Influence of nitrogen fertilization and isoxaflutole on the nodulation of chickpea ('Cicer arietinum')

The effects of soil nitrate and the herbicide, isoxaflutole, on chickpea nodulation were examined in a glasshouse experiment. The treatments consisted of one isoxaflutole-tolerant and one isoxaflutole-sensitive chickpea cultivar, five nitrate concentrations (0, 0.75, 1.5, 3.0, and 6.0 mmol Lˉ¹), and three herbicide rates (0.75 [the recommended rate], and 300 g haˉ¹). The sensitive cultivar was more susceptible to isoxaflutole damage with an increasing herbicide rate and nitrate concentration, compared with the tolerant cultivar. Isoxaflutole at the recommended rate reduced the nodule dry weight of the sensitive cultivar by 51% and by 33% in the tolerant cultivar. The nodule dry weight of the sensitive cultivar was reduced by 28%, 40%, 64%, and 76% with the addition of the 0.75, 1.5, 3.0, and 6.0 mmol Lˉ¹ nitrate concentrations, respectively. In comparison, the nodule dry weight of the tolerant cultivar was reduced by 50% and 79% at the 3.0 and 6.0 mmol Lˉ¹ nitrate concentrations, respectively. In addition, the level of damage from increasing rates of isoxaflutole increased with the highest nitrate concentrations of 3.0 and 6.0 mmol Lˉ¹, regardless of the cultivar. Isoxaflutole at the recommended application rate had a detrimental effect on the nodulation of both chickpea cultivars, but the isoxaflutole-tolerant cultivar suffered less injury than the sensitive one in relation to some growth parameters. The damage to chickpea from the recommended rate of isoxaflutole also increased with soils of higher nitrate content.