3.1. Land preparation
Land flooding period range from 1 to 5 days with an average of (3.2 and 3) days with a high coefficient of variation CV (38.9 and 36.2) for the first and second season respectively, while the sedimentation period range from 4 hours to 24 hours with an average of (14.2 and 14.3) hours with a very high coefficient of variation CV (50 and 43.1) for first and second season respectively (Table 2), high coefficient of variation is an indication of inconsistency planting managing and land preparation which has a negative effect of mechanical transplanting performance. For high transplanting quality, the flooding periods should be shorter than the current ones, and the sedimentation periods should be longer than the current ones, which allow the soil to settle down and to be hard enough to hold and catch the desired number of seedlings in a vertical standing forming high standing angle (range from 80o to 90o), with the standardized spacing, and the least planting losses.
Table 2
Summary of data for land preparation and soil physical properties
Parameter
|
Mean
|
St. Dev.
|
CV
|
Uniformity
|
Max
|
Min
|
Flooding period, day
|
3.1 ± 0.4
|
1.2
|
38.5
|
61.5
|
5
|
1
|
Sedimentation period, hour
|
14.25 ± 2.01
|
6.5
|
45.5
|
54.5
|
24
|
4
|
a Penetration resistance, MPa 10 cm
|
0.12 ± 0.01
|
0.05
|
42.49
|
57.51
|
0.20
|
0.03
|
a Penetration resistance, MPa 20 cm
|
0.38 ± 0.02
|
0.11
|
30.07
|
69.93
|
0.60
|
0.20
|
b Penetration resistance, MPa 10 cm
|
0.17 ± 0.01
|
0.07
|
44.15
|
55.85
|
0.31
|
0.07
|
b Penetration resistance, MPa 20 cm
|
0.24 ± 0.02
|
0.16
|
67.13
|
32.87
|
0.59
|
0.05
|
a Bulk density, g/cm3 10 cm
|
0.82 ± 9.01
|
0.09
|
10.43
|
89.57
|
1.05
|
0.65
|
a Bulk density, g/cm3 20 cm
|
0.83 ± 0.01
|
0.08
|
9.97
|
90.03
|
1.05
|
0.67
|
b Bulk density, g/cm3 10 cm
|
0.84 ± 0.01
|
0.10
|
0.01
|
11.50
|
88.50
|
1.05
|
b Bulk density, g/cm3 20 cm
|
0.85 ± 0.01
|
0.09
|
0.01
|
10.16
|
89.84
|
1.05
|
a Mechanical Transplanting Speed
|
5.06 ± 0.18
|
1.07
|
21.21
|
78.79
|
6.84
|
2.34
|
b Mechanical Transplanting Speed
|
5.04 ± 0.14
|
0.98
|
19.37
|
80.63
|
6.84
|
2.34
|
a Water content % 10 cm
|
78.67 ± 1.02
|
6.24
|
1.02
|
7.93
|
92.07
|
94.63
|
a Water content % 20 cm
|
76.99 ± 0.99
|
6.07
|
0.99
|
7.88
|
92.12
|
94.63
|
b Water content % 10 cm
|
77.43 ± 1.12
|
7.95
|
10.27
|
89.73
|
94.63
|
62.71
|
b Water content % 20 cm
|
73.13 ± 1.19
|
8.48
|
11.60
|
88.40
|
94.63
|
58.66
|
Missing hill/ha
|
5735.0 ± 683.8 (2.9%)
|
2206.7
|
38.5
|
61.5
|
9000
|
1600
|
Floating hill/ha
|
991.4 ± 89.2 (0.51%)
|
287.9
|
29
|
71.3
|
1700
|
366.7
|
Buried hill/ha
|
578.7 ± 20.9 (0.3%)
|
67.3
|
11.6
|
88.4
|
737
|
453
|
Total lost hill/ha
|
7305.1 ± 780. 0 (3.7%)
|
2517
|
34.5
|
65.5
|
11437
|
2587
|
a for the first season, b for the second season |
3.2. Effect of flooding and sedimentation periods on SPR
Flooding the field for 2 to 5 days led to increasing the soil water content up to 100% which led to softening the soil and as it reported in many types of research the negative relation between soil water content and penetration resistance so increasing water content resulted in decrease the soil penetration resistance. Flooding period reduction showed a negative significant effect on soil penetration resistance in 0 to 10 cm depth P < 0.001 and in 11 to 20 cm depth P < 0.001 for both seasons, while it was decreased with the increased flooding period. There was a high negative linear correlation between the flooding period and soil penetration resistance in the topsoil 10 cm R2 = 0.90 and 0.91 and in hardpan 20 cm R2 = 0.83 and 0.85 for the first and second season respectively (Fig. 1). Sedimentation period of the soil also significantly affect the soil penetration resistance positively P < 0.001 for both seasons if soil sedimentation period increased soil penetration resistance increased for, strong positive linear correlation topsoil 10 cm R2 = 0.94 and 0.94 and for hardpan 20 cm R2 = 0.87 and 0.90 for first and second season respectively (Fig. 1). The increase in soil penetration resistance with sedimentation period and that may because the dispersed particles of soil have settled again over time and also the water level in the field has decreased resulting in compacted soil and stable medium of soil layer which following that the soil strength increased and became high (Behera, et al., 2009).
