Overview

The continuing study on the effects of rice hull burning on soil-borne diseases in San Jose and Bongabon showed that fungal populations were much lower in burned plots than in unburned plots. In San Jose, fungal colonies were slightly higher in burned plots treated with compost than in those without compost, implying that compost could be favorable for fungal growth. Onion yields, however, were the same in both treatments. In unburned fields, a similar trend was observed but at lower levels, and with similarly low yields. It would appear that yields were more influenced by rice hull burning than by compost. Plots exposed to rice hull burning produced twice as much yield as those not exposed.

In the Bongabon Demo farm, pink root (Phoma terrestris) incidence and severity were slightly higher in burned fields with compost than in burned fields without compost. In unburned fields, the same trend for pink root was observed. The corresponding onion yields, however, were adversely affected by the armyworm Spodoptera exigua infestation associated with the El Ni?o phenomenon which affected many parts of the country, especially Central Luzon.

Rice hull burning reduced the density and fresh weight of Cyperus rotundus, the major weed in Palestina, San Jose, Nueva Ecija, by 88% and 79%, respectively, over unburned plots. Yields in burned plots were increased by 58% over unburned plots.

Experiments in San Jose showed that the heat caused by rice hull burning was effective in suppressing nematode populations up to a soil depth of 20 cm. Under field conditions, rice hull burning effectively reduced nematode populations with or without compost, resulting in larger and heavier onion bulbs. The experiment in Bongabon Demo farm showed a similar trend, but onion yields were greatly reduced by the armyworm infestation, which largely defoliated the onion plants throughout the field