Nutrient loss by erosion under different land use system in Babon Catchment, Central Java, Indonesia

Nutrient loss by erosion under different land use system in Babon Catchment, Central Java, Indonesia Subagyono KASDI 1,*, T. VADARI 2, SUKRISTIYONUBOWO 2 1 Indonesian Agroclimate and Hydrology Research Institute (IAHRI) 2 Indonesian Soil Research Institute (ISRI) Email: kasdi_s@yahoo.com Abstract Loss of nutrient by erosion from agricultural areas in a sloping land is one of the major causes of land degradation in Indonesia, yet the process by which the nutrient is depleted has often not been answered by appropriate study. The study was conducted in Babon Catchment, Central Java, Indonesia from 2001 to 2004 to elucidate the process of nutrient lost through erosion under different land use systems. Four land use systems were tested, i.e. paddy rice field (PRF) with paddy rice crop based system, Tegalan (TGL) with annual food crops based system, Rambutan (RBT) with Rambutan crop based system and Kalisidi (KLD) with Rambutan and shrub based system. Farmers treated different land management practices in each land use system including tillage and fertilization in PRF, encroachment by tillage for cassava in RBT, and little encroachment by tillage in KLD. Nutrient loss was evaluated based on the actual measurement of N, P and K loss through erosion. In PRF, N, P and K loss through erosion was measured in different land management of farmer practices and improved technology. The results showed that in dry land areas loss of N, P and K in TGL was higher as it was compared with the trees based cropping system of RBT and KLD. As higher as 5.34 kg/ha N, 1.82 kg/ha P and 1.65 kg/ha K leave annually from TGL, which were higher than those leave from RBT (0.001 kg N; 0.004 kg P; and 0.002 kg/ha/year) and from KLD (0.028; 0.132; and 0.077 kg/ha/year). The higher loss of N, P and K in TGL was due to high rate of erosion. In PRF, the loss of N, P and K were respectively 19.00, 6.00 and 10.00 kg/ha/year, higher than those occurred in TGL, RBT and KLD. There was no significant different of nutrient loss through erosion in PRF under farmers practices and improved technology. The highest erosion and loss of nutrient occurred during the tillage. Those losses of nutrients implied to the onsite cost of erosion which has to be paid by farmers. By considering equaled fertilizers based on the nutrient losses, for the PRF cultivation, farmers paid more than US$ 16 per ha annually. Under TGL system, they paid more than US$ 4 per ha annually, but it was little cost (less than US$1 per ha annually) paid if their land was cultivated for tree crops as it was done for RBT and KLD. It implies that in order to reduce onsite cost of erosion, combined conservation measures and efficient fertilizations should be implemented. Keywords: N, P and K losses; Erosion; Paddy rice field (PRF); Tegalan (TGL); Rambutan (RBT); Kalisidi (KLD) Introduction Erosion is widely considered as the major cause of soil degradation. Loss of nutrients is the one of significant cause of degradation prior to erosion. However, most of the study on erosion has been directed on the process of losing soil material and sedimentation with less concern on nutrient loss. Few studies have reported important remarks that loss of nutrient through erosion should be defined with concern to support planning program of nutrient management through fertilization. Agus and Sukristiyonubowo (2001) reported that nutrients loss through erosion under seasonal based cropping system was higher than those under trees based cropping season. This nutrients loss has been noted to reduce income of farmers ranges from 14,600 to 205,400 rupiahs ha 1.yr 1. The study needs some further elaboration to which the major crops nutrients on Nitrogen (N), Phosphorus (P) and Potassium (K) are loss through erosion process. N, P and K are the major important nutrient for crops production, each having its own characteristic against transport by runoff. N and K are more mobile compared with that of P, so those nutrients are easy to transport by water through runoff process. Since N, P and K are incorporated and adsorbed in the soil materials especially clay particle, loss of those nutrients can not be avoided when erosion occurred until soil loss through erosion can be 1

