Effects Of Water And Fertilizer Coupling On Growth And Physiology Of Several Herbaceous Plants In Coal Mining Sites In Desert Area

The northwest arid desert region has arid climate,little precipitation,barren soil and extremely bad environment.The discharge of coal gangue is huge,which occupies a lot of land and causes a variety of pollution to the surrounding soil,atmosphere and water environment.In order to avoid the impact of coal gangue accumulation on the surrounding environment,reclamation and vegetation restoration are the first choice.However,vegetation restoration is faced with difficulties such as soil water shortage,strong evaporation and poor nutrients.It has become an important obstacle restricting the vegetation restoration and conservation of coal mining areas in the arid desert area in the northwest.In order to ensure that several typical herbaceous plants can survive and grow normally in the coal mining area in the arid desert area in the northwest,it is clear that the optimal water and fertilizer application plan is the core problem urgently to be solved in the vegetation conservation of the coal mining area in the desert area.Soil moisture is the main factor that determines the survival of plants,and soil fertility is the key factor affecting whether plants grow well or not.In this study,Melilotus suaveolens Ledeb,Astragalus adsurgens Pall,Agropyron mongolicum Keng and Althaea rosea(Linn.)Cavan.were used as the research objects.Pot experiments and field experiments were conducted to study the effects of water-fertilizer coupling on the growth and physiological characteristics of several herbaceous plants under different soil types and geographical environment,and the comprehensive effects of water-fertilizer coupling of several herbaceous plants were comprehensively analyzed by Analytic hierarchy process(AHP).The optimal water and fertilizer schemes of several herbaceous plants under two soil types were obtained by combining model optimization with plant leaf nutrient diagnosis.It provides an important theoretical basis and practical guidance for the vegetation tending of coal mining traces in the arid desert area of Northwest China.The main conclusions include:(1)The effects of water-fertilizer coupling on the biomass,net photosynthetic rate and water use efficiency of several herbaceous plants under different soil types and geographical environment were studied.It was found that the variation range of water use efficiency of Melilotus suaveolens Ledeb was 0.88?5.35?mol/mmol;Astragalus adsurgens Pall was 0.93?5.40?mol/mmol;Agropyron mongolicum Keng was 0.44?3.41?mol/mmol;and Althaea rosea(Linn.)Cavan.was 0.52?3.63?mol/mmol.Therefore,in the northwest arid desert area coal mining site for vegetation restoration,according to the water use efficiency from high to low,the selected herbs are in order from Astragalus adsurgens Pall,Melilotus suaveolens Ledeb,Althaea rosea(Linn.)Cavan.and Agropyron mongolicum Keng.Soil moisture was the most sensitive to the biomass,photosynthesis and water use efficiency of several herbaceous plants.Phosphate fertilizer(110.96?113.13 kg/hm~2)contributed more to the growth of legume forage than nitrogen fertilizer(81.97?82.09 kg/hm~2),and nitrogen fertilizer(110.09?143.74 kg/hm~2)contributed more to the growth of gramineous forages and miscellaneous grass than phosphate fertilizer(80.54?100.00 kg/hm~2).(2)The effects of water and fertilizer coupling on the growth and physiological characteristics of several herbaceous plants under different soil types were obviously different.Among them,the increase of plant height,leaf or root morphology,biomass,net photosynthetic rate,transpiration rate and other indicators of four herb plants under aeolian sandy soil conditions were higher than that of gray desert soil.This is mixed with aeolian sand by surface sand and parent material,has a strong ability to store water and preserve soil moisture,and the contents of organic matter and available nutrients are higher than those of gray desert soil.However,the leaf water use efficiency of several herbaceous plants in gray desert soil(0.66?2.98?mol/mmol)was significantly higher than that in aeolian sandy soil(0.44?1.80?mol/mmol).This may be due to the fact that the increase of net photosynthetic rate of several herbaceous plants under gray desert soil(38.59?87.89%)was much higher than that of eolian sandy soil(41.20?56.83%).The increase of transpiration rate of several herbaceous plants under gray desert soil(1.82?31.26%)was much less than that of eolian sandy soil(21.00?38.47%).(3)The coupling of water and fertilizer can promote the growth and physiological characteristics of several herbaceous plants in different geographical environments.The increase in plant height,single leaf area,biomass,photosynthesis and water use efficiency of legume forages by water and fertilizer coupling in Lingwu gangue field was significantly higher than those in Wuhai gangue field.Adding phosphate fertilizer(160 kg/hm~2)could significantly improve legume biomass and water use efficiency.When gramineae forage and miscellaneous grasses grow well in Lingwu gangue field,the nitrogen requirement(160 kg/hm~2)is greater than the phosphorus requirement(70 kg/hm~2).However,their survival rate and seedling retention rate in Wuhai gangue yard are very low,which is relatively low in fertility with gray desert soil.Wuhai gangue yard is wide and flat,with many slopes and large slopes.Irrigation can easily cause soil erosion related.(4)By comprehensively analyzing the effects of water-fertilizer coupling on the growth and physiology of several herbaceous plants under different soil types and geographical environment,and combining the comprehensive analysis of water-fertilizer coupling effect with plant leaf nutrient diagnosis,the optimal water and fertilizer scheme for vegetation reconstruction and conservation of coal mining traces in northwest arid desert area was obtained.Among them,leguminous forage grass had a relative water content of 55.00?59.43%(irrigation volume of 900?950 m~3/hm~2),application of urea is 81.97?82.09 kg/hm~2,and application of superphosphate is110.96?113.13 kg/hm~2.Gramineae forage grass had had a relative water content of40.14?59.41%(irrigation volume of 720?950 m~3/hm~2),application of urea 110.09?120.00 kg/hm~2,and application of superphosphate 80.54?100.00 kg/hm~2.Miscellaneous grasses had a relative water content of 55.00?58.02%(irrigation volume of 900?940 m~3/hm~2),application of urea 120.00?143.74 kg/hm~2,and application of superphosphate 90.12?100.00 kg/hm~2.