Oxic Paleustults Research Articles

Dry matter yields and quality of forages derived from grass species and organic production methods (year 111).

This third year work was carried on at Khon Kaen University during the 2008-2009 to investigate dry matter yields of grass, grass plus legumes, grown on Korat soil series (Oxic Paleustults). The experiment consisted of twelve-treatment combinations of a 3x4 factorial arranged in a Randomized Complete Block Design (RCBD) with four replications. The results showed that Dry Matter Yields (DMY) of Ruzi and Guinea grass were similar with mean values of 6,585 and 6,130 kg ha(-1) whilst Napier gave the lowest (884 kg ha(-1)). With grass plus legume, grass species and production methods gave highly significant dry matter yields where Guinea and Ruzi gave dry matter yields of 7,165 and 7,181 kg ha(-1), respectively and Napier was the least (2,790 kg ha(-1)). The production methods with the use of cattle manure gave the highest DMY (grass alone) of 10,267 kg ha(-1) followed by Wynn and Verano with values of 6,064 and 3,623 kg ha(-1), respectively. Guinea plus cattle manure gave the highest DMY of 14,599 kg ha(-1) whilst Ruzi gave 12,977 kg ha(-1). Guinea plus Wynn gave DMY of 7,082 kg ha(-1). Ruzi plus Verano gave DMY of 6,501 kg ha(-1). Forage qualities of crude protein were highest with those grown with grass plus legumes. Some prospects in improving production were discussed.

Soil Nutrients and Liming on Dry Weight Yields and Forage Quality of Signal Grass (Brachiaria decumbens Stapf.), Grown on Korat Soil Series (Oxic Paleustults) in Northeast Thailand

This experiment was carried out at Khon Kaen University Experimental Farm, Khon Kaen University, Thailand during the 2004-2005 aiming to investigate effect of phosphorus (P) and dolomite levels on dry weight yields (DWYs) and forage quality of Signal grass. A 4x3 factorial arranged in a Randomized Complete Block Design (RCBD) was used. Four P levels were: 0, 100, 200 and 400 kg P2O5 ha-1 and three dolomite levels were: 0, 625 and 2,500 kg ha-1. The Signal grass plants were grown on Korat soil series, (Oxic Paleustults). A quadrat with a dimension of 50x50 cm was used for grass yield harvests. Crude Protein (CP), Acid Detergent Fibre (ADF), Neutral Detergent Fibre (NDF) and Dry Matter Degradability (DMD) contents were determined. Tissues phosphorus and calcium contents were also analysed. The results showed that an increase in dolomite levels increased soil pH from 4.4 to 5.1 for levels 1 and 3, respectively. An increase in P levels increased available soil P from 4.56 to 28.38 ppm for levels 1 and 4, respectively. For the first year experiment, dolomite levels had no significant effect on DWYs, whilst P levels significantly increased but only up to level 2. The 2-year average DWYs reached 11,368 kg ha-1 for level 4 of P. With the first year rainy season harvests, P levels had its significant effect on ADF and DMD up to level 2 but not with CP and NDF. For the dry season harvests, P and dolomite levels had no significant effects on forage quality. Dolomite levels had no significant effect on P and Ca contents of the Signal grass tissues but an increase in P levels increased P contents. P and Ca contents, in most cases, were higher for the dry season than the rainy season.

Some Physiological Measurements on Growth, Pod Yields and Polyamines in Leaves of Chili Plants (Capsicum annuum cv. Hua Reua) in Relation to Applied Organic Manures and Chemical Fertilisers