controlled by conservation measures. Land management is also an approach to reduce N, P and K loss through erosion. Profitable land management techniques need to be introduced to increase quality and quantity of crops yield and income of farmers as well as to sustain land resources. Innovative technologies under the correct approach to implement are being a focus to address acceptable agricultural systems. In addition, research on the micro catchment scale (Craswell et al., 1998) is directed to develop such technologies, which are able to protect environmental damage and to be beneficial for farmers (Garrity dan Agus, 1999). These technologies are created by farmers as they need under the facilitation of researchers. The study has been conducted to understand the impact of dynamic of land use system and land management systems on erosion and nutrients losses. Materials and Methods Lowland rice, as terraced paddy rice field (PRF), was found in the valley of Babon catchment. It has total area of paddy field about 17 ha. In general, farmers cultivate rice twice per year. The first cropping season is started in OctoberNovember and harvested in FebruaryMarch and the second cropping season was from MarchApril to JuneJuly. IR64 variety is commonly planted with a spacing of 25 cm x 25 cm. Three dry land micro catchments namely Tegalan (TGL), Rambutan (RBT and Kalisidi (KLD) were selected as well for the experiment. Simple treatments of farmer practices and improved technology were set up. The term of farmers practice was used to represent a common treatment done by farmer, where only 50 kg ha 1 of Urea is applied. Meanwhile, the term of improved technology was used to define a treatment of fertilizer, which has been recommended by Food Crop Institute at District Level as high as 100 kg ha 1 season 1 of each Urea, TSP, and KCl. To assess nutrients balance under the different land used systems (TGL, RBT, KLD, and PRF), nutrients gain and loss were monitored and referred to as input and output data respectively. Although many nutrients show different characteristic in their dynamic, the study has only be directed to assess the dynamic of NPK. In PRF system, input data has been defined including concentration of NPK in fertilizer, rate of fertilizer, discharge, volume and concentration NPK in irrigation water, sediment concentration in irrigation water, NPK concentration in rainfall, total crop residues, and NPK concentration in crop residues, whereas the output data covers discharge, volume of suspended sediment, sediment concentration, rice grains production, rice straw production, NPK concentration in rice grains and straw. All parameters input and output were recorded in both field and laboratory. The basic approach to evaluate nutrients balance is described in Table 1 and 2. In the dry land system, NPK in irrigation water is excluded since there was no irrigation application. To study the effect of land management on nutrient balance, field experiment has been carried out in terraced paddy field. High yielding variety of rice of IR64 was cultivated involving ten cooperative farmers. Other materials, such as balances, plastic bags, bottles, rain gauges, stopwatch, buckets, and chemical materials related to nutrient analysis were used to measure both inputs and outputs parameters accordingly. It has been described before that not all parameters were measured based on some assumptions and limitation, which have been recognized including: The calculated value was based merely on actual measurement of inputs and outputs covered in the system. Total nitrogen, phosphorus, and potassium were the only nutrients considered. The reasons are: (a) N, P, and K are the major elements for crops growth; (b) usually N, P, and K fertilizers in the respective form of Urea (45% N), Super Phosphate36 (36% P2O5) and KCl (60% K2O) are widely applied. 2

If there was no disturbed soil structure by tillage, concentration incoming and outgoing sediments was considerably equal. Therefore, the calculation of soil and nutrient gain and losses were mainly based on the important activities conducted by the farmers. Table 1. Data collected and methods for the INPUTS unit in the assessment of N, P, and K balances at terraced paddy field system Input data Code and Nutrients Data required/collected Method of quantification Mineral Fertilizers IN1: N, P, and K Type of fertilizer applied Amount of fertilizer Applied Nutrient content in fertilizer Organic Fertilizer IN2: N, P, and K Amount of rice straw remain in the field Amount of rice straw recycled Nutrient content in rice straw that remain in the field Nutrient content in recycled rice straw Irrigation IN3: N, P, and K Water level Discharge Nutrient concentration in water Rainfall IN4: N, P, and K Daily, monthly and annual rainfall Nutrient content in rainfall N, P, and K deposition in rainfall / record Study literature (for checking ) B N F IN5: N Only Secondary data/study literature The study on nutrient balance at terraced paddy field has been conducted since beginning of dry season 2001. During this time, farmer practices were monitored by measuring rice yields (rice grains and rice straw production). The yields were sampled in 1 x 1 m plot, repeated three times for each terrace. Started in the rainy season 2001/2002 a simple treatment was developed by introducing dosage of 100 kg ha 1 season 1 each for Urea, TSP, and KCl as recommended by the Food Crops Institute at district level. Fertilizers were spread up to the soil surface during the application. The cropping season of rainy season 2003/2004 was started from October to November 2003 and harvested from February to March 2004. The second cropping season was in the dry season 2004 and began from March/April to June/July 2004. High yielding rice variety