Fig. 1 Linear correlation of penetration resistance versus flooding period (a) first season (b) second season, and versus sedimentation period (c) first season (d) second season
3.3. Effect of soil condition on transplanting working speed
The results of mechanical transplanting working speed showed a big variation as the coefficient of variation was 21.4%, which is very high (Table 2). The working speed of the transplanting machine was affected by the field condition, as the soil was very soft, the speed would be lower, and if the soil was hard enough to carry the machine the speed would be higher.
Soil penetration resistance affects the mechanical transplanting strongly, when the penetration resistance is high, the speed of transplanting becomes high, as the situation facilitates the running of the transplanting machines due to the ability of the top layer of the soil to hold the transplanting machine without sinking or bogging in the mud. The result showed that there was a very strong relationship between soil penetration resistance and mechanical transplanting working speed for both soil depth, R2 was 0.88 and 0.86 for 0 to 10 cm depth, and 0.85 and 0.96 for 11 to 20 cm depth for the first and second season respectively (Fig. 2 and 3). It has been suggested by Singh et al., (1985) that soil penetration resistance values below 0.243 MPa represent the soft soil conditions, while values above 0.490 MPa represent the firm soil conditions. In the study area the mean soil penetration resistance at topsoil 0 to10 cm depth was 0.09 and 0.24 MPa and for the first and second season respectively, while the mean soil penetration resistance at hardpan 11 to 20 cm depth was (0. 0.17 and 0.38 MPa) for first and second season respectively which mean that these soils are too soft.
Fig. 2 The correlation between penetration resistance MPa and mechanical transplanting speed km/h for the depth of 0 to 10 cm for the first season
Fig. 3 The correlation between penetration resistance MPa and mechanical transplanting speed km/h for the depth of 11 to 20 cm for the second season
Soil bulk density affects the speed of mechanical transplanting, where the bulk density was high the speed of the mechanical transplanting will be high. The result showed that there was a strong positive linear correlation ship between bulk density and mechanical transplanting working speed for both soil depth, R2 was 0.56 and 0.52 for 0 to 10 cm depth, and 0.58 and 0.57 for 11 to 20 cm depth for the first and second season respectively (Fig. 4 and 5). The highest bulk density facilitates the working of the mechanical transplanting without bogging or sinking in the soil mud, as the soil was settled and compacted to a certain limit, so the machines work easily and in a straight line. There was a negative effect of water content in the field and the transplanting working speed, as the water content increases, the working speed of mechanical transplanting, and the troubles of working increase. More water content means more soften and loosened soil which abandons the transplanting working. There was a very strong relationship between soil water content and mechanical transplanting working speed for both soil depth, R2 was 0.51 and 0.69 for 0 to 10 cm depth, and 0.52 and 0.70 for 11 to 20 cm depth for the first and second season respectively (Fig. 6 and 7). The statistical analysis showed a positive relationship between transplanting working speed and row spacing R2 = 0.86, planting distance R2 = 0.84, hill/m2, R2 = 0.81, seedlings/hill, R2 = 0.82, and seedlings/m2, R2 = 0.79. The result showed a negative relationship between speed and missing hill/m2, R2 = 0.83, floating hill/m2, R2 = 0.83, buried hill/m2, R2 = 0.73, and total lost hill/m2, R2 = 0.84 (Fig. 8). The highest working speed became an indicator for a well and perfect prepared land, and the lowest working speed and bogging in the soil is an indicator for bad and imperfect land preparation.
