Legume integration in smallholder farming systems for food security and resilience to climate change

PLOS One | https://doi.org/10.1371/journal.pone.0327727 August 13, 2025 9 / 20 Many farmers apply urea, diammonium phosphate (DAP), or blended NPSB to enhance their crop yield and sustain soil fertility (refer to Table 3). A diverse spectrum of chemical fertilizer applications (ranging from 0 kg to 100 kg per hectare) was reported within the region, with some exceptional instances surpassing 100 kg/ha (illustrated in Fig 2. tif). In general, the predominant proportion of farmers utilized 50 kg of fertilizer per hectare, whereas a minority resorted to using 120, 150, 200, or 300 kg of fertilizer per hectare. An inadequate amount of fertilizers (<50 kg/ha) was observed among farmers from the Gamo zone. Notably, an extraordinary application of 200 or 300 kg of fertilizer per hectare was recorded in South Omo. Despite the reported suboptimal agricultural outputs, the majority of households (77.10%) incor- porated urea into their farming practices. As shown in Fig 2, those farmers applied exceedingly small (mostly <50 kg/ha) quantity of fertilizer that might not contribute to the yield. However, as indicated above, application rates remain significantly below the required level. The HHs from the high- lands believed that their farms had good soil fertility, but the yield reported was lower than the farmers who believed that their farms had moderate soil fertility but that productivity could be increased by hiring labor. The use of organic and chemical fertilizers did not result in significantly higher yields compared to farmers who did not

adopt these agricultural practices. However, the application of chemical fertilizers generally enhanced productivity, with the exception of treatments involving NPSB, which did not exhibit a positive effect. Interestingly, 62% of the farmers had plain land and produced 3.61 tons of mean farm product per hectare, which was 1.05 tons higher yield than the yield from valley lands. Some farmers reported using fertilizers against legumes, but their yield was lower than those who did not use fertilizers. The key objective of this study was to know about the use of rhizobia inoculants in the region and only 3% of the farmers heard about it but they never used it. Some HHs reporting no problems with weeds, pests, diseases, and droughts on their farms and they had better farm products. Briefly, challenges encountered on farms more importantly affected the yield of the farmers than the effects of using fertilizers and employing labor. Diversity of crop on farm and farmer’s priority crop It has been a long time since intervention was introduced to farms to improve farm productivity in sub-Saharan Africa. One of such interventions was farm intensification that focused on introducing crop diversification on farms. To understand the diversity of crops growing in smallholder farmers’ field and priority crops of the households, farmers were asked to list type of crops ever grown on their farm. More than 20 crops were recorded, of which maize, sorghum, wheat, barley and teff were reported as the first five priority crops on the farm (Fig 3. tiff).

It was recognized that the cereal crops were the primary crops grown on the farms across the study area (with some exceptions) while the legumes become the second priority crops. Among the legumes, common bean was the number one crop among the second and third priority crops. It was succeeded by sorghum, teff, and maize. The dominance of the common bean as the second and third priority crops would reflect its longtime adoption in the region. The degree of legume intensification within the region was notably suboptimal. Only 16.41% of farmers apply chem- ical fertilizers in conjunction with local legume varieties (refer to Table 3). Conversely, a respectable number of farmers cultivated improved seed varieties without the application of fertilizers on their farms. Among the improved common bean varieties, Nasir, Red Wolayta, Acos, Hawassa Damue, and Sari119 were identified, whereas the maize varieties BH540, BH541, and BH548, along with the sorghum varieties Mirti Zer, Merera, and Gudina, were acknowledged by the farmers. These improved seed varieties were released by agricultural research centers and subsequently introduced to the farming community by agricultural extension agents. 98% of the respondents confirmed that with improved varieties application of fertilizers boosts crop yields. Legume production and potential in the region The primary objective of this research was to ascertain the potential for legume production and its challenges and evalu-

ate the application of rhizobium inoculant (biofertilizer) in enhancing the quality of legume crops in the study site (Fig 4. tiff.