J.L. Maeght1; J.P. Montoroi2; Y. Enet3; S.
J. Wiengwongnam4 and C. Hammecker1
Keywords: Salinity, Electromagnetic Induction, Sandy soils, Rice field, Northeast Thailand
Salinity is a major constraint for rainfed rice production in Northeast Thailand sandy lowlands. Salinity surveys are currently performed using Electromagnetic Induction method (EMI) that is associated with soil conductivity measurements. Previous survey methods have consisted of performing EMI measurements during the dry season with the assumption that capillarity rise was the main cause of salt excess in the top layers of the growing rice. Hydrodynamic studies have demonstrated that in some cases the main process of salt enrichment of the top layer consists of the ascent of salt water from the aquifer during the rice cycle. An adaptation of EMI measuring device was realized in order to allow the surveys to be performed during the flooded period. Measurements in horizontal and vertical dipole configuration were performed in an area of contrasted salinity, comparing the obtained values with the conductivity of soil and water mixtures of the top layer. Measurements during rice flooding period indicated better relationship between salt contents and vertical dipole measurements than those performed during the dry season. Salinity in the top layers in the two different stages was identified with two different processes of spatial distribution: on the one hand, capillarity rise during the drying period, and on the other hand the circulation of saline solutions during the flooded periods. Therefore, EMI measurements during flooded periods should be recommended in salt-affected sandy paddy soils as more accurate and representative of conditions that influence plant performance.
1 Institut de Recherche pour le Développement (IRD), Office of
Science for Land Development, Phaholyothin Road, Chatuchak, Bangkok 10900,
2 IRD, centre d’île de France, 32 Rue Henri Varagnat, F-93143, Bondy cedex , France Cedex
3 Université Paris XII Val-de-Marne, 61 avenue du Général de Gaulle, 94010 Créteil, France Cedex
4 Department of Land Development. Office of Science for Land development, Phaholyothin Road, Chatuchak, Bangkok 10900, Thailand.
Promkutkaew, A.1; O. Grunberger1; S. Bhuthorndharaj2 and A.D. Noble3
Keywords: Cation Exchange Capacity determination methods, sandy and salt-affected soils, paddy fields
Sandy soils of Northeast Thailand have for long been identified as problematic soils. Acidity, salinity, low organic matter contents and low cation exchangeable capacity (CEC) have been established as the main soil constraints to rice production on these sandy soils. CEC values are dependent on clay content, soil organic matter content and soil pH. In the context of sandy salt-affected soils, precise and accurate determinations of low CEC values are often considered problematic and a large number of methods are available to measure this attribute. The objective of the study was to compare the values obtained on a set of 6 samples using different methods of CEC determination in the context of salt-affected sandy paddy soils. Ammonium acetate method at pH 7 and cobalt-hexamine at soil pH methods with or without alcohol pretreatment were compared with compulsive method, with CaCl2 at the same pH. In sandy soil paddy profiles with a low clay content and CEC values measured with compulsive methods, less to 2.67 cmolc kg-1 determinations with ammonium acetate and cobalti-hexamine methods presented linear relationships with the compulsive method results in cmolc kg-1(of soil) CECcobalt = CECcompulsive* 0.45 + 1.84, R2 = 0.93) and (CEC ammonium = CECcompulsive* 0.37 + 1.91, R2 = 0.87). The same type of relationships were established performing previous alcohol treatment in order to remove salts although with lower significance (respectively R2 = 0.56 and R2 = 0.80). These results indicate that using ammonium acetate or cobalt-hexamine methods, in salt-affected sandy soils with a CEC lower 2.67 cmolc kg-1 will lead to overestimation of CEC when compared to compulsive method. This overestimation was found to be independent of pH values and salt-effect.
