| Objective:The change of soil moisture in processing tomato root system was studied in this research, which may give a further understanding of the regulating role of change of root zone soil moisture on tomato growth and yield. This research was conducted to make the physiological regulation mechanism of output and water use efficiency clear, and optimized irrigation system was provided for yield improvement and higher water use efficiency for processing tomato under mulching film drip irrigation in arid.Methods:This 2-year field study was carried out. Experimental treatment consisted of two irrigation modes:DI (surface drip irrigation) where the irrigation line was placed right underneath the plastic mulch and SDI (subsurface drip irrigation) where the irrigation line was placed 30cm below the bed. Surface drip irrigation DI1, DI2 and DI3 were used for soil moisture at place 0-60cm, with moisture content set at (80±5)%, (60±5)%, (40±5)% of field moisture capacity respectively. Subsurface drip irrigation SDI1, SDI2 and SDI3 were used for control of irrigation volume and irrigation time to make them the same as those of surface drip irrigation DI1, DI2 and DI3.Results:(1) In the relative water deficit treatment and each treatment root vertical distribution, root length density and root weight density of root 0～1mm in diameter of the processing tomato of were significantly increased through subsurface drip irrigation treatments, and growth of root system in 0～30cm depth mainly were affected in the early, and following in the 30cm in the late. The weight ratio of vertical distribution of root system of processing tomato in the 30～80cm soil depth under subsurface drip irrigation was significantly higher than under the surface drip irrigation on Red fruit date.On day 14 after flowering, no significant difference was found with the root length density in 0-30cm soil depth in surface drip irrigation and subsurface drip irrigation treatments, but on Red fruits day, root length density in the 30-80cm soil depth under underground drip irrigation was significantly greater than under surface drip irrigation, especially in the state of the relative water deficit.(2) In the level distribution of root system of each treatment, uniformity of root distribution under underground drip irrigation was significantly higher than under surface drip irrigation on Red fruit date, and root length density with the horizontal distribute under subsurface drip irrigation treatments was significantly greater than under the surface drip irrigation treatments, especially in the relative water deficit state.(3) On the effect of changes of soil moisture with dry matter accumulation and distribution of processing tomato after flowering, leaf area index of processing tomato were significantly reduced in the relative water deficit treatment on day 14 after the Flowering date; compared with under surface drip irrigation, in the relative water deficit treatment leaf area index of processing tomato were significantly increased under subsurface drip irrigation on Red fruit date. On day 14 after Flowering date, amount of shoot growth under SDI2, SDI3 treatment were significantly lower than under DI2, DI3, and significant difference were found between SDI2 and DI2, and between SDI3 and DI3; On Red fruit date, plant height and total number of main stem branches, buds of processing tomato under subsurface drip irrigation treatments was significantly higher than the surface drip irrigation, and whether above ground or underground, the rapid growth and development of plant of processing tomato under SDI2, SDI3 have been significantly better than under DI2, DI3, and between SDI2 and DI2, and between SDI3 and DI3 significant difference were found. No significant difference was found with root dry weight density of processing tomato on days 14 after Flowering date under surface drip irrigation and subsurface drip irrigation, but dry root weight density was significantly increased under subsurface drip irrigation on Red fruit date.(4) On effect of water changes in soil with water use efficiency and Yield formation of processing tomato, the water consumption of processing tomato in SDI2, SDI3 were significantly lower than DI2, DI3 on Red fruits date, and It is suggested that in tomato, compared with under surface drip irrigation, water use efficiency was higher under subsurface drip irrigation, especially in the relative water stress condition.(5) On effect of water changes in soil with growth and development process of processing tomato, plants of processing tomato under DI1 entered Setting fruit date in the first, and followed by under SDI1, DI2, SDI2, DI3, finally under SDI3,In general, plants of processing tomato under surface drip irrigation arrive earlier than the corresponding the plants of processing tomato under subsurface drip irrigation on Setting fruit date; In the late, plants of processing tomato under DI3 entered Setting fruit date in the first, and followed by under DI2, SDI3, SDI2, SDI1, finally under DI1.Conculusions:(1) Under adequate soil moisture conditions, compared to under subsurface drip and under surface drip irrigation, no significant differences was found on root growth characteristics. Under subsurface drip irrigation the horizontal distribution ratio of root system of processing tomato were significantly higher uniform than under surface drip irrigation. Compared with under surface drip irrigation, it significantly benefits growth root system of processing tomato under subsurface drip irrigation in the relative water stress condition.(2) In general,canopy photosynthetic rate of processing tomato under subsurface drip irrigation was significantly higher than under surface drip irrigation in the relative water stress condition, while leaf chlorophyll content to the contrary. On dayl4 after Flowering date, the growth of aerial parts of processing tomato significantly was inhibited in the relative water stress condition; Compared to under surface drip irrigation, under subsurface drip irrigation it was significantly beneficial to growth.of shoot of processing tomato in the relative water stress condition on the Red fruit date.(3) Under Subsurface Drip Irrigation water use efficiency of processing tomato was significantly higher than under surface Drip Irrigation in the relative water stress condition. In general, under subsurface drip irrigation fruit weight, fruit number of processing tomato were significantly better than under surface drip irrigation in the relative water stress condition.(4) On the whole process of growth and development of processing tomato, compared with under surface drip irrigation, under subsurface drip irrigation growth and development process of processing tomato was not significantly affected in water sufficient condition, However, in the relative water deficit state, the process of growth and development of processing tomato under subsurface drip irrigation was significantly delayed, and fruit ripening has been delayed.(5) Compared with under surface drip irrigation, in the water relative deficiency state, although under subsurface drip irrigation tomato lycopene content was increased, but the main formation of fruit flavor, free amino acids, soluble protein, soluble sugar, soluble acid content, soluble solids and fruit sugar acid ratio were decreased, and nitrate content in fruit was increased, thus, fruit quality was reduced. |
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