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 ...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.展开更多
Due to infrequent rainfall, high temperatures, and degraded land, the Sahel region often suffers from droughts. The Sahel region is considered as one of the world’s driest and extreme environmental conditions. In ord...Due to infrequent rainfall, high temperatures, and degraded land, the Sahel region often suffers from droughts. The Sahel region is considered as one of the world’s driest and extreme environmental conditions. In order to assess spatiotemporal vulnerability of potential drought impacts, we used remote sensing and ground station data to evaluate drought conditions in the Sahel region from 1985 to 2015. The standard precipitation index(SPI), standard precipitation evapotranspiration index(SPEI), vegetation condition index(VCI) anomaly, along with socioeconomic indicators were performed. In addition, Pearson correlation coefficient(PCC) was computed between drought indices and three main crops(sorghum, millet, and maize) in the region to estimate the effects. The analysis showed that temperature increased by 0.78°C from 1985 to 2015, which had a significant impact on crop yield for sorghum, maize, and millet with a statistical significance value of P > 0.05. In the decade spanning 1994 to 2005 alone, the temperature increased by 0.57°C, which resulted in extreme drought in Algeria, Sudan, Chad, Nigeria, and Mauritania. For the effect of drought on crop production, high significance was noted on the SPI and SPEI-3 timescale: sorghum with SPI-3(r = 0.71) and SPEI-3(r = 0.65), millet with SPI-3(r = 0.61) and SPEI-3(r = 0.72), and maize with SPI-3(r =0.81) and SPEI-3(r = 0.65) during the study period. In the growing season, VCI anomaly had strong correlations with sorghum and millet(r = 0.67 and 0.75, respectively). A significant agreement was also noticed between the combined drought index(CDI) and vulnerability index(VI) in Burkina Faso(r =-0.676;P < 0.00), Mali(r =-0.768;P < 0.00), Mauritania(r = 0.843;P < 0.001), Niger(r =-0.625;P < 0.001), and Nigeria(r =-0.75;P < 0.005). The results show that the above indices are effective in assessing agricultural drought and its impact on crop production in the Sahel, and in identifying areas most affected by drought.展开更多
文摘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.
基金Supported by the National Key Research and Development Program of China(2019YFC1510203 and 2018YFC1506502)Fundamental Research Funds for Central Non-profit Scientific Institution(1610132020014)Open Fund of State Key Laboratory of Remote Sensing Science(OFSLRSS201910)。
文摘Due to infrequent rainfall, high temperatures, and degraded land, the Sahel region often suffers from droughts. The Sahel region is considered as one of the world’s driest and extreme environmental conditions. In order to assess spatiotemporal vulnerability of potential drought impacts, we used remote sensing and ground station data to evaluate drought conditions in the Sahel region from 1985 to 2015. The standard precipitation index(SPI), standard precipitation evapotranspiration index(SPEI), vegetation condition index(VCI) anomaly, along with socioeconomic indicators were performed. In addition, Pearson correlation coefficient(PCC) was computed between drought indices and three main crops(sorghum, millet, and maize) in the region to estimate the effects. The analysis showed that temperature increased by 0.78°C from 1985 to 2015, which had a significant impact on crop yield for sorghum, maize, and millet with a statistical significance value of P > 0.05. In the decade spanning 1994 to 2005 alone, the temperature increased by 0.57°C, which resulted in extreme drought in Algeria, Sudan, Chad, Nigeria, and Mauritania. For the effect of drought on crop production, high significance was noted on the SPI and SPEI-3 timescale: sorghum with SPI-3(r = 0.71) and SPEI-3(r = 0.65), millet with SPI-3(r = 0.61) and SPEI-3(r = 0.72), and maize with SPI-3(r =0.81) and SPEI-3(r = 0.65) during the study period. In the growing season, VCI anomaly had strong correlations with sorghum and millet(r = 0.67 and 0.75, respectively). A significant agreement was also noticed between the combined drought index(CDI) and vulnerability index(VI) in Burkina Faso(r =-0.676;P < 0.00), Mali(r =-0.768;P < 0.00), Mauritania(r = 0.843;P < 0.001), Niger(r =-0.625;P < 0.001), and Nigeria(r =-0.75;P < 0.005). The results show that the above indices are effective in assessing agricultural drought and its impact on crop production in the Sahel, and in identifying areas most affected by drought.