1 IRD – Land
Department Development, Office of Science for Land Development, Phaholyothin
Road, Chatuchak, Bangkok
2 Land Department Development, Office of Science for Land Development, Phaholyothin Road, Chatuchak, Bangkok 10900, Thailand
3 IWMI Southeast Asia, c/o WorldFish Center, Jalan Batu Maung, Batu Maung, 11960 Bayan Lepas, Penang, Malaysia.
Wiriyakitnateekul, W.1; A. Suddhiprakarn 2; I. Kheoruenromne2 and R.J.Gilkes3
Keywords: Light-textured soil, kaolin, CEC, specific surface area
Highly weathered light-textured soils with low chemical activity are common in Thailand and provide significant management constraints. Representative topsoils and subsoils of Kohong, Klong Thom, Sadao, Tasae, Yasothon, Thai Muang, Chalong, and Hang Chat series have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and chemical analyses. Clay-sized particles in the soils range from 76 to 207 g kg-1 (median 139 g kg-1). These soils are acid (pH in water 4.0-4.8), having very low to low organic matter contents (2.4-23.4 g kg-1), low cation exchange capacity (0.6-4.5 cmolc kg-1), and very small to small values of specific surface area (SSA) (2-11 m2 g-1). Kaolin group clay minerals are the major constituents (>70% content) of the clay fraction, with minor amounts of inhibited vermiculite, illite, quartz, and anatase. Goethite is present in most of the soils with hematite in Sadao series (Typic Kandiudults). These soil kaolins exhibit a wide range of crystal sizes ranging between 0.06 to 0.83 µm, and most of the crystals are very small, euhedral, hexagonal platy. They contribute most of the CEC of these soils.
The Fed concentrations in these soils (4-12 g kg-1) are much higher than Feo concentrations (0.2-1.6 g kg-1) with the values of Feo /Fed ranging from 0.05 to 0.23 (median 0.12) indicating that most of the free iron oxides are crystalline which is consistent with XRD measurements. Amounts of Ald and Alo are about equal with median values of 0.7 and 0.4 g kg-1, respectively. These oxide constituents are important for the retention of anionic plant nutrients.
CEC provides a measure of cation retention as does SSA and both properties have linear positive significant relationships with clay content (r = 0.58, 0.93), Ald (r = 0.79, 0.75), Alo (r = 0.81, 0.62), and Feo (r = 0.69, 0.68).
We consider that the small amounts of clay-sized materials in these soils play a vital role in plant nutrient retention and the soils should be managed conservatively to protect these materials.
1 Office of Science for Land
Development, Land Development Department, Chatuchak, Bangkok 10900, Thailand.
2 Department of Soil Science, Kasetsart University, Bangkok 10900, Thailand.
3 School of Earth and Geographical Science, Faculty of Natural and Agricultural Science, University of Western Australia, Crawley, WA 6009, Australia.
Srikhun, W.1 and P. Keerati-Kasikorn1
Keywords: Light-textured soil, P-sorption isotherms, P desorption
Sandy soils which are very common in Northeast Thailand have the capacity to adsorb different amounts of phosphate. This study was undertaken to determine the amount of adsorbed phosphate released from five sandy soils from the region. Adsorption was first carried out by shaking samples of each soil for 30 minutes, twice daily for 6 day, with 0.01 M CaCl2 solution containing phosphate in a concentration range from 1 to 32 mg P L-1. Desorption isotherms were determined in a similar manner by re-shaking the wet samples and their adsorbed phosphate with calcium chloride solution using a soil:solution ratio of 1:10. Measurements suggest that phosphate sorption for all soils were almost irreversible. The adsorption and desorption isotherms of all soils conformed to the Langmuir equation. The adsorption maximum value was used to determine the phosphate saturation. Desorption of adsorbed phosphate increased with increasing saturation percentage. Average desorbability at low saturation (<20%) and high saturation (>80%) was 0.5 and 12% respectively. Dithionite – citrate – bicarbonate and oxalate extractable iron were the major phosphate adsorbents in the study.
