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Journal of Environmental Science and Management 12(1):25-41 (June 2009) ISSN 0119-1144 Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines Januel P. Floresca, Antonio J. Alcantara, Corazon B. Lamug, Corazon L. Rapera, and Candida B. Adalla ABSTRACT Ecosystem services are the benefits people obtain from ecosystems. In lowland rice agroecosystems, these include regulating services on groundwater recharge, nutrient cycling and biological control of insect pests and grain yield provisioning service. These ecosystem services were estimated and analyzed in NIA irrigated and pump irrigated lowland rice farms during wet season 2005 and dry season 2006 in two barangays of Echague, Isabela. Groundwater recharge, which was estimated based on saturated hydraulic conductivity and growing period with standing irrigation water in the paddy, was 2,421.7 m3 ha-1 cropping-1. Soil nutrient cycling, which was estimated using the rice straw yield and its nutrient content, consisted of 16.9 kg N ha-2, 12.0 kg P2O5 ha-2 and 55.8 kg K2O ha-1 cropping-1. Biological control of insect pests by spiders expressed in terms of predator-prey ratio was 9:61 and 7:24 in the wet season 2005 and dry season 2006, respectively. Rice grain yield was 3,530.7 kg-1 ha-1 cropping1. The assessment was done using transdisciplinary research methods. Methodologies in agronomy, soil hydrology and insect ecology were used to estimate the amounts of ecosystem services and environmental psychology was used to explain why farmers used different farm management practices based on their knowledge, attitudes, perceptions and resources constraints. Farm management practices affected the amounts of ecosystem services. Key words: ecosystem services, lowland rice agroecosystems, transdisciplinary research INTRODUCTION Ecosystem services are the benefits people obtain from ecosystem functions (Contanza et al. 1997; Cork et al. 2001; Cork 2001; UN 2003). These include provisioning services such as food, fuel, and fiber; regulating services such as climate regulation and flood control, nutrient cycling and biological control of insect pests. Changes in these services affect human well-being in many ways (UN 2003). Among the direct drivers of change are the external inputs such as irrigation, fertilizers and pesticides. A ubiquitous feature of the Philippine landscapes, rice fields cover 12% of the country’s total land area. Much is known about the economic impact of rice fields and its effects on the social and cultural systems. However, very little research has been done on how rice farms have affected the ecological dynamics of the tropical ecosystems. Considering that majority of the Philippine population depend highly on rice for their nutrition and on rice farming for livelihood, the need to understand the larger ecological implications of allocating scarce lands to rice production is now urgent. A good understanding of how rice fields, as ecosystems, contribute to the wider range of ecosystem services is needed (ARF 2000). The ecosystem services of lowland rice agroecosystem need to be assessed to enhance productivity, food safety, and environmental protection. The assessment of the ecosystem services should be in the context of change in sources and levels of inputs, outputs and environmental burdens brought about by variations in season and cultural practices. This study sought to answer the following Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines 26 questions: 1) How can the ecosystem services on groundwater recharge, soil nutrient cycling, biological control of insect pests and crop yield of lowland rice agroecosystem be measured? 2) Are the magnitudes of ecosystem services of lowland rice agroecosystems affected by the kind and level of inputs brought about by variations in farming practices and cropping seasons? by the farmer according to his knowledge, perceptions, attitudes and resources constraints to implement the farming activities on irrigation, land preparation, seedling establishment, fertilization, pest management, harvesting, marketing and by-product utilization. The farm inputs are obtained either from natural sources (creeks or rivers for irrigation water, organic materials from rice straws or weeds, and biological control agents like spiders) or from man-made sources (inorganic or organic fertilizers, and pesticides). Rice farmers may opt to mainly use man-made inputs rather than natural inputs with some trade-offs on input levels, which would change the output levels (dry grain yield and rice straws) and other ecosystem services. The conceptual framework on the assessment of ecosystem services of lowland rice agroecosystem is presented in Figure 1. The lowland rice agroecosystem is described in terms of its structure and functions. The structure refers to the arrangement by which the components (biophysical and socioeconomic components) are interacting in space and time while function refers to how the various components interact to pr oduce ecosystem ser vices like gr ain production, recharge of groundwater, as well as nutrient cycling and biological control of insect pests. Ecosystem services of lowland rice agroecosystem are outputs produced from the farming activities provided with farm inputs. Outcomes of these outputs vary because of varied kinds and levels of inputs applied for each farm activity and varied biophysical characteristics. The kinds and levels of inputs depends on the farm management practices/technologies opted Lowland Rice Agroecosystem Biophysical Conditions Socioeconomic Conditions • • • • • • • • Climate Topography Soil & Water Resources Flora & Fauna Income/Capital, Land Tenure Technology, Market Perceptions Attitudes/Preferences Kinds & Levels of Inputs Assessment (InputOutput Analysis) • • • • • • • Land preparation Method of planting Irrigation Fertilizer application Pest management Harvesting By-product utilization Ecosystem Services Regulating/Supporting Services (Non-marketed) • • • Groundwater recharge Soil nutrient cycling Biological pest control Grain Yield Provisioning Service (Sale; Household consumption; Seeds; Payment of labor) Figure 1. Conceptual Framework on the assessment of ecosystem services of lowland rice ecosystems. Journal of Environmental Science and Management Vol. 12. No. 1 (June 2009) The provisioning service on grain yield is the amount of palay harvested from the rice plant. Regulating services which include groundwater recharge, soil nutrient cycling and biological control of insect pests are those residual products resulting from the