Analysis of soil moisture conservation techniques with dry season maize crop on hill land at Rubirizi, Rwanda

Abstract

Rwanda is an agriculture based country where crop production is carried out under rain fed situation with wide range of agro climatic conditions. Field experiments were conducted with in-situ soil moisture conservation techniques in bench terraces and unterraced field by using maize crop variety Kathumani from June 2007 to October 2007 by involving three land management practices viz. ridges and furrows, compartmental bunding and control. The study explores the best technical option to resolve the constraints related to water management in rainfed farming in Rwanda. Insufficient rainfall during dry season attracts the need of water harvesting and soil moisture conservation. The study is based on weekly soil moisture analysis in 90cm soil depth. Analysis of rainfall and crop water demand indicates that it is inevitable to provide supplemental irrigation and in-situ moisture conservation for successful crop. Bench terrace increased the average soil moisture content in 90cm soil depth by more than 50 per cent than that of unterraced land. Within the bench terraced field compartmental bunding increased soil moisture by 18.2 per cent higher than plain bed (control) with a coefficient of variation of 20.6 per cent and ridges & furrows increased by 27.8 per cent with coefficient of variation of 29.3 per cent. This indicates that in-situ moisture conservation measures are effective to increase soil moisture compared to plain bed. It is also found that mean soil moisture fluctuation in the soil profile is moderately more at 60cm depth compared to 30 cm irrespective of type of conservation techniques. Performance of ridges & furrows, compartmental bunding and plain land (control) was evaluated in terms of soil moisture conservation. The study reveals that Compartmental bunding performed well in both 30cm and 60cm soil depths followed by ridges & furrows because of consistent soil moisture as evidenced by less coefficient of variation. Higher moisture content in these two techniques is due to water barrier to harvest rainwater. Average soil moisture content for compartmental bunding and ridges & furrows varied between 16 to 17 per cent at both 30cm 60 cm soil depths and 13 per cent for plain bed (control). In all the three techniques, actual soil water during the entire cropping period remains below field capacity posing soil moisture stress. The maize yield was very poor in all the techniques because the soil water depleted to 60 per cent and above from the beginning of the cropping period inferring the need for supplementary irrigation. Plain bed (control) exhibited lowest degree of fluctuation of deficit water indicating poorly influenced by rain fall as compared to ridges & furrows and compartmental bunding. In terms of efficiency of moisture conservation during the cropping period, ridges & furrows performed well with 85.8% followed by compartmental bunding with 75.9 per cent in terraced field. Unterraced field with 15 per cent slope conserved moisture very poorly with 13.9% efficiency inferring importance of bench terraces for efficient soil moisture conservation. Performance of different in-situ moisture conservation practices were analyzed in terms of available water, deficit water, crop water and its effect on maize yield was discussed in this paper.