Influence of mulching and varieties on growth and yield of tomato under polyhouse

The experiment was conducted to study the effect of mulch on growth and yield of tomato varieties under polyhouse condition at Bahir Dar, Ethiopia in 2012 and 2013. The treatments were 4 × 2 factorial combinations of mulching material (Black plastic mulch (BPM), White plastic mulch (WPM), Grass mulch (GM) and no mulch with two varieties (Cochoro and Miya). White plastic mulch recorded significantly tallest plant height followed by black plastic mulch. Significantly highest number of primary and secondary branches per plant were recorded for un-mulched Cochoro variety and mulched with grass, respectively in 2013. Cochoro variety mulched with grass produced significantly highest number of flowers per cluster in 2013. Significantly highest number of fruits per cluster and percent fruit set was registered when Miya variety was grown on grass and black plastic mulch, respectively. Earlier flower, fruit set and maturity of fruits were recorded from plants mulched with white plastic. Significantly early flowering, fruit setting and fruit maturity were recorded inthe Miya variety. The highest marketable fruit yield was obtained with grass mulch treatment (60.90 t ha-1) and the lowest was obtained with no mulch treatment (43.76 t ha-1). The increase in fruit yield gained by the application of grass mulch in polyhouse was attributed to its favorable effect on soil temperature and soil moisture which subsequently created conducive condition for root growth and development. Significantly higher marketable yield was obtained in Miya variety (57.83 t ha-1) as compared to Cochoro variety (44.32 t ha-1).  The mean air temperature regime was 18.7°C (night) to 25.6°C (day) inside the polyhouse which was optimum for plants growth and normal fruits production. Soil temperatures under both plastic mulches were constantly higher than under bare soil and grass mulch. Cost benefit analysis indicates the highest net benefit was obtained on grass mulch. Based on agronomic performance and economic analysis the result of the present study indicated that the superiority of Miya tomato variety grown at grass mulch under polyhouse growing condition. Therefore, application of grass mulch for tomato fruit yield using Miya variety is recommended for producers in the study area. Key words: Mulch, polyhouse, tomato.