| Salinization affects growth and development of plants, which is the main environmental factors limiting agricultural production. All over the world, one in five of all irrigated farming suffer the negative impact of the salinization of soil. Jingyuan County, Baiyin City, Gansu Province, along the Yellow River Irrigation Region, is located in the upstream of the Yellow River,which is an important irrigated agriculture region. Due to the soil types, irrigation pattern, terrain,climate and other reasons, many wetlands and farmlands near the river suffered salinization in the region. The experiment studied the Zizania latifolia plantation age, different planting density and degrees of salinization wetlands and field conditions of drying, to investigate the improvement effects of Zizania latifolia on salinization wetlands and the influence of salinization wetlands on Zizania latifolia growth and yield. We aimed to provide data reference and theoretical basis for planting Zizania latifolia in the northwestern region and improving the salt-affected artificial wetlands. The main results were as followed:1. With the increasing years of planting Zizania latifolia, salt ions contents in soil of the salt-affected artificial wetlands were significantly decreased, which is most evident in surface soil,amomg the above salt ions, the decrease of Na+ and Cl- content is most obvious. The contents of Na+, Cl- and salt ions in 0 to 10 cm soil layer of planting Zizania latifolia 1 year decreased by69.43%, 78.45% and 69.43% respectively, conntents of planting Zizania latifolia 3 years decreased by 77.77%, 87.22% and 77.77% respectively, conntents of planting Zizania latifolia 5years decreased by 96.89%, 98.69% and 96.89% respectively. So extending the years of planting Zizania latifolia appropriately can reduce the salt contents in the soil of salt-affected wetlands effectively.2. Salt-affected artificial wetlands decreased obviously and reduce the plant height, leaf area index(LAI), the number of tillers, the number of effective tillers, the shoot and root biomass,single shoot longitudinal diameter of Zizania latifolia in whole growth stages.With severe salinization, the effects on the growth of Zizania latifolia is most significant(p < 0.05), impacts of mild salinization wetlands on Zizania latifolia is not obvious. Salinization degree of wetlands impacts the growth and yield of Zizania latifolia is characterized by: severe> moderate > mild.3. As the wetland salinization degree aggravating, all kinds of salt ion content in Zizania latifolia increased significantly(p < 0.05), the stems scontain the highest contents of K+ and Cl-,Mg2+ content in the leaf and Na+ content in crust are highest, the highest Ca2+ contents were in roots. Absorption of salt ions mainly accumulated in shoots. Under severe, moderate, mild and no salinization, absorption of Ca2+ in shoots of Zizania latifolia were 33.48kg/hm2, 31.98kg/hm2,27.27kg/hm2 and 28.47kg/hm2; absorption of K+ in shoots were 277.44kg/hm2, 282.52kg/hm2,305.10kg/hm2 and 268.91kg/hm2; absorption of Mg2+ in shoots were 23.16kg/hm2, 19.73kg/hm2,14.87kg/hm2 and 12.31kg/hm2; absorption of Na+ in shoots were 104.12kg/hm2, 65.87kg/hm2,50.57kg/hm2 and 11.93kg/hm2; absorption of Cl- in shoots were 54.66kg/hm2, 52.67kg/hm2,26.11kg/hm2 and 12.89kg/hm2; absorption of salt ions in shoots were 492.86kg/hm2,452.76kg/hm2, 423.93kg/hm2 and 334.50kg/hm2. Removeing the shoots of Zizania latifolia from wetlands can ameliorate the salt-affected wetlands.4. Mg2+, Na+ and Cl- in wetlands were removed mainly by the approximate leaching to below 60 cm soil layer, the decrease of Ca2+ were removed mainly by Zizania latifolia shoots.Under conditions of mild salinization, almost no Ca2+ leaching below 60 cm soil layer; K+ were required by Zizania latifolia for normal growth and development, and Zizania latifolia will absorb K+ to accumulate them in shoots.5. Dense planting can significantly improve leaf area index(LAI), naked stem biomass of Zizania latifolia at the tillering stage, pregnant period and mature period. Sparse planting can significantly increase Zizania latifolia weight and the shoot biomass(dry weight) per hectare.Dense planting can reduce salt ion content in the wetland soil better, and the raesons were: dense planting increased the root in the soil, thus increasing the soil porosity and hydraulic conductivity,promoting the salt leaching down in the water.6. Drying field can significantly improve production indicators of Zizania latifolia, not drying field can better reduce the salt ion contents in the soil of wetlands, mainly because during the drying field, there was no surface water, and soil field capacity is lower than not drying field conditions, thus make salt with the water movement upward ground, or make the salt retented in the soil profile. |
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