Meta-analysis of the effect of biological and organic fertilizers on the yield of black seed (Nigella sativa L.) and cumin (Cuminum cyminum L.)

Abstract
Introduction: sustainable and organic agriculture is becoming an alternative production approach with an emphasis on ecological processes along with guaranteeing human health and the environment. However, there are concerns about the performance of sustainable and organic agricultural production and meeting the demand of a growing population. The purpose of this research was to analyze the statistical analysis of independent experiments of the studies of medicinal plants with a consolidated and quantitative review of the studies and the effect of different inputs on the seed yield of black seed plants (Nigella sativa L.) and cumin (Cuminum cyminum L.).
Materials and methods: Meta-analysis examines and analyzes existing research findings in a specific field. This method allows the researcher to make a more detailed comparison and check by using the information obtained from the previous research and gain a deeper understanding about the phenomena.Based on the Roses method and the selection of related studies, a total of 74 articles were selected, of which 42 were related to black seed and 32 were related to cumin. In relation to each group, Hedges effect size, Bias (using Begg and Mazumdar rank correlation) and Kendall’s tau coefficient were calculated and funnel plots were drawn using Comprehensive Meta-Analysis software. In order to fit and modify funnel charts, dual and Tudy methods were also used.
Results and Discussion: According to the results, the effect size of hedges had the highest effect on black seed yield for mycorrhiza, vermicompost, animal manure, humic acid and biofertilizers (bacteria base) respectively. On the other hand, for cumin, the size of the Hedges effect had an equal effect on the yield of cumin seeds for the manure, mycorrhiza and humic acid groups, respectively, with a slight difference. Also, vermicompost treatment showed a greater effect size than biofertilizer. The results of Begg and Mazumdar's correlation test for all fertilizer treatments were higher than the determined coefficients, which indicates the homogeneity of the meta-analysis studies. Therefore, it is recommended to use these fertilizers in black seed and cumin medicinal plants with 95% confidence. The classic fail-safe N test was also a suitable and significant value in all treatments; which showed the high precision and accuracy of the studies and the results obtained in this research. Evaluation and adjustment of publication bias with Duval and Tweedie's Fit method showed that 5 studies are needed in order to eliminate partial bias error in the meta-analysis of biofertilizer groups in black seed plant. Also, 1 study should be added to the study of the effect of humic acid for cumin and 1 study to the study of the effect of humic acid for each of black seed and cumin plants.
Conclusion: The results of this study emphasize the positive effect of biological and animal fertilizer treatments on the growth and performance of black seed and cumin medicinal plants based on available scientific evidence. Therefore, it can be used in organic cultivation systems as permitted materials and also in combination with chemical fertilizers in common systems and good agricultural practice. In general, the results of the research showed that sustainable and organic agricultural ecosystems have adequate production capacity despite the yield gap compared to conventional agricultural ecosystems, and the yield gap between conventional and sustainable systems can be reduced with integrated management.