Investigating water availability for introducing an additional crop yield in dry season on hill land at Rubirizi, Rwanda Narayanan Kannan a, *, T. Senthivel b , A.J. Rayar a , Mutesa Frank a a Higher Institute of Agriculture and Animal Husbandry, Busogo, B.P. 210, Ruhengeri, Rwanda b Gandhigram Rural University, Gandhigram 624 302, Dindugal District, Tamil Nadu, India 1. Introduction Flow of adequate food supplies to meet rising demand is increasingly threatened by climate change and land degradation due to soil erosion. According to the United Nations, the present world population stands at about 6.3 billion and with an average annual growth rate of 1.3%, this population is estimated to reach 8 billion in 2025 (United Nations Population Reference Bureau, 2004). Majority of the world’s population lives in the emerging and least developed countries. The increase in numbers of mouths to be fed and the improving diet requirement is increasing the food demands. The main challenge in this regard remains how to double the global food production in general and in Asia and Africa in particular in the next 25 years. Though total area in the world is 13,390 Mha, very little of the land surface – nearly 1500 Mha (11%) – is currently used for agriculture. The potentially cultivable land is estimated at about 3000 Mha. The land which is fertile and suitable for cultivation had already been brought under the plough. The land which can be brought into production will not be as fertile and productive as the land currently under cultivation. Therefore, a doubling of production can be achieved only by suitable strategies of soil and water conservation and water management and by improving soil fertility. The total irrigated area in the world is about 260 Mha or about 17% of the cultivated area, of which two- thirds is in the developing countries. Such lands are marginal, spread over poorly productive environments and with meagre production capabilities, thus limiting the scope for increasing production. Water conservation techniques involving and in situ moisture conservation techniques and engineering measures need to be emphasized for feasible adoption in rain-fed agriculture to increase land productivity. In sub-Saharan Africa, over 60% of the population depends on rain-based rural economics, generating about 30–40% of the regions’ GDP (World Bank, 1997). Rain-fed agriculture is practiced on approximately 95% of agricultural land, with only 5% under irrigation (Rockstrom et al., 2002). However in this part of the world, yields from rain-fed agriculture are low, oscillating around 1 tonnes/ha (Rockstrom, 2001). Many researchers suggest that the low productivity in rain-fed agriculture is more due to sub-optimal performance related to management aspects than to low physical Agricultural Water Management 97 (2010) 623–634 ARTICLE INFO Article history: Received 6 April 2009 Accepted 29 November 2009 Available online 24 December 2009 Keywords: Soil moisture conservation Crop water demand Water availability Efficiency Irrigation Maize ABSTRACT The study explores the potential of introducing an additional crop during dry season in Rwanda, comparing the efficiency of in situ soil moisture conservation techniques to sustain rain-fed agriculture. Comparative study of in situ soil moisture conservation techniques in bench terraces and unterraced field with maize crop had been conducted from June 2007 to October 2007. Bench terrace increased the average soil moisture content in 90 cm soil depth by more than 50% than that of unterraced land. Within the bench terraced field compartment bund and ridges and furrows increased soil moisture by 19.5% and 27.9% higher than plain bed. In terms of efficiency of moisture conservation, ridges and furrows performed well with 85.8% followed by compartment bund with 75.9% in terraced field. Unterraced field conserved moisture very poorly with 13.9% efficiency inferring importance of bench terraces for soil moisture conservation. No maize grain yield was recorded in all the techniques because soil water depleted to 60% and above from the beginning of the cropping period inferring the need of supplementary irrigation. Analysis of rainfall, crop water demand and in situ moisture conservation reveals exciting opportunities for water productivity enhancements by integrating components of water management within the context of rain-fed farming through water harvesting and supplemental or microirrigation for dry spell mitigation. Detailed analysis is needed for feasibility of lift irrigation with different crops under different altitudes to derive suitable policy for hill land irrigation. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: kannan051968@yahoo.co.in (N. Kannan). Contents lists available at ScienceDirect Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat 0378-3774/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2009.11.011