Effect of Moldboard types, Two depths of Tillage and Two speeds of Tractor in some Physical Properties and Pulverization of Soil

A factorial experiment under randomized complete block design with three replication was conducted in the field in a collage of the Agricultural Engineering Science/ University of Baghdad in March 2022, to study the effect of two types of moldboard slatted and general purpose in some physical properties, pulverization of soil, the volume of disturbed soil and number of clods > 10 cm under two depths of tillage 15 and 25 cm and two speeds of tractor 4.146 and 7.224 km. h -1 . Slatted moldboard recorded a least (best) number of clods > 10 cm 4.58 clod. m -2 , soil bulk density 1.259 g.cm -3 , higher porosity 52.48 % and higher volume of disturbed soil 804.14 m 3 . h -1 . Depth of tillage 25 cm a got higher volume of disturbed soil 967.21 m 3 . h -1 . Depth 15 cm got lower number of clods > 10 cm 4.91 clod. M -2 , 1.209 g.cm -3 and higher porosity 54.35 %. Speed of the tractor 7.224 km. h -1 got higher volume of disturbed soil 983.79 m 3 / h and least number of clods > 10 cm 7.50 clod/m 2 . Speed of tractor is 4.146 km. h -1 got least bulk density 1.259 g.cm -3 and best porosity 52.48 %.


Introduction
In the Iraqi fields, the moldboard plow is the most implement common and widely used in primary tillage. The main purpose of the all kinds of moldboard plows for cut, lifting, inverting and pulverizing the furrow slice, therefore the moldboard plow achieve most of the aims of primary tillage. The bulk density is one of the physical properties of the soil that is affected by the movement of tractors and agricultural machinery over soil surface, which leads to compaction of the soil and increase soil density, while tillage operations leads to fragmentation, increasing soil size and decreasing soil density and increasing soil porosity (17). Choosing the tractor speed appropriate to the plowing depth, full tank tractor and operator skill increases the efficiency of the tillage process (1 and 15). Soil porosity is pore spaces facilitate the availability and movement of air or water within the soil environment, soil porosity determines how well liquids, gases, and heat can be stored and transmitted within the soil matrix, A greater porosity often indicates greater storage and transmission ability (25). Plowing agricultural fields improving the soil physical properties and prepared a suitable seedbed for germination and root growth (20). Muhsen (22) found in the silt loam soil decreased bulk density 7.09 and 3.03 % when increase speed of tractor from 2.54 to 5.77 km. h -1 , and soil porosity increased 6.57 and 3.44%. Volume of disturbed soil affected by the depth of tillage and the speed of tractor and increases with their increase. Alrweshdy et.al (8) fund the higher speed of tractor got the highest volume of disturbed soil. Alseah (9) fund increasing speed of tractor from 1.5 to 2.53 km.h -1 increase the volume of disturbed soil from 441.4 to 813.5 m 3 . h -1 . The pulverization index is a criterion for the ability of the plow to break up and moldering the soil, it is affected by the type of plow, depth of tillage, speed of tractor (plowing), texture of the soil and moisture of the soil (7 and 11). AL-Hashimy (6) mention that the appearance of tillage is one of the most important indicators of tillage efficiency. The aim of the study is to know and compare the performance of two types of moldboards, general purpose and slatted moldboard, which is designed and manufactured by the researchers, in volume distributed, number of clods > 10 cm, some physical properties of the soil (bulk density and soil porosity) and Pulverization index.

Performance Parameters
Volume of disturbed soil The amount of soil raised by the plow during the plowing process for a known time and depends on the depth of plowing and the practical productivity, its unit is cubic meters per hour, and calculated by followed the equation ( 13 and 18): Where SVD is soil volume disturbed in m 3 .h -1 , EFC is Effective Field Capacity in (ha/h), dt was depth of tillage (m), Va was actual speed tractor in km/h, Wp was working actual width plow in m, ft coefficient estimate time for primary (0.75 -0.85), and used 0.80 in these experiments (19) and 0.1 and 10000 was factor conversion.

Number of clods > 10 cm
Represents the appearance of tillage, the number of clods that appear after plowing the soil whose size is greater than 10 cm per square meter of the plowed soil. It calculated by calculating the number of clods with a size of more than 10 cm remaining above a half-square meter sieve (0.5 m × 0.5 m), the distance between one wire sieve and another 10 cm, then multiply the number of clods by four, so that its expression becomes the number of clods per square meter ( 18 and 8 ).

