Effects of key design parameters of tine furrow opener on soil seedbed properties

Abstract

The structural parameters of tine furrow openers have significant effects on soil property of seed furrow in no-till planting, thereby affecting crop growth and yields. In order to analyze the effects of key parameters of tine furrow openers on soil properties (soil bulk density, soil water-stable aggregates (WSA), and soil disturbance) of the surface soil layer of 0-10 cm and surface straw disturbance, the tine furrow openers with different structural parameters, including cutting edge thickness, cutting edge curve, penetration clearance angle and rake angle, were designed and tested under no-till conditions. Orthogonal test and single factor test were performed to analyze the effects of different parameters. Results showed that the rake angle, cutting edge thickness and cutting edge curve had significant effects on cross-sectional area of furrow (A^sub f^) and disturbance of surface straw; the rake angle had a significant effect on soil bulk density. Soil types and operating depth had significant effects on soil disturbance caused by tine furrow openers. The concave type tine furrow opener produced the lowest soil disturbance and soil bulk density of seed furrow, the highest surface straw disturbance and the greatest content of WSA (>0.5 mm). With increasing rake angles of tine furrow opener, the width of seedbed (W^sub sb^) and the A^sub f^ decreased first and then increased, respectively, while the width of soil throw (W^sub st^) and the height of ridge (H^sub r^) increased. The W^sub sb^ and A^sub f^ created by tine furrow opener with 60° rake angle were significantly lower than that with others, respectively. The tine furrow opener with rake angle ranged from 45° to 60° created the lowest soil bulk density. As the penetration clearance angle increased, the content of WSA (>0.5 mm) decreased, but the effect of penetration clearance angle on the content of WSA (<0.5 mm) was not significant. The cutting edge thickness (<2 mm) had no significant effects on soil properties of seedbed. This study could provide a reference for optimal design of the tine furrow opener to create more suitable seedbed environment, and promote the application of the light no-till planters.

Headnote

Abstract: The structural parameters of tine furrow openers have significant effects on soil property of seed furrow in no-till planting, thereby affecting crop growth and yields. In order to analyze the effects of key parameters of tine furrow openers on soil properties (soil bulk density, soil water-stable aggregates (WSA), and soil disturbance) of the surface soil layer of 0-10 cm and surface straw disturbance, the tine furrow openers with different structural parameters, including cutting edge thickness, cutting edge curve, penetration clearance angle and rake angle, were designed and tested under no-till conditions. Orthogonal test and single factor test were performed to analyze the effects of different parameters. Results showed that the rake angle, cutting edge thickness and cutting edge curve had significant effects on cross-sectional area of furrow (A^sub f^) and disturbance of surface straw; the rake angle had a significant effect on soil bulk density. Soil types and operating depth had significant effects on soil disturbance caused by tine furrow openers. The concave type tine furrow opener produced the lowest soil disturbance and soil bulk density of seed furrow, the highest surface straw disturbance and the greatest content of WSA (>0.5 mm). With increasing rake angles of tine furrow opener, the width of seedbed (W^sub sb^) and the A^sub f^ decreased first and then increased, respectively, while the width of soil throw (W^sub st^) and the height of ridge (H^sub r^) increased. The W^sub sb^ and A^sub f^ created by tine furrow opener with 60° rake angle were significantly lower than that with others, respectively. The tine furrow opener with rake angle ranged from 45° to 60° created the lowest soil bulk density. As the penetration clearance angle increased, the content of WSA (>0.5 mm) decreased, but the effect of penetration clearance angle on the content of WSA (<0.5 mm) was not significant. The cutting edge thickness (<2 mm) had no significant effects on soil properties of seedbed. This study could provide a reference for optimal design of the tine furrow opener to create more suitable seedbed environment, and promote the application of the light no-till planters.

Keywords: tine furrow opener, key parameter, no-till planter, soil disturbance, straw cover, bulk density, soil water-stable aggregates

DOI: 10.3965/j.ijabe.20160903.2259

(ProQuest: ... denotes formulae omitted.)

