Study On Fragmentation Properties Of Paddy Soil And Wheat Seedling Response

Paddy soil in South China is highly cohesive, easily condensable and hard to be managed. Thus there is a need to investigate proper soil tillage methods for improved system output from rice-wheat rotations. Both laboratory and field experiments were conducted to systematically assess paddy soil fragmentation mechanics and to quantify post-tillage soil structures. Two tillage treatments, i.e. no-till and rotary till, were made to compare the influence of tillage methods on soil structures and the effects on wheat stem, leaves and yield. By quantifying tillage effects on soil fragmentation and the influence of soil fragmentation on wheat performance, the objective of this research was to investigate the optimum tillage system for the rice-wheat rotation and to evaluate the influence of soil fragmentation on wheat performance.Fragmentation characteristics of yellow brown soil and paddy soil were investigated with laboratory testing. Results found that non-standard Proctor compaction was an effective method to provide an enlarged set of controlled physical states for soil mechanical study. The acquired soil mechanical properties were more stable, and thus were more helpful for soil fragmentation test. Soil fragment fractal dimension and specific soil fragmentation energy were two indices suitable for soil structure quantification. Under same compacting works, same soil volumes and soil moisture contents, yellow brown soil was more easily compacted and condensed than paddy soil.Both post-paddy soil and post-wheat soil were rotary tilled and the torque of rotary shaft was measured. The torque of the rotary shaft and the resultant soil fragmentation were evaluated for different working conditions achieved by regulated forwarding speed, rotary speed of the rotor and the arrangements of knife installation. Results shown that soil surface relief and machine stability were two main factors significantly influencing machine performance. Cross arranged rotary knives resulted into well leveled tillage pan, but the torque was the highest.Continued field experiment during the last 3 years illustrated rotary torque dynamics for different working conditions. Results shown that soil fragment fractal dimension and mean diameter were 2 suitable indices for the quantification of paddy soil fragmentation. Mean diameter of soil fragments was not precise enough to quantify soil fragment size distributions. When soil moisture is below the plastic limit, soil fragmentation fractal dimension is decreasing logarithmically with increased water content. Fractal dimension is more precise in illustrating soil fragmentations and also increased with the enhanced energy input.Multi-dimensional data of wheat stem and leaves was collected from scanning and digital image processing. This technique can be used to identify wheat growing dynamics in a refined temporal and scale manner. A low cost but more practical system thus integrated with hardware and software was suitable for high-throughput phenotype analyzing. Post-paddy wheat was very much dynamical in its seedling stage. Stem and leaf indices in each stage differed dramatically in each period and each year, indicating the high dynamics of the environmental factors that influenced wheat growing.Indices of wheat performance related to different tillage treatments were compared. A higher yield was attainable when the soil was under the best fragmentation state, which requires a proper torque, energy consumption and soil fragmentation. Above this, enough wheat seedling stand was a prerequisite for the high yield. Despite the proper management of soil structure with tillage, the weather influence on wheat seedling and yield was another factor need consideration.