Dự án nông nghiệp " Major Cropping Soils of Gia Lai Province, Vietnam, and Soil Constraints to Productivity of Major Upland Crops Grown by Smallholders " ppt

Attachment 1 009/06 VIE: Improving capability of provincial extensionists for assessing soil constraints to sustainable production through the use of the SCAMP decision support system. Major Cropping Soils of Gia Lai Province, Vietnam, and Soil Constraints to Productivity of Major Upland Crops Grown by Smallholders PW Moody A and Phan Thi Cong B A Queensland Department of Natural Resources and Water, Indooroopilly, Qld 4068, Australia B Institute of Agricultural Sciences of Southern Vietnam, Ho Chi Minh City, Vietnam 1. Introduction The Soil Constraints and Management Package (SCAMP) has been developed to identify soil constraints to crop production by considering a range of key soil properties (Moody and Phan Thi Cong 2008; Moody et al. 2008). Once these constraints have been identified, management practices that ameliorate or modify these constraints can be formulated. Crops vary in their tolerance to soil constraints and a soil property limiting the productivity of one crop may not be a limitation to the productivity of another crop. Therefore, once the constraints of a particular soil type have been identified, the soil can then be assessed for its ability to potentially support the production of specific crops. The objectives of this report are to:  review existing information on the identification and extent of upland cropping soils in Gia Lai Province, Vietnam.  identify the major soils used for smallholder cropping, and determine their constraints by the application of SCAMP.  identify the major crops/cropping systems used by smallholders in Gia Lai Province, and document the specific soil requirements of these crops/cropping systems.  link soil constraints to the soil requirements of the major upland crops and develop management guidelines for the management of specific soil types for specific crops. 2. Major Soils used for Smallholder Cropping The areal extents of the different soil groups (FAO-UNESCO classification) that occur in Gia Lai Province are presented in Table 1. Table 1. Areal extent of Soil Groups in Gia Lai Province. Source: Le Trung Lap, 2000. Soil Groups Area (ha) Proportion (%) Chromic and Haplic Acrisols Acric,Humic and Vetic Ferralsols 756,433 49 Dystric and Gleyic Arenosols Luvisols 364,638 23 Leptosols 164,752 11 Alumic, Hyperdystric and Chromic Acrisols Acric, humic and Vetic Ferralsols 90,481 6 Mollic Fluvisols Luvic and Fluvic Phaeozems Cambisols 64,218 4 Dystric Gleysols 16,774 1 Others 92,275 6 TOTAL 1,549,571 The land forms of Gia Lai have been classified (Berding et al., 1999) as:  Hills and low mountains,  Basaltic plateaus,  Gently to rolling uplands on metamorphic or granitic rocks or on recent alluvium and  Depositional areas. 2 Topography (slope) limits the agricultural use of many areas of Gia Lai, and the major soil groups of agricultural importance are the Ferralsols and Acrisols occurring on the basaltic plateaus and gently to rolling uplands. These soil groups comprise about 49% of the land surface of the province (Table 1, line 1). 3. Soil Constraints and Management Practices for Sustainable Crop Production In a recent study (Moody et al. 2008), sites identified on the 1:100,000 soils map of Gia Lai Province as 'Red-brown soils on basalt' (Ferralsols) and 'Grey soils on acid igneous rocks' (Acrisols) (Le Trung Lap, 2000) were selected from the basaltic plateaus and gently to rolling uplands areas. Fourteen Ferralsols were sampled under a range of land uses (maize-upland rice, maize-cassava, rubber, coffee, eucalypt plantation, fruit trees, cashew) in Dak Doa, Mang Yang, Chu Pah, Ia Grai, Duc Co, Chu Prong and Chu Se Districts of north west Gia Lai Province. Sixteen Acrisols were sampled from various positions (upper, mid, lower slope) in the landscape under several land uses (maize, cassava, sugarcane, vegetables) in the vicinity of Dak Po Village, Dak Po District in the east of Gia Lai Province. Mini-pits were dug at each site and SCAMP Level 1 and Level 2 assessments made (Table 2). A composite 0-15 cm soil sample was taken from each site to represent the plough layer and analysed for