Fig. 4 The correlation between bulk density g/cm3 and mechanical transplanting speed km/h for the depth of 0 to 10 cm
Fig. 5 The correlation between bulk density g/cm3 and mechanical transplanting speed km/h for the depth of 11 to 20 cm
Fig. 6 The correlation between water content % and mechanical transplanting speed km/h for the depth of 0 to 10 cm for the first season
Fig.7 The correlation between water content % and mechanical transplanting speed km/h for the depth of 11 to 20 cm for the second season
Fig.8 The correlation between mechanical transplanting speed km/h vs. floating hills/m2, buried hills/m2, missing hills/m2, and total lost hills/m2
For broadcasted direct seeding, there were big variations in the working speed in general, but it was lesser than those of transplanting machines. Even for the same operator, there were big variations in the working speed CV = 14.9%, which affect the flow rates of the seeds that are directed to a certain equal area and that affect the seed distribution seeds/m2, which means uneven plant density per square meter.
3.4. Depth of Transplanting
The maximum depth of transplanting was recorded as 4.4 and 4.8 cm for the first and second seasons respectively. Depth of transplanting was found to decrease with the sedimentation period, there was no significant difference in transplanting depth among treatments. A strong positive linear correlation between depth of planting with sedimentation period R2 = 0.95 and 0.94 for the first and second season respectively. It was noticed that the depth of transplanting was affected negatively by the flooding period. The higher the flooding period the lower the depth of transplanting and vice versa. There was a strong negative correlation between transplanting depth with flooding period, R2 = 0.95 and 0.91 for the first and second season respectively. Also, the depth of transplanting is affected severely by the soil penetration resistance. In this study, the higher the soil penetration resistance the higher the depth of transplanting. In the present study, the depth of transplanting was set at 5 cm. There was a strong positive linear correlation between depth of planting and penetration resistance in topsoil layer 10 cm R2 = 0.97 and 0.98 and in the hardpan layer, 20 cm R2 = 0.83 and 0.97 for first and second season respectively. Depth of transplanting is also affected by water depth in the field where the depth of water increased the depth of transplanting decreased and vice versa. There was a strong positive linear correlation between depth of transplanting and water depth during transplanting R² = 0.79 and 0.67 for the first and second season respectively.
3.5. Effect of soil properties on planting losses
Puddling harms the topsoil layer by loosening it more than the required level because the puddling operation performed in very high moisture content, it also, consumes a large quantity of the total water requirement in rice because farmers flood the field up to 10 cm for more than 2 days avoiding following Rice Check standard requirement. For efficient working of self-propelled rice transplanting machine, a suitable puddle soil condition, degree of puddling, an optimum depth of puddling, optimum bulk density, the standardized water depth, and soil strength of the puddle wheel should be done following the standard. This affects the spacing of transplanted paddy in the rows and between rows, the number of planting seedlings within the hill, degree of vertical standing, and depth of planting which should be maintained within the standardized system to obtain high quality of transplanting.