1 Department of Land Resources and Environment, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand.
Caignet, I.1; A. Iserentant 1;
W. Wiriyakitnateekul2; S. Suksan2;
J.L. Maeght2; C. Hartmann2 and B. Delvaux1
Keywords: Sandy soils, clay mineralogy, proton-consumption, clay dissolution
Poorly fertile sandy soils are widespread in Northeast Thailand. This represents a serious threat to local farmers and constrains economic development in the region. Here, we evaluate the fertility of these soils. We studied the physico-chemical and mineralogical properties of five pedons along a transect located at 25 km Southwest of Khon Kaen, respectively under forest (F), sugarcane (SC) and in paddy fields (PF1, PF2, PF3). All soils have a very low organic matter content (<1%). They differ in weathering stage and mineral reserve. The well drained soils under the F and SC are more weathered than the poorly drained PF profiles. Kaolinite is the major phyllosilicate in F and SC, whereas smectite is the dominant clay mineral in PFs. In the toposequence, the total content of major alkaline and alkaline-earth cations (TRB), i.e. mineral reserve, is confined to the clay fraction (<2 µm). From PFs to SC and F, it decreases with decreasing CEC and total Mg content, as well as with the disappearance of smectite and the appearance of 1:1-2:1 mixed layered clay minerals. In addition, KCl-extractable Al becomes the major cation on the effective CEC in the well drained soil profiles. We propose that clay minerals act here as key proton-consumers. As such, smectite dissolution is supported by a high content of exchangeable Mg relatively to Ca, and by the XRD detection of 1:1-2:1 interstratified clays. Such clay minerals represent, indeed, an intermediate stage in the processes of smectite dissolution and kaolinite formation in low silica and freely drained soil environments. The conservation of the clay exchanger must be a key objective in the management and use of these poor sandy soils. In addition, in situ soil monitoring is required to further assess the dissolution of 2:1 clay minerals and the proposed corresponding Mg-depletion.
1 Université Catholique de Louvain, Faculté d’Ingénierie
Biologique, Agronomique et Environnementale, Croix du Sud 2/10, 1348
2 Land Department Development, Office of Science for Land Development, Phaholyothin Road, Chatuchak, Bangkok 10900, Thailand.
Tawornpruek, S.1; A. Suddhiprakarn 1 and I. Kheoruenromne1
Keywords: Sugarcane production, light textured soils, chemical and physical properties, suitability assessment
A study on the potential of Quartzipsamments to support the growing of sugarcane on the Southeast Coast, Thailand was undertaken on four representative soil areas. The methodology used in this study included pedon analysis of soils in the selected areas, laboratory analyses of their physico-chemical properties, mineralogy, micromorphological characteristics and assessment of their properties related to sugarcane crop requirements.
Results of the study revealed that these soils are Quartzipsamments deposited on the coastal plain. They are deep soils developed mainly on local alluvium and wash deposits derived from granite. Their micromorphological characteristics show subangular to subrounded quartz grains as the major fabric component. Their texture ranges from sand to loamy sand and their bulk density ranges from moderately low to high (1.40-1.82 Mg m-3). Chemical analysis of soils indicates that they have a strong acid to neutral reaction (pH 5.1-6.8). They have very low to low organic matter contents (0.2-9.4 g kg-1), very low total nitrogen (0.01-0.03 g kg-1), very low to high available phosphorus (1-95 mg kg-1) and very low to low available potassium (1.5-46.8 mg kg-1). The soils have very low to medium cation exchange capacity (2-11 cmolc kg-1). Their base saturation percentage varies widely from 4-77%. Their electrical conductivity ranges from 0.1-1.9 dS m-1 indicating no salt-effect.
Fertility assessment results indicate that most of these sugarcane-growing soils have low fertility except for a single area where the soil has a moderate fertility status. Their potential based on suitability assessment indicates that most of them are moderately suited but one profile is not suited for sugarcane growing because of its sandy texture and strongly acid condition. A recommended approach to increase their potential for sugarcane growing includes an emphasis on soil organic matter conservation and a more intensive soil-fertilizer management. A continuing effort on soil-fertilizer management is clearly needed to maintain effectiveness in sugarcane growing on these soils.
