Root Responses To Heterogeneous Nutrient Distribution And Soil Mechanical Impedance And Management Strategy

Plants require a root system that delivers adequate water and nutrients for shoot growth, and to anchor them in the soil. The optimum distribution of root length depends mainly on the distribution of water and nutrients in the soil and the soil physical properties. These factors can directly influence root growth, distribution and function, and then have effect on plant growth and its production (yield). Based on this, the related studies were conducted on two parts of work:reviewed and case study. Firstly, the novel thinking of our work simplify the interaction of root-soil interface, and then further understand the mechanisms of root and soil interaction through the way of explore the time-space relationship within root-soil water-soil impedance. Secondly, we used soil-filled rhizotrons to simulate the nutrient distributed situation to determine the effects of horizontal stratification of nutrient-rich zones within different layers of the soil profile in water-limited environments on root growth and crop yield; we used sand cultural system to test the effect of impedance to root growth on root (root angle) and shoot architecture of wheat; we introduced plant growth promoting rhizobacteria (PGPR) to explore the mechanism of the growth promotion effect of localized nutrient supply on maize growth. These studies will help researchers and breeders to better understand the interaction between plant and soil, thus, will play an important role in future crop production and food security. Key points of the results and progress were summarised as follows:1. Root elongated in structured soil and its effect on root growth and function. There are lots of works on the maximum explore the root plasticity to improve nutrient efficiency. In this part of research, we specific focus on the issue of how the roots response to the properties of soil per sue (soil water content, soil mechanical impedance, soil pore and the heterogeneous of structured soil). We try to simplify the interaction of root-soil interface, and then further understand the mechanisms of root and soil interaction through the way of explore the time-space relationship within root-soil water-soil impedance.2. Heterogeneous nutrient distribution can modify root growth and water uptake. Nutrient enrichment of the surface layer was the most effective at promoting deep roots, higher water uptake and yield under water-limited conditions. Following terminal drought at the end of the experiment (Days60to65), deeper roots (below1m) were most abundant in the rhizotrons which only had a surface (0-40cm) layer of nutrientrich soil. Uniform nutrient placement resulted in the fewest deep roots (0-80cm). Uniformly rich in nutrients were the least effective in water uptake from depth,80mm water use compared with nutrient enrichment of the surface layer150mm.3. The severity of leaf stunting due to root impedance is related to the Rht allele. Impeded roots had a smaller angular spread, the angular spread of roots decreased from55°to43°from the vertical, but the genotypic effects were weak. Root impedance reduced leaf elongation and the number of tillers. Leaf area and total root length provided a common relationship across all genotype x treatment combinations. Leaf stunting in Cadenza was more severe. 4. Decreased root ethylene production following V. paradoxus5C2inoculation could account for further increased in maize root growth under localized nutrient distributed. When plants were grown under localised nutrient supply, rhizobacterial inoculation further enhanced shoot biomass by12%and root length density by50%. Localised nutrient supply stimulated ethylene production from roots by54%compared to the broadcast treatment, but rhizobacterial inoculation prevented this increase in root ethylene evolution, the ethylene release content was decrerased56%.