The means, standard deviation, and coefficient of variation of missing, buried, floating, and total lost hills per hectare are shown in and per square meter of transplanting performance are shown in Table 2 and Table 3 respectively. The percentage of total hill losses/ha was (3.6 and 3.9%) for the first and second season respectively (Fig. 9) and this amount of losses still within the permitted limit as the Japanese test code for transplanting machines using the mat type of seedlings prescribes a maximum of 5% defective hills for acceptable transplanting (Singh et al., (1985). Percentage of missing seedling/ha was (3 and 3.2%), floating hill (0.5 and 0.5%), and buried seedling (0.3 and 0.30%) for the first and second season respectively.
The important field parameters that affect transplanting quality are water depth, degree and depth of soil puddling, and soil flooding and sedimentation periods. The result showed strong negative correlation between missing hills with soil penetration resistance, the number of missing hill increases with reduction of soil penetration resistance in depth of 10 cm R2 = 0.95 and 0.98, and in-depth 20 cm R2 = 0.90 and = 0.98, strong negative correlation between floating hills with soil penetration resistance in depth of 10 cm R2 = 0.92 and 0.77, and in-depth 11 to 20 cm (R2 = 0. 0.88 and 0.64), strong negative correlation between buried hills with soil penetration resistance in depth of 10 cm R2 = 0.89 and 0.91, and in-depth 20 cm R2 = 0.77 and 0.82 strong negative correlation between total lost hills with soil penetration resistance, in-depth of 10 cm R2 = 0.95 and 0.98, and in-depth 20 cm R2 = 0.90 and 0.96 for first and second season respectively (Fig. 10).
Fig. 9 Percentage of hill planting losses of transplanting for the first and second season
Fig. 10 Linear correlation between penetration resistance and planting losses for transplanting (a) for the first season and (b) for the second season
3.7. Effect of water depth on planting losses
Flooding the field to a depth of 10 to 15 cm for long period leads to insufficient bearing strength to carry the machine and support the planted seedlings by creating softened and loosened soil and thus decreasing the penetration resistance and that is the main reason for planting losses. The result showed a strong positive linear correlation between water depth and missing hill but it is clear that polynomial correlation is stronger than the linear correlation. The linear correlation between water depth and missing hill/ha was strong R2 =0.79 and 0.65 and the polynomial correlation R2 =0.92 and 0.87, the linear correlation between water depth and floating hill R2 =0.85 and 0.91 and the polynomial correlation R2 =0.94 and 0.93, and the linear correlation between water depth and buried hill R2 =0.94 and 0.85 and the polynomial correlation R2 =0.94 and 0.91, and for total lost hill/ha there was a strong linear correlation with water depth R2 =0.80 and 0.70 and the polynomial correlation R2 =0.93 and 0.89, for first and second respectively (Fig. 11). The study showed that when the water depth is high and the soil is too soft and loosened, which lead the soil to stick with the transplanting machine wheels and planting becomes difficult and the transplanting machine bogged several times which led to more hill losses and unplanted area and messy field soil that need hand replanting which is normally not done with the same quality and density and spacing uniformity as transplanting machine does. It was concluded that maximum water depth should not be more than 2.5 cm in the field at the time of transplanting to reduce the drag force for the self-propelled transplanting machine. (Islam et al. 2015) reported that care should be taken to level the land before transplanting and water height should be maintained uniformly to avoid seedling submergence and floating hill.
Fig 11 Linear correlation between water depth and planting losses for transplanting (a) in the first season (b) in the second season
The study showed that the mean water depth in the field at the time of transplanting was 3.01 and 3 cm for the first and second season respectively, and the maximum water depth was 7 cm in low areas in the fields and this is considered as high water depth and it made many troubles for machine performance. The result showed that there was a big variation in water depth the coefficient variation CV was 14.24 and 16.63% for the first and second season respectively, the farmers do not follow the guidelines and instructions that included in Rice Check to flood the field for two days up to 5 cm water depth and the water level should not exceed 5 cm, and there should not be stagnant water, whereas the farmers flood the fields for 4 to 5 days up to 10 to 15 cm water depth and the drainage is very poor due to unlevelled land. In IRRI standard fields may need to be drained for two days to stop seedlings floating. Well puddled and leveled field is required with no standing water on the surface because it creates more floating hills (Guru et al., 2018). When the water in the field is more at the time of transplanting, the seedlings are not fixed properly in the soil and start floating. In general, for mechanical transplanting, it has been recommended that the depth of the puddle should be 5 cm and water depth not more than 2.5 cm.
