Effect of Mineral and Organic Fertilizer on the Performance of Cassava (Manihot esculenta Crantz) in the Pissa region of the Central African Republic

Cassava (Manihot esculenta Crantz) is ranked the third most crucial tropical food crop contributing 32% of the world'sfood root and tuber production after potatoes, contributing 45% of the total to food security (FAOSTAT, 2016). This plant is widely cultivated and is the staple food of households in tropical and subtropical regions FAO (2014). Its starch-rich terrified roots are consumed. Also, the leaves are consumed as a vegetable in some countries (Celcos et al. (2012). Cassava is also suitable for industrial utilization and can be processed into flour, chips, starch, ethanol, and other non-food products (Balagopalan, 2009). In the last century, cassava has transitioned from a subsistence to a more commercial crop (Onyenwoke & Simonyan, 2014). Cassava is highly adaptable and can grow indifferent agroecological settings, and it can also grow on low-fertility soils and has the advantage of flexibility in harvest periods (El-Sharkawy, 2014). It can withstand prolonged droughts and erratic rainfall (Okogbenin et al., 2013). Therefore, it is considered a highly resilient crop in the face of current climatic changes (Jarvis et al., 2012). Thus, cassava can be crucial in tackling food insecurity and hunger in the face of climate uncertainty (Biratu et al., 2018).

In Africa, cassava is the second most important food source in terms of calories consumed per capita (Roothaert & Magado, 2011). Sub-Saharan Africa is the largest cassava producer globally: For instance, out of the 277 million tons produced worldwide in 2013, 158 million tons were from Africa (Bennett, 2015). Cassava is also the first food crop in the Central African Republic (CAR), which plays a vital role in household food security, especially in rural and urban areas. It is the staple food of more than 95% of Central Africans (Zinga et al., 2006). Central African agriculture remains the heart of economic development, employing 75% of the active population and contributing 45% of the Gross Domestic Product (GDP). The CAR wonderland enjoys a myriad of natural resources, comprising of vast arable land, covering about 15 million hectares, of which only 800,000 hectares are annually cultivated. Also, the average area cultivated per agricultural worker is 0.53 hectares; it has five zones within which cassava and other crops are cultivated, but the productions are not the same since each zone has specific characteristics. Despite all its resources, there is a considerable yield gap between actual productivity in farmers' fields and the potential cassava productivity (Ezui et al., 2016). The yield gaps between farmer and researcher-managed trials remain large; for instance, In Nigeria, Adiele et al. (2020) reported a root dry matter yield of 35 t ha-1 compared to 2.51 t ha-1 obtained on farmers' fields in Africa (De Souza et al., 2017).

Given its tolerance to various climatic stresses (El-Sharkawy, 2005), cassava is usually grown in nutrient-depleted soils with little or no input of fertilizer (Howeler, 2002), thus the low yields. Trials in Africa, Brazil, and India showed increased cassava root yield production with fertilizer application (FAO, 2013). Research in DR Congo (Munyahali et al., 2017) and Zambia (Biratu et al., 2018) has shown that fertilizer can improve cassava yield. Hence, bridging the yield gap lies on abetter understanding of soil organo-mineral fertilization.

Further, application of soil amendments at appropriate doses does not only increase crop yield but also preserves the soil'sproductive capacity during crop’sgrowth cycle (Palm et al., 2001; Akanza et al., 2001). Agricultural soils in some CAR regions have alow level of intrinsic fertility. This notwithstanding, the use of mineral and organic fertilizers on food crops in rural areas remains insignificant due to the low purchasing power of farmers and input scarcity in the market (Akanza and Yao – Kouamé, 2011). Organic resources play an essential role in soil fertility management, for instance, animal manure, a locally available resource, improves soil structure for easier root penetration and development. It can also contribute to long-term soil organic matter formation and improve soil biological properties (Blanchet et al., 2016). Additionally, nutrients contained inorganic manure are released more slowly and are stored for a longer time (Rani et al., 2022). However, cassava is an exhausting plant, given the mineral mobilizations that its cultivation entails at the end of the cycle (Pouzet, 1988; Raffaillac & Nedelec, 1984; Troupa & Koné, 2003). Therefore, sustaining cassava tuber production, which has been on the decline (IRAD, 2013), is dependent on the use of both organic and mineral fertilizers.

Previous studies conducted on cassava show that mineral elements such as N, P, K, Ca, and Mg are essential in increasing cassava tuber yield (Ngome et al., 2013). This calls for mechanized farming systems that use fertilizer among other inputs. On the contrary, little attention has been given to the potential of organo-mineral fertilization in combating soil fertility problems in cassava fields (Biratu et al., 2022). In the current study, we report on the potential of integrated management practices in improving cassava yield. The central hypothesis is that cow manure and mineral fertilizer will achieve higher cassava yields than the sole application.