SCIENCE CITY OF MUÑOZ, Nueva Ecija — Research results at the Philippine Rice Research Institute (Philrice) show that the system of rice intensification or SRI that reportedly produces high yields even without applying inorganic fertilizers is not really any better than the conventional method of planting in the Philippines.

SRI, which was developed in Madagascar, is now being promoted in the Asia Pacific region as a more economical way for farmers to lessen production cost.

The method of planting rice for SRI uses 14-day old seedlings and only one seedling is planted per hill, unlike the conventional way which uses two or more per hill.

SRI also applies intermittent irrigation to keep the soil saturated during the vegetative growth period. Minimum water application or shallow flooding (1 to 3 cm) is practiced during the reproductive period starting the panicle initiation stage.

Rotary weeding and spot hand weeding control the weeds. Organic fertilizer is applied 3 to 4 weeks before transplanting at the rate of 3 tons a hectare (t/ha) during the dry season and 5 t/ha during the wet season.

To find out if this system really works under Philippine condition, PhilRice researchers Rizal G. Corales, Sando D. Canete, Evelyn F. Javier, Dr. Eulito U. Bautista and Dr. John de Leon compared the SRI with the conventional rice production system and modified SRI for two seasons - dry and wet.

Under the modified SRI system, the researchers supplemented organic fertilizer with inorganic nitrogen fertilizer based on leaf color chart (LCC) readings. During the dry season, they applied 60 kg of inorganic nitrogen fertilizer (equivalent to 133 kg urea) and 69 kg of inorganic nitrogen fertilizer (equivalent to 153 kg urea) during the dry and wet seasons, respectively.

In contrast, 21-day old seedlings were used in the conventional rice production system. Two to three seedlings were planted per hill. The rice plants were continuously flooded, 5 to 10 cm deep, throughout the entire growing period. Weeds were controlled with herbicide application and hand weeding.

Inorganic fertilizers were applied during the critical growth stages at the rate of 120-60-60 kg nitrogen, phosphorus and potassium (NPK) during the dry season and 90-40-40 kg NPK during the wet season.

Results indicated that the inbred rice variety Minerva produced lower yield under the SRI and modified SRI than under the conventional method during the dry season. During the wet season, SRI produced significantly lower yield than the modified SRI and conventional method.

Similarly, hybrid rice produced significantly lower yields in the SRI and modified SRI than in the conventional method during the dry season. The SRI produced much fewer productive tillers than the conventional method because of the smaller amount of available nutrients. However, the three methods did not significantly differ in yield during the wet season.

Economic analysis showed that with hybrid rice, the net income from SRI during the dry season was 30 percent lower than from the conventional method. The net income from the modified SRI was also 15 percent lower than from the conventional method.

Although the production cost in the conventional method was higher than in the two other methods, the difference in cost was easily compensated by the increase in yield.

During the wet season, however, the net incomes of hybrid rice under the modified SRI and SRI were 15 and 9 percent higher than the conventional method, respectively.

With inbred rice, the net income from SRI was 34.54 percent and 5.81 percent lower than the conventional method during the wet season, respectively, the research showed.