Abstract
Experiments were conducted in Yala 2010 and Maha 2010/11 to determine the effects of N sources and purple nutsedge ( Cyperus rotundus L.) densities on purple nutsedge growth and its interference with onion ( Allium cepa L.) as organic amendments can promote weed management. A 3×4 factorial design with four replicates per treatment was adopted. The treatments were three different purple nutsedge densities (0, 20, 40 plants/m 2 ) with four N sources i.e. cattle manure, gliricidia ( Gliricidia sepium ) leaves, improved compost and inorganic fertilizer (urea). Onion (variety Vethalan ) and purple nutsedge were allowed to grow together for 12 week. The results of the two experiments were combined as the treatment by season interaction was not significant (p>0.05). Onion bulb yield was significantly affected by purple nutsedge density and N source. No significant (p>0.05) effect of N sources on purple nutsedge biomass was observed at a density of 20 plants/m 2 whereas at 40 plants/m 2 , the effects were significant. Onion N concentration was high when grown with improved compost, whereas N concentration in purple nutsedge was low in this treatment. Purple nutsedge tuber weight and tuber number were significantly (p Tropical Agricultural Research Vol. 23 (4): 290 – 299 (2012) DOI: http://dx.doi.org/10.4038/tar.v23i4.4864
Highlights
Onion (Allium cepa L.) belongs to the family Alliaceae and is a popular vegetable grown for its pungent bulbs and flavorful leaves
At a purple nutsedge density of 40 plants/m2, significant difference in onion yield was observed between Gliricidia and inorganic fertilizer application treatments
These findings clearly indicate that in the presence of purple nutsedge in onion plots, improved compost application produced the highest onion yield
Summary
Onion (Allium cepa L.) belongs to the family Alliaceae and is a popular vegetable grown for its pungent bulbs and flavorful leaves. It is consumed at its young green stage or after its full development and maturity when it is harvested in the form of a dry bulb. In the Eastern province of Sri Lanka, almost all spicy dishes contain onion as an important ingredient used for cooking purposes. Purple nutsedge (Cyperus rotundus L.), an economically important perennial weed in 92 countries, is classified as the world's worst weed due to its extensive distribution and competitiveness (Holm et al, 1977). Experience has shown that purple nutsedge is the one of the serious weeds in onion fields in Batticaloa Sri Lanka, which significantly reduces the onion yield
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