1 Department of Soil Science, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
Maquère, V.1, 2;
J.-P. Laclau2; J.L.M. Gonçalves3; A.V. Krushe4;
M.F.G. Rosias6 and J. Ranger7
Keywords: Eucalyptus, biogeochemical cycles, soil solution, chemistry, nitrate, aluminum, fertilization, Brazil
The present paper is part of a comprehensive approach currently developed in Brazil to study biogeochemical cycles at the ecosystem level in Eucalyptus grandis plantations. It aims at assessing changes occurring in water chemical composition throughout their transfer in the soil, during the first year after planting. A lysimetry was installed in a 5-year-old E. saligna stand. Lysimeters were strategically positioned within a compartment of E. saligna prior to the clear felling of the stand that would allow the assessment of a fertilization experiment planned on the same site for the next rotation. About 180 zero-tension lysimeters were installed in the upper soil layers and 136 ceramic cups were setup horizontally down to a 3 m depth and connected to an automatic vacuum pump. After the harvest of the E. saligna stand, a fertilization experiment of E. grandis improved seedlings was initiated using a complete randomized block design, with 6 blocks and 5 treatments. The objective was to compare the influence of different amounts of ammonium sulphate and sewage sludge fertilizations on biogeochemical cycling. At the end of the rotation, nutrient concentrations in soil solutions were low whatever the depth and the lysimeter type. After clear felling, soil solution ionic balances were dominated by NO3- and Al3+, whose concentrations increased substantially. No obvious change in concentrations was observed for all other elements. A proton unbalance, resulting from the interruption of NO3- uptake by plants after harvesting, might be responsible for the aluminium accumulation in soil solutions. After planting, fertilizer inputs were responsible for increasing concentrations of all elements applied until 1 m deep. Twelve months after planting E. grandis, the chemistry of soil solutions at 3 m deep had not developed. The monitoring of soil solution chemistry is going on in order to quantify the effects of these different fertilizations on deep drainage nutrient losses.
Fast growing Eucalyptus plantations cover approximately 3 millions hectares in Brazil. This sector is of great economical importance since the Eucalyptus-plantation production supplies the Brazilian cellulose and paper industry as well as the metallurgy industry through the production of vegetal charcoal. Due to several decades of research, the productivity of these plantations now ranges from 30 to 50 kg ha-1 year-1 according to soil characteristics and water availability (Gonçalves et al., 2004).
The ecological impact of Eucalyptus plantations has been widely discussed around the world (Cossalter and Pye-Smith, 2003). In particular, water consumption by eucalypt stands has been extensively investigated. But few studies have ever assessed the influence of silviculture on superficial water chemistry. Such studies are nonetheless necessary to identify and foster practices minimizing the silvicultural impact on the water table chemistry of afforested catchments.
A comprehensive approach is currently being conducted at the University of São Paulo to study the biogeochemical cycles of nutrients in Eucalyptus grandis plantations. This project is developed at the ecosystem level in an experimental stand representative of large areas of plantations in Brazil. The overall aim of the study is to assess the consequences of silviculture, and more particular of different fertilizer inputs, on water quality and long-term soil fertility by measuring water and nutrient fluxes throughout the ecosystem. The present paper focuses on changes occurring in soil solution chemical composition during the first year after planting.
Materials and methods
The study was conducted at the ESALQ/USP experimental station of Itatinga (23º02′S, 48º38′W). The annual mean precipitation is 1,300 mm and the annual mean temperature is 20ºC. Figure 1 shows the time course of rainfall and temperature over the sampling period. The selected site is representative of the typical relief of the São Paulo Western Plateau. The maximum altitude of the area is 863 m. The slopes are flat to undulating (3%) in the experimental stand. The lithology is composed of sands, Marilia formation, Bauru group. The soils are “Latossolos Vermelho-Amarelo” according to Brazilian classification. Soil analysis showed that sand content was >75%, whatever the soil layer, down to >6 m.
Figure 1. Time course of average temperature (ºC) and total precipitation (mm) at the experimental site
The Itatinga experimental station has been covered for 60 years with Eucalyptus saligna plantations. These stands were first planted in 1945 on pasture and have been managed in short rotation coppices for fire wood production since then. The experimental design was implemented in 2003 in a 6 ha coppice harvested in 1997, and planted in 1998 with Eucalyptus saligna. Tree spacing was 3 m X 2 m and only a NPK (10:20:10) starter fertilization of 300 kg ha-1 was applied.
A lysimetric design was installed at the beginning of 2003 in the 5-year-old E. saligna. Lysi-meters were positioned appropriately for a fertilization experiment planned on the same site for the next rotation, after the harvest. A 3 months period was left for soil stabilization, and then nutrient fluxes were monitored over a 9 month period prior to the harvesting of the stand (from July 2003 to February 2004). In February 2004, the stand was clear felled and the stumps killed using glyphosate. Improved E. grandis seedlings were planted on the same planting rows at half-distance between the stamps, without any soil preparation. The previous stocking density was maintained (2 m × 3 m spacing).
