No abstract

Current rise in concentration of tropospheric ozone (O 3 ) has deleterious effect on growth and yield of crops. Wheat is one of the most O 3 sensitive crops. Application of Chemical antioxidants may be beneficial to lessen the harmful effects of O 3 on crops. A two year study growing wheat (variety PBW550) was carried at the farms of Indian Agricultural Research Institute, New Delhi in 2010-11 and 2011-12 to evaluate the efficacy of some natural and environment friendly antioxidant chemicals in ameliorating the negative impacts of elevated ozone on growth and productivity of wheat. The treatments were i) charcoal filtered air (CF) ii) 1% ascorbic acid (AA), iii) 100 ppm quercetin (Q), iv) 10% marigold leaves extract (Tagetes patula var pusa arpita) (T) and v) elevated O 3 control (C). Additional 25-35 ppb of O 3 over the ambient levels was maintained in all open top chambers except the CF treatment. The seasonal daily average O 3 concentration in ambient air was 38 ppb in 2010-11 and 29 ppb in 2011-12 during the crop growth period. The exogenous application of antioxidants increased the levels of endogenous leaf ascorbic acid. The activity of antioxidant enzymes (superoxide dismutase, catalase and peroxidase) was lowered by 5 to 34% in antioxidants sprayed plants as compared to elevated O 3 control (C). The application of antioxidants increased the yield of wheat by 23-26% in AA, 13-15% in Q and 8-10% in T as compared to C. The micronutrient (Cu, Fe, Zn and Mn) content of wheat grains on application of exogenous ascorbic acid was higher. The application of antioxidant chemicals was effective in alleviating the negative impacts of elevated O 3 on enzyme activity and nutritional quality of wheat which increased the growth and yield of the crop.

SUMMARYA field experiment was carried out at the farm of Indian Agricultural Research Institute, New Delhi to quantify the effect of elevated carbon dioxide (CO2) and different levels of N fertiliser application on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from soil under maize. The experiment included five treatments: 60 kg N ha−1 under ambient CO2 (385 ppm) in open plots, 120 kg N ha−1 under ambient CO2 (385 ppm) in open plots, 160 kg N ha−1 under ambient CO2 (385 ppm) in open plots, 120 kg N ha−1 under ambient CO2 (385 ppm) in open top chambers (OTC) and 120 kg N ha−1 under elevated CO2 (500 ± 50 ppm) in the OTC. Peaks of N2O flux were observed after every dose of N application. Cumulative N2O emission was 13% lower under ambient CO2 as compared to the elevated CO2 concentrations. There was an increase in CO2 emissions with application of N from 60 kg ha−1 to 160 kg ha−1. Higher yield and root biomass was observed under higher N treatment (160 kg N ha−1). There was no significant increase in maize yield under elevated CO2 as compared to ambient CO2. The carbon emitted was more than the carbon fixed under elevated CO2 as compared to ambient CO2 levels. The carbon efficiency ratio (C fixed/C emitted) was highest in ambient CO2 treatment in the OTC.