Evaluation of cultural practices (surface burning, deep ploughing, organicamendments) for management of rice root-knot nematode in rice-onion cropping system and their effect on onion (Allium cepa L.) yield

Rice hull burning (RHB) is a traditional cultural practice of many onion gr owers in San Jose City, Nueva Ecija, Philippines, mainly for weed control a nd increased yield. The resulting carbonized rice hull (ash) is incorporate d into the soil during land preparation before transplanting of onion. Stud ies to evaluate the effect of RHB on the population of the rice root-knot n ematode, Meloidogyne graminicola, and onion yield were conducted in a farme r's field naturally infested with the pathogen. Burning of 15-cm-deep rice hulls significantly reduced the nematode populations in the soil and increa sed onion yield. Increasing the thickness of rice hulls burned to 30 cm dee p resulted in a yield increase of 44.2% over no RHB and 11.9% over 15-cm-de ep rice hulls, while the yield increase with 15-cm-thick hulls was 28.8% ov er no RHB. Plots that received rice hulls 30 cm deep also produced 37.7% mo re large bulbs for export than those plots that received 15-cm-deep hulls, and 151.7% more than those plots with no RHB. Deep ploughing did not signif icantly affect nematode populations compared with standard ploughing. Organ ic amendment did not contribute to an increase in onion yield and has no ef fect on the population of rice root-knot nematode.