1 Introduction

Furrow openers are the key component for conservation planter to create suitable seedbeds[1]. Good soil conditions in seedbeds can provide a suitable temperature regime and soil water content for crop germination and growth. Two main types of furrow openers, disc, may have different performances in creating seedbeds[2]. Generally, disc openers, which need a larger vertical force to penetrate hard soil, are mainly used on large no-till planters, while tine furrow openers are mainly used on small and medium no-till planters because of its better ability of soil penetration. Comparing with disc furrow opener, the tine opener requires lower vertical force and larger traction force[3].

In China, the disc type planters are too large, heavy, and expensive for popularization and application, while the tine based, small and inexpensive no-till planters are widely used[4]. Reasonable structures of tine furrow openers for these planters are required to create suitable seedbed environment and reduce operation resistance in the no-till straw-mulched fields[5]. The no-till seedbed can improve moisture holding capacity and promote the crop growth[6]. According to the requirements of no-till planting, the seedbed with fewer soil disturbance produced by tine furrow opener, is conducive to crop growth[7,8]. However, the existing research of agronomic characters showed that seedbed with suitable soil disturbance can promote crop emergence and obtain high yield under no-till planting conditions. And the seedbed quality is affected by different structures of tine furrow opener. Currently, many researchers designed various furrow openers with different structural parameters[9-11], and studied their operation performances in fields covered by residues. The influences of seedbeds in the early growth stage of wheat were studied by Yao et al.[12], and these seedbeds were created by different furrow openers (the tine opener, the single disc opener, and the rotary opener). It was found that the soil disturbance and the counts or the number of the adventitious root in the soil layer created by rotary opener were larger than that with others. The single disc opener created the lowest soil disturbance. The rotary opener was a strip-till device which used the powered rotary blades to chop soil, crop residues and straws, and made the better passing capability on seeding and fertilizing furrow openers. Godwin[13] demonstrated that structural parameters of the opener were the main factor on affecting the soil loosening and movement. Solhjou et al.[14] analyzed the effects of rake angle of furrow opener on soil disturbance of seedbed. It was shown that the lower rake angles increased the movement from deeper soil layers into the seed zone. The larger rake angle opener disturbed a smaller furrow size and achieved slightly more furrow backfill.

Others studied the effects of furrow openers and its key design parameters on draft force and soil disturbance under different operation conditions. The cross-sectional area increased with the increase of rake angle and wedge angle. Many researchers[15-18] built the mathematic and discrete element model of furrow openers to analyze the draft force and soil disturbance under different conditions of opening speeds, soil bulk density, and moisture content. Hasimu and Chen[19] studied the effects of three different seed openers (hoe, winged hoe, and spoon) on soil disturbance and draft force through soil bin test. With the increase of working depth, soil disturbance and force created by openers increased. The hoe opener had better performance than the others. Ebubekir et al.[20] studied the influences of different types of furrow openers (hoe, shoe, and shovel type) and operation speeds on soil properties and draft force. For all the types of furrow openers, the draft force increased and ridge height decreased with the increase of operational speed. Shovel type furrow opener required the least draft force. Chaudhuri[21] stated that the furrow openers affected the backfill of the soil with increased depth in laboratory and field experiments. The soil disturbance of disc-type furrow opener was also less than that of hoe-type furrow opener. After harvesting the previous crops, the crop straw and stubble were used to cover the ground surface. Disc-type openers did not perform well in no-till field with hard soils and residue cover because the disc-type openers need a larger vertical force to squeeze into the soil and easily pushed the dry soil, straw and stubble into furrow, while hoe-type openers generally performed better on penetration capacity. Mohler et al.[22] and Karayelet al.[23] analyzed the influences of different types of furrow openers on horizontal and vertical distribution of seedbed soil. The existing researches mainly analyzed the properties of seedbed created by different type furrow openers and how these openers affect crop growth under various field conditions. Few studies of the key structural parameters of tine furrow openers, mainly focused on analyzing the effects of openers on draft force. Furthermore, there was no comprehensive analysis of soil properties affected by the key structural parameters of tine furrow openers.

