Herbicide resistance can be avoided

By Sosimo Ma. Pablico

There’s nothing to fear about herbicides for as long as it is applied only when extremely necessary as practiced in integrated weed management or IWM.

In a nutshell, this was gist of studies by PhilRice (Philippine Rice Research Institute) researchers led by Dr. Madonna C. Casimero with the collaboration of DA researchers and municipal agriculturists in Dingle and Barotac Nuevo, Iloilo and Rizal and Aliaga, Nueva Ecija.

IWM involves a combination of cultural management practices such as good land preparation, intermittent water management, and minimal herbicide application, Earlier, PhilRice researchers found that continuous use of an herbicide family results in the development of herbicide resistance in weeds of lowland rice.

Results of the studies consistently showed that IWM resulted in better weed control, increased yields, and higher profits than the farmers’ practice.  The farmers’ predominant weed control practice in the four towns was herbicide application with increasing doses whenever the weeds could not be totally controlled.

The weed control strategies in IWM indicated a positive cumulative effect in providing a season-long control of weeds.  Consequently, the density and fresh weight of weeds were very low.

Dr. Casimero, a native of Balungao, Pangasinan and now PhilRice’s acting deputy executive director for research, reported that IWM was most beneficial to farmers whose fields are at the tail end of the irrigation system, particularly in Barotac Nuevo and Aliaga.  Significant reduction in the dry weight of weeds was observed in the two sites during the dry and wet seasons.

The yields obtained in the four sites varied depending on their location relative to the irrigation system.  In Dingle and Rizal, the average grain yields of IWM plots during the dry season were 4.05 t/ha and 6.77 t/ha, respectively.  These yields were higher than that of the farmers’ practice by 600 kg and 700 kg, respectively. 

The researchers noted that the two sites are at the head end of the irrigation system and, hence, farmers did not have difficulty in obtaining water and in implementing intermittent water management.  Although lower yields were obtained in the two sites during the wet season, yields of IWM plots were still higher by 250 kg in Dingle and 600 kg in Aliaga.

In contrast, the grain yields were much lower in Barotac Nuevo and Aliaga, as the sites are at the tail end of the irrigation system.  Grain yield in Barotac Nuevo was 3.47 t/ha, while Aliaga got 3.70 t/ha. 

Dr. Casimero said the lower grain yield can be attributed to insufficient water supply during the reproductive stages as reported by the farmers.  With ample water supply during the wet season, yields of the IWM plots were much higher than that of farmers’ practice plots.

Cost and return analysis showed that with IWM, farmers can get an added profit ranging from P3,000/ha in areas where water is limiting to P7,304/ha in areas with good water supply during the dry season.  Higher income was obtained during the wet season in both sites. 

With the application of IWM, Nueva Ecija and Iloilo farmers increased their yields by 10 per cent and 15 percent, respectively.  They saved about P1,000 of production cost in the IWM plots.

These results indicate that when weed management is done properly, farmers can save on production costs, get better yields and higher profits, and at the same time avoid the development of herbicide resistance.

(For past columns, click http://sundaypunch.prepys.com/archives/category/opinion/harvest-time/)

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