| There is a shortage of fresh water resources and serious overexploitation of groundwater in Hebei low plain.Adjusting planting structure and developing water-saving irrigation technology are effective ways to alleviate water resources crisis and ensure sustainable development of agriculture.In recent years,with the implementation of the system of’water-saving pressure mining’and’fallow rotation’in groundwater over-exploitation funnel area of Hebei Province,the use of maize monoculture mode instead of winter wheat-summer maize annual cropping mode at the cost of water ecology has become an important measure to change the mode of agricultural development and reduce groundwater consumption in this area.In order to explore the suitable irrigation measures and sowing date of maize under the adjustment of agricultural planting structure,experiments on irrigation and sowing date of maize were carried out in Hengshui City of Hebei Province from May to October 2019 and 2020.Two irrigation treatments were set in the experiment,which were irrigation once after sowing and irrigation once after sowing+irrigation once from large bell mouth to filling stage（irrigation was controlled by soil moisture content in 0～60 cm soil layer,and the lower limit of irrigation was 65%of field water capacity）,which were denoted as W1 and W2 in turn,and border irrigation was adopted with irrigation quota of 75 mm;Each irrigation treatment set four sowing dates,respectively,5th May（D1）,20th May（D2）,5th June（D3）and 20th June（D4）.The effects of different irrigation times and sowing dates on soil moisture distribution in maize field were explored.The response characteristics of maize growth and yield components to irrigation and sowing dates were revealed.The water consumption and water use efficiency of maize under different irrigation and sowing dates were clarified.The suitable irrigation times and sowing dates for one-ripening maize under water-saving and stable yield conditions were given.The main results are as follows:（1）Affected by rainfall,irrigation and evaporation and transpiration,soil moisture distribution in 0～100 cm soil layer of maize at different growth stages varied greatly.From seedling stage to maturity stage,the average soil moisture content in 0～40 cm soil layer of each treatment showed a trend of first decreasing,then increasing and then decreasing with the growth process.Irrigation treatment mainly affected the soil moisture content of 0～40 cm soil layer from silking to maturity of maize.Under W2condition,the soil moisture content of 0～40 cm soil layer was higher than that of W1.Under the same water condition,the 0～30 cm soil moisture content of D1 and D2treatments at the early stage of maize growth was generally lower than that of D3 and D4 treatments,and the difference between treatments after silking stage was relatively small.（2）The duration from flowering and silking to maturity of maize could be prolonged by increasing irrigation times.Compared with W1,maize under different sowing dates in 2019 and 2020 had 2～4 d and 2～3 d late maturity,respectively.Under the same irrigation condition,the duration of maize growth period decreased first and then increased with the delay of sowing date.The treatment with the shortest duration of maize growth period was D3.Compared with D3,the duration of maize growth period under other sowing dates under W1 and W2 conditions in 2019 increased by 2～6 d and1～5 d,respectively,and increased by 2～6 d and 1～6 d in 2020.（3）Increasing irrigation times had promoting effects on morphological growth indexes such as plant height,stem diameter,leaf area index（LAI）,physiological indexes such as chlorophyll relative content,transpiration rate,net photosynthetic rate,leaf water use efficiency（LWUE）and aboveground dry matter quality from flowering and silking to maturity.Under the same water condition,each index first increased and then decreased with the delay of sowing date.Among them,the maximum LAI and LWUE were D3 and D2 under the conditions of flowering and silking stage W1 and W2,respectively.Compared with other sowing date treatments,the LAI of D3 treatment increased by 5.2%～27.5%and 8.2%～22.8%under the conditions of W1 and W2 in 2019,respectively,and the average LWUE of D2 treatment increased by 5.9%～13.3%and1.7%～15.8%,respectively.In 2020,LAI of D3 treatment increased by 17.5%～39.6%and 15.4%～40.6%under two water conditions,respectively.The mean LWUE of D2treatment increased by 2.6%～14.2%and 2.5%～6.3%,respectively.（4）Two-year experiment showed that irrigation had no significant effect on grain yield,sowing date had very significant effect on grain yield,and their interaction had no significant effect.Increasing irrigation times can prolong the duration of rapid grain growth period,improve the average grain filling rate,increase the 100-grain weight,and then improve the yield.Compared with W1,the grain yields of maize under different sowing dates in 2019 and 2020 under W2 conditions increased by 0.9%～13.1%and 1.7%～12.2%,respectively,and the difference between treatments with the same sowing date was not significant.Under the same irrigation condition,the average grain filling rate and grain yield increased first and then decreased with the delay of sowing date.The highest yield under the two water conditions in 2019 was D3,which increased by 13.8%～73.9%and 6.7%～69.8%compared with other sowing dates.In 2020,the treatments with the highest yield under W1 and W2 were D3 and D2,respectively,with the increase rates of 8.1%～62.5%and 0.9%～52.6%,respectively,compared with other sowing dates.（5）The increase in irrigation times increased the total water consumption during maize growth period and reduced the water use efficiency（WUE）.Compared with W1,the water consumption during maize growth period under different sowing dates in2019 and 2020 increased by 11.9%～20.3%and 16.8%～21.9%,respectively,and WUE decreased by 3.3%～14.1%and 3.0%～17.2%,respectively.Under the same water condition,there was no significant difference in water consumption among different sowing dates（except 2019 W2D1）,and WUE first increased and then decreased with the delay of sowing date on the whole.In 2019,the treatment with the highest WUE under the two water conditions was D3,which increased by 6.0%～83.8%and8.3%～93.1%compared with other sowing dates,respectively.The treatments with the highest WUE under W1 and W2 in 2020 were D3 and D2,which were 13.0%～55.1%and2.8%～60.7%higher than those under other sowing dates,respectively.（6）Considering the characteristics of maize growth and development,yield,irrigation amount,water consumption and water use efficiency and other factors,under the maize mono-cropping planting mode in the groundwater over-exploitation area of low plain in Hebei Province,high maize yield and water use efficiency can be obtained by suitable sowing+only irrigation of Mongolian head seedling water.From the perspective of water saving,stable yield and high efficiency,it is recommended that the suitable sowing date of maize monoculture planting mode in the study area is 5th June,irrigation once,that is,seedling water after sowing. |
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