Level 3 attributes (Table 2). Table 2. Attributes determined for each application level of SCAMP. SCAMP level Attributes Level 1 Texture, colour (moist) of soil matrix and mottles, structure and consistence (moist), drainage class, permeability class, slope, erosion hazard, gravel content, compaction Level 2 Field pH (water and 1M KCl), field EC, dispersion class, infiltration rate Level 3 Organic C, clay %, P fixation capacity, exchangeable Ca, Mg, Na and K, extractable acidity (H +Al), ECEC, pH buffer capacity (calculated) From these data, SCAMP (Moody and Phan Thi Cong, 2008) was used to identify the constraints of these two major soil groups to sustainable production (Table 3). Table 3. SCAMP descriptors for 14 Ferralsols and 16 Acrisols of Gia Lai Province, Vietnam. Number of sites with the attribute is in parentheses. Attribute Ferralsols Acrisols Texture L (9); LC (5) L (10); C (2); LS (4) Erosion hazard er(slight) (9), er(moderate) (2), er(high) (2), er(very high) (1), er(slight) (3); er(moderate) (2); er(high) (6); er(very high) (3); er(extreme) (2) Water pathway drainage (7); drainage + runoff (7) drainage (8); drainage + runoff (5); runoff (3) Acidity surface a (14); subsurface a (12) surface a (2); subsurface a (1) Acidification hazard ar(low) (14) ar(low) (2); ar(moderate) (12); ar(high) (2) Low nutrient retention e (12) e (3) High P fixation i (14) Low organic C om (2) Low K reserves surface k (1); subsurface k (1) surface k (1); subsurface k (7) Variable charge characteristics geric (4) Hard-setting hs (2) Compaction comp (4) 3 These assessments indicate that the Ferralsols are predominantly loamy in texture, with a range of erosion hazards depending on site slope. The main pathways of water movement are by drainage or runoff plus drainage. They typically have a low soil pH (<5.2 in water) but a low acidification hazard because of their high organic C and clay content. ECEC is typically very low (<4 cmol c /kg) and they have a high P fixation capacity. The variable charge component of several of the soils is near, or at, the point of zero net charge (pH KCl -pH water ranging between -0.10 and 0.10). The Acrisols are predominantly loamy in texture, although a loamy surface over a sandy subsurface sometimes occurs. Erosion hazard ranges from slight to extreme depending on site slope. Drainage is the main pathway of water movement in half of the sites, with the remainder exhibiting runoff plus drainage or runoff pathways. Acidity constraints are not common, but most of the soils have a moderate acidification hazard because of their low clay and organic matter contents. Low subsurface K reserves commonly occur. Hard-setting surfaces or compaction occurred at several sites. The main constraints identified for the Ferralsols were acidity (a), low nutrient retention (e), high P fixation (i), and variable charge characteristics (geric), with drainage being the most common pathway of water movement (Table 2). With these constraints, the SCAMP database would indicate the following management strategies for sustainable productivity: a: Acid tolerant crops should be grown as a short term response to this constraint. For long term sustainability, a liming program should be commenced with regular monitoring of soil pH. e: CEC should be increased by increasing soil organic matter content (retaining crop residues, adding organic residues, growing cover crops or companion green manure crops) in association with a liming program to increase soil pH and therefore the variable charge component of CEC (e.g., Aitken et al., 1998; Phan & Merckx, 2005). The practicality of adding high activity clays to increase permanent charge could be assessed (e.g., Noble et al., 2004). i: The high P-fixation capacity indicates that high rates of P fertiliser will be required or special P management practices (i.e. sources and method of P fertiliser application) will need to be implemented. P fertilization in minimum input cropping systems should be directed toward the use of minimal P rates applied in bands or pockets close to the seed, and the use of crops with low P-demand. Band or spot placement of water-soluble P fertiliser applications will decrease the loss of P availability by fixation. However, such placement