Conducted by ERDB
Completed on 2009
Completed
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The implementation of the 3-year project is premised on the following hypotheses: (1) adoption of the package of technology for Ht corn will result in weed shifts and reduce weed populations (-impact); (2) decline in weed population and seed abundance will cause a decline in avian fauna particularly the seed and insect-eaters commonly associated with agriculture , hence a decline in wild biodiversity (- impact); and (3) adoption of minimum tillage practices as prescribed in the package of technology for Ht corn will cause an improvement in soil conditions and reduction in soil erosion, which is likely to improve crop yield (+ impact).
The project covered the corn-corn production system as practiced in Tigaon, Camarines Sur (Region 5) and the rice-corn production system in Magalang and Arayat, Pampanga (Region 3). The experimental sites are located close to known centers of biodiversity, namely, Mt. Isarog National Park and Mt. Arayat National Park, respectively. A total of 5 hectares each of conventional hybrid corn (DK 818) and herbicide-tolerant (Ht) corn (DK 818 Round-up Ready) was initially established during the wet season planting in Tigaon by way of partnership and sharing of resources with local farmers in the area. Similar approach was adopted in Arayat and Magalang and data collection commenced during the rice season.
As of project completion (September 2009), the project has completed data collection in six growing seasons of corn in Tigaon Camarines Sur (3 wet and 3 dry seasons) and 2 wet season rice and 3 dry season corn in Magalang and Arayat, Pampanga.
For the upland corn-corn production system in Tigaon, Camarines Sur, a significantly higher weeds species richness, and diversity and lower weeds density were obtained in the herbicide tolerant compared with the conventional corn field. The higher species richness and diversity in the Ht corn field maybe attributed to the increase in the number of broad leaves/weeds rather than grasses. Nonetheless, there were . no significant effects of season and the type of corn used on total biomass of weeds for both the Ht and conventional corn field. Significant interaction was obtained only between period/stage of weeds sampling and the type of corn used (P≤0.5%). The most dominant species in all stages of both the Ht and conventional corn was Rottboellia conchinchinensis except in some stages of Ht corn where the most dominant was Ludwigia octovalvis, Ageratum conyzoides, Borreria laevis, which are all broad leaves weeds.
The analysis of variance for species richness of above ground fauna revealed significantly different levels during wet and dry season assessment and during the different stages of corn growth (P≤0.05). No significant differences was, however obtained for species richness in the Ht and conventional corn field which no significant impact on above-ground arthropods. No significant differences on the impact on soil arthropods and avi-fauna was likewise seen between the Ht corn and conventional corn-field. The more dominant types of birds observed in the corn fields and adjacent forest edge during different stages of corn growth are composed primarily of insectivores (insect-eating birds) and herbivores ( plant-eating birds). Classification of the avifauna according to feeding guilds showed that in corn fields, the mean percentage of insectivores was 59%; herbivores, 20%; omnivores, 18%; and canivores, 4% . In the adjacent forest edge close to the corn field, 46% were insectivores; 36%, herbivores; 15%, omnivores and 5%, carnivores. More species were identified in the forest edge than the corn field regardless of the type of corn used but the density or number of birds observed, showed significant difference between the two types of corn fields.
The soil fertility status appeared not to be affected by the type of corn planted because the condition of the soil remained at its poor state even after 6 seasons of planting. The soil erosion rate was apparently higher in the conventional corn field than the HT corn field. On this aspect, rainfall appears to be major contributory factor.
For the lowland rice-corn production system in Magalang and Arayat, Pampanga, no significant difference in seasonal, periodic (i.e. stage of crop growth) and type of corn used (i.e. Ht and conventional corn after rice) was obtained in terms of species richness in both fields. Significant interaction among the three main variables was noted (P≤0.5%) only between season and period. Consequently, species diversity of both fields were observed to be comparable throughout the period of study.
Weeds abundance (total biomass) and weeds density (number of weeds counted) were found to be significantly affected only by period of sampling (P≤0.05%) but not by the season nor the type of corn used after the rice. These findings on weeds show the efficiency of the herbicide tolerant corn as an alternate to the conventional hybrid and the usual laborious off-barring and hilling-up cycle of arresting weeds. There is no impact on the subsequent rice as manifested by the significantly similar profile and diversity of weeds throughout the 3 year period of the study.
The profile of above ground arthropods both for the rice and corn production seasons presents a combination of phytophagous and predatory insects which
were distinctly different except for Micraspis discolor (lady bird beetle) which was present both in the rice and corn crop in all stages of crop growth.
Statistical analysis of data on soil arthropods showed no significant difference in species richness between the rice-Ht corn and rice-conventional corn fields regardless of season or crop grown, period of crop growth and the type of corn used. The density of the soil arthropods counted was also found to be not significantly different in both sites throughout the 3-year period of the study.
Classification of the avifauna that were spotted in the two sites during the different stages of crop growth (Table 33) showed that insectivores dominate the avifauna that frequent the rice and corn fields including their adjacent forest edges.
Based on the results of the 3-year study on herbicide tolerant corn in the upland corn-corn and lowland rice-corn production system, no significant impact on above-ground and soil arthropods and avi-fauna maybe traced to the used of herbicide tolerant corn. Its fast rate of adoption which was only approximately 80% in Tigaon upon project completion from 20% when the project started in 2006 lends proof to the effectiveness of the crop as a suitable replacement to the traditional and laborious hand weeding practices in the area. In Pampanga, the herbicide tolerant corn was first introduced in the area when the project started and has gained popular support from the farmers due to high yield and less labor requirement.
Following the ecosystems approach, a negative impact in one component does not necessarily imply a bad state of the ecosystem. It is the interaction among the several components that make up the ecosystem that decides whether a system will be sustainable or not. In some instances, economics remains to be the major deciding factor.