Effect Of Water And Fertilizer Integration On Tomato Physiology And Utilization Efficiency Of Water And Nitrogen

Fertigation is a high-efficiency water and nitrogen utilization method that integrates irrigation and fertilization.It can directly supply water and nitrogen to crop roots,which helps to increase water and nitrogen absorption of crops.Because the imapact of fertigation on crop physiological process is not clear,therefore,this research used greenhouse pot experiment to study the effects of water and nitrogen supply on the physiological response process of tomato plants and the effect of water and nitrogen use efficiency.The optimal coupling model of water and fertilizer was defined to promote tomato growth,improve tomato yield and quality,and improve the effectiveness of water and nitrogen.In order to study the effects of fertigation on tomato physiological response and water and nitrogen use efficiency,the experiment set up three water levels?WH?,moderate water stress?WM?and severe water stress?WL??90%,70%and 50%soil water holding capacity?and high?NH?,medium?NM?,low?NL?three nitrogen levels(3.0,2.0 and 1.0 g N pot^-1).In order to study the effect of soil water,nitrogen application amount and N frequency on tomato water and nitrogen utilization,two water levels W₁ and W₂?60%and 80%soil water holding capacity?,two nitrogen levels N₁ and N₂(1.5 and 3 g N pot^-1),and three nitrogen application frequencies F₁ F₂ and F₃?once every 12 days,6 days,4 days?were set in the experiment.The stable isotope technique was used to determine the gas exchange,water status,leaf and root hormone levels in tomato leaves,?¹³C and?¹⁸O and?¹⁵N in plants,tomato biomass and water and nitrogen absorption and utilization efficiency.The results are as follows:1.The dry matter accumulation of tomato plants is closely related to soil moisture and nitrogen.There is a significant positive linear relationship between the dry matter quality of tomato leaves,stems,fruits and roots with the amount of irrigation.Under the conditions of WH and WM,the increase of nitrogen content increased the dry matter content of the above-ground part of tomato significantly,and the dry matter of above-ground treatment of NH and NM increased by 19.8%-45.4%compared with NL treatment.2.Soil moisture determines the water status of the plant.The change of soil water content produces hydraulic signals,regulates the stomatal opening and closing of the leaves,and the stomatal conductance?g_s?is significantly reduced under WL conditions,and is significantly improved under WH conditions.At the same time,soil water stress promoted the generation of ABA,which is a negative correlation between root ABA concentration and soil water content.The ABA concentration under WL condition increased significantly by 131.3%-178.5%than the condition of WH.The water stress increased the ABA chemical signal in the root system and regulated the opening and closing of the leaf stomata.The hydraulic signals generated by soil moisture changes and the root ABA chemical signals jointly regulate the opening and closing of leaf stomata and water use efficiency.3.Soil moisture and nitrogen affect the leaf gas exchange process.The influence of moisture on g_s and intrinsic water use efficiency?WUE_i?is more significant,while the effect of nitrogen is smaller.With the change of soil moisture,the changes of g_s and WUE_i have obvious rules,g_s decreases with the increase of water stress,and WUE_i increases with the increase of water stress.Under WL conditions,the decrease of g_s resulted in the increase of?¹³C composition and?¹⁸O value,WUE increased,and g_s showed a significant negative correlation with?¹³C composition and?¹⁸O value.The change of?¹³C is not only affected by the pores,but also by the photosynthetic capacity of the leaves.The specific leaf nitrogen content represented the photosynthetic capacity of the leaves,and the?¹³C was significantly positively correlated with the specific leaf nitrogen content.Compared with?¹³C,?¹⁸O is mainly regulated by leaf stomatal opening and closing and transpiration.Therefore,?¹³C and?¹⁸O can be measured to determine whether water use efficiency is mainly determined by stomata or photosynthesis.The study found that under the condition of water and fertilizer integration,compared with the influence of nitrogen,the regulation of WUE of plants,g_s plays a leading role.4.Under the condition of water and nitrogen integration,water,nitrogen and nitrogen application rate affected the growth of tomato.With the decrease of water and nitrogen application rate and nitrogen application rate,the leaf area of tomato decreased and the dry matter content of aboveground decreased.Soil moisture The decrease of water and the increase of nitrogen dosage can increase the tomato WUE,the nitrogen application frequency has an improvement effect on WUE,and the F₂ nitrogen application frequency increases the tomato WUE.The reduction of soil moisture and nitrogen use reduced the nitrogen uptake of tomato plants,and the nitrogen application rate of F₂ increased the nitrogen uptake of crops.It is recommended to use every 6 days nitrogen application frequency for fertigation to obtain high yield and improve WUE and nutrient uptake.