ecological processes (water and nutrient cycle, predation) during the rice growing period. Groundwater recharge is the output derived from the percolation/infiltration of irrigation water applied in the rice fields. It is dependent on the porosity of the soil that regulates its flow rate through the soil. Groundwater recharge volume builds as standing water remains in the fields during the cropping period. Nutrient cycling is the reuse of mineralized nutrients in the rice plant dead biomass (rice straw) for the next rice cropping. The more rice straws are recycled, the higher the nutrient cycling. This depends on the farmer’s preference or decision to manage the rice straw whether to use it for compost, or just leave them in the field to be plowed under, pile or burn. Plowing under rice straw left in the field undergoes anaerobic decomposition that emits large amounts of methane that contribute to global warming. Biological control of insect pests is the natural regulation of insect pest population through predation of spiders that consume insect pests, which result in the prevention of crop damage. Due to slow effect of biological control to control pests, farmers use insecticides with varied toxicity levels. The more toxic insecticides kill more predators. The quantified magnitudes of ecosystem services would be used as the basis for valuation of the economic benefits derived from these ecosystem services. The total economic value of ecosystem services will be used as basis for decisions and policies to protect lowland rice lands from conversion to other non-agricultural uses. The general objective of this paper was to elucidate the assessment of grain yield, groundwater recharge, soil nutrient cycling and biological control of insect pests as ecosystem services of lowland rice agroecosystems with different sources 27 sources of irrigation and cropping seasons. Specifically, the paper explained the following methodologies: 1. Estimation of the magnitude of each of the four ecosystem services; 2. Analysis of the effects of the different farm management practices (e.g. irrigation, method of planting, fertilizer application, pest control) and biophysical conditions (e.g. soil type, cropping seasons) on the ecosystem services; 3. Analysis of the farmers’ behaviors (shown from their existing farm management practices) and attitudes toward each ecosystem service; and 4. Discussion of the significance and implications of the magnitudes of the four ecosystem services. MATERIALS AND METHODS Selection of the Study Sites, Sample Farms and Farmer Respondents The study sites were selected based on the source of irrigation, landscape position of the farms and training of farmers on IPM for lowland rice production. The lowland rice farms in Barangay Sta. Monica represented the NIA irrigated farms in the floodplain while those in Barangay San Manuel represented the pump irrigated farms on rolling areas. A total of 12 sample farms were randomly selected in each study site using simple random sampling without replacement. The farmers of these sample farms were the respondents for personal interview on socio-demographic and economic information, rice cultural practices, crop yield and profitability of rice farming and perceptions of and attitudes toward the ecosystem services. The names of the farmer respondents were identified from the masterlist provided by agricultural technicians (ATs) of the Department of Agriculture (DA), Echague, Isabela. Personal interviews were conducted using a pre-tested survey questionnaire. 28 Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines Assessment of Ecosystem Services of Sample Farms The assessment of four ecosystem services of the sample farms focused on the estimation of grain yield, groundwater recharge, soil nutrient cycling and biological control of insect pest of rice. The quantification was basically done using input-output analysis. The kinds and levels of inputs were determined from farmers interview on method of land preparation and growing period of direct seeded or transplanted lowland rice, frequency and time of irrigation, kinds of fertilizers used (inorganic, organic or foliar) amount applied, method (basal or topdress) and time of application, kinds and amount of pesticides used (insecticides, herbicides and molluscicides), frequency/time of application, price of pesticides. Rice grain and straw yield were determined. Estimation of groundwater recharge. The recharge of groundwater is the infiltration (percolation) of surface water from soil top to the Vadose water zone and farther to the aquifer in the rice field during the rice-growing season. The estimation of the amount of recharged water was based on three factors: effective area of rice field, soil infiltration rate, and number of irrigation days when fields had standing water (Matsuno et al. 2002). The estimated groundwater recharge of a farm is the product of saturated hydraulic conductivity (mm d-1) and total number of days the rice fields were saturated with water. The equation to estimate groundwater recharge is as follows: GWR = 10 KT x DWS where: GWR = volume of groundwater recharge (m3 ha-1) KT = saturated hydraulic conductivity (mm day-1) DWS = days of water saturation of rice fields Measurement of saturated hydraulic conductivity (KT). Since the soils in the rice fields were saturated, soil infiltration (or percolation) was estimated using Darcy’s saturated hydraulic conductivity (KT) - falling head method. 2.3 x a x L H1 KT (cm s-1 at ToC) = -------------------- x log10 --Axt H2 a H1 = 0.598 x --- x log10 --------t (H-H1) where: a = cross-sectional area of stand pipe (cm2) L = length of soil sample (cm) A = cross-sectional area of soil sample (cm2) H1 = height from water level of bath to initial water level in stand pipe H2= height from water level of bath to final water level in stand pipe = H – H1 Three sample points in each sample farm were established with three eight-inch dm x 30 cm deep permeameters made of GI sheet. The permeameters were inserted into the paddy soil up to the hard pan and its reading gauge (1 cm diameter hose) was filled with water up to 50 cm level. Readings on the downward logarithmic trend of water were recorded every hr for eight hrs measurement. Estimation of Soil Nutrient Cycling. Soil sampling was done once before plowing for each cropping season. Two sets of composite soil samples (approximately 1 kg) were collected from the paddy fields of each sample farm– one set for wet season (WS) 2005 and one set for dry season (DS) 2006. The samples were air dried and analyzed for total N and