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Objective In order to meet the challenge of freshwater resource scarcity and soil salinization in the southern border region,this study investigates the effects of brackish water drip irrigation on the distribution of substrate water and salt,growth and yield of facility tomato under the yellow sand cultivation mode.Moreover,the study explores the dynamic growth change of tomato by using the Logistic model to determine the threshold of mineralization for brackish water drip irrigation of facility tomato under the yellow sand cultivation mode in the southern border region,thus providing the theoretical basis and technological support for the efficient use of brackish water in facility agriculture in the region. Method In this experiment,five irrigation water mineralization treatments of 2 g/L(T1),3 g/L(T2),4 g/L(T3),5 g/L(T4)and 6 g/L(T5)were set up with yellow sand substrate facility tomato as the research object,and freshwater irrigation as the control(CK)was used to investigate the effect of brackish drip irrigation on the distribution of substrate water salinity,the growth and development of the facility tomato,the constituent factors of yield,and the efficiency of irrigation water use under the yellow sand cultivation mode. Result Under the yellow sand cultivation mode,the water content and salinity of the substrate of each treatment during the whole reproductive period were positively correlated with the mineralization of irrigation water,and both increased with the increase of the mineralization of irrigation water;the average water content of the substrate of each treatment from 0 to 25 cm in different reproductive periods of tomato reached the maximum in the flowering and fruiting period,of which the increase of the average water content of the substrate of 2 g/L was not obvious when compared with that of the CK treatment.The average water content of the substrate of 2 g/L significantly increased when the mineralization increased to 3 g/L or more.Compared with the CK treatment,the increase in the average water content of 2 g/L substrate was not obvious.When the mineralization increased to more than 3 g/L,the average water content of substrate was significantly higher,increased by 7.51%,10.67%,14.44% and 18.10%,respectively;the average salinity of 0-25 cm substrate at different fertility periods of tomato reached a peak at the end of fruiting,of which the salt accumulation effect of T3,T4 and T5 treatments was more obvious,and the salt content of the substrate was as high as 8.49,9.82 and 10.50 g/kg.Tomato plant height,stem thickness and dry matter growth showed an S-shaped trend of gradual increase and then basically unchanged with the advancement of fertility.The logistic model could be used to accurately describe the dynamic growth process of tomato plant height,stem thickness and dry matter accumulation under different treatments of irrigation water mineralization.The determination coefficient R2 of the fitting equation was above 0.94.The growth indexes,total yield and irrigation water use efficiency of tomato showed a trend of increasing and then decreasing with the increase of irrigation water mineralization,in which the total yield and irrigation water use efficiency of 3 g/L reached 47.17 t/hm2 and 15.22 kg/m3,respectively,which were significantly higher than those of the other treatments. Conclusion Considering the growth and development of tomato and yield and other factors,this study recommends 2-3 g/L irrigation water mineralization for facility tomato under yellow sand cultivation mode,which can effectively alleviate the shortage of fresh water and soil salinity.This study provides scientific basis for the large-scale popularization of sand cultivation of tomato in the southern border area.
JIANG et al. (Mon,) studied this question.