A nitrogen fertilization experiment was then initiated using a complete randomized block design, with 6 blocks, 5 treatments and 100 trees per plot. The fertilization treatments imposed were those classically used by Brazilian companies on these soil types: all mineral fertilizers but N (T1) (Control), all mineral fertilizers (T3), and sewage sludge fertilization (T5). Nutrient fluxes were measured in these three treatments (T1, T3, T5) in blocks 1, 2 and 3. Blocks 4, 5 and 6 were installed to sample trees at various ages without disturbing the lysimetry design (Table 1). T2 and T4 treatments were installed to help establish a response curve to N inputs. The fertilizations applied in each treatment are presented in Table 1.
The soil solution sampling equipment was installed in blocks 1, 2 and 3 of treatments T1, T3, T5 according to a systematic constant scheme. Throughfall solutions were collected from 12 funnels systematically located beneath the trees in each one of the 9 experimental plots. In each plot, 3 sets of 9 narrow zero-tension lysimeters (40 × 2.5 cm) were installed beneath the forest floor, and zero-tension plate lysimeters (50 x 40 cm) were introduced at 15, 50 and 100 cm deep (5 at each depth) from pits backfilled after installation with the horizons in their natural arrangement. The litter and soil solutions were collected in polyethylene containers situated downhill in closed pits. Moreover, 4 replicates of tension lysimeters were installed horizontally at the depths of 15 cm, 50 cm, 1 m, and 3 m in each plot. They were connected to a vacuum pump and automatically maintained at a constant suction of -70 kPa. Ceramic-cup solutions were collected in glass bottles. All lysimeters were set up representatively near and between the trees to take into account spatial variability. In each plot, lysimeters of same type and depth were connected to one collector in order to reduce the number of chemical analyses. Chemical analyses of solutions collected by each ceramic cup separately were performed in a few blocks and depths in order to estimate the spatial variability (data not presented). Rainfall solutions were collected in a 1 ha opened area, next to the experimental plots.
Table 1. Experimental treatments and fertilization strategies imposed
4 equal partsat planting
40 kg ha-1
120 kg ha-1(commercial fertilization)
360 kg ha-1
350 kg ha-1 Ntotal
10 t ha-1 sewage sludge (Barueri, SP)
2 equal parts at planting at 8 months
Solutions were collected each week from July 2003 to June 2005. A composite sample for each type of collectorwas prepared every 4 weeks. The solutions were filtered (0.45 µm) and the pH was measured. SO42-, NO3-, NH4+, Cl-, H2PO4-, K+, Ca2+, Mg2+, Na+ were analysed by chromatography (Dionex). Al, Fe, Si and dissolved organic carbon (DOC) were determined by ICP and Shimadzu equipment for each depth, treatment and collector type on a three-block composite sample.
Soil solution ionic balances were computed considering the species: SO42-, NO3-, NH4+, Cl-, H2PO4, K+, Ca2+, Mg2+, Na+, H+. NO2 and Fe concentrations were very low so that they were neglected in the calculations. As the pH of soil solutions were between 4 and 5 until 1 m deep, aluminium was considered as Al3+ in this first preliminary approach.
The whole study will help to relate the soil solution characteristics to the dynamics of biomass and nutrient accumulation in the stands, as well as of nutrient returns to the soil with litter fall and forest floor decomposition.
Results and discussion
Nutrient concentrations in soil solutions were low (<100 µmolc L-1) over the 9 months of monitoring at the end of stand rotation, whatever the depth and the type of lysimeter (Laclau et al., 2004). A similar behaviour was observed in other tropical forest plantations. This confirms the species ability to prevent deep drainage nutrient losses as soon as the root system is completely developed (Lilienfein et al., 2000; Laclau et al., 2003a).
Clear felling sharply increased nitrate concentrations in surface (0-50 cm) soil layer solutions, and this, without any fertilizer application (Figure 2). This pattern suggests that the sudden interruption of N uptake by plants resulting from herbicide application, combined with the production of mineral N by the mineralization of soil organic matter and forest residues, led to an accumulation of mineral N in these soil layers.
