Optimisation Of The Tillage Tool Design For Wheat Rotary Strip-till Planter

The extension of conservative agriculture and sustainable farming system in the South China rice-wheat rotation is increasingly demanding for no-till seeding technologies for post-paddy seeding of wheat.As the cropping rotation in the South China has marked difference from the North farming systems,e.g.small plot size,irregular and scattered fields,high soil water content and compacted root zone soil,no-till seeding machineries adaptable in the North China farming land do not function well in the South China.Present researches are mainly concerned with system optimization on the no-till seeding machine,paying more attention to its integrity and the design of anti-clogging mechanisms.Few researchers have dealt with the interactive mechanisms between the rotary tiller tools and the soil,neither the optimized design of the rotary tiller tools.Due to the importance of tillage quality to seed germination and crop growth,optimized design of the rotary tiller tools for strip-till seeding in the rice-wheat farming system is critically important for the improvement of system performance and seeding quality.Performance of a rotary strip-till planter is inherently related to the tillage quality,which is governed by the tillage tool type,rotational speed and soil properties.Interactive mechanisms between soil engaging tool and the soil are difficult to be interpreted.Therefore,EDEM simulation was applied for an in-depth investigation on the inter-relationship between the tool and the soil.The simulated result was further evaluated in the field tillage test,from which a number of key elements affecting tillage performance were identified.With both simulated and experimentally acquired results in hands,we were able to propose an optimized design of a rotary tiller tool for wheat rotary strip-till planter.Related works are:A thorough investigation on the tillage performance of typical tillage tools were made,based on both simulation and field testing.Results showed that,in rotary tilling process,three soil-engaging stages were identifiable,i.e.the soil-cutting stage in which the tillage tool cut into the soil,the soil moving stage,in which the cut soil moved with the tillage tool,and the soil throwing stage,in which the soil was thrown backword and detached from the tool.Rotary speed was found a major influencing factor for soil fragmentation.Increased rotary speed led to improved soil fragmentation and energy consumption.No significant difference was identified for soil fragmentation and energy consumption when different tillage tool types were used.Soil throwing performance of a tillage tool is a key factor affecting tillage back-fill.An enhanced soil throwing performance was conducted by the IT225 blade.A large amount of soil was thrown outside the tillage.In both 380 and 510 r/min,IT225 was found to provide the least amount of tillage back-fill.The soil-throwing performance of the straight blade was insignificant and the tillage back-fill was the highest.Soil aggregates produced by the staright blade was the largest,thus the back-filled soil state was not suitable for seeding operation.Soil failure pattern was a key factor affecting the shape uniformity of the seedbed.IT225 induced a cutting action,which soil failure pattern was resulted from a cutting effect.,leading to an uniform tillage shape regardless the rotary speed.The chisel-type blade engaged the soil and up-lifted the soil,inducing a tensile failure pattern.The seedbed walls were resulted from soil tensile cracks.As uncontrollable cracks on the soil fragmentation process,the chisel-type blade produced an irregular seedbed shape with a poor confinement of the soil disturbance.Depending on the simulated and field-tested results,a new type rotary tiller tool for the wheat rotary strip-till planter was designed,termed as MB blade.The MB blade was constructed with two staright blades and two chisel-type blades.The 2 staright blades cut the soil ahead of the chisel-type blades,producing a uniform shape of seedbed walls while an irregular seedbed shape could be achieved.The chisel-type blades provided good soil fragmentation,which is a complement to the ineffective soil pulverization performance by the staright blades.This combination of the staright blades and the chisel-type blades can achieve satisfactory soil fragmentation and fine seedbed shape.Both simulation and field test showed that the MB blade provided the more uniform seedbed shape as compared with chisel-type blade,regardless rotary speed.Application of the staright blades significantly improved the soil back-fill.Even in rotary speed of 510 r/min,the MB blade could still achieve 40%soil back-fill in the seedbed.The seedbed sidewalls pressing and smearing effects were large with MB blade,due mainly to the contact of the staright blades with seedbed sidewalls.This not only increased the risk of damaging the soil structure of the seedbed sidewalls,but also impeded crop root elongation.With this consideration,a modified roaty tillage tool named as GMB blade was designed on the basis of the MB blade.Both field test and simulation analysis with 3D reconstruction showed that the GMB blade provided a laminated seedbed sidewall,with the bottom 3-6 cm layer soil structure on seedbed sidewall well protected.Compared with MB blade,the GMB blade significantly reduced seedbed sidewall smearing.This "controlled radius design" for the GMB blade provided the maximum protection on the soil structure for wheat growth,while the soil backfill was guarranteed by the retaining effect of the staright blades.In the rotary speed higher than 280 r/min,GMB blade provided comparable soil fragmentation,soil back-fill and soil disturbance with the MB blade.Root system architecture digitizer and Pro-E assisted modeling technique was applied to quantify and visualize wheat root development in different stages under different treatments.MB and GMB blade were compared with the 3D topology and wheat root coverage rate,topological tendency of wheat root angle and root elongation.Results showed that reduced soil structure damage by the GMB blade induced the minimum restriction on root elongation by the tillage.In 30 days after seedling stage,when the soil structure rehabilitated and improved effect of inter-crop competition,no restriction on wheat growth remained for the GMB-treated tillage.Considering the uniformity of the seedbed sidewall,improved soil fragmentation and soil back-fill,and the well-protected soil structure by the GMB blade,the GMB blade was recommended as an rotary tillage tool of wheat rotary strip tillage planter.The GMB blade was a combination with commercially available blades,without significant changes of blade geometry.This is also beneficial for reduced cost without improved technique for mass production.As for cases of small-holder farming systems,it is easy to change the traditional no-till seeder into strip-tillage with a replacement of GMB blades.