The critical period of weed interference in one variety of chickpea was determined in field experiments carried out at two sites, Tabriz 2002 and Kermanshah 2003, Iran. Chickpea culture was either kept free of weeds for 0, 12, 24, 36, 48 and 60 days after crop emergence (DAE) or weeds were allowed to grow for 0, 12, 24, 36, 48 and 60 DAE. In these experiments, chickpea yield increased with increasing duration of weed-free period and was reduced by increasing duration of weed-infested period. Unweeded conditions for the entire growing season caused 66.4% and 48.3% seed yield reduction when compared with the treatment that was weed-free throughout the growing season, at Tabriz 2002 and Kermanshah 2003, respectively. The results indicated that chickpea must be kept weed-free between the five-leaf and full flowering stages (24-48 DAE) and from the four-leaf to beginning of flowering stages (17-49 DAE) at the two sites, respectively, in order to prevent >10% seed yield loss. At both sites, reduction in seed yield, because of the increased weed interference period, was accompanied by simultaneous reduction in plant dry weight, number of branches, pods per plant and 100-seed weight. This was supported by significant and positive correlations between these traits and chickpea seed yield. There was no significant correlation between the number of seeds per pod and seed yield. A linear regression model was used to describe the relationship between weed dry weight and seed yield loss.

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In order to investigate the effects of salinity on the early seedling growth of chickpea, four chickpea cultivars, Jam, Hashem (kabuli type: large seeded genotypes with light salmon colour), Kaka and Pirooz (desi type: small seeded genotypes with different colours), were grown in pots containing soils with 0.9 (control), 2.6 and 4.9 dSm -1 salinity. The shoot/root ratio of Pirooz was consistently reduced by increasing salinity at all sampling stages. Under saline conditions, the reduction in seedling growth, shoot water content, root and shoot K + concentration and the increase in root and shoot Na + concentration were more severe in the kabuli type than in desi type cultivars. Considering path coefficients, increasing seedling K + concentration and uptake of water from the soil favoured salt-stressed seedling growth. Increasing K + content alleviated the deleterious effects of root Na + to a greater extent than that of shoot Na + . On the other hand, a higher percentage of the decrease in seedling growth as the result of Na + was due to shoot K + deficiency than to root K + deficiency.