A global meta-analysis on surface and drip fertigation for annual crops under different fertilization levels

So far, many studies have examined the effects of surface (FF) and drip (DF) fertigation compared to surface (FC) and drip (DC) irrigation along with fertilization at different levels of fertilizer on crop yield indices, nutrient use efficiency (NUE), and irrigation water productivity (WP); however, each of them have been conducted under different conditions. Because of the scattered results and the lack of a general conclusion from the published results, conducting a meta-analysis as a structured method for arriving at an overall conclusion regarding the effects of different fertigation methods on different indices is essential. This study was conducted to examine the effects of surface and drip fertigation methods and different fertilizer application levels on crop yield, NUE, and WP. To this end, eight global databases of publications (e.g., Scopus and Web of Science) were reviewed. A total of 5494 studies were extracted, of which 32 studies met the entry criteria for the meta-analysis. To assess the effects of fertigation, each study was used to extract the effect sizes for each index. A total of 119 effect sizes were obtained for crop yield, 85 for NUE, and 84 for WP. The meta-analysis results showed that surface and drip fertigation methods increased the average yield by 20%. NUE and WP on an average increased by 26% and 51%, respectively. Based on the reported results, the optimal fertilizer application level is 75% of the recommended dose, which can reduce fertilizer use by 25% without significantly reducing the yield. In general, fertigation can be recommended as an effective operation for improving the proposed indices examined in both surface and drip fertigation methods.