The experiment was carried out at the Faculty of Agriculture, Ubon Ratchathani University during November 2006 to July 2007. A Completely Randomized Design (CRD) with four replications was used. Six treatments were allocated into two experimental fields, i.e., field A, animal manures added soil. Field B, chemical fertilizers added soil and both fields have been used for chili cultivation for more than 5 years and they belong to Warin soil series (Oxic Paleustults). The results showed that mean values of soil pH and organic matter % of field A were much higher than field B but mean values of nitrogen % and phosphorus were much higher for field B than field A. Exchangeable potassium were inadequately available in all treatments. All treatments of field B gave excessive amounts of available phosphorus at a toxic level. T3 of field A gave higher plant height, total dry weight plant(-1), pod fresh and dry weights plant(-1) than T5 of field B. Of overall results in terms of growth and yields of chili plants, field A gave much better advantages over field B. The CO2 uptake and CO2 in leaves were higher for field A than field B. Polyamines of putrescine (Put), spermidine (Spd) and spermine (Spm) of T2 were affected by stress conditions due to previous applied chemical fertilisers. Available phosphorus mean values in most treatments were excessively available. Amounts of polyamines in chili leaves due to the added organic manure and chemical fertilizers (T3 up to T6) were not cleared.

Effect of Cutting Heights on Productivity and Quality of King Napier Grass (Pennisetum purpureum cv. King Grass) under Irrigation

An experiment to study the effect of cutting heights on yield and nutritive values of King napier grass (Pennisetum purpureum cv. King grass) was conducted on sandy loam, Korat soil series (Oxic Paleustults) under irrigation during June 2006 to November 2007 at Khon Kaen Animal Nutrition Development Research Center, Thailand. Four treatments of cutting height at 0 (T1), 5 (T2), 10 (T3) and 15 (T4) cm above ground level in randomized complete block design with 4 replications were employed. The results showed that the Total Dry Matter Yield (TDMY) and Average Dry Matter Yield (ADMY) (65,707.5, 67,070.0, 69,697.5 and 71,403.1 kg/ha/year ; 5,973.4, 6,096.4, 6,336.2 and 6,491.2 kg/ha/cut, respectively) were significantly higher (p<0.05) in T4 than T1. There were no significant differences in CP and DMD among treatments, ranging from 12.1-12.9 and 75.5-76.6%, respectively but the percentage of ADF, NDF and ash were highly significantly different (41.7-43.5, 64.6-66.2 and 13.1-14.7%), respectively. Based on this research, it can be concluded that cutting height can affect the forage DM yield and nutritive values of King Napier grass. Cutting 35 day interval at 15 cm height above ground level could be the optimal level for harvesting King Napier grass in Northeast of Thailand.

Fertiliser strategies for improved nutrient use efficiency on sandy soils in high rainfall regimes

Fertiliser application strategies for maize (Zeamays L.) production on sandy soils under high rainfall regimes need to be carefully designed to minimise nutrient losses through leaching and maximise crop yield. Experiments were conducted to determine N, P, and K leaching in sandy soils with 3-6% clay in surface layers under maize production, and the effectiveness of different N, P, and K fertiliser timing and splitting strategies on leaching of N, P, and K and on maize yield. In a column experiment on an Oxic Paleustult (Korat series) with 3% clay, leaching of N, P, and K from fertiliser (114N-17P-22K in kg ha-1) was significant under simulated rainfall, but decreased to negligible levels with 3-5 split applications of fertiliser. Maize N and K uptake increased with 3-5 split applications, but not P uptake. Despite continued intense rainfall and further fertilizer additions, leaching was not recorded after day 30, and this was attributed to the effect of plant water uptake on reducing deep drainage. Split applications of fertilizer maintained NP and K in the 0-30 cm layer during 30-60 days when maize nutrient demand was likely to be at its highest, while in the recommended fertilizer regime NPK in the surface layers declined after 30 days. In a field experiment on an Oxic Paleustult (Korat series) with 6% clay, 3-4 splits of fertiliser increased N and K uptake and increased maize yields from 3.3 to 4.5 Mg ha-1. Postponing basal fertiliser application from pre-planting to 7-15 days after emergence increased uptake of N, P, and K and grain yield emphasising the greater risk of nutrient losses from fertiliser applied at planting than later. Strategies designed to reduce the amount of nutrients applied as fertiliser at planting, such as split application and postponing basal application can decrease the risk of leaching of N, P, and K from fertiliser and improve nutrient use efficiency, and grain yield of maize on sandy soils under high growing season rainfall regimes.

