| The low plain area around the Bohai sea is one of the regions with the lowest water resources per capita in China.There are 2.66 million hm2 of low-yielding saline-alkali farmland and 666,700 hm2 of saline-alkali wasteland in this region,which restrict the development of agriculture and the improvement of crop yield in this area.The purpose of the study was to explore the ways of improvement and development of the saline-alkali land,to ease the tension between population and land requirement,and to promote the winter wheat yield and the water use efficiency?WUE?in the saline-alkali wheat area.A field research was carried out in three consecutive wheat growing seasons from 2015 to 2018 and winter wheat was used under a double cropping system of winter wheat and summer maize.Four treatments were set up:biological organic fertilizer?FF?,sediment of Yellow River?SS?,the mixture of biological fertilizer and Yellow River sediment?SF?,and the control treatment?CK?.The main results of this study were as follows:?1?The SS and SF treatments increased the the proportion of<0.25 mm aggregates in the 0-30 cm soil layer.Application of the Yellow River sediment or bio-organic fertilizer both reduced the soil bulk density,increased the total porosity of the topsoil layer,the effective soil porosity and the soil saturated water conductivity.Generally speaking,the mixed application of biological fertilizer and Yellow River sediment performed the best soil improvent effect.?2?SS caused low water storage in the 0-10 cm soil layer,which resulting in low soil water content in the 20-40 cm soil layer,but being beneficial to the water storage in the 60-80 cm soil layer.The water in 30-60 cm soil layer was most sensitive to irrigation and rainfall.After irrigation,SS,FF and SF all reduced soil salt content in different degrees.The desalination of salt in 60-80 cm soil layer was the largest.The desalination rate of FF,SS and SF was 0.03%,0.07%and 0.06%,respectively.SS showed best effect for promoting soil salt leaching to deep soil.The least desalination soil layer was 20-30 cm,with treatment SS and SF desalted by 0.042%and 0.022%,and FF showed no desalinization but a 0.002%increase.?3?According to the distribution characteristics of water and salt ions in wheat fields in winter,the influence mechanism of freezing-thawing on water and salt movement was revealed.Before the freezing and thawing,the soil moisture content first decreased and then increased with the increase of soil depth.The soil moisture content in the 30-40 cm soil layer was smallest.EC was significantly higher in 0-30 cm soil than in other soil layers.The pH value increased with the soil depth.After freezing and thawing,the distribution of soil moisture is characterized by that the moisture content in the 0-60 cm soil layer increased with the increase of the soil depth,and the moisture content in the 60-80 cm soil layer decreased abruptly,while the moisture content in the soil layer below 80 cm rises rapidly.EC increases with soil depth.The pH value in the soil layer of 10-30 cm is greater than other soil layers,and the pH value below30 cm increased with the increasd in soil depth.In salt-return period,the soil moisture content of 0-20 cm soil is significantly lower than that of the soil below 20 cm.EC was significantly higher than that of soil below 20 cm.The accumulation of various ions is mainly in the soil layer of 0-20 cm.The redistribution characteristics of soil moisture and salt ions before and after freezing and thawing can be used as the theoretical basis for the prevention and improvement of salinized soil.The laws of ion migration are different,because their migration process is affected by their solubility,temperature,channel connectivity and continuity.Under the conditions of this study,the volume moisture content of the 0-20 cm soil layer during the spring salinization period was less than 15.15%,and various ions were concentrated in the soil layer.?4?This study revealed the physiological mechanism of improving photosynthetic performance and promoting source and sink conversion of wheat by mixing sediment from the Yellow River and applying bio-organic fertilizer.The net photosynthetic rate of flag leaf after flowering showed a decreasing trend for all treatment.The average values of each treatment were SF,FF,SS and CK in descending order during flowering--20 d after flowering.SF,FF and SS were more than 12%,10%and 4%higher than CK compared with CK,respectively.Especially at 20 d after flowering,SF,FF and SS could still maintain high photosynthetic performance,which were 26%,9%and 2%higher than CK.The photosynthetic potential changes with the growth process in a unimodal curve.The photosynthetic potential reached its maximum at the boot-flowering period,and decreased rapidly 30 days after flowering.It is shown as SF,FF,SS and CK in order from large to small.The photosynthetic potentials of SF,FF and SS were 25%,9%and 7%higher than those of CK at the booting-flowering period.The photosynthetic potentials of SF,FF and SS were 41%,24%and 13%higher than that of CK after flowering.Source-sink index of SF,namely the whole growth period before and after flowering,source production capacity was the highest and were 34.06%,40.52%and 28.15%higher than CK,respectively.The yield composition index,namely ear number,total grain number and capacity of the largest potential and effective pool of SF were also the highest and 22%,22%,27%and 24%higher than CK,respectively.At the same time,the yield,source conversion rate after flowering,grain leaf ratio and HI of SF were the highest,and 26%,5%,2%and 2%higher than CK.In this study,the effective storage capacity of wheat was positively correlated with total spike number and grain number per spike.The total spike number and grain number per spike are the key factors affecting winter wheat yield in saline-alkali land.Mixing the Yellow River sediment or applying bio-organic fertilizer can improve the photosynthetic performance of wheat,increase the production capacity of source and promote the conversion of source and sink.Combining the advantages of mixing Yellow River sediment with the application of bio-organic fertilizer,it has the best effect and is more conducive to the improvement and sustainable development of coastal saline soil.?5?The grain quality of wheat was improved by mixing the sediment of the Yellow River or applying bio-organic fertilizer.Mixing the sediment of the Yellow River can improve wheat wet gluten,wheat protein content,precipitation index and falling index,reduce the starch content,water absorption,formation time,stability time and lowest viscosity of wheat seeds,and improve the processing quality of wheat.The starch content,water absorption,formation time and the lowest viscosity of winter wheat grains were increased by applying bio-organic fertilizer.The peak viscosity,attenuation value,final viscosity,regeneration value and peak time of winter wheat could be reduced by mixing the sediment of the Yellow River or applying bio-organic fertilizer.Among them,the treatment with the sediment of the Yellow River and bio-organic fertilizer reduced the most.?6?The addition of Yellow River sediment or application of bio-organic fertilizer can increase the water storage in the soil layer 0-200 cm before jointing of winter wheat,increase the water consumption from jointing to maturity and its proportion in the total water consumption,promote the utilization of soil water storage and deep soil water by winter wheat,and thus increase the biomass and grain yield of winter wheat.The yield level was between 3317.77-5449.52 kg·hm-2 for 3 consecutive years.The highest grain yield was obtained by mixing Yellow River sediment with bio-organic fertilizer,which increased by 35%-51%compared with control.The range of farm evapotranspiration was 352.85-394.89 mm,and the control treatment was the lowest?352.85-386.17 mm?.The water use efficiency of farmland was between9.01-13.96 kg·m-3 and the treatment with the Yellow River sediment mixed and biological organic fertilizer(12.02-13.96 kg·m-3)was the highest,which was 33%-48%higher than the control.Organic fertilizer treatment and Yellow River sediment treatment increased by 9%-32%and 9%-18%compared with control.Grain yield of winter wheat was positively correlated with dry matter accumulation and total panicle grain number.The relationship between WUE and water consumption,WUE and yield of winter wheat was conic.In this study,WUE increased rapidly with grain yield.It is different that the performance of WUE increase and decrease with the increase of water consumption.Considering the yield,harvest index and water use efficiency,the best treatment was to mix the sediment of the Yellow River with bio-organic fertilizer. |
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