of IR64 was planted with spacing of about 25 cm x 25 cm. Six farmers have been involved in this study, three of them receiving the farmer practices treatment and the rest treated with improved technology. Farmers involved in the study increased with some numbers reaching to 10 farmers in the rainy season 2002/2003 and became 12 farmers in dry season 2003. Rice was planted from late December 2002 to January 2003. It was about two months delay compared with that in 2001/2002. The results in the rainy season 2002/2003 have been discussed with the farmers coming up with the idea to modify treatment for the dry season 2003. The treatment of the rainy season 2002/2003 was, then, combined with 66% of recycled rice straw. This treatment has been continued to monitor in the current year of 2004. The overall treatments directed to each three farmers are as follow: (1) farmer practices as control; (2) farmer practices + recycled rice straw; (3) improved technology; and (4) improved technology + recycled rice 3

straw. In the year of 2002/2003 contribution of rainfall was taken into account, therefore, nutrient balance was calculated according to the differences between inputs (the fertilizer addition, irrigation, crop residues, recycled rice straw, and rainfall) and outputs (erosion and removal by harvest). Rainfall was sampled once per month from all rain gauges. Table 2. Data collected and method for OUTPUT unit in the assessment of N, P, and K balances at terraced paddy field system Output data Code and Nutrients Data required/collected Method of quantification Harvested Product OUT1: N, P, and K Rice grain yield Nutrient content in rice grain Crop residues OUT2: N, P, and K Rice straw production Amount of recycled rice straw Erosion OUT3: N, P, and K Water level Discharge of outlet Nutrient concentration in suspended sediment Amount of rice straw for feeding Nutrient content in rice straw Sediment concentration Soil and nutrient losses Estimation based on field measurement : Soil loss = q x sediment concentration Nutrient loss = soil loss x nutrient concentration in sediment Leaching OUT5: N and K Secondary data/ Study literature. It may be neglected since there is pan layer that water can not pass through Soil erosion at terraced paddy field was measured from the land preparation (plowing, harrowing, and puddling) to rice harvesting. Since the measurement was emphasized on the soil lossgain and nutrient lossgain, therefore, samples of suspended sediment were taken from the main out let, the last terrace where the runoff goes out to the river, and the main inlet. The discharge of the main out let was determined using tipping bucket method. The bucket of 11 liter was used to measure discharge and to collect sediment samples. In addition, the relationship of water level and discharge of the inlet, where the water from the canal come to the first terrace, was determined as the product of water velocity (measured using float method) and the cross sectional of the flowing water at the gauge was measured. During land preparation, suspended samples were collected every 10 minutes, started from the first runoff at the Vnotch of the main outlet to the stage where color of suspended load became relatively the same as the one of incoming water through inlet. These samples were mainly taken to analyze sediment concentration. To determine nutrient in the run off water during land preparation, samples and discharge measurement were taken every 30 minutes. Meanwhile incoming nutrients from canal was sampled and monitored three times a day at 08:00, 12:00 and 16:00 o clock. 4

For the first and the second fertilizations, in flowing and out going sediments were sampled three times a day at 08.00, 12.00, and 16.00 o clock during a week before and after fertilizer applied. During these periods the farmers opened both inlet and outlet. When the fertilizers were added, both were closed for two days. So far, to monitor N, P, and K concentration in the water irrigation and rainfall, samples were taken once a month. The procedures and formula described by Sukristiyonubowo et al. (2003) were used to calculate soilnutrient losses and gains. Sediment concentration was determined in the laboratory and calculated as follow (Ceisiolka and Rose, 1998): Sediment Concentration = Oven dry mass sediment (1) Vol. of (sediment + water) Suspended load is calculated based on formula described by Hashim et al. (1998) and Tarigan and Sinukaban (1989) as follow: Suspended Load = Discharge x Sediment Concentration (2) Since the nutrient loss through erosion is the result of sediment yield and nutrient content of sediment, it is calculated as follow (Brata, 1999; Hashim et al., 1998): Nutrient loss = Soil loss x Concentration of nutrient in sediment (3) In the initial study, nutrient balance at terraced paddy field was calculated as the differences between inputs and outputs. The changes of nutrient in the soil were not taken into consideration. Nutrient inputs were accounted from the fertilizer addition, irrigation, and recycled rice