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Archives (2002) : Soil & Water

Understanding a total production system by Virginia A. Duldulao

January-March 2002 Volume 4 No. 1

The paper I presented during the National Research Symposium is very simple. It is the synthesis of a series of experiments we had been conducting since 1993 to 1999. We characterized the nitrogen dynamics of different cropping patterns such as the seasonal distribution of nitrate and ammonium in farmers' fields before and after each crop. Then we tried to find out what can be done to prevent the downward movement of nitrate. Remember that nitrate can contaminate our groundwater. We also found cases of infantile methemoglobinemia in the test site where the farmers applied fertilizers weekly. This is impaired respiratory system among infants or simply 'blue babies'. One cause of this is too much fertilizers being applied by our farmers that leach down to the groundwater. Finally, we tried to determine the most efficient fertilizer rate so the farmers do not spend unnecessarily."

Dr. Epifiana O. Agustin of the Mariano Marcos State University (MMSU), Batac, Ilocos Norte, talks of her winning paper, "Rainfed lowland rice-based cropping system of Ilocos Norte: Show window for future diversified and cropping systems." This won for her and her co-authors, who are from the International Rice Research Institute (IRRI) and MMSU, the AFMA Outstanding R&D Paper Award (Unpublished) Crop Science Midstream/Downstream category. This is a project of the Rainfed Lowland Rice Consortium of the Philippine Rice Research Institute (PhilRice), IRRI, and MMSU.

The study seems simple but the knowledge product generated has great applications to our rice-based production systems especially in areas where diversified farming is practiced. Moreover, the farmers can control the leaching of nitrate into their groundwater which is also their source of drinking water.

The researcher assumes that if the biophysical environment is conducive to intensification, rainfed rice production systems in other parts of Asia may also change overtime and acquire the essential features of the production systems of Ilocos Norte where the experiments were conducted. Moreover, production systems will be commercialized and diversified as access to market improves. Thus, this production system can be a model for other areas and countries that have similar characteristics with that of the province where the experiments were conducted.

Characteristics of the area
Ilocos Norte has four major ecosystems but most of the agricultural activities are concentrated in the central lowlands. Rice is the most common crop during the rainy season and planted in about 60,000 ha. The province practices a highly diversified cropping system during the dry season. The farmers grow various food and cash crops such as tobacco, garlic, mungbean, onion, sweet pepper and tomato. Melon, vegetables and corn are sometimes planted as monocrop or intercrop. All these are watered from groundwater irrigation. The farmers intensify their production system by applying greater amounts of inorganic fertilizer, irrigation and pesticides to the cash crops.

The cropping patterns practiced include: rice-tomato-corn; rice-garlic-mungbean; rice-mungbean-corn; rice-sweet pepper-corn; rice-tobacco; rice-garlic-corn; rice-tomato; rice-pepper; and rice-garlic. This sytem intensifies the use of the land and may not be sustainable if the farmers do not understand what happens after each crop.

What's in the cropping system?
"At the start, we characterized the nitrogen dynamics of the different cropping systems and found that there is too much nitrate left after each crop. While this nitrogen can also be lost in the atmosphere, most of it is leached down," Dr. Agustin explained.

"Our problem, therefore, is to prevent the downward movement of nitrate so that it does not contaminate our groundwater. There is one barangay that is planting pepper after rice and the farmers fertilize their plants weekly, so you just imagine how much fertilizer that is. In the next study, we planted nitrate catch crops that would use the nitrogen left after rice or during the dry to wet transition period (DWTP). We tried corn, indigo, and mungbean. We found that corn efficiently used the fertilizer at the upper layer of the soil at 15 to 30 days after planting and indigo at the lower layer beyond 30 days after planting. Indigo, however, can not give the farmers any income so they may not like to plant it. But if we can only convince them that this is a good source of nitrogen for their rice and can enhance soil texture then this can help in sustaining agriculture," Dr. Agustin relates.

Dr. Agustin recommends the planting of both corn and indigo to reduce the leaching of nitrate during the entire DWTP.

"Finally, we wanted to reduce the nitrogen input for pepper because we are bothered by our observation of 'blue babies' in the test area for pepper, thus, our third study. And truly, we found that the farmers were applying too much fertilizer uselessly. Their fertilizer rates ranged from 133 kg to 366 kg per hectare. There is no reduction in the pepper yield even if the farmers only applied 266 kg per hectare," Dr. Agustin concludes. "We wish that the Department of Health will also get into the picture and find out the culprit in the 'blue baby' phenomenon in one of our test sites," she added.

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