Purpose Four different types of composts were assessed in two methods of application for their potential to support organic tomato yield. Methods A 2-year experiment was conducted using four different soil conditioners: cow manure (CM), household compost (HC), spent mushroom compost (SMC), and vermicompost (VC). Three different application rates (10, 20, and 30 t ha−1 for all composts except VC and 3, 6, and 9 t ha−1 for VC) were included as a second factor. Two methods of fertilizer placement (as a row behind the root area and broadcast on the field) were considered as a third factor. Results The yield was influenced by different soil conditioners and placement method in the first year; in the second year, just interactions were significantly different. Treatments with CM showed significantly higher tomato yield in the first year (103 t ha−1) compared to other composts, but in the second year, SMC produced a higher yield (58 t ha−1). The experiment indicated that the treatment with CM in high level with broadcast application had higher dry matter (DM) production (3.1 t ha−1) in 2014, and treatment with CM in low rate and broadcast application had higher DM production (5.8 t ha−1) in 2015. Conclusion Compost broadcast on the plots showed a higher yield production in case of similar rates and compost type. The proper rate of compost application is dependent on the method of compost placement.

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