Meta-analysis of combinative application of organic and inorganic fertilizers on effect of yield and qualities of tomato

Objectives With the advancement and implementation of the action of organic fertilizers partial substitution of fertilizers, scientists have carried out a large number of relevant experiments in China. This study integrated the scattered results, quantitatively analyzed the comprehensive effect of combinative application of organic and inorganic fertilizers on the yield and quality of tomato, to provide references for the further development of the action in China.

Methods The data were obtained from China National Knowledge Infrastructure (CNKI), Web of Science, Science Direct and VIP literature database. Using keywords of “tomato” and “yield”, 32 papers that met the meta-analysis standard were selected. The data of combinative application of organic and inorganic fertilizers and single fertilizer treatment in the literature were extracted. The effective data of tomato yield, Vc, soluble sugar and nitrate content were 98, 39, 33 and 21 groups, respectively. Using single fertilizer treatment as control, the reaction ratio was selected as the effect value, and the Meta-analysis method was used to analyze the effects of combinative application of organic and inorganic fertilizers (COI) on tomato yield and qualities, and to analyze the factors affecting yield effect, including years and farmlands, soil organic and pH and field management practices.

Results The fail-safe factors of tomato yield and quality effect data processed by meta-analysis was greater than 5n+10 (n is the number of the sample), therefore, the result was highly reliable. Except for tomato soluble sugar concentration database, the funnel plots of other databases that used for meta-analysis were symmetric (P>0.05) and there was no publication bias. Compared with single chemical fertilizer controls, COI significantly increased tomato yield by 7.1% (5.13%−9.07%); significantly increased Vc and soluble sugar content by 21.2% (10.3%−33.3%) and 14.3% (3.7%−15.6%), respectively; significantly reduced the nitrate content by 19.4% (27.9%−9.7%). The results of classification analysis of yield showed that the year and farmland region had significant effects on tomato yield response, and the longer the COI conducted, the higher the yield increase rate in the tested areas, except in Northeast farmland, where the yield increase was not significant. Tomato yield increase was significantly and positive correlated with soil organic matter content (R²=0.9288), but significantly and negatively correlated with soil pH value (R²=0.7230). In regarding to field management practices, the yield increasing rate of tomato inside greenhouse was higher than open-field; modern commercial organic fertilizers produced higher yield than traditional organic fertilizer did. The tomato yield increase effect was significant at all levels of planting density and inorganic fertilizer application rate, and the higher yield (10.7%) was obtained by controlling the application rate of inorganic nitrogen fertilizer within N 200 kg/hm².

Conclusions Compared with single-fertilizer, combinative application of organic and inorganic fertilizers can significantly improve tomato yield and improve tomato qualities, and the longer the application period of organic and inorganic application, the more obvious the effect, and the effect of greenhouse cultivation is better than in open field. Organic and inorganic application can increase the soil organic matter content and delay the decline of soil pH, which is an important reason for the combinative application of organic and inorganic fertilizers effect. Commercialized procession of organic materials is an effective way to improve the effect of organic fertilizer.