Abstract: A Meta study was conducted to quantitative analysis on alleviating effects and influencing factors of summer maize drought by fertilization and irrigation, and to provide a theoretical basis for dealing with summer maize drought disaster. A total of 56 literatures on summer maize drought experiment were obtained through literature search, including 26 literatures on fertilization and 30 literatures on irrigation. Taking no measures as the control, Meta-analysis was conducted to investigate the alleviating effects and its influencing factors of fertilization and irrigation on summer maize drought. The results showed that: under drought stress, fertilization and irrigation significantly increased summer maize yield by 19.30% and 25.19%, respectively, compared with no measures. Different types of fertilizer had different alleviating effects on drought. Applying constant fertilizer and trace fertilizer could increase summer maize yield by 20.55% and 10.10%, respectively. Nitrogen fertilizer is the most commonly used of the constant fertilizers, among them, the application of controlled urea had the best effect, which could increase summer maize yield by 31.63% under the condition of drought, followed by the application of conventional urea in batches, with the yield increase rate of 20.73%, and the yield increase rate of conventional urea by all base application was the lowest, which was only 11.69%. In the range of 315kg·ha⁻¹ N application amount, the yield increase rate of summer maize was positively correlated with the N application amount. Soil bulk density and organic matter content also have an impact on the fertilization effect under drought conditions, and the fertilization effect was better on soils with low bulk density and high organic matter content. When planting density was higher, the alleviating effect of fertilization on summer maize drought decreased, but was not significant. When drought stress occurred in different growth stages of summer maize, the alleviating effect of irrigation was different. When drought continued in the whole growth period, the alleviating effect of irrigation was the best, and the yield increase rate reached 42.98%. The effect of irrigation on alleviating drought in tasseling-grouting stage was better than that in other growth stages. Soil bulk density and organic matter content had significant influence on irrigation effect, the lower soil bulk density and the higher organic matter content, the better alleviating effect of irrigation on summer maize drought. The planting density also had an effect on the irrigation effect, and the alleviating effect of dense planting decreased. For different summer maize varieties, the alleviating effect of irrigation on drought-sensitive cultivars was significantly better than drought-tolerant cultivars. In conclusion, both fertilization and irrigation could significantly alleviate drought of summer maize. The effect of fertilization was greatly affected by fertilizer type and the method of application, and the application effect of controlled fertilizer was better. Irrigation is the most direct and effective way to alleviate drought during the critical water-demanding period of summer maize. The effects of the two drought mitigation measures for summer maize were affected by soil properties and planting density, and the alleviating effect of irrigation was better than fertilization under different soil bulk density and planting density , and these factors should be considered in the specific implementation.

Key words: Fertilization, Irrigation, Summer maize, Yield, Meta-analysis