Competitive Performance of Purple Nutsedge (Cyperus rotundus L.) and Onion (Allium cepa L.) as Affected by Different Sources of Nitrogen

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/m²) 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/m² whereas at 40 plants/m², 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<0.05) suppressed by improved compost. The study indicated that improved compost application maximizes benefits to the onion crop and minimizes any inadvertent benefits to purple nutsedge. Information from this study could be utilized to develop more efficient fertilization strategies as components of integrated weed management programs in onion production systems under field conditions.

Tropical Agricultural Research Vol. 23 (4): 290 – 299 (2012)

DOI: http://dx.doi.org/10.4038/tar.v23i4.4864