Photosynthetic responses of canola and wheat to elevated levels of CO2, O3 and water deficit in open-top chambers

The effects of elevated CO2 (700 ppm) and O3 (80 ppb) alone and in combination on the photosynthetic efficiency of canola and wheat plants were investigated in open-top chambers (OTCs). The plants were fumigated for four weeks under well-watered and water-stressed (water deficit) conditions. The fast chlorophyll a fluorescence transients were measured after 2 and 4 weeks of fumigation, as well as in control plants, and analyzed by the JIP-test, which is a non-destructive, non-invasive, informative, very fast and inexpensive technique used to evaluate the changes in photosynthetic efficiency. Biomass measurements were taken only after 4 weeks of fumigation. The performance index (PItotal), an overall parameter calculated from the JIP-test formulae, was reduced by elevated CO2 and O3 under well-watered conditions. In the absence of any other treatment, water stress caused a decrease of the PItotal, and it was partly eliminated by fumigation with elevated CO2 and CO2 + O3. This finding was also supported by the biomass results, which revealed a higher biomass under elevated CO2 and CO2 + O3. The decrease in biomass induced by elevated O3 was likely caused by the decline of photosynthetic efficiency. Our findings suggest that elevated CO2 reduces the drought effect both in the absence and presence of O3 in canola and wheat plants. The study also indicates that elevated O3 would pose a threat in future to agricultural crop

Poultry manure enhances grass establishment at a quarry rehabilitation site in subtropical South Africa

The rehabilitation of a quarry was conducted with selected grass species in northern KwaZulu-Natal, South Africa. The seed cocktail applied contained Chloris gayana, Cynodon dactylon, Digitaria eriantha, Eragrostis curvula, Panicum maximum and Paspalum distichum. Three treatments used were: No soil enhancement (control), poultry manure application, and commercial fertilizer application. Four months after sowing, the percentage grass cover per 1 m2 of treatment was 33% for the control, 65% where manure was applied and 76% with fertilizer application. Both fertilizer and manure applications promoted the colonization of grass species. Fertilizer application significantly increased biomass of grass (P_0.05). Poultry manure resulted in higher biomass of approximately 5 g per m2 more than the control; however the mean was not significantly different from the control (P_0.05). These results suggest that fertilizer application prior to seed sowing in a rehabilitated quarry provide the highest biomass after four months. The application of poultry manure proved to be a cheaper option to increase aboveground plant cover in a rehabilitated area, but it is less effective than fertilizer in terms of biomass production.http://www.academicjournals.org/ajar/PDF/pdf2011/4%20Jan/Maliba%20et%20al.pdfhttp://dx.doi.org/10.5897/AJAR10.88