The objective of this study was to determine which key structural parameters (including cutting edge thickness, cutting edge curve, penetration clearance angle, and rake angle) of tine furrow opener had significant effects on soil properties (soil bulk density, soil water-stable aggregates, and soil disturbance) and surface straw disturbance of the seed furrow under no-till conditions.

2 Materials and methods

2.1 Description of test furrow opener

The test tine furrow openers were designed to analyze their effects on soil properties and straw disturbance of seed furrow. To eliminate the interference of other factors, all designed tine furrow openers (Figure 1) had the same structural parameters except the four variable parameters (including rake angle, penetration clearance angle, cutting edge thickness, and cutting edge curve).

Rake angle (?): It is the angle between the working edge of furrow opener and the ground surface, which has certain effects on the penetration performance and working resistance of furrow opener. The rake angle was determined to be greater than 30°[14].

Penetration clearance angle ( β): It is the angle between the subsurface of furrow opener and the ground surface, which affects the penetration performance and the flatness of furrow bottom. The penetration clearance angle was determined to be less than 12°.

Cutting edge thickness (t): With the increase of the thickness of cutting edge, the abrasion resistance of furrow opener improved and the working resistance also increased. The determined thickness was less than 2 mm.

Cutting edge curve: The cutting edge of furrow opener is used to cut soil and affects the movement of soil and surface straw. Four types of cutting edge curve including lineartype (T1), convex type (T2), concave type (T3), and linear-curvilinear combination type (T4) were selected to analyze the impacts on operation effect.

Four levels were set for each of the four structural parameters according to the above analysis, shown in Table 1.

The height (h) of tine furrow openers was determined by depth of the furrow. Meanwhile, the growth of wheat can be affected by seeding depth. The shallower seeding depth was beneficial for crop emergence, and degraded the drought resistance and cold resistance performance. With the increase of the seeding depth, the effect of water retention and heat preservation was reinforced, however, the deeper seeding depth will lead to lower emergence rate. Studies showed that, the seeding depth of 5 cm was beneficial for crop emergence[24,25]. Meanwhile, the fertilizer should be placed below the seed in the furrow, and the suitable distance between the seeds (GBT20865-2007) and the fertilizer is about 3 cm to 5 cm. So the maximum opening depth was about 10 cm that can place seed and fertilizer in the appropriate place of furrow.

According to the different structural parameters determined by the L16(45) orthogonal table[26], 16 types of furrow opener were designed (Table 3). To eliminate the influences from other factors, sizes of the furrow opener were consistent except the above four structural parameters. The height (h) and the width (d) of tine furrow openers were designed as 15 cm and 4 cm respectively. Furrow openers were fabricated using 65Mn steel plate (5 mm in thickness) with conditioning treatment. The different shapes and parameters of furrow openers were shown in Figure 2.

The point O at the bottom of the furrow opener was assumed as the origin of coordinate system, then the two end points of the cutting edge curve were point O(0, 0) and point A(xa, h).

(1) When the cutting edge curve was linear type (Figure 2a), the relationship among rake angle (α), height of furrow openers (h) and x-coordinate value of point A was:

... (1)

Thus the x-coordinate value of point A, calculated by Equation (1), was shown in Equation (2).

... (2)

(2) When the cutting edge curve was concave type or convex type (Figures 2b and 2c), the circle, where the cutting edge curve was in, passed through the ordinate origin O(0, 0). The point O'(xO', yO') and R were the center and the radius of the circle, respectively. Then the equation of the circle was assumed as:

... (3)

If the cutting edge curve was concave type (Figure 2b), the x and y values of the center point O'(xO', yO') were presented in the following equations.

... (4)

So the equation of the circle was,

... (5)

The x-coordinate value of point A was calculated by y-coordinate (ya=h). It was

... (6)

Similarly, if the cutting edge curve was convex type (Figure 2c), equations of the circle and x-coordinate value of point A were calculated by Equation (7) and Equation (8) as concave type curve edge in Figure 2b.