will concentrate roots around the fertiliser and this may reduce root exploration of the soil profile. In areas that have short term droughts, this may limit yield because of restricted root access to soil water. An initial, reduced rate, broadcast fertiliser application accompanying a banded application should allow a more uniform root distribution. Soil P test levels should be determined periodically to monitor soil P status. geric: These soils have little net variable surface charge and therefore they have a very limited capacity to retain nutrient cations (eg. calcium and potassium) or anions (eg. nitrate) in the surface soil. Fertiliser will need to be applied in small frequent applications in accord with crop nutrient demands. Liming the surface soil to pH (in water) 5.5 will increase the ability of the soil to retain cations by increasing net negative variable charge, and this is an important management option. Addition of organic materials such as green manure crops should be considered because this may also increase net negative variable charge. 4 With respect to the Acrisols, the most commonly identified constraints were low- moderate organic matter ratings, low K reserves particularly in subsurface layers, and the soil physical problems of hard-setting surfaces and compaction. Some individual sites suffered from impeded drainage leading to waterlogging and ponding of water. To address these constraints, the SCAMP database would indicate the following management strategies: om (low-moderate): Increasing the levels of organic matter in these soils would improve nutrient supply, increase CEC, increase water holding capacity and increase pH buffer capacity. The management of soil organic matter in tropical soils involves mulching and incorporation of ‘green manure’ crops such as legumes or forage grasses, retaining all crop residues in the field where the crop has grown, not burning crop residues, minimum or zero tillage farming systems, strip or alley cropping and application of organic materials (such as animal manure, composted municipal waste, sewage sludge, and locally available industrial organic wastes) obtained from off-site. k: Potassium fertilisers or organic amendments having a significant content of K will need to be applied. In soils with low K reserves in the subsurface layer, it is likely that crops will exhibit K deficiency during periods of drought. In these circumstances, placement of K fertilisers below the seed at sowing or mixing K fertiliser through the soil in the planting hole is a more efficient management strategy than sidedressing K fertilisers on the soil surface. Crops should be closely monitored for K deficiency symptoms. hs, comp: Hard-setting surfaces reduce infiltration rate and cause poor crop establishment, while compaction layers restrict root growth and limit rooting depth causing drought stress to crops. Retaining crop residues and applying surface mulch should be used to maintain soil surface moisture thus minimising hard-setting. To minimise compaction risk, soils should only be cultivated when drier than their plastic limit, and tillage and machinery traffic should be avoided when soil is wetter than its plastic limit. 4. Major Upland Crops grown by Smallholders Agricultural census data were used to identify the major upland crops grown by smallholders in Gia Lai. Crop areas are presented in Table 4. Crops occupying greater than 5% of the arable land are: rice, maize, cassava, sugarcane, rubber and coffee. Rubber is not grown by smallholders. 5 Table 4. Crop areas of Gia lai Province. Smallholder crops are shaded. Crop Area (ha) Proportion (%) Rice 63883 20.4 Maize 40486 12.9 Cassava 24297 7.8 Vegetables 7618 2.4 Peanut 3787 1.2 Soybean 35 0.0 Tobacco 2350 0.8 Sugarcane 15543 5.0 Cotton 5184 1.7 Rubber 57307 18.3 Coffee 77530 24.8 Cashew 12354 3.9 Pepper 2609 0.8 TOTAL 312983 5. Soil Suitability for Major Upland Crops grown by Smallholders SCAMP assessments of the Ferralsols and Acrisols (section 3 above) have identified several soil constraints to crop productivity. Several of these constraints have effects on crop productivity, irrespective of the crop grown; erosion (er), low CEC (e), high P fixation (i), low organic carbon (om), K deficiency (k), variable charge characteristics (geric), hardsetting characteristics (hs) and compaction layers (comp). However, crops vary in their tolerance to other constraints such as drainage and acidity; while a particular soil attribute or constraint might be a major limitation to the productivity of one crop, it may pose only a minor limitation to another. The FAO (1976) framework for land evaluation uses five classes to categorise the suitability of a specific soil/landscape unit for growing a particular crop (Table 5). To facilitate the use of SCAMP for this application, individual soil attributes/constraints identified for the Ferralsols and Acrisols have been rated according to their effects on the sustainable production of the major upland crops grown by smallholders in Gia Lai (Table 6). Ratings are based on collation of information in Williams (1975), Landon (1984), Page (1984), Schaffer and Andersen (1994), Robinson (1996) and Dierolf et al. (2001). 6 Table 5. Soil suitability classes [Source: FAO 1976] Suitability Class Criterion Description 1 Highly suitable Soil is suitable for sustainable production of the crop without ameliorative measures. 2 Moderately suitable Soil is suitable for sustainable production of the crop if minor ameliorative measures are applied (e.g. liming, mounding to improve local drainage). 3 Marginally suitable Soil is only suitable for sustainable production of the crop if major ameliorative measures are undertaken (e.g. large scale drainage works). 4 Currently not suitable Soil is not suitable for sustainable production of the crop. Table 6. Suitability class of soil attributes/constraints for production of specific crops. SCAMP descriptor Paddy rice Maize Cassava Sugarcane Coffee Texture S 4 2 2 2 2 L 1 1 1 1 1 C 1 1 2 1 1 O 4 3 2 3 3 Drainage 1 (g) 2 4 4 4 4 rating 2 (g - ) 1 4 3 3 4 3 3 3 3 2 3 4 4 1 2 1 2 5 4 1 1 1 1 6 4 1 1 1 1 Slope (%) 0-2 1 1 1 1 1 2-5 2 1 1 1 1 5-10 3 2 2 2 2 >10 4 3 3 2 3 Soil pH a - 1 2 1 1 2 a 2 3 2 2 3 Salinity s - s 2 3 3 4 3 4 2 4 3 4 Drought tolerance L L H L L Main nutrient /water uptake zone (cm) <50 80-100 >100 >100 >100 Nutrient needs High N req'd High N, K req'd Tolerates low fertility High N req'd High N, K req'd 7 The following comments apply to the management practices that may need to be undertaken to meet the requirements of individual crops in addition to those already outlined in Section 3 above. Texture S: Because of the low inherent plant available water content of sandy soils, irrigation may be required for crops of low drought tolerance such as maize, sugarcane and coffee. Using surface mulches of plant residues will reduce evaporation and conserve soil moisture. For crops with high nutrient demands such as maize, sugarcane and coffee, the low ECEC of sandy soils requires that nutrient cations such as potassium are applied in split applications at rates in accord with crop demand. Growing green manure crops or applying plant material from these crops (eg. Tithonia) will temporarily increase the nutrient holding capacity (i.e. CEC) of the soil. C: Root crops such as cassava are not suited to clayey soils because of harvesting difficulties. Clayey soils are unsuitable for crops that do not tolerate prolonged soil wetness such as coffee; the low permeability of clayey soils causes them to remain wet for a longer period than soils of lighter texture. Drainage Soils with imperfect or poor drainage are unsuitable for crops that cannot tolerate waterlogged conditions such as coffee and maize, and raised beds and large scale drainage works must be undertaken if such crops are to be grown. Acidity a: Soils with this constraint are unsuitable for crops with a low or moderate tolerance to Al and/or Mn toxicity such as maize and coffee unless a comprehensive liming program is undertaken. a - : These soils require a liming program if they are being used to grow crops of low tolerance to Al toxicity such as maize and coffee. Applying Tithonia residues to acidic soils has been shown to ameliorate soil acidity by increasing soil pH. An added benefit of using fused magnesium phosphate (FMP) as a P fertiliser is that it also has a liming effect. Main nutrient/water uptake zone Crops with a comparatively shallow active rooting