| The cultivated land in Hetao Irrigated District had the following problems:high salinization degree,water resource shortage and low utilization rate,and the sharp drop of policy-based diversion of water from the Yellow River further aggravates the contradiction between agricultural water and diversion of water.It was the key to sustainable agricultural development Hetao Irrigated District,that how to use water efficiently and alleviate the contradiction between saving water and increasing production.In agricultural production,the amount of irrigation water and the depth of groundwater affect the absorption and utilization of water and nutrients by crops and the level of soil salinity,which indirectly affect crop yield.It was of great practical significance to the healthy development of agriculture in Hetao Irrigated District to explore the influence of groundwater depth and irrigation amount on farmland water and soil environment and crop growth,and put forward the reasonable irrigation amount and groundwater depth.Therefore,field experiments were carried out in 3 burial depths S1（1.4m）,S2（1.8m）,S3（2.2m）and 3 irrigation levels W1（90mm）,W2（110mm）and W3（135mm）in the agricultural experimental demonstration area of Progresong Village in Hetao Irrigated District.The aim was to provide theoretical basis for alleviating soil salinization and increasing production and saving water in irrigated areas.The specific research results were as follows:（1）Under the same irrigation amount,the average soil water content in shallow groundwater depth area S1 area was 5.0%higher than that in deep groundwater depth area S3area;The contents of ammonium nitrogen and nitrate nitrogen decreased first and then increased with the deepening of soil depth,and the contents of ammonium nitrogen and nitrate nitrogen tended to be enriched in the deep soil（80-100 cm）with water migration in the late growth period.The salt accumulation in the plough layer（0-60 cm）ranged from 327.46g·m-2to1060.43g·m-2,accounting for 58.7%-73.3%of the salt accumulation in 1m soil,and was negatively correlated with the groundwater depth.Based on the soil salt accumulation suitable for maize growth.It was suggested that the average groundwater depth was 1.75m-2.0m and the irrigation amount was 107.5mm-114.1mm during the growth period of saline land in Hetao Irrigation District,which could alleviate soil salinization.（2）The mean values of irrigation deep leakage were 40.88mm,20.81mm and 23.87mm,primary water>secondary water>tertiary water.Treatment S3W1αvalue the ratio of total irrigation deep leakage to irrigation quota was the lowest,which was 20%,and the irrigation water utilization rate was higher and the water-saving effect was better.Theβvalue the ratio of phreatic evaporation to irrigation quota of S1W1 was the highest,reaching 39%,and the phreatic evaporation was fully utilized.When the irrigation amount was 90-113.2mm and average groundwater depth was 1.75-2.0m,soil salinization could be alleviated and water resource waste can be reduced.From the perspective of phreatic evaporation,phreatic evaporation could be reasonably used when average groundwater depth was 1.6-1.9m and irrigation amount was 107.6-118.5mm,and soil secondary salinization could be effectively prevented.Therefore,based on irrigation water leakage and phreatic evaporation,it was suggested that the average groundwater depth in Hetao Irrigation District should be 1.75-1.91m,and the irrigation amount should be 107.6-113.2mm.（3）Compared with seedling stage,maize plant height and stem diameter at jointing stage increased by 270%and 33%,respectively,with faster growth rate;Leaf area index was significantly different between grain filling stage and harvest stage;Under the same groundwater depth,the difference of lai under different irrigation amount was up to 9.5%.From the perspective of maize yield,the suitable average groundwater depth was 1.70-1.88 m,and the irrigation amount was 107.3-135 mm.From the perspective of water use efficiency,the suitable average groundwater depth was 1.75-1.85 m,and the irrigation amount was107.2-116.5 mm.Considering yield and water use efficiency,it was suggested that the average groundwater depth should be controlled between 1.75-1.85 m and the irrigation amount should be 107.3-116.5 mm in Hetao Irrigation District.To sum up,to reasonable use of deep diving evaporation,the decrease of water leakage,to reduce the amount of magnetism of soil salt accumulation,reduce nitrogen loss,improve the maize yield and water use efficiency,achieve the goal of saving water resources,alleviate the soil salinization,salinization of Hetao Irrigation District of arable land,optimizing average groundwater buried deeply 1.75-1.85 m,the irrigation amount was 107.6-113.2 mm. |
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