... (7)

... (8)

where, Equation (7) represents the equation of the circle where convex type cutting edge curve was in, Equation (8) represents the x-coordinate value of point A.

(3) When the cutting edge curve was linear-curvilinear combination type (Figure 2d), the segment OD and segment DA of cutting edge curve were a straight line and circular arc which was a part of the circle. The segment OD was tangent to segment DA and the tangent point was D(xd', yd'). The x-coordinate value (xd') of point D was calculated by the y-coordinate value (yd') which was set up to be the constant value (d'). The circle, where the segment DA of cutting edge curve was, did not pass through the ordinate origin O(0, 0). The equations of the circle and x-coordinate value of point A were determined by the same analysis mentioned above.

... (9)

... (10)

where, Equation (9) represents the equation of the circle where segment DA of cutting edge curve was, Equation (10) represents the x-coordinate value of point A.

2.2 Site and equipment description

The field experiments were conducted from 2012 to 2014 at Zhuozhou Experiment Station (39°28'N, 115°56'E), Hebei, China. The soil types were sandy loam and loam. The soil pH value was 7.8 and the soil organic contents ranged from 1% to 1.9%. The annual average rainfall is 617 mm, which always concentrates in summer. In this annual double cropping regions, two crops are planted in sequence each year (October for wheat and June for maize). Before the field experiment, the field was covered by corn stover which was chopped by smashed straw machine and evenly threw to the soil surface. Penetration resistance, an indicator of soil compaction, was measured by a soil compaction meter (Field ScoutTM SC900) with 60°apex angle, 12.83 mm cone base diameter, and 45 cm maximum measuring depth. The value of penetration resistance was recorded at each 2.5 cm interval. At the same depth, the undisturbed soil samples were randomly collected with a manual stainless steel core samplers, and the samples were used for measuring moisture content (db) of dry soil and soil dry bulk density by oven drying method. The disturbed soil samples were collected with sealable plastic bag, and the proportions of soil water-stable aggregates of the disturbed soil was measured by the wet-sieving method. Soil conditions of the experiment field were tabulated in Table 2.

Field experiments were carried out using a field integrated testing system and a furrow opener suspension bracket (Figure 3) designed by China Agricultural University[27]. The system consisted of rear suspension test platform and data collecting section. Parameters such as draft force, fuel consumption, and operating speed can be measured by the test platform hauled by tractor. Experimental data were collected by data collecting section of the system. The operating speed can be set up and adjusted to meet with experimental requirement by the system. In the experiment, the suspension bracket was connected to the test platform by three-point hitch. The experimental furrow openers were mounted on traverse beam of the suspension bracket by U-shaped bolt and can be adjusted up and down according to the operating requirement.

If the seeding speed was too high (>7 km/h), it might result in the decline of metering device performance[28,29] and then increase the seed breaking rate. With the increase of seeding speed, the distance of soil lateral throwing increased and the wet and dry soil mixed which affected the performance of backfill soil and the seeding quality. Studies showed that the seeding speed less than 7 km/h was better for improving the seeding performance and opening quality.

2.3 Measurements

Soil disturbance quantity: During the opener was operating in the field, the soil was disturbed and most of the disturbed soil was turned over, which formed two ridges on both sides of the seeding furrow. The distance between the outer edges of the two ridges was defined as Wst. The distance between the two peaks of the ridges in both sides of furrow was the ridge to ridge distance (RRD). The rest of the disturbed soil formed the shallow groove in the furrow. The profile of the groove was represented by the second line (the disturbed soil surface) in Figure 4. The disturbed soil was carefully removed until the contour of the furrow was clearly observed. The disturbed soil surface and the contour of the furrow were drawn on a transparency paper for measuring easily. The width of the furrow top was the maximum width of seedbed (Wsb) on the original soil surface. The distance from the peak of the ridge to original soil surface was the height of ridge (Hr). The above soil disturbance parameters[30] were illustrated in Figure 4.

Among these parameters, the Af was calculated by the following equation:

... (11)

where, w is the width of furrow opener, cm; Wsb is the maximum width of seedbed, cm; t is the depth of furrow, cm. All the measurements were replicated for five times and the average value was calculated.