Soil solution ionic balances were dominated by NO3- and Al3+, and the concentrations of other elements were little influenced by clear felling during the first months (data not shown). The accumulation of NO3- in soil solutions was thus linked with the release of Al3+ in soil solutions. The hypothesis formulated to explain such behaviour was that the interruption of NO3- uptake by plants leaded to a proton unbalance which might be responsible for the accumulation of aluminium in soil solutions. Indeed, after clear felling, the protons released during the nitrification were no more removed from soil solutions by plant anion uptake and thus, accumulated in the soil solution (Van Breemen et al., 1984). The H+ may then have desorbed the Al3+ on the ion-exchange sites and solid phase dissolution, leading to an increase of aluminium concentrations in soil solutions. As an increase of Si concentration in soil solutions was also observed after clear cutting, some mineral weathering may also have occurred under H+ influence, releasing mineral Si and Al in soil solutions.
After the planting, fertilizer inputs were responsible for an increase in surface layer concentrations in all elements applied (K+, Cl-, NH4+, SO42-, Ca2+, Mg2+). It resulted in increasing sums of cations and anions as well as the predominance of the elements brought by fertilization in the ionic balance, as for NH4, Mg and Ca regarding cations (Figure 3). The sum of cations was then very high (>7,000 µmolc L-1) but declined with depth and time until reaching more common values at 3 m deep. At this depth, the sum of cations was approximately 200 µmolc L-1, that is, of the same order of magnitude of total cationic concentrations observed before clear felling and confirms previous observations under Eucalyptus plantations in the Congo (Laclau et al., 2003a). These values confirm the nutrient poorness of these sandy soils. In comparison, total cationic charges reported in solutions collected in undisturbed Eucalyptus native forests in Australia were about 1,000 µmolc L-1 (Adams and Attiwill, 1991; Attiwill et al., 1996) as in most studies in temperate forest ecosystems (e.g. Beier and Hansen, 1992; De Vries et al., 1995; Cortez, 1996; Marques and Ranger, 1997).
Figure 2. Time course of nitrate and aluminium concentrations (mg L-1) at different soil depths according to the fertilization applied. T1: 0 N; T3: 30 kg N ha-1 at age 0, 6, and 12 months; T5: 5 t ha-1 of sludge waste (180 kg N ha-1) applied at age 0 and 8 months. Vertical bars represents standard deviations when n ≥3
In the case of aluminium and nitrates, this enrichment was cumulated in treatments T3 and T5 to the first accumulation mentioned above (resulting from herbicide application). During the winter 2004, nitrate concentrations reached 80 mg L-1 in the top soil (15 cm deep, solutions sampled by ceramic-cup lysimeters). After September 2004, the rainfall events led to a decrease in nitrate concentrations at 15 cm deep. Nitrates were then leached to deeper soil layers, as well as uptaken by tree roots to support the growth. The nitrate concentration peaked at 50 cm deep from September 2004 to February 2005, where it reached 95 mg L-1 in T5. It reached the depth of 100 cm from January to May 2005 where it ranged up to 60 mg L-1 in T3 and T5 (Figure 2). Fifteen months after clear felling the E. saligna stand and twelve months after planting E. grandis, the soil solution chemistry of deeper layers (300 cm deep) had not been modified. Soil moisture sensors (TDR) installed in the experiment showed that preferential drainage were not the dominant transfer process in this sandy soil, which was consistent with the time course of NO3-concentrations at 3 m deep.
Figure 3. Time course of cations (µmolc L-1) at different soil depths in treatment 3.Valency attributed to each cation: H+, Na+, N-NH4+, K+, Mg2+, Ca2+, Fe3+, Al3+
Moreover, soil solution concentrations can be compared to nutrient uptake by the trees. At 1 year of age, the total dry biomass (above and below-ground) of the stands were 9,380, 12,430 and 10,920 kg ha-1 in treatments T1, T3 and T5, respectively (Laclau et al., 2005). The amount of nutrients taken up from the soil during the first year of growth ranged from 70 to 104 kg N ha-1, 4 to 9 kg P ha-1, 31 to 46 kg K ha-1, 31 to 45 kg Ca ha-1, 10 to 17 kg Mg ha-1, according to treatment. A sharp increase in Leaf Area Index (LAI) was observed during the first rainy season (LAI ranged from 0.4 to 0.7 at age 6 months and from 2.0 to 2.7 at age 1 year). During the second year of growth, the tree uptake should considerably increase: at the end of the first year of growth, the root system had already reached 3 m deep, and during the second year of growth stand nutrient requirements will be maximal (Laclau et al., 2003b). Moreover, evapo-transpiration is expected to increase in this stand until canopy closure at age 2 years. The drainage flux should then considerably decrease until 3 m deep during the second year of growth. Beyond 3 m deep, soil moisture sensors (TDR) installed in this experiment will make it possible to quantify the drainage fluxes and therefore the losses of nutrients. These losses are expected to be low since during the first year of growth the soil solution enrichment had not reach 3 m yet, and since as seen before, the nutrient uptake by the trees is expected to increase significantly during the second year of growth.