available P, K and Zn at the DA Soils Laboratory, Ilagan, Isabela. The gap between the farmers’ actual fertilizer application and recommended levels were determined. Soil nutrient cycling was estimated in terms of the potentially recyclable soil nutrients (N, P, K) provided by rice straw biomass for the next cropping season. The recent data of Obcemea et al., (2005) on nutrient contents of rice straw (0.48% N, 0.34% P2O5 and 1.58% K2O) were used. The estimated amount of rice straws was based on a grain-straw ratio of 1:1 wherein the dry grain yield (kg ha-1) was approximately equivalent to the biomass (kg ha-1) of rice straws produced. Rice straws left in the fields and piled after threshing were also estimated using samples collected from a one sq. m. area in each farm. The samples were sun dried, weighed and calculated on a per hectare basis. These rice straws left in fields could undergo anaerobic decomposition in paddy soils, which would emit larger amounts of greenhouse gases such as methane Journal of Environmental Science and Management Vol. 12. No. 1 (June 2009) (CH4) and ammonia (NH3) that contribute to global warming. If the rice straws are burned, CO2 and smog will also be emitted. Estimation of Biological Control of Rice Insect Pests. Biological control of rice insect pests was estimated in terms of the predator-prey ratio which is the ratio of sample population of generalist predators specifically spiders to sample population of insect pests (including worms and flying insects) which were collected using sweep net. The sweep net was used for sampling insects such as leafhoppers, worms, rice bugs and spiders. The efficiency of the method depends on the stage of the crop, the speed of sweeping, the angle of the net and the type of insect being sampled. Sampling is best done in the early morning or late afternoon when insects and spiders are usually most active. Collection of spider and insect pest samples for each farm was done at 50-70 days after sowing (DAS) during the booting to heading stages. Estimation of Grain Yield. Using the data obtained from personal interviews with farmer respondents, grain yield was estimated in terms of the dry grain equivalent of the total harvest (threshed yield) without deducting the amount of palay utilized for various purposes such as sold either fresh (newly threshed) or dried grain, payments in-kind for irrigation service fee (ISF) to NIA, harvester share, thresher share as well as palay stored for household consumption and seeds for the next cropping. The equivalent dry grain yield was based on observed shrinkage of about 19.4% of newly threshed yield according to one of the farmer respondents. Statistical Analyses The biophysical characteristics of the rice landscapes were described using means and ranges. The socio-demographic/economic characteristics of the farmer respondents and their behaviors as shown in their existing farming practices were described using frequency analysis. Also, using a five-point Likert scale of agreements or disagreements, the farmers’ attitudes toward each ecosystem service were analyzed using frequency analysis. 29 Comparison of means using t Test (paired for even data and two sample equal variance for uneven data) was used to compare the estimated ecosystem services among farms with different sources of irrigation, cropping seasons and methods of seedling establishment. Analysis of variance was used to determine differences in predator-prey ratios among three types of insecticides (green, blue and yellowcoded). RESULTS AND DISCUSSION Biophysical Characteristics of the Study Sites Location and Accessibility. Barangay Sta. Monica is located three km southwest of Barangay Ipil, Echague, Isabela, the major palay trading center located at Maharlika Highway. On the other hand, Barangay San Manuel is located 10 km southwest of Barangay Ipil. Both study sites (Barangays Sta. Monica and San Manuel) are accessible to all types of vehicles through a gravel barangay road. Topography. The landscape of Barangay Sta. Monica is generally flat with patches of slightly rolling areas in the western part. Its elevation ranges from 70 to about 100 m above sea level (masl). The 12 sample farms were situated within 70 – 75 masl (Figure 2). On the other hand, the landscape of Barangay San Manuel is rolling with elevations ranging from 70 to about 100 masl. The 12 sample farms are situated within 70 – 80 masl (Figure 3). Climate. The climatic conditions in the two study sites are similar. They belong to Type III which is characterized by no pronounced wet and dry season, relatively wet from May to October, dry for the rest of the year. Water Resources. Based on rainfall pattern in Echague, Isabela obtained from the Philippine Astronomic, Geophysical, and Astronomical Services Administration (PAGASA) Agromet Station at Isabela State University, the amounts of water available for irrigation in the wet and dry seasons were 191.9 and 111.0 mm mo-1, respectively. 30 Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines Figure 2. Topographic and land use map of Barangay Sta. Monica showing the 12 NIA irrigated sample farms in the 322 ha rice landscape. Figure 3. Topographic and land use map of Barangay San Manuel showing the 12 pump irrigated sample farms in the 250 ha rice landscape. Journal of Environmental Science and Management Vol. 12. No. 1 (June 2009) The surface water resources of Barangay Sta. Monica are the NIA - Magat River Integrated Irrigation System (MRIIS) gravity earth canals and creeks (draining to the Ganano River). However, farmers depend primarily on the NIA irrigation canal as the source of irrigation water for their year-round (two croppings) rice production. On the other hand, the surface water resources of Barangay San Manuel are the impounded creeks (locally called “tanggal”) draining to the Dumatata River. Farmers depend primarily on centrifugal pumps for irrigation of rice fields in their year-round (two croppings) rice production. Farmers’ Existing Farming Practices Irrigation. Irrigation by flooding was done two days before plowing the paddy fields. The rice farms in Barangay Sta. Monica were served with the NIA irrigation canals while in Barangay San Manuel, farmers used centrifugal pumps to draw irrigation water from nearby impounded creeks (“tanggal”). Land Preparation. Land preparation in both sites was similar. Most of the rice paddies were prepared using hand tractor and draft animals. Rice Variety Used. Most rice farmers used one inbred rice variety per cropping that was either purchased from traders or DA, or exchanged with other farmers. Late maturing hybrid rice varieties such as Mestizo 1 (M1) were used for wet cropping season while early maturing varieties such as M3 were used for dry season cropping. Method of Planting. Planting was done either by direct seeding or transplanting. In Barangay Sta. Monica, most farmers (58.3%) practiced direct seeding while in Barangay San Manuel, about 92% practiced transplanting. Fertilizer Application. All farmers were applying fertilizer without conducting soil analysis. Most farmers did not burn rice straws, but only left them in the fields after harvest and after threshing, piled the rice straws in one paddy. Foliar fertilizers were used by mixing with insecticides and sprayed at late vegetative to flowering stages. 