Straw disturbance quantity: The disturbance of surface straw was measured by the difference of the straw coverage rate before and after tests. The straw coverage rate was measured by meter stick method[31]. First, the meter stick (which was marked at every 0.5 m interval) was placed on the ground surface. Second, the number of all marks on the meter stick was counted as the total number (N). When the marks on the meter stick covered on the straw, the marks were counted as the record number (n) in measuring area. This study mainly analyzed the effects of different tine furrow openers on straw disturbance quantity. The result was directly measured after the opening operation and the furrow was open. The meter stick was placed along the two diagonals of the measuring area. The length and the width of the measuring area were determined by the maximum distance of soil throw (Wst) and the length of meter stick respectively. Straw coverage rate, calculated as the ratio of the record number (n) and the total number (N), was shown in Equation (12).

... (12)

The difference of straw coverage rates before and after each test, used to show the effect of furrow opener on straw disturbance during the opening operation, was defined as the straw disturbance quantity (η), as shown in Equation (13).

... (13)

where, Δ0 is the straw coverage rate before test; Δ is the straw coverage rate after test.

Soil bulk density: As mentioned, seeding depth was set as 5 cm to improve the crop emergence rate and crop yield[25]. Soil bulk density of seedbed was analyzed because loose soil can promote emergence rate and root growth. Soil samples at 10 cm depth were randomly collected with a manual stainless steel core samplers (size: [straight phi]50.4 mm × 50 mm) to measure the soil bulk density. All the soil cores were weighed and dried at 105°C for 48 h. Dry soil cores were weighed again to determine dry bulk density[7].

Soil water-stable aggregate: The disturbed soil samples were collected from seed furrow (after each test) for measurement of soil aggregate stability. Each soil sample was first passed through an 8 mm sieve which helped break the soil clods and separate pebbles and stable clods (>8 mm). Before analysis, soil samples were air-dried for 24 h in the laboratory with room temperature. Soil water-stable aggregate distribution was determined by placing the soil sample on a nest of sieves, immersing directly in water, and agitating the sieves up and down 35 mm for 15 min in water (30 cycles per minute). Proportions of stable aggregates of >0.106-0.25 mm, >0.25-0.5 mm, >0.5-1.0 mm, >1.0-2.0 mm, and >2.0 mm were calculated by drying and weighing the soil remaining on each sieve[32].

2.4 Experimental design

Orthogonal test: Under the operating speed of 4 km/h and the depth of 10 cm, 16 types of furrow openers were tested to analyze the effects of tine furrow opener on soil dry bulk density, cross-sectional area of furrow (Af), and surface straw disturbance, and determine the key parameters of furrow opener. The effect was studied in the loam soil with straw coverage rate of 93%.

Single factor test: Four structural parameters (including cutting edge thickness, cutting edge curve, penetration clearance angle and rake angle) of tine furrow opener were studied to analyze their effects on soil bulk density, WSA, and the soil and surface straw disturbance, respectively. Those experiments were conducted in two soil types (sandy loam and loam) with different straw coverage rates of 43%, 68% and 93%, respectively. According to the above analysis, the operating speed was selected as 4 km/h and the operating depths were selected as 5 cm and 10 cm for putting the seed and fertilizer into the furrow.

2.5 Data analysis

To reduce experimental error and ensure the accuracy and reliability of the experimental data, all the trials were replicated in triplicate and averaged. An ANOVA was used to assess the effects. When the ANOVA indicated a significant F -value, multiple comparisons were performed by the least significant difference method (p<0.05). The SPSS software package (19.0) was used for all the statistical analyses. Figures were generated by Origin9.1 software.

3 Results and discussion

3.1 Analysis of orthogonal experiment

As indicated in Tables 3 and 4, the order and contribution rate of every experimental factor on each target index was determined by orthogonal experiment and range analysis.