3.9. Effect of flooding and sedimentation period on planting losses
The result showed that the flooding period has a significant effect on the percentage of floating hills P < 0.001, buried hills P < 0.001, missing hills P < 0.001, total lost hills significantly P < 0.001 in both seasons. The lower percentages of floating hills, buried hills, missing hills, and total lost hills were observed for one-day flooding periods, they decreased with the increase of the flooding period. There were a strong positive linear correlations between flooding period vs. floating hills, R2 = 0.91 and 0.82, buried hills, R2 = 0.85 and 0.92, missing hills, R2 = 0.91 and 0.90, and total lost hill R² = 0.92 and 0.92 for first and second season respectively (Fig. 12). The highest percentage of floating hills, buried hills, missing hills, and total lost hills were observed after the longest flooding period which was 5 days. Those planting losses might be reduced by sufficient settlement of soil after the final preparation of the land by decreasing of flooding period from 5 to 1 day because surface soil of field avoided to became too soft and loosening whereas the soil of was settled down enough to reduce floating and buried hills and to reduce the picker missing hills.
Fig. 12 Linear correlation of planting losses versus flooding period for the first season (a), second season (b), and versus sedimentation period for the first season (c) and second season (d)
For perfect machine performance, the soil sedimentation period after puddle should be at least about 48 hours for heavy soils. The result showed a big variation in the sedimentation period between a different field with a high coefficient of variation 49.95 and 43.13% and that due to scarce of the number of tractors and the farmers need to till their fields. For ease of transplanting machine, soil sedimentation period after puddle should be enough to avoid machine bogging and inefficient performance. The sedimentation period has a significant effect on floating hills P ≤ 0.001 and < 0.001 for the first and second season respectively, buried hills highly significant P < 0.001 for both seasons, missing hills/ha, and lost hills/ha P < 0.001 for both seasons. The percentage of floating hills, buried hills, missing hills/ha, and total lost hills/ha decreased with an increase in the sedimentation period. The highest percentages of mean floating hills, buried hills, missing hills, and total lost hills were after the shortest sedimentation period of 4 hours, and that may be due to the weakness of the seedling anchorage in wet soils and the movement of soil and water along with buoyancy. The lowest percentage of floating hills, buried hills, missing hills, and total lost hills were observed after 24 hours of sedimentation period and that due to the proper anchorage of seedlings with soil and less flow of puddled soil and water with the float at this sedimentation period. With the increase in sedimentation period soil got more strength and it became more coherent over time, also the flowing of the soil decreased along with buoyancy, this caused and led to the decrease in the buried and floating hills direct (Garg 1976; Kanoksak et al. 1988; Khan and Gunkel 1988). There was a high negative correlation between the sedimentation period and floating hills/ha, R2 = 0.89 and 0.77, buried hills/ha, R2 = 0.81 and 0.91, missing hills/ha, R2 = 0.97 and 0.94, and total lost hill, R² = 0.96 and 0.95 for the first and second season respectively (Fig 12).
4.3. Water Irrigation Practices Quality
Table 6. Shows the water irrigation practices. Water management is a very important and crucial role in achieving a high grain yield.
