E T A L . 146

body ( Fig . 2 b ) tills the Ap horizon (0 – 200 mm) shown in (1) of Fig . 4 , and (2) is obtained . With the second plough body , the Aw horizon (200 – 400 mm) is then tilled and is transferred backwards and put on the B horizon as shown in (3) of Fig . 4 . The broken Aw horizon and B (400 – 600 mm) horizon are then tilled together by the third plough body and are raised on the mouldboard of the third plough body as shown in (4) of Fig . 4 and drop down from the end of the mouldboard , so that a random mixing is obtained as shown in (5) . Subsequently , the first mouldboard plough body tills the next Ap horizon , inverting the Ap furrow slice thus covering the mixed soil in the preceding furrow so that (6) of Fig . 4 is obtained .

3 . Results and discussion

3 . 1 . Optimum plough width

The draught as a function of the working width of the second plough body is shown in Fig . 5 . The working depth was 100 mm for the Aw horizon . The draught was nearly constant regardless of the working width . The draught was not af fected by the working width as the area of the soil section disturbed re- mained constant , about 1 ? 9 3 10 4 mm 2 , for all working widths of the plough bodies .

The draught as a function of the working widths of

3

2

1

0 100 200 300

Working width of secondplough body b, mm

Dra

ught

Fx,

kN

Fig . 5 . Draught of second plough body as a function of the working width , b . Working depth , h was 100 mm of Aw

horizon

3

2

1

0 100 200 300

Working width of second and thirdplough bodies b, mm

Dra

ught

Fx,

kN

Fig . 6 . Total draught of the second and third plough bodies as a function of working width , b . Working depth , h was Aw ( 1 0 0 mm ) 1 B ( 1 0 0 mm ) 5 2 0 0 mm . s second and third

plough bodies together ; d third plough body alone

the second and third plough bodies is shown in Fig . 6 (Mark s ) . The working depth was 200 mm (Aw 100 mm and B 100 mm) . The draughts for 115 mm and 155 mm working widths were similar but the draught of the 230 mm working width was much larger . This was due to the area of the trapezium soil section disturbed in Fig . 7 a being similar for 115 mm and 150 mm working widths but increased for 230 mm working width .

The photograph in Fig . 7 a was analysed and the results of soil mixing and transfer rates are shown in Fig . 8 c and 8 b (mark s ) . From the analysis of Fig . 7 b , the results of soil clod size are shown in Fig . 8 a (mark s ) . The definitions of mixing , transfer rates and soil clod size are given in Part 1 . 3 The soil mixing rate was greater than 0 ? 8 , indicating that good soil mixing was achieved . The transfer rate varied considerably around 0 ? 5 and an optimum amount of the Aw horizon was transferred into the B horizon . Hence , the soil mixing and transfer rates were similar regard- less of the widths of the second and the third plough bodies . The clod size was also not af fected by the plough width .

3 . 2 . The friction of the mouldboard

Figure 9 shows the draughts of the slat and the plate mouldboards (mark s ) . The second and third plough bodies operated together here and the total working

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Fig . 7 . Soil displacement after ploughing . Total working depth was 2 0 0 mm and working width 1 5 0 mm . ( a ) and ( c ) show rear y iews of soil sections obtained by cutting the tilled soil . ( b ) and ( d ) show y iews looking down on the soil bin ( a ) and ( b )

caused by the three - stage subsoil mixing plough . ( c ) and ( d ) caused by the two - stage subsoil mixing plough

depth was 200 mm . In Fig . 9 , the draught of the plate mouldboard was about 1 ? 4 times that of the slat mouldboard . This draught dif ference is due not only to the reduction in the soil to metal friction but also to dropping of the soil between the slats . The soil dropped between the slats because the soil used in the soil bin tests was soft compared with that occurring in the field . Thus the reduction in draught of the slatted mouldboard as compared with the plate mouldboard , may be greater in the model tests than would occur in the field .

3 . 3 . The ef fect of the second plough to till the Aw horizon

In order to represent the two-stage subsoil mixing plough , the second plough body in Fig . 3 was removed and the Aw and B horizons (working depth of 200 mm) were tilled using the third plough body

alone . The soil mixing and transfer rates and the soil clod size are shown in Fig . 8 (mark d ) . The soil mixing and transfer rates were not influenced by the use of one plough body alone or two plough bodies together , but the clod size was significantly af fected by it . This is clear from Fig . 7 d which shows that when the soil was tilled by one plough body , many large clods were produced ; the largest one was about 10 4 mm 2 as shown in Fig . 8 a .