Bulk density
Bulk density of soil is usually determined from a core sample (cylindrical section) which is taken by driving a metal corer in to the soil at the desired depth and horizon.
Bulk density was measure before and after soil tillage by used core sample 5×5 cm. Three replication (samples) for each treatment we dried in oven at 105 C for 24 hours and weighed, then calculated from equation (12): Where bd is the dry bulk density (g.cm -3 ), ms is weight of the dried soil sample (g), and vt is total volume of the soil sample (cm 3 ).

Soil Porosity
Soil porosity refers to the fraction of the total soil volume that is taken up by the pore space (21). Porosity was measure by equation 3 according to (12), an assumed Practical density was 2.65 g. cm -3 .
Where P is porosity %, td is practical density (g. cm -3 ) and bd is Practical density 2.65 g.cm -3 .

Pulverization Index
After conducting the tillage operation according to the experimental design, the field was left to dry for a week, then three random samples were taken from each treatment according to depths of tillage 15 and 25 cm and weighed, then sieved manually using six different diameters sieves 100, 50, 30, 12, 5 and 2 mm, weigh the remaining soil above each sieve according to the total weight of the sample by collecting soil accumulated weights on each sieve and then calculated the percentage of each weight on each weight on each sieve, according to the method mentioned in (7, 10, 16 and 21 ) Where PI is Pulverization Index (mm), ∑Wi is weight of soil collected on each sieve (kg), Xi is average diameter of the sieve used before and the sieve used after (mm), W is sample total weight (kg).

Results and Discussion
Volume of disturbed soil Result showed the depth of tillage was significant effect on volume of disturbed Slatted moldboard recorded least value 4.5 clods.m -2 , while general purpose moldboard got 12.5 clods. m -2 , because the soil slice slip and collides with the slats in slatted moldboard, which is exposed to dismantling and broken, while in general purpose the soil    -3 , and that because of increase fragmentation soil factor when increase speed of tractor, that result agree with (5). Moldboard was significant effects on bulk density, slatted moldboard recorded 1.259 g. cm -3 , while general purpose moldboard was 1.280 g. cm -3 , and that because of increased fragmentation and volume of soil occupied by the plowed in slatted moldboard more than general purpose moldboard. Interaction depths of tillage and speeds of tractor were significant effects on bulk density, depth 15 cm and speed of tractor 4.146 km. h -1 recorded least value 1.204 g. cm -3 , while depth 25 cm and speed 7.224 km.h -1 recorded higher value 1.345 g.cm -3 . Interaction depth of tillage and moldboards types were significant effects on bulk density, depth15 cm and slatted moldboard recorded least value 1.201 g. cm -3 , while depth 25 cm and general purpose moldboard got higher value 1.342 g. cm -3 . Interaction speeds of tractor and moldboards types were No significant. Interaction among depth of tillage, speed of tractor and moldboards were significant effects on bulk density, depth 15 cm, speed of tractor 4.146 km.h -1 and slatted moldboard recorded best value 1.194 g. cm -3 , while interaction depth 25 cm and speed 7.224 km/h and general purpose moldboard was 1.359 g. cm -3 ( fig.5).

Porosity
Result showed the depths of tillage was significant effects on the porosity, increase depth of tillage result decreasing porosity, depth 15 cm recorded higher porosity 54.351 %, while 25 cm was 49.820 %, and that because of increase the bulk density which lead to decrease the porosity, that result agree with (5). Speed of tractor was significant effects on the porosity, increasing speed of tractor result to decrease the porosity, speed 4.146 km. h -1 was recorded higher value 52.480 %, while speed 7.224 km. h -1 recorded 51.691 %, and that because of increase the speed of

Interaction depth of tillage, speed and moldboard types
tractor lead to increase press the soil and increase the bulk density which lead to decrease the porosity, that result agree with (5). Moldboard was significant effects on the porosity, slatted moldboard recorded higher porosity 52.483 %, while general purpose moldboard was 51.688 %, and that result affected by bulk density. Interaction depths of tillage and speed of tractor were significant effects on porosity, depth of tillage 15

Pulverization Index
Result showed the depths of tillage was significant effects on pulverization index, depth of tillage 15 cm recorded best (least) pulverization index value 34.08 mm, while 25 cm got 51.32 mm, because of increase depth of tillage leads to increase the volume of distributed soil, which contain large diameters of clods, so the pulverization index increasing, that result agree with (7, 10, 23 and 24 .7).

Conclusion
Finally, in light of these findings, it can be concluded slatted moldboard were achieved best results, volume of disturbed soil, minimum number of clods > 10 cm, bulk density, porosity and better pulverization index. Depth of tillage 15 cm got least number of clods > 10 cm, bulk density, high (best) porosity and best pulverization index. High speed of tractor 7.224 km. h -1 achieved higher volume of disturbed soil, least number of clods> 10 cm and least pulverization index.