Profitability of diammonium phosphate use in bush and climbing bean-maize rotations in smallholder farms of Central Burundi

Abstract

A B S T R A C TSoil fertility decline is a major constraint to bean (Phaseolus vulgaris L.) and maize (Zea mays) production in the Central Highlands of Burundi. Nutrient sources, specifically fertilizers, are paramount to increasing the production in the regions. Hence, improving fertilizer use efficiency is considered as a key factor towards sustainable intensification. The use of grain legumes with low harvest indices, such as climbing beans, are assumed to improve soil fertility and fertilizer use efficiency. This study compares the rotational effects of bush and climbing bean varieties on maize and evaluates the profitability of diammonium phosphate (DAP, fertilizer in the bean-maize rotations in 59 smallholder farms of Mutaho district, Gitega Province in Central Burundi. The application of DAP fertilizer significantly increased the grain yields by 14% and 21% for bush and climbing beans, respectively (P < 0.001). Positive effects of bean varieties were large for about 80% of the farmers. Climbing beans in general yielded more than bush beans for about two thirds of the farmers and fertilizer effects were positive. In the bean-maize rotations, the fertilizer induced on average a yield increase of 8% and 22% for maize following bush and climbing beans, respectively. Maize grain yields were significantly (P < 0.001) higher following climbing beans than following bush beans. The value cost ratio (VCR) more than doubled compared with the common practice (bush bean-maize rotation). Variation was substantial, and for approximately 67% of the farmers, DAP application was profitable (VCR > 2 $ $ −1 ) in a climbing bean-maize rotation while 45% of the farmers in a bush bean-maize rotation. Regression tree analysis showed that targeting fertilizer use to soils with higher C and clay content, and ensuring timely planting are the predominant factors to ensure fertilizer response and profitable returns. This study confirms the need for integrated soil fertility management (ISFM), and that a combination of judicious fertilizer use, an improved grain legume (climbing bean) and adjustment to local conditions (targeting to responsive soils) maximizes economic returns of legumecereal rotation systems.

2020 Annual trends and outlook report: Sustaining Africa's agrifood system transformation: The role of public policies

“…A recent review of MVCR estimates for maize plots in Africa indicates that fertilizer use is either unprofitable or only marginally profitable in many contexts . Similar studies on profitability of fertilizer application on maize farms arrive at similar conclusions for farms in Benin (Tovihoudji 2018), Burkina Faso (Theriault, Smale, and Haider 2018), Burundi (Niyuhire et al 2017), Ethiopia (Rashid et al 2013), Ghana (Ragasa and Chapoto 2017), Nigeria (Liverpool-Tasie 2017), Tanzania (Mather et al 2016), and Zambia (Burke, Thom, and Black 2017). Factors correlated with returns to fertilizer use include agroecological context and production systems (for example, irrigated versus rainfed, high-potential versus fragile production zones) and soil characteristics (for example, soil pH levels).…”

The response of climbing bean to fertilizer and organic manure in the Northern Province of Rwanda

“…The differences in yields observed could be linked to differences in past management practices among the participating farmers. Increased yield of climbing bean when organic and inorganic fertilizers are combined has been reported elsewhere (Niyuhire et al, 2017). Manure is reported to increase the crop yield and responses to applied fertilizers (Rurangwa et al, 2018), and past manure application was identified as the most factor affecting yields and yields response to applied fertilizers (Njoroge et al, 2019).…”

“…The indeterminate growth of climbing beans allows them to provide a continuous supply of green leaves and pods as well as dry grain throughout the growing season (Sperling and Muyaneza, 1995;Wortmann et al, 2001). Strong residual effects have been reported when maize is grown after climbing bean, which are attributed to the large amounts of above-and belowground crop residues (Niyuhire et al, 2017), changes in microbial activities (Turco et al, 1990), and access to more P (Bainville et al, 2005). Climbing beans also provide valuable residues for livestock feed.…”

Assessing intensification options of common bean cultivation to improve food security on smallholder farms in the Northern Highlands of Tanzania

“…Previous studies have also indicated that other rotational benefits are derived from the improvement of soil properties and increase in mycorrhizal infection as well as shielding against disease and pests to the subsequent maize crop (Argaw et al, 2015;Gan et al, 2015;Munishi et al, 2015). The findings of the present study are also consistent with studies conducted elsewhere (Wahbi et al, 2016;Niyuhire et al, 2017). Kamanga (2002) pointed that the subsequent cereal crop utilizes at least 50% of the N returned to the soil through the incorporation of dead and decomposed legume residues over the growing season.…”