straw, whereas nutrient losses were calculated from erosion and removal by harvest. For the year 2003, contribution of rainfall to nutrient input is included in the system. Results and Discussion Soil Loss through Erosion under Different Land Use Systems Temporal variation of soil loss under different land use is depicted in Figure 1. In general, soil loss under seasonal based cropping system (TGL) was higher compared with that under trees based cropping system (RBT and KLD). Under TGL system, the soil lost can be control by implementing soil conservation measure using grass planting either in the strip system or it is planted in the lip of the terrace. The grass has been planted was Benggala grass (Panicum maximum). After a year grass planting, the soil lost can be reduced as much as 50% in the first year and almost 90% after the second year (2003). At the third year, the soil lost was tended to increase but its increase was far lower compared with that before grass planting (2001). Generally, the soil loss occurred on year 4 increased compared with that occurred on several years before. The significant increase has been obviously observed under RBT and KLD systems. The reason is that there was land encroachment done by farmers to be used for cassava and the seasonal crops. This encroachment significantly increased soil loss. For sustainable implementation of conservation measure, grass planting has been combined with cattle fattening as an alternative to the conventional intensive annual crop cultivation in the TGL catchment. This strategy was based on lessons learnt from elsewhere in Indonesia that farmers adoption of alternative technologies is determined by the economic contribution of the measure to the household economy. Grass can be cut for fodder, while manure of the cattle can be best alternative for organic fertilizer for increasing soil productivity. This can also be better alternative for increasing farmers income. 5

25 Sediment Yield (t/ha) 20 15 10 Susp load Bed load T : Tegalan R : Rambutan K : Kalisidi 5 0 T2001 T2002 T2003 R2001 R2002 R2003 K2001 K2002 K2003 Figure 1. Soil loss through erosion under different land use in dry land areas of Babon catchment Nutrients Loss through Erosion under Different Land Use Systems Loss of N, P and K in TGL catchment was higher as it compared with the trees based cropping system (Figure 2). In TGL system, the loss of N, P and K were respectively 5.34; 1.82; and 1.65 kg/ha/year, higher than that in RBT system (0.001; 0.004; and 0.002 kg/ha/year) and mix of rambutan and shrub (0.028; 0.132; and 0.077 kg/ha/year). The higher loss of N, P and K in TGL was due to high rate of erosion (Table 3). By considering equaled fertilizers based on the nutrient losses, for the PRF cultivation, farmers paid more than US$ 16 per ha annually. Under TGL system, they paid more than US$ 4 per ha annually, but it was little cost (less than US$1 per ha annually) paid if their land was cultivated for tree crops as it was done for RBT and KLD. N, P and K (Kg/ha/year) TGL 10 8 6 4 2 0 N P K RBT KLD TGL 0.15 0.12 0.09 0.06 0.03 0 N, P, and K (Kg/ha/year) RBT, KLD Figure 2. N, P and K losses by erosion under different land management system in dry land areas in wet season 2003/2004 The different erosion between TGL and RBT systems has reported by Vadari et al. (2003). RBT has large canopy, which intercept direct impact of rainfall, so the erosion rate can be reduced. As far as the erosion control is concerned, the trees based cropping system is better 6

than that of seasonal based cropping system. If the seasonal based cropping system is prefer, soil and water conservation should be implemented to reduce soil nutrients losses. Generally, N, P and K has a negative balance in the rice field meaning that there was higher amount of nutrient loss from the rice field than the one enter to the field. This condition occurred especially under traditional management by farmers as it has been shown by the negative nutrient balance (Table 4). By applying the fertilizer, P in the rice field can be increased, while its loss can be reduced to enrich the P content in the soil. Table 3. N, P and K loss and on site cost of soil erosion Land use Nutrient loss and Equaled fertilizers (kg/ha/year) Cost 4) Tegalan Rambutan Kalisidi Rice field * N Urea 1) P 2 O 5 SP36 2) K 2 O KCl 3) 5.340 0.010 0.028 19.000 11.609 0.002 0.061 41.300 1.820 0.004 0.132 6.000 5.056 0.011 0.367 16.670 1.650 0.002 0.077 10.000 2.750 0.003 0.128 16.670 (US$/ha/year) 4.050 0.004 0.140 16.350 1) Urea contains 46% of N 2) SP36 contains 36% of P 2 O 5 3) KCl contains 60% of K 2 O 4) Price of Urea, SP36 and KCl fertilizers were respectively 1,500; 2,200 and 3,000 rupiahs per kg (1 US$ = 9,090 rupiahs as of May 2, 2007 curse) * Land management under farmer practices Table 4. The balance of N, P and K in the terraced paddy rice field Components N Balance P Balance K Balance FP IT FP IT FP IT Inputs Fertilizer Irrigation Straw Total Outputs Loss through harvest: Grain Straw Loss through erosion: Suspended load Bed load