The draught results in this case are shown in Figs 6 and 9 (mark d ) . In both Figs 6 and 9 , when the 200 mm deep soil was tilled by only the third plough body , the draught was increased . This was due to large soil clods which were produced as shown in Fig . 7 d and the large soil clods had dif ficulty in flowing onto the mouldboard and hence a larger draught was required .

The results in Figs 6 , 8 and 9 suggest , that in order to decrease the draught and reduce clod size , three plough bodies should be used ; one each for the Ap ,

K . A R A Y A E T A L . 148

(a)

(b)

10

5

0

1·0

0·5

0

1·0

0·5

0

Clo

d si

ze A

, 103

mm

2

Tra

nsfe

r ra

te o

f Aw

to B

,T

Aw

-BM

ixin

g ra

te, M

x

Working widths of second andthird plough bodies b, mm

100 200 300

(c)

Fig . 8 . Soil mixing rate , transfer rate and soil clod size as a function of working width , b . Working depth , h was Aw ( 1 0 0 mm ) 1 B ( 1 0 0 mm ) 5 2 0 0 mm . s second and third

plough bodies together ; d third plough body alone

the Aw and the B horizons ( Fig . 2 b ) . The slat mouldboard should be used since it gives the lower draught . The optimum working widths of the second and third plough bodies appear to be 150 mm , which gave the smallest draught and a wider working width than the nominal width of the implement .

Slat Plate

3

2

1

Dra

ught

Fx,

kN

0

Fig . 9 . Draughts of slat and plate mouldboards . Working depth , h was Aw ( 1 0 0 mm ) 1 B ( 1 0 0 mm ) 5 2 0 0 mm . s second and third plough bodies together ; d third plough

body alone

4 . Conclusions

1 . The draught of a model three-stage subsoil mixing plough was af fected by the working width when the working depth was 200 mm . This is due to the area of the trapezium of soil section disturbed being increased by the larger working width .

2 . The soil mixing rate was in all cases more than 0 ? 8 and good soil mixing was obtained . The transfer rate varied around 0 ? 5 and an optimum amount of the Aw horizon was transferred into the B horizon . The soil mixing and transfer rates were constant regardless of the widths of the second and the third plough bodies .

3 . The clod size produced was not af fected by the plough width but was significantly reduced by using two plough bodies as compared with only one .

4 . The draught of the plate mouldboard was about 1 ? 4 times that of the slat mouldboard .

5 . When the 200 mm deep soil was tilled by the third plough body alone , the draught was increased . This was because large soil clods were produced and the large soil clods had dif ficulty flowing onto the mouldboard .

6 . In order to minimize draught and clod size

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produced , three plough bodies should be used , one each for the Ap , the Aw and the B horizons . The slatted mouldboard should be used as the draught was lower than that of the plate mouldboard . The op- timum working widths of the second and third plough were 150 mm which gave the smallest draught and a wider working width than the nominal width of the implement .

References 1 Zhao D ; Liu F ; Jia H Transforming constitution of

planosol solum . Journal of Chinese Scientia Agricultura Sinica 1989 , 22 (5) : 47 – 55

2 Araya K Influence of particle size distribution in soil compaction of planosol solum . Journal of Environmen- tal Science Laboratory , Senshu University 1991 , 2 : 181 – 192

3 Araya K ; Kudoh M ; Zhao D ; Liu F ; Jia H Improvement

of planosol solum : Part 1 , experimental equipment and methods and preliminary soil bin experiments with ploughs . Journal of Agricultural Engineering Research 1996 , 63 : 251 – 260

4 Araya K ; Kudoh M ; Zhao D ; Liu F ; Jia H Improvement of planosol solum : Part 2 , Optimisation of design of roll – in ploughs in soil bin experiments . Journal of Agricultural Engineering Research 1996 , 63 : 261 – 268

5 Araya K ; Kudoh M ; Zhao D ; Liu F ; Jia H Improvement of planosol solum : Part 3 , Optimisation of design of drop – down ploughs in soil bin experiments . Journal of Agricultural Engineering Research 1996 , 63 : 269 – 274

6 Araya K ; Kudoh M ; Zhao D ; Liu F ; Jia H Ploughs to improve planosol solum : Part 4 , Psuedogley soil field experiments with prototype roll – in and drop – down ploughs . Journal of Environmental Science Laboratory , Senshu University – Hokkaido . 1995 , 4 : 235 – 242

7 Araya K ; Kudoh M ; Zhao D ; Liu F ; Jia H Improvement of planosol solum : Part 4 , Field experiments with prototype roll – in and drop – down ploughs . Journal of Agricultural Engineering Research 1996 , 63 : 275 – 282