Influence of tied-ridge-furrow with inorganic fertilizer on grain yield across semiarid regions of Asia and Africa: A meta-analysis

Abstract

Background: In semiarid areas, low productivity of crops has been attributed to lack of appropriate soil moisture conservation practices since droughts and soil erosion are rampant in most areas of this region. Consequently, ridge-furrow rainwater harvesting is widely used in these regions across the globe. Despite ridge-furrow being widely practiced, tied-ridge-furrow has not been extensively adopted by small-scale farmers in semi-arid regions. Consequently, the effectiveness of tied-ridge-furrow as a viable method of increasing crop yield has received less attention.

Methodology: For large-scale implementation, a detailed assessment of how ridge furrow, tied-ridge-furrow with fertilizer, tied-ridge-furrow with mulching and tied-ridge-furrow without mulching or fertilizer influence crop yield in different agro-environments under varying climatic conditions is needed. This study used the PRISMA guidelines to determine the impact of tied-ridge-furrow rainwater harvesting technique with mulching or fertilizer on sorghum (Sorghum bicolor) and pearl millet (Pennisetum glaucum) grain yields.

Results: Sorghum grain yield increased by 17% greater in tied-ridge-furrow without mulching or fertilizer in comparison to flat planting. This may be due to increase in soil organic carbon in the region (9 g kg^-1). Grain yield of millet significantly increased by 20-40% in Africa from 18 study observations in tied-ridge-furrow with fertilizer application as compared to tied-ridge-furrow without mulching or fertilizer treatments. This might be due to the significant increase in total nitrogen by 13-42% in the soil at <50 mg kg^-1 quantity which had an effect size of 469.14 [65.60, 872.67]. In terms of soil texture, grain yield of millet and sorghum significantly increased in heavy textured soils (clay loam, silt clay, and clay soils) with an effect size of 469.14 [65.60, 872.67] compared to light and medium-textured soils of zero effect sizes. Millet and sorghum grain yields in tied-ridge-furrow with mulching, on the other hand, were not significantly different from those in flat planting. This may be due to the mulching materials used in those tests.

Conclusion: In view of yields of sorghum and millet increased significantly by 32% and 17% in tied-ridge-furrow without mulching or fertilizer treatment compared to flat planting and tied-ridge-furrow with fertilizer treatment compared with tied-ridge-furrow without mulching or fertilizer treatment, respectively, this study recommend the use of fertilizers in a tied-ridge-furrow system to increase grain yield in semiarid areas compared to flat planting. Again, the study recommends more research on tied-ridge-furrow systems with other organic mulches and fertilizers in semiarid areas.

Keywords: Fertilizer; Grain yield; Mulching; Rainwater harvesting; Tied-ridging.

Figure 1. Flowchart of literature identification, and screening for use in this study. Adapted from PRISMA (Moher et al., 2009).

Figure 2. Experimental locations from the peer-reviewed publications in Ethiopia for the meta-analysis. ArcGIS 10.6 software (ESRI, Redlands, California) was used to produce the map.

Figure 3. Experimental locations from the peer-reviewed publications in Nigeria for the meta-analysis. ArcGIS 10.6 software (ESRI, Redlands, California) was used to produce the map.

Figure 4. Experimental locations from the peer-reviewed publications in China for the meta-analysis. ArcGIS 10.6 software (ESRI, Redlands, California) was used to produce the map.

Figure 5. Odds ratios of crop yields in (A) flat planting compared to tied ridge. (B) tied ridge compared to tied ridge with fertilizer. The error bars signify 95% confidence intervals, and the values above the bars indicate the number of observations (n).