The contribution rate order of the factors' effects on both soil bulk density and soil disturbance (Af) was the same as follows: rake angle > cutting edge thickness > cutting edge curve > penetration clearance angle. The order of four factors' effects on the surface straw disturbance quantity was cutting edge curve > rake angle > cutting edge thickness > penetration clearance angle.

The result of variance analysis was tabulated in Table 5. Rake angle significantly (p<0.05) affected the soil bulk density. Marginal effects of cutting edge thickness and cutting edge curve were not significant (p<0.05). All the factors except penetration clearance angle had significant influence on both of soil disturbance (Af) and surface straw disturbance.

As shown in Tables 4 and 5, rake angle was determined as the main factor which affected soil bulk density and soil disturbance. The significant effects of cutting edge curve and cutting edge thickness on disturbance of surface straw resulted from their direct contact with the soil and the surface straw, which was in accordance with the research by Yao[10].

3.2 Soil disturbance

The indexes of soil disturbance affected by cutting edge curve and rake angle were shown in Figures 5 and 6. The quality of soil disturbance increased with increasing operating depth in both loam soil and sandy loam soil, and that was more significant in loam soil. It was because the adhesive force and shear strength are larger in loam soil which promoted the disturbance quality to the side soil[15,18]. Concave type furrow opener had the lowest Wsb, Wst and Af, and the largest Hr, as shown in Figure 5.

Compared with linear type (T1), convex type (T2) and combination type (T4), the Wsb caused by concave type (T3) tine furrow opener decreased by 6.73%, 8.20% and 2.49% in loam soil at 10 cm depth, respectively; and decreased by 4.39%, 1.01% and 2.59% in sandy loam soil at 10 cm depth, respectively. However, the Wsb caused by linear type (T1) was lower than that of others in loam soil, and there was no significant difference in sandy loam soil at 5 cm depth (Figure 5a).

Compared with linear type (T1), convex type (T2) and combination type (T4), the concave type (T3) tine furrow opener increased the Hr by 18.9%, 24.6% and 10.2% in loam soil at 10 cm depth; 17.8%, 20.2% and 7.3% in sandy loam soil at 10 cm depth; 41.9%, 49.8% and 17.5% in loam soil at 5 cm depth, respectively. However, the Hr caused by combination type (T4) was greater than that of others in sandy loam soil at 5 cm depth (Figure 5b).

Compared with the linear type (T1), convex type (T2) and combination type (T4), the Wst caused by concave type (T3) tine furrow opener decreased by 5.3%, 6.2% and 7.7% in loam soil at 10cm depth, respectively; decreased by 6.4%, 10.7% and 10.3% in sandy loam soil at 10 cm depth, respectively. A similar trend was observed in loam soil at the depth of 5 cm, concave type (T3) tine furrow opener decreased by 5.9%, 8.9% and 11.6%, respectively. There was no significant difference in sandy loam soil at 5 cm depth (Figure 5c).

Compared with the concave type (T3) tine furrow opener, the Wst caused by linear type (T1), convex type (T2) and combination type (T4) increased by 7.0%, 3.2% and 5.4% in loam soil at 10 cm depth, respectively; the Wst caused by linear type (T1), convex type (T2) and combination type (T4) increased by 7.1%, 3.5% and 5.3% in sandy loam soil at 10 cm depth, respectively. However, there was no significant difference at 5 cm depth (Figure 5d).

In addition, it was concluded that concave type cutting edge curve helped to reduce soil disturbance. Sánchez-Girón et al.[33] found that the shape of opener and it's rake angle affected the Af. The study confirmed that soil was influenced by the squeezing and cutting action of furrow opener's cutting edge and moved along the edge direction in the opening operation.

