| Maize is the main food crop in Northeast China,and the depth of groundwater in Northeast China varies according to geographical location.Therefore,it is of great significance to explore the response law of maize to different groundwater depth and how to use groundwater resources efficiently.To study the effects of groundwater depth on maize growth,crop coefficient and water consumption,seven treatments with different groundwater depths were established by groundwater depth simulation system in this study,which were 1.0(D1.0),1.5(D1.5),2.0(D2.0),2.5(D2.5),3.0(D3.0),3.5(D3.5)and 4.0m(D4.0),respectively.The value of maize plant height,leaf area,root growth,dry matter accumulation,maize water consumption,water use efficiency and maize crop coefficient among proposed treatments were compared and analysed.The main results are as follows:(1)The effect of different groundwater depth on the main growth indexes of maize under mulch drip irrigation is different.The plant height of D1.0 treatment was significantly greater than that of other treatments.As the groundwater depth increased,the maize plant height decreased first and then increased.The maize leaf area index increased first and then decreased as maize gowth.The leaf area indexof D1.0 treatment was largest.At the jointing stage,the instantaneous water use efficiency of D2.5 treatment was the highest.In 2017,the instantaneous water use efficiency of D2.5 treatment was 2.67% ~ 19.54% higher than that of other treatments,and it was 2.57% ~ 25.31% higher than other treatments in 2018.During the heading stage,the leaf instantaneous water use efficiency decreased first and then increased with the increase of the groundwater depth.The leaf instantaneous water use efficiency of D2.5 was the highest.Compared with other treatments,the D2.5 treatment improved leaf instantaneous water use efficiency by 18.12% ~ 43.24% and 6.47% ~ 46.89% in 2017 and 2018,respectively.(2)Root length,root surface area,and root volume of different groundwater depth treatments are increasing with the advancement of the growth period.The increase range is 46% to 249% in 2017 and 57% to 280% in 2018.And the increase range in each treatment was significantly different(P<0.05).During jointing and grouting maturity,the dry matter accumulation of stems and leaves decreased first and then increased with the increase of groundwater depth.Yield decreased first and then increased with the increase of groundwater depth.The yield was the largest in D1.0 treatment,and in D 3.0 treatment the yield was the lowest.The yield of D1.0 treatment was 337 ~ 1417 kg·hm-2 and 365 ~ 1790 kg·hm-2 higher than that of other treatments in 2017 and 2018,respectively.Multivariate regression and path analysis were adopted to exlore the effects of dry matter and root system on maize yeild.The results showed that the depth of groundwater affected yield by affecting root growth and dry matter accumulation.There was a significant positive relationship between root length and thickness in heading-silking stage,and maize yield.The maize yield had markedly negative relationship to root surface area,dry matter accumulation in stems and leaves at the headingsilking stage,and root surface area at the filling stage.(3)Based on the dual-crop coefficient method,the evapotranspiration of maize under different groundwater depth conditions was explored.The results showed that the daily water requirement of maize under D1.0 treatment was about 0.1% ~ 10.8% higher than that of other treatments.The rank of water consumption in the four growth stages was mid-stage> rapid develop period>late stage> initial stage.With the increase of groundwater depth,the average evaporation coefficient of maize increases.The average base crop coefficients of D1.0,D1.5,D2.0,D2.5,D3.0,D3.5,D4.0 were 1.14,1.10,1.06,1.04,1.04,1.08,and 1.09,respectively.With the growth of maize,the maize transpiration changed as M-shape,and the evaporation was showed a decreasing trend. |
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