Greenhouse gas emissions and plant characteristics from soilcultivated with sunflower (Helianthus annuus L.) and amended with organic or inorganic fertilizers.

Abstract

Agricultural application of wastewater sludge has become the most widespread method of disposal, but the environmental effects on soil, air, and crops must be considered. The effect of wastewater sludge or

urea on sunflower's (Helianthus annuus L.) growth and yieldJ the soil properties, and the resulting C0(2) .and N(2)0 emissions are still unknown. The objectives of this study were to investigate: i) the effect on soil properties of organic or inorganic fertilizer added to agricultural soil cultivated with sunflower, ii) how • urea or wastewater sludge increases C0(2) and N(2)0 emissions from agricultural soil over short time

periods, and iii) the effect on plant characteristics and yield of urea or wastewater sludge added to agricultural soil cultivated with sunflower. The sunf,ower was fertilized with wastewater sludge or urea or grown in unamended soil under greenhouse conditions while plant and soil characteristics, yield, and greenhouse gas emissions were monitored. Sludge and urea modified some soil characteristics at the onset of the experiment and during the first two months but not thereafter. Some plant characteristics were improved by sludge. Urea and sludge treatments increased the yield at similar rates, while sludge- . amended soil significantly increased N(2)0 emissions but not C0(2) emissions compared to the other

amended or unamended soils. This implies that wastewater sludge increased the biomass and/or the yield; however, from a holistic point of view, using wastewater sludge as fertilizer should be viewed with concern.