It had significantly greater soil disturbance at the depth of 10 cm than that at the depth of 5 cm, and there were significant differences among those openers with different rake angles (Figure 6). The Wsb increased first and then decreased with increasing rake angles. The lowest Wsb appeared with 45°and 60°rake angle at 10 cm and 5 cm depth, respectively (Figure 6a). The Hr and Wst increased with increasing rake angles. The Hr was larger by 7.4%-13.6% and 1.6%-6.6% in loam soil than that in sandy loam soil at the depth of 10 cm and 5 cm, respectively (Figure 6b). Tine furrow opener with 75° rake angle increased Wst by 8.3% and 15.4%, compared with 30° rake angle at the depth of 10 cm and 5 cm, respectively (Figure 6c). With the increase of rake angle, Af increased first and then decreased. The Af had the smallest value when the rake angle was 60°(Figure 6d). It was concluded that tine furrow opener with rake angle ranged from 45°to 60°created the lowest soil disturbance because soil was lifted up by furrow opener with smaller rake angle and pushed with larger rake angle.

3.3 Straw disturbance quantity

Appropriate amount of straw coverage could improve soil moisture content and promote crop growth[34]. However, excessive amount of straw coverage would increase soil temperature and delay the emergence time[35]. The straw disturbance quantities affected by tine furrow opener with different structural parameters (including cutting edge thickness and cutting edge curve) under different straw coverage rates were shown in Figure 7.

Straw disturbance quantity increased with increasing straw coverage rate. The straw disturbance quantity was 11.0%, 12.5% and 17.0% under the coverage rate of 43%, 68% and 93%, respectively. Under the same coverage rate, there were no significant differences (p<0.05) and no obvious variety regulation on straw disturbance quantity among 0-2 mm cutting edge thickness (Figure 7a). Meanwhile, research by Bobobee and Gebresenbet[36] on shear performance of cutting edge indicated that, the draft force and the anti-blocking capacity of furrow opener were improved with the decrease of cutting edge thickness, respectively. The straw disturbance quantity caused by cutting edge curve was 9.3%-13.8%, 11.6%-15.7% and 14.6%-20.7% under the coverage rate 43%, 68% and 93%, respectively. The concave type (T3) tine furrow opener created the highest straw disturbance quantity. Compared with concave type (T3), furrow opener with linear type (T1), convex type (T2) and combination type (T4) reduced the disturbance quantity by 25.9%, 32.2% and 11.2%, respectively, under the coverage rate of 43%; reduced by 21.5%, 25.9% and 14.0%, respectively, under the coverage rate of 68%; reduced by 16.3%, 29.3% and 10.6%, respectively, under the coverage rate of 93% (Figure 7b).

Yao[10] had the same results on straw disturbance quantity. There were significant differences among the four cutting edge curves under the same coverage rate because soil moved along the edge direction and affected the straw movement[37]. It was found that cutting edge had significant influence on the disturbance of the soil and surface straw, however, the abrasion should be considered in design.

The soil bulk density caused by different tine furrow openers in loam soil was larger than that in sandy loam soil (Figure 8).

Concave type (T3) furrow opener created the smaller soil bulk density than others. Compared with concave type (T3), linear type (T1), convex type (T2) and combination type (T4) furrow opener increased the soil bulk density by 3.5%, 0.9% and 0.9% in loam soil, and increased by 2.7%, 3.6% and 2.7% in sandy loam soil, respectively (Figure 8a). With the increasing rake angle, soil bulk density decreased first and then increased. With 60°rake angle, the furrow opener created the lowest soil bulk density of 1.082 g/cm3 in loam soil and 1.051 g/cm3 in sandy loam soil. The soil bulk density created by furrow opener with 60°rake angle was lower than that by 30°, 45°and 75°rake angles in loam and sandy loam soil, respectively (Figure 8b). With the increase of penetration clearance angle, soil bulk density decreased first and then increased. Compared with 0°, 4°and 12° penetration clearance angle, furrow opener with 8°penetration clearance angle, which produced the lowest soil bulk density (1.14 g/cm3) in loam soil, and decreased soil bulk density by 4.4%, 0.9% and 2.6%, respectively. However, furrow opener with penetration clearance angle ranged from 4°to 8°, which created the lowest soil bulk density (1.07 g/cm3), decreased soil bulk density by 2.0% and 2.8% compared with 0° and 12° penetration clearance angle in sandy loam soil, respectively (Figure 8c).