31 Pest Control. The most common rice insect pests observed by the farmers were green leaf hopper (GLH), armyworm, cutworm and rice bug. Most farmers claimed that rice bug was the most damaging and thus mandatory spraying of insecticide was done once or twice during the milking stage. Golden kuhol damaged the crop during the seedling stages. Harvest and Postharvest. Harvesting in all the sample farms was done manually using scythe. Threshing in all the sample farms was done using mechanical thresher. Hauling was done through cart (“patuki”) pulled by carabao. In the absence of mechanical dryers, sun drying of grain was the common practice of farmers. In both barangays, the farmers’ produce was usually sold to the trade center in Barangay Ipil, Echague, Isabela. Reduction of Inputs. The farmers employed certain techniques to conserve/minimize irrigation, fertilizer and pesticide inputs and/or reduce losses. They were able to save half to two bags inorganic fertilizer (urea) by using organic fertilizers. The use of organic fertilizer also resulted to reduction in water application. A farmer also observed lessening of top dress of paddy where rice straws had been piled in the previous planting. More farmers applied their knowledge on IPM by monitoring first their fields (e.g., see if there were more flying insects) before applying pesticides. Farmers Attitudes toward Ecosystem Services Attitudes toward Groundwater Recharge. Most of the farmers (92%) in the NIA irrigated farms agreed that groundwater recharge is an important source of irrigation water, 75% agreed that irrigation water in the rice fields infiltrates into the soil and recharges groundwater, and 83% agreed on the need for the protection of the watershed/subcatchment to sustain the availability of groundwater. About 83% of the farmers in the pump irrigated farms strongly agreed that groundwater recharge is an important source of irrigation water, 75% strongly agreed that irrigation water in the rice fields penetrates the soil and recharges groundwater, and 83% strongly agreed on the need for the protection of the watershed/subcatchment to sustain the availability of groundwater. 32 Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines Attitudes toward Soil Nutrient Cycling. In the NIA irrigated farms, 58% of the farmers agreed and 42% strongly agreed that rice straws left in the fields contain nutrients usable by rice plants for the next cropping, and that decomposed rice straws would improve soil fertility and would reduce application of commercial inorganic fertilizers. On the other hand, in the pump irrigated farms, 83% agreed and 17% strongly agreed that rice straws left in the fields contain nutrients usable by rice plants for the next cropping, and that decomposed rice straws would improve soil fertility and would reduce application of commercial inorganic fertilizers. Attitudes toward Biological Control of Insect Pests. Most farmers in both study sites agreed that there are a number of beneficial arthropods (insects, spiders) present in rice fields that feed on insect pests; beneficial insects/predators/ spiders are killed when spraying pesticides; more spiders are killed when more frequent spraying are done or more toxic pesticides are applied; and pesticides have harmful effects on human health. Attitudes toward Grain Yield. Based on the five-point Likert Scale, most farmers agreed (83.3%) and some strongly agreed (16.7%) that their rice yield provides sufficient food and income for their household’s basic needs, even extra incomes for education, appliances and purchase of farm equipment as well as providing them inputs or payments for inputs (e.g. irrigation service fee and farm labor). Assessment of Groundwater Recharge Water management practices in the study sites. In Barangay San Manuel, centrifugal pumps were used to lift water from the impounded water (“tanggal”) along creeks to the farm and applied every three days with 5 cm of flood water in the paddy while in Barangay Sta. Monica, NIA gravity irrigation system provided continuous flooding of 5-15 cm d-1 (2-6 inches) depth. For the direct seeded rice crop, the rice fields were irrigated for 106 and 96 days during the WS 2005 and DS 2006, respectively. On the other hand, for the transplanted rice crop, the fields were irrigated for 94 and 86 days during the WS 2005 and DS 2006, respectively. Bhuiyan et al. (1995) reported that less water was used during land preparation for wet seeded rice (WSR) because of shorter time to complete land preparation activities compared with transplanted-rice farms. In WSR, seeds required only 24–36 hrs of soaking and incubation to be ready for sowing in the field. In the transplanted-rice scheme, seedlings were nurtured in the seedbed for about one month and farmers would not prepare the land unless the seedlings were ready for transplanting. In other countries such as China, where land preparation was already very short, seedlings were raised in well-confined places such that farmers can irrigate just the seedbeds without having to spread irrigation all over the field (Guerra et al. 1998). Saturated hydraulic conductivity and groundwater recharge. The mean saturated hydraulic conductivity of the soils in the NIA irrigated farms was 2.4 mm d-1 while in the pump irrigated farms was 2.8 mm d-1 as shown in Table 1. There were no significant differences in saturated hydraulic conductivities among farm types because the study sites belong to the same soil type which is Cauayan clay loam. Table 1. Saturated hydraulic conductivity of soils of the sample farms in the study sites, CY 2006. Site NIA Irrigated Farms Pump Irrigated Farms Hydraulic conductivity (mm d-1) 2.4 2.8 Comparison of Means NIA vs pump irrigated farm is not significant (ns) In the NIA irrigated farms, the mean estimated groundwater recharge for direct seeded rice was 2,669.3 m3 ha -1 cropping-1 while the estimate for transplanted rice crop was 1,854.0 m3 ha-1 cropping-1. In the pump irrigated farms, the mean estimated groundwater recharges were 2,626.0 and 2,503.6 m3 ha-1 cropping-1 for direct seeded and transplanted crops, respectively (Table 2). The estimated groundwater recharges significantly differed among direct seeded and transplanted rice crops in the NIA irrigated farms 33 Journal of Environmental Science and Management Vol. 12. No. 1 (June 2009) but not in the pump irrigated farms where most farms (11 out of 12 farms) where transplanted. The direct seeded rice crop required a longer growing period with standing irrigation water in the paddy than the transplanted rice crop. The estimated groundwater recharges in the wet season crop were significantly higher than those in the dry season crop in both sites (Table 2). During the wet season when farmers used late maturing varieties, the growing period was longer. Early maturing varieties were used in the dry season. The total irrigation requirement of rice (evapotranspiration + seepage and percolation losses) is 1,750 mm cropping-1 or 17.5 mm d-1 (for 100 days crop growth period) (Bouman, 2001). Percolation of irrigation water into the groundwater of lowland irrigated landscape contributes to groundwater recharge. This could be used for irrigation when this is pumped out from the area. It could contribute about 13.7% of irrigation water in NIA irrigated farms and about 16% in pump irrigated farms if groundwater would be used. Farmers’ behavior and attitudes toward groundwater recharge. The existence of small water impoundments (“tanggal”) along creeks and even from non-impounded creeks enabled the farmers in the pump irrigated farms to use surface water instead of groundwater with shallow tube well (STW) pumps to irrigate their rice fields. They used transplanting method instead of direct seeding to reduce fuel consumption for pumping irrigation water. On the other hand, there was no indication on the need for pumping groundwater by farmers in the NIA irrigated farms despite late arrival of irrigation water in the main canal considering their location being in the downstream of the Magat Dam in Ramon, Isabela which is about 35 km away. Most of the farmers practiced direct seeding because of sufficient and continuous supply of irrigation water from the main canal. In spite of their recognition of the importance of groundwater for irrigation, farmers in both study sites did not have activities (either as individual or as organized group) to protect the groundwater through the protection of the subcatchment’s natural vegetation or watershed as the major source of groundwater recharge. Assessment of Soil Nutrient Cycling Fertilizers applied in the sample farms. Actual application of inorganic fertilizers by farmer respondents did not match with the fertilizer recommendations based on the soil chemical analysis. There was an apparent excessive use of urea (46-0-0) and complete fertilizer (14-14-14) which farmers applied as topdress. All farmers were not able to apply the recommended 10 kg ZnSO4 ha-1 before planting. In the NIA irrigated farms, the levels of N applied was only significantly higher than the recommended levels in WS 2005 for inbred rice plants, while for hybrid rice plants, the levels of N applied did not differ significantly with recommended levels in both cropping seasons (Table 3). On the other hand, in the pump irrigated farms, the levels of N applied for inbred rice plants did not significantly differ with recommended levels among cropping seasons while for hybrid rice plants, the levels of N applied in both cropping seasons were significantly lower than the recommended levels. Only the actual levels of P application for Table 2. Groundwater recharge (m-3) in the study sites, WS 2005 and DS 2006. Method of Planting NIA Irrigated Farms Pump Irrigated Farms Mean Direct seeded WS 2005 2,801.4 (7) DS 2006 2,537.1 (7) WS 2005 2,756 (1) DS 2006 2,496 (1) 2,663.9 Transplanted 1,936.4 (5) 1,854.0 (5) 2,614.9 (11) 2,392.4(11) 2,300.6 Comparison of Means Direct Seeded vs Transplanted NIA Irrigated Farms (WS + DS) significant at 5% Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines 34 hybrid and inbred rice plants were significantly different during DS 2006 in the NIA irrigated farms (Table 3). Rice straws left in the fields after harvest were plowed under and mixed with saturated soil during land preparation for the succeeding crop with short fallow period. However, large amounts of rice straws underwent anaerobic decomposition in paddy soils that emit greenhouse gases (GHGs) like methane (CH4) and nitrous oxide (N2O). These GHGs contribute to global warming. Estimated rice straw production. The estimated rice straw yield for the inbred rice was higher in WS 2005 than in DS 2006 in both study sites (Table 4). Similar pattern was observed for hybrid rice in the pump irrigated farms. The amount of rice straw left in the field was significantly lower than the straw yield with inbred rice in WS 2005. Overall, about 81% of the rice straw was left in the field. The rest was piled in a paddy where mechanical threshing was performed. The estimated rice straw plowed under in the NIA irrigated farms was 3,208.33 and 2,750.00 kg ha-1 for WS 2005 and DS 2006, respectively, while the estimated rice straw biomass plowed under in the pump irrigated farms were 3,083.33 and 2,500.00 kg ha -1 for WS 2005 and DS 2006, Table 3. Comparison between the recommended and actual fertilizers levels (kg ha-1) for inbred and hybrid rice plants in the two study sites, WS 2005 and DS 2006. Fertilizer Use Recommended Actual Recommended Actual NIA Irrigated Farms Pump Irrigated Farms WS 2005 DS 2006 WS 2005 DS 2006 N P205 K20 N P205 K20 N P205 K2O N P205 K20 Inbred rice plants 59.1 25.5 34.1 78 22 31.5 60 30 15 75 25 30 84.5 27.5 24.9 86.6 26 23 70.1 28.6 12.7 76.9 37 18 Hybrid rice plants 120 30 30 100 23.3 15 120 30 30 105 54 24 70.6 52.6 24.5 67.1 42.6 19 Comparison of Means NIA Irrigated Farms (WS 2005) N significant Recommended vs Actual fertilizer level for hybrid Pump Irrigated (WS 2005) N significant Pump Irrigated (DS 2006) N significant Actual fertilizer levels for Inbred vs Hybrid Pump Irrigated ( DS 2006) P 0.003 significant Table 4. Rice straws yield and left in the fields after harvest by plant type, WS 2005 and DS 2006. Parameter Straw yield (kg ha-1) Straw left in the field (%) NIA Irrigated Farms Inbred WS 2005 DS 2006 4,125.2 3,396.9 (11) (10) 78 85 Comparison of Means Pump Irrigated Farms Hybrid Wet Dry 2005 2006 2,739.0 (2) 73 P 2 samples; equal variances Rice Straw Produced vs Rice Straw Left after Harvest NIA Irrigated , Inbred (WS 2005) 0.009 significant Inbred Wet Dry 2006 2005 3,178.8 2,809.5 (6) (4) 84 80 Hybrid Wet Dry 2005 2006 3,986. 