| Saline alkali soil in Hetao Irrigation District of Inner Mongolia accounts for 68.65%of the total cultivated land area.The problem of salinization of farmland is prominent,which severely limits the agricultural economy and sustainable development.Sunflower cultivation is the main method in the area,and single cultivation for many years has led to various diseases and insect pests in farmland.In addition,years of shallow tillage and plowing have resulted in thickening of the bottom layer of the soil plough and shallowing of the plough layer,seriously affecting the growth of crop roots in the soil space,thus reducing crop yield.In order to solve the above problems,this study takes saline alkali tolerant sorghum as the experimental material,studies the effects of two tillage methods on saline alkali soil properties,and the effects of different fertilization rates on sorghum growth indicators,and explores the appropriate fertilization rates for crops under the condition of smash ridging,to provide theoretical research for vigorously promoting the smash ridging.The main conclusions are as follows:(1)Smash ridging can break the bottom layer of soil plough,significantly reduce the bulk density of soil at a depth of 20-40 cm,increase soil porosity and improve soil water holding capacity.In particular,it has a significant impact on the soil layer at a depth of 20-30 cm,and the soil bulk density is reduced by 0.23 g/cm3.(2)The content of water-stable aggregates in the soil of smash ridging and conventional cultivation is mainly 0.5-1 mm and 0.25-0.5 mm.The total content of>0.25 mm diameter water stable aggregates in the different soil layers is higher than that of conventional cultivation.In mature period,the total amount of soil water stable aggregates in 0-20 cm and 20-40 cm depth under smash ridging increased by 36.80%and 19.30%respectively compared with conventional cultivation.This shows that the smash ridging can increase the content of soil water-stable aggregates and is conducive to the formation of soil water-stable aggregates with larger particle size.(3)Smash ridging provides favorable conditions for the survival of microorganisms in deep soil.The number of bacteria,fungi and actinomycetes colonies and their total colonies in smash ridging soil are generally higher than that in conventional cultivation in each growth period,and the increase rate of bacteria,fungi and actinomycetes colonies in 20-40 cm depth of smash ridging is generally higher than that in 0-20 cm depth.At jointing stage,the total number of soil microbial colonies in 0-20 cm and 20-40 cm depth of smash ridging increased by 25.13%and 41.42%respectively compared with conventional cultivation.(4)Smash ridging promotes leaching of saline alkali ions in soil by spring sinks,reduces salt and pH in surface soil,and provides good conditions for seed germination,thus improving seed germination rate.Smash ridging and application of base fertilizer can increase the seedling emergence rate of sorghum,and smash ridging has a more significant increase in the seedling emergence rate of sorghum.(5)Smash ridging has a promoting effect on the growth of sorghum root length density,surface area density,root volume and dry weight,especially on sorghum root length.(6)The agronomic efficiency of nitrogen fertilizer under the condition of smash ridging firstly increases and then decreases with the increase of fertilization amount.When the fertilization amount of potassium chloride-diammonium-urea under the condition of smash ridging is 120-180-300 kg/hm2,the fertilizer is saved by 20%compared with the conventional cultivation,the sorghum yield is increased by 593.98 kg/hm2 and the economic benefit is increased by 1681 yuan/hm2.The goal of saving fertilizer,increasing production and increasing efficiency can be achieved. |
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