During the opening process, furrow openers with larger penetration clearance angle made soil fall back into the furrow early and broke up soil. And the soil on the sides and bottom of seed furrow was compacted by furrow openers with smaller penetration clearance angle[38]. Chaudhuri[21] found that the operating depth of furrow opener had influences on the width of seedbed and backfilling soil and thus affected the soil bulk density.

3.5 Soil water-stable aggregates

Soil water stable-aggregate (WSA) reflected the surface area and porosity of soil in field. The WSA (1-10 mm) had good soil porosity which was beneficial to air permeability, water holding capacity of soil and crop growth[39]. At the soil depth of 10 cm, different structures of tine furrow opener affected the percentage of WSA with different particle sizes (Table 6). With increasing particle sizes, the content of WSA decreased first and then increased in the seed furrow. The content of WSA (>0.25-0.5 mm) was higher than others, and the content of WSA (>1.0 mm) was the lowest. That was consistent with the original soil of the operational area. Under the same treatment, the percentage of each particle size of WSA in loam soil was larger than that in sandy loam soil, especially the WSA (>0.25-1.0 mm).

The concave type (T3) tine furrow opener produced the larger content of WSA (>0.5 mm) and the lower content of WSA (≤0.5 mm) than other types. There were significant differences on WSA (>0.25-0.5 mm), while the differences were in significant on other particle sizes among cutting edge curves (p<0.05).

There were no significant differences on each particle size of WSA with various rake angles (p<0.05). The content of WSA (<2 mm) increased with increasing rake angles, but it was not significant. The content of WSA (<2 mm) caused by 75°rake angle was 0.1%-3.2% larger than 30°rake angle, because the tine furrow opener with a larger rake angle pushed soil and damaged the WSA. During the process of soil cutting, the tine furrow opener with smaller rake angle caused less damage to WSA.

As penetration clearance angle increased, the content of WSA (>0.5 mm) decreased. There were no significant differences on WSA with various penetration clearance angles (p<0.05).

In conclusion, soil disturbance had larger influence on WSA (>0.5 mm). Less soil disturbance reduced the damage of WSA which was related to the research conducted by Du et al.[40]. Meanwhile, Arvidsson et al.[41] found that different geometric structures of opener and soil conditions had different soil fragmentation.

4 Conclusions

In this study, different key structural parameters of tine furrow openers were designed to analyze the effects of soil bulk density, WSA, soil disturbance on soil properties and surface straw disturbance of seedbed. The rake angle had significant effect on cross-sectional area of furrow (Af), soil bulk density and surface straw disturbance. The cutting edge thickness and cutting edge curve had significant effects on Af and surface straw disturbance respectively. The cutting edge was the key structural parameter affecting soil and surface straw disturbance. The concave type furrow opener produced the furrow with the lowest width of seedbed (Wsb), width of soil throw (Wst), and Af in no-till planting. It also had the highest surface straw disturbance and the Hr. The tine furrow opener with rake angle between 45°and 60° produced the lowest Wsb and Af. The Hr and Wst increased with the increasing rake angles. The cutting edge thickness (≤2.0 mm) had no significant effects on disturbance of surface straw. Concave type furrow opener produced the lower soil bulk density and greater content of WSA (>0.5 mm) than others. When the penetration clearance angle ranged from 42to 82, the tine furrow opener created the lowest soil bulk density. As the penetration clearance angle increased, the content of WSA (>0.5 mm) decreased, and there were no significant differences on WSA (≤0.5 mm). This study can provide supports for the design of tine furrow opener and promote the application of the light no-till planters.

Acknowledgments

We acknowledge that this work was supported by the Program for Innovative Research Team in Ministry of Education of China (Grant No. IRT13039) and the National Natural Science Foundation of China (Grants No. 51175499). We thank all the graduate students working at the Conservation Tillage Research Center, Ministry of Agriculture, for proving their inputs to this work.

Sidebar

Citation: Zhang X C, Li H W, Du R C, Ma S C, He J, Wang Q J, et al. Effects of key design parameters of tine furrow opener on soil seedbed properties. Int J Agric & Biol Eng, 2016; 9(3): 67-80.

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