Nutrient Utilization and Yield Response of Lentil (<i>Lens culinaris</i> Medikus) to <i>Rhizobium</i> Inoculant and Sulphur Fertilization

Abstract

Lentil (Lens culinaris Medikus) is a major food crop in Ethiopian. It is affordable protein source and important in sustaining soil fertility through nitrogen fixation. However, its current national productivity of 1.46 t ha-1 is lower than its potential due to inadequate agronomic management practices, nutrient imbalance and lack of indigenous or commercial Rhizobium strains of lentil. Therefore, the field experiment was conducted at Ada'a district under rain-fed condition during 2016/17 main cropping season to assess the role of S and Rhizobium inoculant on nodulation, nutrient utilization and yield response of lentil. The experiment consisted of three levels of S (0, 20 and 40 kg ha-1) and Rhizobium inoculant (un-inoculated and inoculated) in a factorial combination using Alemaya lentil variety as a test crop. The experiment was conducted using randomized complete block design with three replications. The result showed the interaction of sulphur fertilization and Rhizobium inoculant were significant on days to flowering, number of nodules plant-1 , nodule dry weight plant-1 , number of seeds pod-1 , aboveground dry biomass, seed yield, seed S uptake, haulm S uptake, total S uptake, sulphur agronomic and recovery efficiency as well as sulphur harvest index. Application of 40 kg S ha-1 without Rhizobium inoculant led to produce the highest seed yield (2.27 t ha-1) and delayed days to flowering (46 days) of lentil whereas, the highest nodule dry weight plant-1 (1.1mg) and sulphur harvest index (17.68%) were obtained at the rate of 40 kg S ha-1 under Rhizobium inoculations. On the other hand the maximum number of nodule plant-1 (15.60), number of seed pod-1 (1.99), total aboveground dry biomass (8.22 t ha-1), Sulphur agronomic efficiency (32.11kg ha-1), sulphur recovery efficiency (66.00 kg ha-1) were obtained in response to sulphur application at 20 kg ha-1 under Rhizobium inoculations. Moreover, Rhizobium inoculation without S fertilization gave the highest seed (3.88kg ha-1), haulm (23.33kg ha-1) and total S uptake (24.89 kg ha-1). Rhizobium inoculation without S application had high net benefit, relatively low variable cost with an acceptable and maximum MRR for lentil production in Ada'a district. However, since the experiment was conducted only for one season and one site, repeating the trial at different sites as well as in the same trial site would be important in order to draw sound recommendation.