Effects Of Soil Moisture Temporal Variation On Growth,Physiology And Water Use Efficiency Of Maize And Lettuces

In order to explore the effects of soil moisture temporal variation on the growth,physiology and water efficiency of corn and lettuce,in this paper,negative pressure irrigation?NPI?and artificial irrigation?AI?,respectively,are used to form stable and volatile soil moisture in pot experiments of corn and lettuce.Effect of different treatments on the dynamic changes of soil moisture,total water consumption,agronomic traits,photosynthesis,physiological indexes,biomass allocation and water use efficiency of maize from jointing stage to maturity stage and lettuce from four-leaf stage to maturity stage were analyzed.The main conclusions drawn from the study are as follows:1.Negative pressure irrigation could keep the water content of the pot soil of maize and lettuce basically stable.The water supply pressure of corn test was controlled within-15?-5 kPa,and the volume water content of soil was controlled within 6.83%?12.89%.The water supply pressure of lettuce test was controlled in the range of-9?-3 kPa,and the volume water content of soil was controlled in the range of 22.5%?35.1%.2.Stable soil moisture conditions were beneficial to the growth,photosynthesis,dry matter accumulation and improvement of water use efficiency of maize and lettuce.Compared with 78%FC with medium temporal variability,the plant height,stem thickness,and leaf area of maize are increased by 32.6%,14.2%and 32.7%;SPAD value and net photosynthetic rate were higher in leaves of maize;dry matter mass,dry grain weight,water use efficiency of biomass and water use efficiency of yield of maize were significantly increased by 38.9%,106.6%,28.8%and 87.3%under 53%FC with weak temporal variability.The soil moisture content of-9 kPa and AI₂ was basically the same,but compared with the beginning of water control,the plant height,leaf number,maximum leaf length and maximum leaf width of lettuce under-9 kPa on the 28th day after water control increased by 129.4%,40.4%,166.6%and 75.4%,respectively,compared with AI₂;At the beginning of water control?1 day after water control?,the photosynthetic index?P_n,C_i,G_s,T_r?of-9 kPa in lettuce leaves was slightly lower than AI₂,but 11 to 28 days after water control,the photosynthetic index of-9 kPa was higher than AI₂;The total fresh weight,total dry weight,water use efficiency of fresh biomass,water use efficiency of dry biomass of lettuce under-9 kPa are increased by 107.5%,29.3%,87.7%,17.5%,respectively,compared with AI₂.3.When the variation of soil moisture time is basically the same,that is,under the same irrigation technology,the higher the soil moisture content,the more favorable the biomass accumulation of maize and lettuce.Under stable weak temporal variation conditions,within the range of 38%FC?53%FC,the dry matter mass and kernel dry weight of maize increased with the increase of water content.The total fresh weight and total dry weight of lettuce showed-3 kPa>-6 kPa>-9 kPa under negative pressure irrigation,and AI₁?80%FC?90%FC?>AI₂?70%FC?90%FC?under conventional irrigation.4.Water use efficiency of biomass and?¹³C in bract were very significant positive correlation in the maize mature period.Water use efficiency of fresh biomass and?¹³C in leaves was significantly positive correlation in the lettuces mature period.