Meta-analysis of Saffron (.Crocus sativus L) Agronomical Researches, with an Emphasis on the Consumption of Organic Fertilizers and Agronomical Practices in Iran

Studies that investigated the impact of organic fertilizers (manure, compost and biological fertilizers) and agronomical practices (density, method, date and depth of planting) on saffron yield have a long history in Iran. Due to the distribution and inconsistency in the results obtained from different studies, a meta-analytic approach was used in the current study. for this aim, 47 organic fertilizers studies and 44 agronomical practices studies were selected from 202 gathered studies and analyzed. The criteria for the selection of studies were the adequacy of data for the present meta-analysis. Among the individual fertilizer studies, manure fertilizer had the highest impact on saffron dry weight (g= 1.493) at 95% confidence interval. Average amount, 40 to 50ton/ha of cow manure, 20 to 30ton/ha of compost that is used as a combination with Biofertilizer (Nitroxin with Nitrogen-fixing bacteria) were more effective than higher amounts of these fertilizers will be alone. Among the agronomical practices studies, plant density had the highest and depth of planting had the lowest effect size on economical yield and number of flower. The optimal density for maximum yield was 50-100 corm per (m2), optimal consumed weight average 9-12 ton per hectare observed, optimal weight of any corm was 10-20 (g). Among planting methods, row-mass method was the best optimal (inter-planting was 20 cm and intra-planting 10 cm). The best planting dates was the end of May and the first decade of Jun. Optimal planting depth was 15-20cm. Homogeneity between organic fertilizers studies was accepted and the homogeneity between agronomical practices except depth of planting studies was accepted. This heterogeneity was caused by factors such as age of farms and different regions that had the most impact on heterogeneity and effect size. The present meta-analysis aims to provide a better understanding of agronomical and fertilizers management and offer the best possible management for this crop.