Effect of Pesticide Residues (Sevin) on Carrot (Daucus carota L.) and Free Nitrogen Fixers (Azotobacter spp)
Since the pesticides are considered as an essential component for crops production through controlling pests, they have shown a negative effect on crops and soil environment when used intensively. This experiment was conducted at Wadi Soba farm (Sharq Elneel) Khartoum, Sudan. It aimed to study the effect of Sevin residuals on carrot growth and Azotobacter spp. colonies growth. Carrot planted in late February 2013, Sevin pesticide (2.5 L/ha and 5 L/ha) was added to estimate plant height, dry weight, the number of plant leaves and the number of Azotobacter spp. colonies isolated from the carrot rhizosphere (0 - 15 cm). The obtained results showed that the Sevin recommended dose (2.5 L/ha) relatively had a positive effect on the plant height, dry weight, and the number of plant leaves. The average of plant height for recommended dose was 59.67 cm compared to control (53.67 cm) and high dose (27.33 cm). The average of plant dry weight obtained by the recommended dose was 503.33 g and for control was 476.67 g and for high dose was 166.7 g, it decreased 67% from control and recommended dose. The average of plant leaves number were 25.34, 13.66 and 21.33 for recommended dose, high dose and control respectively, the number of leaves increased about 16% by recommended dose and decreased 35% by high dose. The average of Azotobacter spp. colonies obtained by high dose of Sevin demonstrated a lower numbers which were 20 × 104, 5.67 × 106 and 0.33 × 108 compared with control (78.33 × 104, 44 × 106 and 15.33 × 108) and the recommended dose (64 × 104, 33 × 106 and 7 × 108). The high dose of Sevin had a negative effect on both carrot growth and Azotobacter spp. colonies growth.