IJAAR 1 (2013) 133-140 ISSN 2053-1265 Effects of different mulches on the yield and productivity of drip irrigated onions under tropical conditions Baba I. Y. Inusah*, Alexander Nimo Wiredu, Julius Yirzagla, Michael Mawunya, and Mohammed Haruna Council for Scientific and Industrial Research-Savannah Agricultural Research Institute (CSIR-SARI) P. O. Box 52, Nyankpala,Tamale, Ghana. Article History ABSTRACT Received 26 September, 2013 Received in revised form 21 October, 2013 Accepted 30 October, 2013 Key words: Allium cepa, Andropogan grass, Guinea savannah Agro-ecological zone, Sandy soils. Article Type Full Length Research Article There are still a lot of gaps in knowledge on how different types of mulch from organic sources can be used to improve the sustainability of irrigated onion production; and this requires further investigation. An experiment was therefore set up at the Savannah Agricultural Research Institute Tamale, Ghana, to investigate the influence of mulching with different straw materials, on the yields and productivity of onions, variety ‘White Creole’. The trial comprised three treatments: No Mulch (T1), mulching with Andropogan grass straw (T2) and mulching with rice straw (T3) at three tonnes per hectare each. The experiment was conducted from April to mid-July 2010 (dry season) and repeated between February and May 2011, both under drip irrigation. The soil of the experimental field was categorised as sandy loam, with pH 5.8. The results of the trial indicated that different types of organic based mulch such as grass and rice straw could contribute significantly to improved onion productivity and yields under tropical conditions. Onion bulb yield of T2 (10.58 t-ha -1 ) was significant (P<0.05) and over 60% higher than T3 (6.63 t-ha -1 ); and over 230% greater than T1 plot yields (3.20`t-ha -1 ). Analysis of the economic returns of the mulching technologies revealed a benefit-cost ratio of 2.31 and marginal rate of returns of 140 for T2, suggesting that this technology is dominant over T3 or T1 technologies and is therefore recommendable to irrigated onion farmers. ©2013 BluePen Journals Ltd. All rights reserved INTRODUCTION Mulching of agricultural fields with stones or organic materials is an agricultural strategy that dates back beyond ancient Egypt. For more than a thousand years, mulching has been used in several parts of the world to evade drought and increase crop yield (Dale and Lightfoot, 1996). The practice of mulching has been utilised to great advantage in the development of horticultural crops (Smolikowski et al., 2001; Meyer et al., *Corresponding author. E-mail: iiybaba@yahoo.com. Tel: +233 0244838574 /0209953817. 1970) and has been proven to significantly improve the growing conditions of vegetables grown in the tropics, including onions (Coleo et al., 1996; Abdal et al., 2000; Abu-Rayyan and Abu-Irmaileh, 2004). Mulch is any material placed on the soil surface to conserve moisture, lower soil temperatures around plant roots, prevent erosion and reduce weed growth. Mulches can be derived from either organic or inorganic materials (Meyer et al., 1970; Smolikowski et al., 2001; Rumpel et al., 2003). Mulching does not perform instant miracles, but it encourages better plant growth and development. These benefits accrue whether plants are growing in the coolest mountain conditions in Vietnam, the hot humid