Abstract
Soil water deficit is a major production-limiting factor in the predominantly rainfed agriculture of the Ruzizi plain, eastern Democratic Republic of Congo (DRC). Appropriate soil and water conservation (SWC) practices would be a valuable option for maximizing water uptake by plants in the context of water demand and supply unbalance. This study assessed the efficiency of selected SWC practices in improving water and nutrient (nitrogen and phosphorus) balances along the slope gradients in Ruzizi plain using a three-season field experiment. The SWC practices, tied ridges and Zaï pits, improved the cumulative soil water balance by 148.7 and 21.1%, respectively, compared to conventional tillage. In the same order, the maize (Zea mays L.) yield performance significantly varied with SWC practices: tied ridges (2.16 t ha-1) out performed the Zaï pits (1.48 t ha-1) and conventional tillage (1.58 t ha-1). Besides, the tied ridges reduced the total nitrogen losses by 34.4–49.8%, compared to conventional tillage. However, SWC practices were only reliable when daily rainfall amounts were at reasonable threshold (>10 mm) and on low slope gradients (<8%). Therefore, tied ridges provide an opportunity as a component of an integrated soil water and nutrient management strategy to sustain the rainfed maize production in Ruzizi plain. Key words: Tied ridges, Zaï pits, rainfall variability, slope gradient, dryland, Zea mays L.
Highlights
The Zaï pits differed from the conventional tillage only for the surface runoff (15.83 vs. 18.92%)
This study assessed the effects of soil and water conservation (SWC) practices on soil water and nutrient balances along the slope gradient in the Ruzizi plain
Tied ridges provided a high cumulative soil water balance, reduced frequency of days with water deficit, and the surface runoff. This translated in high maize yield on this SWC practice compared to Zaï pits and conventional tillage
Summary
Rainfed agriculture covers 80% of the world's cultivated land and contributes ~60% of the global crop production. In sub-Saharan Africa (SSA)’s drylands, soil water and nutrient deficits are major production-limiting factors (Cofie and Amede, 2015). Water deficit is often associated with erratic rainfall, high evapotranspirative demands (ETP) and inadequate soil water management practices (Alexandris et al, 2008; Ndehedehe et al, 2018). Low soil fertility stems mainly in the low use of external inputs and overexploitation of lands. These regions are consistently food insecure as a result of the food demand and production unbalance
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