Meta-analysis of hail netting effect on fruit firmness in 'Fuji' apple

The effect of hail netting on fruit characteristics in 'Fuji' apple is intensively researched, with rather inconsistent and often contradictory results. Meta-analysis (MA) is a set of statistical techniques developed for the purpose of objective comparison of research originating from independent studies. The general significance and the size of the treatment effect i.e., fruit firmness in 'Fuji' apple can be estimated reliably by meta-analysis using metadata. The meta-analysis of that effect provides statistically valid, hence scientifically sound general conclusions. This study is conducted in order to provide the researchers and interested practitioners the general rules regarding the effect of various hail netting in 'Fuji' apple across multiple environments. In the databases a search has been conducted for adequate studies and chosen were the ones exploring the effect of hail nets on fruit firmness in 'Fuji' apple. Techniques of meta-analysis have been carried out on those data, and results are provided and interpreted. The total of 24 treatment metadata were recorded with details regarding control, variation, type of netting, cultivar, sample size, trees, orchard and climate, forming a matrix of 26x24, i.e., 624 metadata from 7 different researches, regarding data from 1124 measured treated fruits plus the equal number of fruits in the control. The result is that hail netting in general has statistically significant effect on fruit firmness in 'Fuji' apple under dark netting. Dark nets decrease the fruit firmness in 'Fuji' apple by 5% or 0.3 kg cm(-2). However, this effect of darker nets producing heavier shade is relatively small and its practical significance depends on intended postharvest treatments.