Table 6
Practice Quality of Water Irrigation
DAY LAST DAY
|
Water level
|
Right source
|
Right amount
|
Right time
|
Right place
|
Quality Index
|
P
|
N
|
P
|
N
|
P
|
N
|
P
|
P
|
|
5–7 DAP
|
5
|
100
|
0
|
100
|
0
|
100
|
0
|
100
|
0
|
100
|
1–5 DAT
|
5
|
100
|
0
|
100
|
0
|
100
|
0
|
100
|
0
|
100
|
15–40
|
5
|
100
|
0
|
63.3
|
36.7
|
56.7
|
43.3
|
66.7
|
33.3
|
71.7
|
40–50
|
10
|
100
|
0
|
36.7
|
63.3
|
40.0
|
60.0
|
36.7
|
63.3
|
53.3
|
70
|
10
|
100
|
0
|
36.7
|
63.3
|
40.0
|
60.0
|
36.7
|
63.3
|
53.3
|
80–90
|
10
|
100
|
0
|
43.3
|
56.7
|
36.7
|
63.3
|
33.3
|
66.7
|
53.3
|
90–100
|
0
|
100
|
0
|
36.7
|
63.3
|
40.0
|
60.0
|
33.3
|
66.7
|
52.5
|
110–120
|
0
|
100
|
0
|
36.7
|
63.3
|
40.0
|
60.0
|
33.3
|
66.7
|
52.5
|
Average
|
100
|
0
|
50.5
|
49.5
|
50.5
|
49.5
|
48.6
|
51.4
|
62.4
|
• 5–7 DAP = for direct seeding method, 1–5 DAT = for transplanting method |
• P = positive. N = negative |
Water management is a very important and crucial role in achieving a high grain yield. In terms of choosing the right source which means here the right equipment and tool to irrigate the field in a short time, all farmers use the right sources, in terms of the right amount as mentioned very specifically with the required in Rice Check as in Table 6. About 50.5% of the farmers follow the standard, in terms of the time of irrigating the field, 50.5% follow the right time as mentioned in Rice Check, and for the place that water should cover which should be all the area through the field, 48.6% of the farmers covered the whole area with the adequate amount of water, whereas 51.4% of them do not perfectly cover the field because the amount of water is not enough besides the leveling of the land is not like the standard mentioned in Rice Check as it should be 100% leveled ± 5 cm and this degree of leveling could not be achieved unless farmers use laser leveling and that is costlier and not available in a wide range.
Farmers do not follow Rice Check in terms of the required water depth, and there was a big variation of water depth through the fields due to the imperfect land leveling. There were much water drainage and leakage during pesticide spraying and fertilizer broadcasting and that leads to losses, leaching, and environmental contamination. Most of the farmers do not drain the water 15 days before harvesting, this leads to destroying the soil by combine passing, and making grooves that prevent the whole drainage after harvesting thus delaying the tillage operation for the next season. Many times during the season, there was a low level of water, which may affect the grain filling, and reduce the fertilizer efficiency, and farmers should take more tension to maintain the level of water at 10 cm, this is very important for increasing the yield.
Farmers do not care about the required schedule of water irrigation for the rice plant and the required depth of water. Many times during the season, plants suffer from insufficient and inadequate water, which affects the grain yield. Also during fertilizers broadcasting and pesticide spraying operations, all the gates in or out of irrigation or drainage should be closed, but in reality, many times during these operations the gates were open because farmers forgot that. Also, the farmers do not keep the depth of water at the required level during these operations, which affects the quality of operations, especially during fertilizer broadcasting operations, and that share and cause fertility losses. Improve water control by better irrigation and drainage to achieve full potential yield rice is missing in the farming system. Producing optimum rice yields through continuous flooding irrigation with 10 to 15 cm of water depth is optimum for fertility efficiency, fighting weeds, grain filling, and high grain yield. Land leveling also affects the uniform and even distribution of the water in the field.
In terms of water irrigation efficient practices, 47.38% of farmers follow Rice Check. About 49.52% of farmers do not give the rice the adequate water amount, about 49.52% do not open the irrigation gate or close the drainage gate at the right time especially before and after fertilizer broadcasting and pesticides spraying operations, about 51.43% of them do not cover the whole area of the field with water due to unleveled land and inadequate water amount. About 63.33% do not drainage their field before harvesting and about 60% of them do not drain the field before harvesting at the right time, which cause a big problem in preventing drainage of the field after harvesting and preventing burning the straws and slashing the field and delaying first plowing due to the high water level.