3,436.9 0 (6) (8) 88 79 35 Journal of Environmental Science and Management Vol. 12. No. 1 (June 2009) ha-1 K2O for WS 2005 and 12.0 kg ha-1 N, 8.5 kg ha-1 P2O5, 39.5 kg ha-1 K2O for DS 2006 (Table 5). respectively (Table 4). Rice straws produced after threshing were usually piled in one paddy (for all the sample farms) to decompose for the next season crop. The estimated amounts of rice straw piled after threshing in the NIA irrigated farms were 22 and 21 % of the straw yield for WS 2005 and DS 2006, respectively while in the pump irrigated farms, these were 14 and 21 of the straw yield for WS 2005 and DS 2006, respectively (Table 4). Soil nutrients from rice straws piled after threshing. The amount of rice straws piled in one paddy after threshing was higher in the wet than in the dry season. However, its full utilization depends on farmers’ preference either to compost or use these for other purposes (e.g., mushroom production). If the piled rice straws were burned, large amounts of nutrients (80% of N, 25% of P and 21%of K) would be lost and large amounts of smog air pollutant and CO2 would be emitted to the atmosphere that could eventually contribute to global warming (Mandal et al. 2004). Soil nutrients in rice straws produced. Obcemea et al. (2005) reported that the nutrient content of rice straw was 0.48%N, 0.34%P2O5 and 1.58%K 2O. Based on these values, the estimated amounts of nutrients in the rice straws in the NIA irrigated farms were 19.7 kg ha -1 N, 14 kg ha-1 P2O5, 64.9 kg ha-1 K2O for WS 2005 and 15.8 kg ha-1 N, 11.2 kg ha-1 P2O5, 51.9 kg ha-1 K2O for DS 2006 (Tables 5). On the other hand, in the pump irrigated farms, these were 17.2 kg ha-1 N, 12.2 kg ha-1 P2O5, 56.6 kg ha-1 K2O for WS 2005 and 15.1 kg ha-1 N, 10.7 kg ha-1 P2O5, 49.7 kg ha-1 K2O for DS 2006 (Tables 5). Farmers’ behaviors and attitudes toward soil nutrient cycling. All farmer respondents did not scatter in the rice field composted rice straws, which were piled after threshing from the previous crop, because they perceived it to be laborious and time-consuming. Although farmers did not burn the rice straws, which may have resulted to large amounts of nutrients loss and carbon dioxide and smog emission that could contribute to global warming, benefits from rice straw utilization were not maximized. Farmers appreciated the fertilizer potential of rice straw but did nothing to fully utilize it. Soil nutrients from rice straws plowedunder. The nutrients (N-P2O5-K2O) from rice straws plowed under in the NIA irrigated farms were 15.4 kg ha-1 N, 10.9 kg ha-1 P2O5, 50.7 kg ha-1 K2O for WS 2005 and 13.2 kg ha-1 N, 9.4 kg ha-1 P2O5, 43.5 kg ha-1 K2O for DS 2006. On the other hand, in the pump irrigated farms, these were 14.8 kg ha -1 N, 10.5 kg ha -1 P2O5, 48.7 kg Assessment of Biological Control of Insect Pests Insect pests and spiders population and Table 5. Nutrient content of the rice straw yield, rice straw left standing in the field and of the harvested rice straw with threshed panicles. WS 2005 and DS 2006. Site Total Rice Straw Yield N P2O5 NIA Irrigated Farms Pump Irrigated Farm Site- mean (2 SITES) 19.7 17.2 18.5 14.0 12.2 13.1 NIA irrigated Farms Pump Irrigated Farms Site-Mean MEAN (2 SEASONS) 15.8 15.1 14.4 16.9 11.2 10.7 10.9 12.0 Rice straw Left in the field Harvested Rice Straw with Threshed Panicle Nutrient Content (kg ha-1) ** K2 0 N P2O5 K2 0 N WS 2005 64.9 15.4 10.9 50.7 4.3 56.6 14.8 10.5 48.7 2.4 60.8 15.1 10.7 49.7 3.4 DS 2006 51.9 13.2 9.4 43.5 2.6 49.7 12.0 8.5 39.5 3.1 50.8 12.6 8.9 41.5 2.8 55.8 13.9 9.8 45.6 3.1 P2O5 K2 0 3.1 1.7 2.4 14.3 7.9 11.1 1.8 2.2 2.0 2.2 8.7 10.2 9.3 10.2 Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines 36 predator-prey ratios. The dominant insect pests collected in 100 m2 sample areas using sweep net at booting to heading stages (50-70 DAS) were green leaf hopper (GLH), cutworm and armyworm, which were the prey, while the dominant predator species of spiders were Lycosa and Tetragnata. The mean predator-prey ratios in the NIA irrigated farms were 10:92 and 6:23 for WS 2005 and DS 2006, respectively while in the pump irrigated farms, these were 9:31 and 7:26 for WS 2005 and DS 2006, respectively (Table 6). The predatorprey ratio did not significantly differ among plant types (hybrid vs. inbred) and study sites but significantly higher during WS 2005 than in DS 2006 for inbred rice plants in the NIA irrigated farms. This was due to remarkably high population of insects in WS 2005 than in DS 2006 (Table 7). The relatively high temperature and humidity during the wet season offered a more favorable condition for insect pests. Table 6. Predator-prey ratio in NIA and pump irrigated farms, WS 2005 and DS 2006. NIA Irrigated Farms Direct Seeding (n = 7) Transplanting (n = 5) Mean Pump Irrigated Farms Direct Seeding (n = 1) Transplanting (n = 11) Mean Mean (2 Sites) WS 2005 Predator: Pest Ratio 7:91 14:92 10:92 DS 2006 Predator: Prey Ratio 5:29 7:14 6:23 20:6 8:33 9:31 9:61 10:13 2:27 7:27 7:26 Comparison of Means WS 2005 vs DS 2006 NIA Irrigated (Inbred) significant at 5% level All the predator-prey ratios exceeded the ability of a Lycosa to consume 45 brown plant hoppers d-1 as cited by Settle et al. (1996) or a predator-prey ratio of 1:45. However, there is no information on consumption rate of spiders for GLH and cutworms/armyworms. Meanwhile, considering that spiders are generalist predators, such values could be adopted. Toxicity and costs of pesticides used. Farmer respondents used 32 different brands of pesticides which are approved by the Fertilizer and Pesticide Authority (FPA). These pesticides belong to different toxic categories (color codes) ranging from green (least toxic), blue (moderately toxic) and yellow (highly toxic) pesticides. Red (extremely toxic) pesticides, which are banned, were not used. Most of the farmer respondents in pump irrigated farms used green-coded insecticides, molluscicides and herbicides (Table 7). However, in NIA irrigated farms, most of the farmer respondents (58.3%) used 1 liter of Direk, a moderately toxic herbicide which was applied at 2-4 days after planting/sowing (DAP/DAS) and its price was P760 l-1. About 25% of farmer respondents used 1 liter of Nurelle, which is a yellow-coded (highly toxic) insecticide at 15 DAT and this costs P795 l-1. Cymbush and Smash, a green-coded insecticide, were used at 60-65 DAT. Green-coded pesticides were the cheapest. The