## 3 Results  
### Overall Effect of Organic Fertilizer on Tomato Yield and Quality  
The overall effect of organic fertilizers on tomato yield and quality variables (Figure 2). Specifically, increased organic fertilizers significantly improved the tomato yield by 42.18% (95% CI: 36.22% to 48.38%). For tomato quality, increased organic fertilizers significantly improved TSS by 11.86% (95% CI: 7.55% to 16.33%), SS by 42.18% (95% CI: 25.51% to 61.06%), and SAR by 6.17% (95% CI: -8.9% to 23.75%). SAR indices of tomatoes treated with organic fertilizers did not change. Organic fertilizers significantly increased lycopene by 23.95% (95% CI: 10.65% to 38.86%), VC by 18.97% (95% CI: 15.26% to 22.80%), and nitrate by 8.36% (95% CI: 1.52% to 15.66%), compared to the no-fertilization. The regression analysis revealed that tomato VC was linearly and positively correlated with soil organic matter, while TSS, SS, SAR, and nitrate were non-linearly correlated. Similarly, tomato vitamin C was linearly and significantly positively correlated with total soil nitrogen, while TSS, SS, SAR, and nitrate were non-linearly correlated with total soil nitrogen (Figure 3). Effect of Organic Fertilizer Combined with Soil Organic Matter, Total Soil Nitrogen, and Type of Organic Fertilizer on Tomato Yield  
It can be concluded that when soil organic matter is <20 g\(\cdot\)kg\({}^{-1}\) (95% CI: 28.15% to 45.99%) or \(\geq\)20 g\(\cdot\)kg\({}^{-1}\) (95% CI: 28.98% to 52.49%), the application of organic fertilizers has no effect on the tomato yield (Figure 4a). In terms of total soil nitrogen, for total soil nitrogen <0.1 g\(\cdot\)kg\({}^{-1}\), 0.1-1 g\(\cdot\)kg\({}^{-1}\), and >1 g\(\cdot\)kg\({}^{-1}\), the tomato yield increased by 73.64, 40.96, and 38.69%, respectively (Figure 4b). Subgroups were made based on the type of organic fertilizers, and a significant increase in tomato yield was observed for each type (Figure 4c). Animal organic fertilizer improved the yield by 50.53%, organic plant fertilizer by 35.78%, animal-and-plant mixed organic fertilizers by 37.16%, and other organic-fertil types by 31.98%. Except for animal organic fertilizer, there was no significant difference in the tomato yield among the other three types of organic fertilizers, and the 95% confidence intervals for each group overlapped. The soil pH was divided into two subgroups (Figure 4d). When the soil pH was \(\geq\)7, the effect of organic fertilizers on the tomato yield was 33.04% compared with that of no fertilizers. When the soil pH was \(\mathcal{C}\), the effect value of increasing organic  
Figure 2: Organic fertilizers’ effect on tomato yield and quality. Points represent the mean effect, while bars represent 95% confidence intervals. The numbers at the right side of the confidence intervals represent the sample sizes. TSS, total soluble solids; SS, soluble sugar; SAR, sugar/acid content ratio; VC, vitamin C.  
fertilizers on the tomato yield was 60.06%, indicating a significant yield. Depending on the cultivation type, the effect of applying organic fertilizers on the yield in field experiments was 44.26%, compared to 27.26% in the greenhouse (Figure 4e). Effect of Organic Fertilizer Combined with Soil Organic Matter, Total Soil Nitrogen, and Organic-Fertilizer Type on TSS  
When the soil-organic-matter content was \(\geq\)20 g\(\cdot\)kg\({}^{-1}\) and \(<\)20 g\(\cdot\)kg\({}^{-1}\), the tomato's soluble solid content increased by 14.17% and 11.47%, respectively (Figure 5a). For the total soil nitrogen content, when the total soil nitrogen was \(>\)1g\(\cdot\)kg\({}^{-1}\) and 0.1-1 g\(\cdot\)kg\({}^{-1}\), the tomato's soluble solids increased by 13.89% and 7.66%, while \(<\)0.1 g\(\cdot\)kg\({}^{-1}\) had no change in soluble solids (Figure 5b). With the increase in soil total nitrogen content, the effect of organic fertilizers on improving tomato soluble solids tended to be positive and significant. Different organic fertilizers had different effects in regard to improving tomato soluble solids (Figure 5c).