| Water is the source of life,the root of everything and one of the important resources of human survival and development indispensable.At present,with the development of economy and society in our country,the problem of shortage of fresh water resources has become increasingly prominent,which has become a bottleneck restricting economic and social sustainable development in China.The new method of drip irrigation under mulch can effectively alleviate the contradiction between supply and demand of fresh water resources in China.It is an important basis to ensure the high yield of summer squash that explore the appropriate level of water and salt under different treatment of salinity and upper and lower limits of irrigation.In this paper,the field experiment and theoretical analysis were used to study the effects of different irrigation water salinity and water and salt coupling on soil water and salt distribution and growth of summer squash under drip irrigation mulch.The control factors of the effect of different irrigation salinity on the growth of summer squash were the salinity of irrigation water.Three levels were selected and they were 1.7g/L?3.5g/L ? 5.1g/L.During the growth period of summer squash,the quantity of irrigation was controlled by irrigation upper and lower limits.The upper limit of irrigation was 90% of the field water holding capacity,and the lower limit of irrigation was 70% of the field water holding capacity.Specific research results are as follows:(1)The vertical distribution of soil moisture of different salinity treatments before irrigation were increasing with the increase of the depth of the soil.The distribution of soil moisture was close to roughly elliptical,the top of the drip is the highest soil moisture content,the farther away from the dripper,the smaller the water content.After the different degree of mineralization,the wetting body and the moisture content are different.When the mineralization degree is higher,the wetting body is narrower and the soil moisture content is higher.The average water content of the soil under the three salinity treatments showed a wave-like trend with time,and the numerical values of the three were in the range of 20 ~ 50 cm depth: 5.1g/L> 3.5g/L> 1.7g/L.(2)The distribution of soil salinity in different salinity treatments was consistent with the increase of soil depth,and the salt size and distribution of the three treatments were close.After irrigation,the soil salinity showed ellipsoidal distribution,the farther away from the position of the dripper,the greater the soil salinity.The salinity values of the three treatments were: 5.1g/L> 3.5g/L> 1.7g/L.Drip irrigation under the membrane can make the surface of the soil leaching into the deep soil,and away from the root concentration area.At the end of the whole growth period,the soil salinity under the three kinds of salinity treatment showed a decreasing trend with depth.1.7g/L treatment of salt area is mainly concentrated in 20~30cm soil layer,3.5g/L and 5.1g/L treatment of salt area is mainly concentrated in 20~40cm soil layer.(3)The emergence rate,plant height,leaf area index,root fresh weight,canopy fresh weight and root / shoot ratio of the summer squash were different with the same dynamic trend.The emergence rate and plant height of different salinity treatments increased rapidly with time,and then gradually became stable trend,while the leaf area index showed a gradual increase and then gradually decreased trend.The root fresh weight and canopy fresh weight under different salinity treatments showed a tendency to increase gradually with time,while the root / shoot ratio showed a decreasing trend.The emergence rate and leaf area index under different salinity treatments were 1.7g/L> 3.5g/L> 5.1g/L.The plant height after 1.7g/L and 3.5g/L treatment was similar,and significantly greater than 5.1g/L treatment.The root / shoot ratio of different salinity treatments was 5.1g/L> 3.5g/L> 1.7g/L.The effects of water and salt coupling on the growth of summer squash were four factors.Three factors were the growth stages of the summer squash,the seedling stage,the pumping stage and the flowering period,and the three growth stages of the summer squash were set with three water levels,and the upper and lower limits of irrigation are 70% ~ 90% ?FC,60% ~ 80% ?FC,50% ~ 70% ?FC,and the other factor is water quality factor,and three irrigation salinity levels are set,respectively 1.7?3.5 and 5.1g/L,using orthogonal test design,a total of 9 treatments(T1 ~ T9).Specific research results are as follows:(1)The average water content of soils under different water and salt treatments has the same trend with time,and all have a jagged fluctuation characteristic.The mean values of soil salinity under different water and salt coupling conditions showed the same trend with time,and decreased gradually under 1.7g/L and 3.5g/L treatment,but at 5.1g/L,big change trend.The higher the upper limit of irrigation and the higher salinity,the higher the soil moisture content.The greater the salinity of irrigation water,the greater the average soil salinity.The upper and lower limits of irrigation had no significant effect on soil salinity.(2)The plant height and leaf area index under different water and salt coupling conditions have the same trend,and the plant height increased gradually and then stabilized,and the leaf area index increased first and then gradually decreased.The higher the water content in the soil,the smaller the degree of mineralization,the greater the plant height and leaf area index of the squash.(3)The water consumption of crops under different water and salt coupling conditions increased gradually with time,that is,seedling stage <flowering stage <flowering period.With the increase of the salinity of irrigation water,the water consumption of summer squash gradually decreased.Squat production from large to small order: T2 treatment> T1 treatment> T5 treatment> T6 treatment> T9 treatment> T7 treatment> T8 treatment> T4 treatment> T3 treatment.The yield of summer squash increased gradually with the increase of salinity of irrigation water.The optimal water-salt coupling irrigation scheme is: salinity of 1.7g/L,seedling 70% ~ 90% ?FC,60% ~ 80% ?FC,and 70% ~ 90% ?FC.The optimum water consumption was 296 mm,which was in accordance with the quadratic parabolic relationship between the total output of the squash and the total water consumption under the brackish drip irrigation.(4)On the basis of the experiment,the water and salt production function model of summer squash was established with the modified Jensen model,and the water sensitivity index ? was expressed as follows: flowering period> pumping stage> seedling stage The results showed that the model had high simulation accuracy and could be used to predict the yield of summer squash. |
PDF Full Text Request