blue- and yellow-coded pesticides were more expensive than the green-coded ones. Predator-prey ratio by toxic categories of insecticides. Predator-prey ratios using combined samples from before and after spraying and grouped according to toxic categories (color codes) of insecticides with practically the same volume (l ha-1) applied are presented in Table 8. Although apparently, the absolute values of predator-prey ratios were higher in green-coded insecticides than in blue- and yellow-coded insecticides for both the study sites and cropping seasons, there were no significant differences in their magnitudes. Farmers’ behaviors and attitudes toward biological control of insect pests. High and increasing cost of pesticides constrained farmers to apply pesticides based on product dosage recommendations. Farmers’ knowledge from IPM training enabled them to reduce application by observing first the fields before they spray. However, farmers’ limited knowledge on toxic categories (color codes) of pesticides trapped them to use highly toxic pesticides. Spraying of highly toxic yellow-coded insecticides killed more predators that naturally regulate insect pest population of rice. Their existing practice of reducing their 37 Journal of Environmental Science and Management Vol. 12. No. 1 (June 2009) Table 7. Brand names, toxic categories (color codes), quantity and costs of pesticide applied by farmers in the study sites, CY 2005. Brand Name NIA Irrigated farms Herbicide Direk Forward Rogue 2-4D Machete Nominee Grassedge Insecticide Chix Cymbush Magnum 5EC Smash Nurelle Vindex Amihan None Molluscide Aquadin Baylucide Control Maso Net Surekill Color Code* Frequency Distribution Count % QTY Unit Unit-Price Blue Blue Blue Green Green Green Yellow 7 1 1 2 1 3 1 58.3 8.3 8.3 16.7 8.3 25.0 8.3 1.07 1 1 0.42 1 0.58 1 liter bot liter liter liter liter liter 1473 560 Blue Green Green Green Yellow Yellow Green 3 3 2 3 3 1 1 1 25.0 25.0 16.7 25.0 25.0 8.3 8.3 8.3 0.5 0.25 0.5 1 1 1 1 liter bot liter liter liter liter liter 690 650 450 450 795 350 350 Green Green Green Green Green Green 1 4 1 1 1 5 8.3 33.3 8.3 8.3 8.3 41.7 1 2 1 10 4 1 box liters liter sachets packs box 850 980 800 80 85 800 6 1 3 2 50.0 8.3 0.79 0.4 0.67 3 liters liter quart packs 338 1300 527 88 1 1 8 2 1 3 8.3 8.3 66.7 16.7 8.3 25.0 1 2 0.66 1 0.33 0.67 quart liter liter bag liter liter 420 620 458 520 900 433 6 1 1 1 1 50.0 8.3 8.3 8.3 8.3 0.58 1 0.5 4 2 liter kilo pack sachets kilos 843 320 250 95 920 Pump Irrigated Farms Herbicides Machete Green Nominee Green Sofit Green Sonic Green Insecticides Cyclone Green Decis R Green Magnum 5EC Green Furadan Yellow Karate Yellow Vindex Yellow Molluscides Baylucide Green Metabait Green Snail Kill Green Sure Kill Green Trap Green Green = Toxic category 4 (Least toxic) Blue = Toxic category 3 (Moderately toxic) Yellow = Toxic category 2 (Highly toxic) 699 350 800 400 Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines 38 insecticide application would address conservation of spiders as biological control agents, however, their lack of information regarding toxic categories (color codes) of pesticides would have a threat to biological control of rice insect pests ecosystem service and pose human health risk. Assessment of Grain Yield Dry grain yield. The dry grain yields in the NIA irrigated farms were 4,110.3 kg ha-1 for WS 2005 and 3,287.3 kg ha-1 for DS 2006 while in the pump irrigated farms, these were 3,582.4 kg ha-1 for WS 2005 and 3,142.8 kg ha-1 for DS 2006 (Table 9). There were no significant differences in the dry grain yield among plant types (hybrid vs. inbred), methods of planting (direct seeded vs. transplanted) and study sites (Tables 9 and 10). Direct seeding of inbred plants was mor e preferred in wet season than in dry season. fertilizers in order to attain their maximum yield potentials. However, farmers applied significantly lower amounts of actual fertilizers applied particularly for N as compared to the recommended levels for hybrid rice (Table 3). Farmers managed hybrid rice plants in the same way as inbred rice plants wherein they applied practically the same levels of fertilizers both for inbred and hybrid rice as there was no significant difference in fertilizer usage for these crops. Farmers’ behaviors and attitudes toward grain yield. In terms of increasing grain yield, most of the farmers in both barangays disagreed and some strongly disagreed (mostly those who attended trainings on IPM and organic farming) on the continual application of inorganic fertilizers and pesticides. With this attitude, farmers resorted to the use of hybrid rice that has high yield potential to apply their knowledge from the training on hybrid rice production. Hybrid rice plants require higher amounts of Table 8. Predator-prey ratio and kind and amount of insecticide applied (l ha-1). WS 2005 and DS 2006. Kind of Insecticide NIA Irrigated Farms WS 2005 DS 2006 Predator: Amount Predator: Amount Prey Ratio of Insec- Prey of Insecticide Ratio ticide Applied Applied ( l ha-1) ( l ha-1) Pump Irrigated Farms WS 2005 DS 2006 Predator: Amount Predator: Amount Prey of Insec- Prey of InsectiRatio ticide Ratio cide Applied Applied ( l ha-1) ( l ha-1) Green* Blue* Yellow* 0.27 (8)** 0.153 (3) 0.165 (4) 0.59 (11) 0.44 (4) * 0.8 0.7 0.8 0.50 (8) 0.50 (3) 0.27 (4) 0.5 0.5 0.5 0.8 0.6 0.41 (11) 0.35 (11) 0.5 0.5 ** number of farms Green = Toxic category 4 (Least toxic) Blue = Toxic category 3 (Moderately toxic) Yellow = Toxic category 2 (Highly toxic) Table 9. Grain yield (kg ha-1) with different planting methods in NIA and pump irrigated farms, WS 2005 and DS 2006. Site/ Method of Planting NIA Irrigated Farms Direct Seeded (n = 7) Transplanted (n = 5) Sub-mean Pump Irrigated Farms Direct Seeded (n = 1) Transplanted (n = 11) Sub-mean Mean (2 Sites) WS 2005 DS 2006 Mean 3,890.7 4,417.8 4,110.3 3,101.0 3,548.1 3,287.3 3,495.8 3,982.9 3,698.8 2,416.8 3,688.4 3,582.4 3,846.4 2,416.8 3,208.8 3,142.8 3,215.0 2,416.8 3,448.6 3,362.6 3,530.7 Journal of Environmental Science and Management Vol. 12. No. 1 (June 2009) 39 Table 10. Grain yields (kg ha-1) of different plant types with two methods of planting in the NIA and pump irrigated farms, WS 2005 and DS 2006. Plant Type Direct seeded Transplanted Transplanted Inbred Inbred Hybrid NIA Irrigated Farms WS 2005 DS 2006 3,890.7 3,101.0 4,535.4 4,087.4 2,739.0 In spite of the use of high yielding hybrid rice variety by farmers who attended training on hybrid rice production, there was still a problem of low yield, i.e. the hybrid yield potentials were not attained. Farmers who planted hybrid variety provided