The biogeochemical cycling study in progress in this Brazilian eucalypt plantation showed a clear influence of clear felling on nitrate and aluminium. Despite high rainfall amounts, one year after planting, they had not reached the depth of 3 m yet. This pattern, as well as TDR sensors installed in the experiment, suggests that preferential drainage was negligible in this sandy soil. The monitoring of soil solution chemistry will go on during the second year of growth.
This study is expected to assess whether the fast development of eucalypt root system and the high nutrient requirements of the early growth make it possible to avoid large nutrient losses by deep drainage, despite the relatively high amounts of fertilizers applied.
We thank the São Paulo Research Support Foundation FAPESP (Project 02/11827-9) for providing financial support.
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1 ENGREF, 19 avenue du Maine, 75732 Paris Cedex 15
France, E-mail: email@example.com
2 CIRAD,UR80, département Forêts, TA 10/C, 34398 Montpellier Cedex 5, France.
3 ESALQ/USP. Departamento de Ciências Florestais, Av. Pádua Dias, 11, Caixa Postal 530, CEP 13400-970, Piracicaba, SP, Brazil.
4 CENA/USP. Laboratório de Ecologia Isotópica. Caixa Postal 96, Av. Centenário, 303, CEP: 13400-970 Piracicaba, S P, Brazil.
5 CENA/USP. Laboratório de Biogeoquímica Ambiental, Caixa Postal 96, Av. Centenário, 303, CEP: 13400-970 Piracicaba, SP, Brazil.
6 CENA/USP. Laboratório de Química Analítica, Caixa Postal 96, Av. Centenário, 303, CEP: 13400-970 Piracicaba, S P, Brazil.
7 INRA, Biogéochimie des écosystèmes forestiers, 54280 Seichamps, France.
Murakami, M.1;S. Amkha1; K.
Inubushi1; K. Yagi2; D. Tulaphitak3;
T. Tulaphitak3and P. Saenjan3
Keywords:Methane and CO 2 emissions, paddy rice, saline sandy soils
In recent years, atmospheric composition of greenhouse gases has been changing rapidly. Since methane (CH4) is continuing to increase its concentration faster than other greenhouse gases such as carbon dioxide (CO2) and nitrous oxide (N2O), methane attracts attention internationally as an important greenhouse gas. The paddy field occupies one of major sources of the methane. In this r esearch, production potential of the greenhouse gases in tropical saline sandy paddy soil was investigated and the influences of fertilization and methods of crop establishment on these gases fluxes were also examined in tropical saline sandy paddy fields. The soil samples were collected from three paddy fields (Ban Kota, Ban Don Do, Ban Kham Pia) in Khon Kaen, Thailand and used inr laboratory incubation experiments to measure CH4 and CO2 product potential, mineral N, soluble organic carbon and ferrous iron changes during the incubation. Mor eover, we measured greenhouse gas fluxes by the closed-chamber method in Ban Kota paddy field. Methane production varied widely among soils, but similar trends were observed with CO2 production, although not as other parameters. Methane and CO2 emissions were higher from broadcasted rice crops when compare with transplanted plots but no obvious difference was found between organic and chemical fertilization treatments.
School of Science and Technology, Chiba University, Matsudo, Chiba, Japan Chiba
271-8510 Japan, e-mail: firstname.lastname@example.org
2 National Institute for Agro-Environmental Sciences, Tsukuba, Japan.
3 Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand.