Abstract
The present paper illustrates the results obtained on oat (Avena sativa L.), Somesan variety, concerning growth, grains and straw yields and also of macroelements accumulation (N, P, K, Ca, Mg) when various doses of sewage sludge were applied associated or not with mineral fertilization. Sewage sludge application produced significant increase of plant height starting with equivalent dose of 100 kg N/ha, meanwhile the highest height was observed in the case of plants fertilized with doses equivalent with 300 and 400 kg N/ha. With the increase of sewage sludge dose it has been observed the straw yield increase, this being statistically assured starting with sewage sludge equivalent dose of 100 kg N/ha. Sewage sludge fertilization, accompanied or not by mineral fertilizers, evidenced that nitrogen contents in oat grains increases with applied sewage dose, being significant from an equivalent dose of 200 kg N/ha. Low sewage doses equivalent with 200-300 kg K/ha evidenced for potassium concentration in oat grains a significant decrease in comparison with untreated variant, meanwhile mineral fertilization generated a significant increase of potassium levels in oat grains. Calcium contents in oat grains present a significant increase after sewage sludge fertilization and at a dose equivalent with 600 kg N/ha, the calcium levels (0.24%) increased 3 times in comparison with untreated variant (0.08%). Sewage sludge fertilization, associated or not with mineral fertilizers, did not produced significant changes of magnesium levels in oat grains, found concentrations being considered as normal values.
Highlights
Resulted from municipal wastewater treatment plants, sewage sludge is a nutrient rich organic material, used as fertilizer and soil conditioner
Mineral fertilization led to significant oat grains yield in comparison with unfertilized variant
Sewage sludge application associated with mineral fertilizers does not provide significant statistical increases of grains yield and straw yield but these parameters are slightly higher in comparison with the variants fertilized organic only
Summary
Resulted from municipal wastewater treatment plants, sewage sludge is a nutrient rich organic material, used as fertilizer and soil conditioner. Considerable number of research papers has been accomplished worldwide on the effects of sewage sludge on soil and various crops. Some studies indicated that successive application during seven years of 100 t/ha municipal sewage sludge for wheat and maize crops produced an increase with a percent of organic carbon from soil [1,2]. Organic fertilization with compost obtained from municipal sludge with a dose of compost equivalent to 400 kg N/ha led to significant increases of mobile phosphorus levels in soil [4]. Mihalache et al [5] reported that sewage sludge application generate significant increase of soil organic carbon, total nitrogen, mobile forms of phosphorus and potassium, the highest effects being encountered for 240 t/ha sewage sludge dose
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