inadequate fertilizers to their crops. This was due to high and even increasing price of fertilizers. Moreover, farmers either applied excessive or inadequate amounts of appropriate kinds of fertilizers because they did not have basis on the right kinds and amounts of fertilizer to be applied that could have been determined through soil analysis. CONCLUSIONS AND RECOMMENDATIONS The theoretical contribution of the study to the body of knowledge in ecosystem services of lowland rice agroecosystem are elucidated based on the following results: a) Direct seeding results in higher groundwater recharge than transplanting; b) Plowing under of rice straw provides more potentially recyclable soil nutrients than the harvest straw with threshed panicle; c) Application of more toxic or yellow-coded insecticides (such as Chlorpyrifos) reduces predator-prey ratio more than the less toxic insecticides like the green-coded ones; and d) Use of hybrid rice variety does not guarantee substantial increase in grain yield if recommended levels of fertilizer application is not followed. These results consistently elucidate a theory that farm management practices and technologies resorted to by farmers according to their knowledge, perceptions, and attitudes within their resources (financial, information, market) either increase or reduce ecosystem services. In terms of the methodological contribution, the study produced a highly quantitative ecosystem services assessment of lowland rice agroecosystem using integrated biophysical and socio-economic Pump Irrigated Farms WS 2005 DS 2006 3,331.2 2,809.5 3,986.0 3,436.9 research methods from various disciplines. For the quantitative estimation and analysis of groundwater recharge and soil nutrient cycling, soil science and agricultural engineering (irrigation and hydrology) are needed. Methodologies on insect ecology and agronomy are used to estimate and analyze biological control of rice insect pests and grain yield provisioning service. Environmental psychology is needed to analyze farmers’ actual behaviors expressed in terms of farm management practices in relation to their knowledge (e.g. training on IPM), perceptions of problems and constraints and attitudes toward ecosystems services. As rational beings, farmers manage their farm within their capital and resource and time constraints without considering environmental consequences and degrading ecosystem services. Analysis of these socio-economic factors and available resources in the farm is needed in identifying strategies (including incentives and regulations) to promote ecosystem service enhancing practices and discourage ecosystem service degrading practices. The cumulative effects of ecosystem services like soil nutrient build-up and biological control of insect pests could be monitored continuously. The practical contribution of the study is in terms of the quantified magnitudes of ecosystem services of lowland rice agroecosystem that would be used to promote farm management practices that enhance these ecosystem services while reducing environmental burdens such as the following: a) The use of hybrid rice following the recommended levels and methods of fertilizer application will increase grain yield to attain the yield potentials and rice straw production which would enhance soil nutrient cycling; b) Proper management and maximum utilization of rice straws as compost would contribute to reduction of GHG (methane and N2O) emission that has high global warming potential; c) With dependable 40 Assessment of Ecosystem Services of Lowland Rice Agroecosystems in Echague, Isabela, Philippines supply of irrigation water, direct seeding and the use of late maturing varieties for wet season would contribute to increased groundwater recharge; and d) The use of green-coded insecticides which are safe to human health would enhance effectiveness of spiders as biological control of insect pests and would further lead to reduction in the cost of pesticides inputs. Results of the present study strongly suggest that the following issues and topics be studied further: a) Comparative analysis of impacts on global warming of rice straw burning and anaerobic decomposition of rice straw by plowing under; b) Estimation of the seepage of irrigation water from the paddy in higher slopes which is re-used as irrigation water at lower slopes; and c) Landscape ecological management of watersheds and subcatchments as sources of irrigation. The recommendations and implications are as follows: a) The quantified amounts of ecosystem services could be readily valued using appropriate valuation techniques (e.g., market value for grain yield and replacement costs for non-marketed ecosystem services such as groundwater recharge, soil nutrient cycling and biological control of rice insect pests); and b) Information on the farm management practices and technologies that enhance ecosystem services should be shared with the farmers and the public. 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CLSU, Munoz, Nueva Ecija. agroecosystems in Echague, Isabela, Philippines” funded by the Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), Los Baños, Laguna and the Isabela State University, Echague, Isabela. Open Academy For Philippine Agriculture (OPAPA). 2006. Rice varieties and varietal selection. Pinoy Farmers Internet. http://www.openacademy.ph ABOUT THE AUTHORS Paningbatan, E.P. 1989. Procedures for Soil Analysis. Department of Soil Science. Technical Paper # 1. UPLB. Renewable Energy Institute/Ca Poly San Luis Obispo. 1997. Overview: Rice straw and the environment. Alternative Uses of Rice Straw in California. Final Report 94-330. Prepared for California Air Resources Board, Research Division, 2020 L Street, Sacramento, CA 95814. Settle, W.H., H. Ariawan, E. Tri Astuti, W. Cahyana, A.L. Hakim, D. Hindayana, A. Sri Lestari and Pajarningsih. 1996. 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The Likert Scale. http:// www.cultsock.ndirect.co.uk/MUHome/cshtml/ psy/likert.html United Nations (UN). 2003. Millennium Ecosystem Assessment Conceptual Framework. (MA). http/ www.millenniumassessment.org United Nations (UN). 2007. Global Report, Chapter 1. Context, Conceptual Frame work and Sustainability Indicators. 18 March 2007. International Assessment of Agriculture, Science and Technology for Development (IAASTD). h tt p: // www. a g a ssessm en t. or g/ d ocs/ IAASTD_Global_ C1_Main_text_Apr07.pdf ACKNOWLEDGEMENT This article is part of the doctoral dissertation of Dr. Januel P. Floresca titled “Assessment and valuation of ecosystem services of lowland rice † Deceased.