Total Balance (kg/ha/year) 90.0 40.0 22.0 6.1 6.1 11.0 62.0 5.5 4.7 75.0 174.0 11.6 50.8 86.0 45.0 22.0 73.0 140.0 131.0 61.0 19.0 211.0 71.0 146.0 102.0 19.0 267.0 93.0 FP: Farmer Practices; IT: Introduced Technology 20.1 4.3 6.0 30.4 18.8 22.2 12.1 6.1 40.4 10.4 26.0 103.0 10.0 139.0 53.0 50.0 11.0 78.0 139.0 22.0 171.0 11.0 204.0 65.0 Due to their mobility, N and K are relatively easy to leach. The balance of both nutrients was respectively 71.0 and 93.0 kg.ha 1.year 1 and 53.0 and 65.0 kg.ha 1.year 1 under Farmer s practices and fertilizer technology application. This balance has shown that the role of management to reduce the loss of nutrients and to its enrichment is very important. If so, the enrichment of nutrient in the soil can be achieved. When the 66% of rice straw was left in the field, concentration of especially N and K can be increased more than double. This increase of nutrient will be higher, if the fertilizer was applied. 7

In the studied site, rice straw is used for fodder and farmers generally take it all from the field by which there was no source of organic matter and nutrient especially N and K. To provide an alternative for farmers to have source of organic matter and fodder, the study introduced the use of straw as much as 66%. The straw application has a significant contribution on nutrient enrichment in the soil as shown by the positive nutrient balance. Conclusions In dry land areas loss of N, P and K from the area under seasonal based cropping system was higher compared with that from the area with the trees based cropping system. Intensive cultivation and the dynamic of land cover in area with seasonal based cropping system lead to high soil loss. Loss of N, P and K from TGL were as high as 5.34 kg ha 1 year 1 N, 1.82 kg ha 1 year 1 P and 1.65 kg ha 1 year 1 K, which were higher than those leave from RBT (0.001; 0.004; and 0.002 kg ha 1 year 1 ) and from KLD (0.028; 0.132; and 0.077 kg ha 1 year 1 ). The higher loss of N, P and K in TGL was due to high rate of erosion. Nutrient loss in the area under rice base cropping system (PRF) with intensive land management system is the highest among the land use systems treated. Loss of N, P and K were respectively 19.00, 6.00 and 10.00 kg ha 1 year 1, higher than those occurred in TGL, RBT and KLD prior to erosion and harvesting system. There was no significant different of nutrient loss through erosion in PRF under farmers practices and improved technology. The highest erosion and loss of nutrient occurred during the tillage. Those losses of nutrients implied to the onsite cost of erosion which has to be paid by farmers. By considering equaled fertilizers based on the nutrient losses, for the PRF cultivation, farmers paid more than US$ 16 per ha annually. Under TGL system, they paid more than US$ 4 per ha annually, but it was little cost (less than US$1 per ha annually) paid if their land was cultivated for tree crops as it was done for RBT and KLD. To reduce onsite cost of erosion and nutrient loss, conservation measures and appropriate land management techniques have to be implemented in combined with efficient use of fertilizers. Minimum tillage by puddling in rice field can be applied to minimize disturbance and to reduce soil loss through erosion. References Agus, F. and Sukristiyonubowo. 2001. Nutrient loss and on site cost of soil erosion under different land use systems in South East Asia. CrossCountry Analysis. Paper presented at MSEC Assembly, Hanoi 1015 December 2001. 15p. Ceisiolka, C.A.A. and C.W.Rose. 1998. The measurement of soil erosion. In Soil erosion at multiple scale. Principles and methods for assessing causes and impacts. CABI Publishing in Association with IBSRAM. p.287302 Craswell, E.T., C.Niamskul, and F.W.T. Penning de Vriest, 1998. Catchment approach to combating soil erosion in Asiathe Managing Soil Erosion Consortium. p 161173. In F.W.T. Penning de Vries, F. Agus, and J. Kerr eds.: Soil Erosion at Multiple Scale: Principles and Methods for Assessing Causes and Impacts. CABI Publishing in Association with IBSRAM. Garrity, D.P., and F. Agus. 1999. Natural resource management on a watershed scale: What can agroforestry contribute? pp. 165193 In Lal, R. (ed.) Integrated Watershed Management in the Global Ecosystem, CRC Press, Washington, D.C. Herschy, Reginald W. 1985. Stream flow measurement. Elsevier Applied Science Publishers, England. 553 p. Hashim, G.M.; K.J.Caughlan; and J.K. Syers. 1998. Onsite nutrient depletion: An effect and a cause of soil erosion. In Soil Erosion At Multiple Scale. Principles and Methods for Assessing Causes and Impacts. CABI Publishing in Association with IBSRAM: 207222 Sukristiyonubowo; Robert L. Watung; and F. Agus. 2003. Nutrient balance under terraced paddy field system at Babon Catchment Indonesia. Paper presented at MSEC Assembly held in Vientiane, Lao PDR. Tarigan, S.D.; and N. Sinukaban. 2001. The role of paddy fields as sediment filter: Case study in Way Besai Watershed, Lampung. Prosiding Seminar Nasional Multifungsi Lahan Sawah. Bogor 1 May 2001: 2937. 8