depth will not be as sensitive as deeper rooted crops such as coffee and sugarcane to constraints such as a compaction layer (comp). Conclusions Ferralsols and Acrisols are the major arable soil groups in Gia Lai. The constraints to crop production which commonly occur in the Ferralsols are acidity, low nutrient cation retention, high P fixation and variable charge characteristics, with drainage being the most common pathway of water movement. For Acrisols, commonly occurring constraints are low-moderate organic matter ratings, low K reserves particularly in subsurface layers, and the soil physical problems of hard- setting surfaces and compaction. Some Acrisols have impeded drainage leading to waterlogging and ponding of water. 8 The crops most commonly grown by smallholders in the province are: paddy rice, maize, cassava, sugarcane and coffee. Individual crop tolerances to some of the identified constraints vary, and so soil management responses to ameliorate or minimise the effects of these constraints on crop productivity will also vary. However the use of a liming program and application of green manures to the Ferralsols is required by all crops, while improving drainage, maintaining a surface mulch, and applying green manures are essential practices for the Acrisols. References Aitken, R.L., Moody, P.W. & Dickson, T. 1998. Field amelioration of acidic soils in south-east Queensland. I. Effect of amendments on soil properties. Australian Journal of Agricultural Research, 49, 627-637. Berding, F.R., Tran Mau Tan, Truong Dinh Tuyen, Tran Van Hue, Deckers, J. & Langhor, R. (1999). Soil Resources of Gia Lai Province. National Institute of Agricultural Planning and Projection (Vietnam) and Katholieke Universiteit Leuven (Belgium). Dierolf, T., Fairhurst, T. and Mutert, E. 2001. Soil Fertility Kit. Potash and Phosphate Institute: Singapore. FAO. 1976. Framework for land evaluation. Soils Bulletin No. 32. FAO:Rome. Landon, J.R. (ed.) 1984. Booker Tropical Soil Manual. Longman Inc.: New York . Le Trung Lap (2000). Land use and sustainable development for soil resources of Gia Lai Province. Proceedings of Workshop on Environment and Sustainable Development of the Central Highland. Pleiku, Sept 2000. Department of Science, Technology and Environment, Pleiku. Moody, P.W. & Phan Thi Cong (2008). Soil Constraints and Management Package (SCAMP): Guidelines for Sustainable Management of Upland Soils in the Tropics. ACIAR Technical Report (In Press). Australian Centre for International Agricultural Research, Canberra. Moody, P.W., Phan Thi Cong, Legrand, J. & Nguyen Quang Chon (2008). A framework for identifying soil constraints to the agricultural productivity of tropical upland soils. Soil Use and Management (In Press). Noble, A.D., Ruaysoongnern, S., Penning de Vries, F.W.T., Hartmann, C. & Webb, M.J. 2004. Enhancing the agronomic productivity of degraded soils in northeast Thailand through clay-based Interventions. In: Water and Agriculture (eds. Seng, V., Craswell, E., Fukai, S. & Fischer, K.), ACIAR Proceedings No. 116, ACIAR, Canberra, pp. 147-160. Page, P.E. 1984. Tropical Tree Fruits for Australia. QDPI Information Series QI 83018. Queensland Department of Primary Industries: Brisbane. 9 Phan & Merckx Phan, T.C. & Merckx, R. 2005. Improving phosphorus availability in two upland soils of Vietnam using Tithonia diversifolia H. Plant and Soil, 269, 11-23. Robinson, J.C. 1996. Bananas and Plantains. CAB International: Oxon. Schaffer, B. & Andersen, P.C. 1994. Handbook of Environmental Physiology of Fruit Crops. CRC Press: Florida. Williams, C.N. 1975. The Agronomy of the Major Tropical Crops. Oxford University Press: London. 10 . Province, Vietnam, and Soil Constraints to Productivity of Major Upland Crops Grown by Smallholders PW Moody A and Phan Thi Cong B A Queensland Department of Natural Resources and Water,. are to:  review existing information on the identification and extent of upland cropping soils in Gia Lai Province, Vietnam.  identify the major soils used for smallholder cropping, and. their constraints by the application of SCAMP.  identify the major crops /cropping systems used by smallholders in Gia Lai Province, and document the specific soil requirements of these crops/ cropping