Date Published: July 01, 2018
Author(s): Endalkachew Wolde-meskel, Joost van Heerwaarden, Birhan Abdulkadir, Sofia Kassa, Ibsa Aliyi, Tulu Degefu, Kissi Wakweya, Fred Kanampiu, Ken E. Giller.
•On MPN assessment, native rhizobium population size on the study site was less than 10 cfu g−1 of soil.•On a wide range of on-farm trials, inoculation (I) increased chickpea grain yields for 99% of target farmers.•I and P fertilizer in combination, resulted on average, in a 38% yield increase over the control plots.•Variation in response to rhizobium inoculation was mostly independent of agro-ecology and soil type.•Rhizobial inoculation offers a cheap and highly effective means for the sustainable intensification of smallholder agriculture.
Chickpea (Cicer arietinum L.) is globally the third most important food legume after common bean and soybean (Namvar and Sharifi, 2011). It is widely cultivated by smallholders in Mediterranean and semi-arid climates but in Africa is largely restricted to the cool highlands of Ethiopia (Anbessa and Bejiga, 2002). However, it also grows in Sudan under irrigation and rain-fed systems and is an increasingly important crop in Tanzania. In 2014, Ethiopia produced almost 60% of Africa’s total chickpea (FAOSTAT, 2014; Ojiewo, 2016). The total area of chickpea in Ethiopia has increased from 168,000–230,000 ha over the past decade (CSA, 2014), with desi varieties grown mainly for the local market and the larger seeded, Kabuli varieties largely for export. Yet productivity of chickpea remains low, with national average yield of 1.7 t ha−1 (BTL, 2013; FAOSTAT, 2014; CSA, 2016, CSA, 2017), far below the potential yield of 4–5 t ha−1 reported on experimental stations (Bejiga and van der Maesen, 2006; Fikre, 2016).
On a wide range of on-farm trials, covering diverse agro-ecological locations over four regions in Ethiopia, inoculation and P fertilizer application increased chickpea grain yields. Despite considerable and seemingly random variation, the response to these inputs was consistently positive. Yields were greatest when both I and P were applied together in combination, with an average increase of 38% over the control plots. No compatible chickpea rhizobia were detected in half of the soil samples tested while the population was less than 10 cfu g−1 of soil in the remainder, explaining why inoculation benefits chickpea growth and yield. Thus, inoculation, alone or in combination with P, enhanced the nodulation of chickpea, stimulated nitrogen fixation and increased N uptake. This is the first time that the benefits of rhizobial inoculation for enhanced nitrogen fixation and yield of chickpea have been demonstrated across large numbers of smallholder farms in Africa. Together with small amounts of P fertilizer, rhizobial inoculation offers a cheap and highly effective means for the sustainable intensification of smallholder agriculture.