An Evaluation on Intensity of Infection of Pseudocercospora Leaf Spot Disease of Cowpea Cultivars (Vigna unguiculata L. Walp), With Respect to Infector Rows, Dates of Inoculation and Cultivars, Grown Under Field Conditions in Northeast Thailand

This investigation was carried out at the Experimental Farm, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand to evaluate intensity of infection of Pseudocercospora Leaf Spot disease of cowpea cultivars, grown under field conditions with the use of Yasothon soil series (Oxic Paleustults). The experimental design used was a strip split plot design with four replications. The experiment consisted of three factors, i.e., with and without infector rows (Factor A), with and without inoculation and inoculated dates, i.e. none inoculation, inoculated at days 15 and 30 after sowing of seeds in main plots (Factor B) and three cowpea cultivars of KVC7, KKU25 and IT81D-1228-14-1 (Factor C). The results showed that the use of infector rows of cowpea plants (KKU25) being sown at 15 days before sowing seeds of cowpea cultivars in main plots gave a similar intensity of disease as those infector rows being sown at 30 days before sowing seeds of cowpea cultivars in main plots but significantly higher than without infector rows. Pathogenic disease being inoculated to the cowpea plants at 15 days after the sowing of seeds in main plots gave significantly higher intensity of disease than none inoculation. The establishment of infector rows at 15 days ahead of the sowing of seeds in main plots together with an inoculation of the disease at 15 days after the sowing of seeds in main plots gave the best results in evaluating amount of the infected disease. Thus infector rows surrounded the main plots are required whenever trials on disease evaluation are taken place.

Effect of Land Preparation Methods on Growth, Seed Yields of Jasmine 105 Paddy Rice (Oryza sativa L.) and Growth of Weeds, Grown in Northeast Thailand

This experiment was carried out on a grower's paddy field, Ban Som Hoeng Village, Kantarawichai, Mahasarakham Province, Northeast Thailand with the use of Roi-Et soil series (Oxic Paleustults) in the rainy season of the 2006 (May to November) to investigate effect of land preparation methods on rice plant heights, amounts of weeds and seed yields of Jasmine 105 aromatic paddy rice (Oryza sativa L.). The experiment was laid in a Randomized Complete Block Design (RCBD) with four replications. The results showed that plant height due to treatments was significantly highest for T3 but T3 was similar to T2, whilst T1 (control) was the least. Mean values of dry weight of narrow leaf type of weeds, in most cases, were significantly lowest with T3 followed by T2 and T3, particularly at the final two sampling periods. Broad leaf type of weeds was significantly highest with T2 throughout the experimental period, whilst T1 and T3, in most cases, were similar. Unfilled seeds were significantly highest with T3 but similar to T1 but T2 was the lowest, whilst filled seeds were significantly highest with T3, both T1 and T2 gave a similar weight. Numbers of panicles m(-2) were significantly highest with T3 but T3 was similar to T2, whilst T1 was the least. Seed size or 1000-seed weight was significantly highest with T3, whilst T2 and T1 were similar. Seed yield was highest and highly significant with T3 (1,136.25 kg ha(-1)) but T3 was similar to T2 (1,083.31 kg ha(-1)), whilst T1 was the lowest (487.50 kg ha(-1)). Land preparation method of T3 treatment may be recommended as the first choice, whilst T2 may be used as an alternative choice.

Effects of Phosphorus and Potassium on Growth, Yield and Fodder Quality of IS 23585 Forage Sorghum Cultivar (Sorghum bicolor L. Moench)

This growth analysis experiment was carried out at Khon Kaen University Experimental Farm, Khon Kaen, Northeast Thailand in the 2000, in order to justify the effects of phosphorus (P) and potassium (K) levels added to Yasothon soil series (Oxic Paleustults) on dry matter yield and fodder quality of IS 23585 forage sorghum cultivar. The experiment was laid in a 4x4 factorial arranged in a randomized complete block design (RCBD) with four replications. The P levels used were 0, 37.50, 75.00 and 150.00 kg P2O5 ha(-1) and K levels were 0, 56.25, 112.50 and 225.00 kg K2O ha(-1). The results showed that total dry weight (yield) and other growth parameters in most sampling periods significantly increased with an increase in K levels but the increase was only up to K1. Higher levels of both P and K had no significant effect on total dry weight (yield) and other growth. There were no consistent trends due to both P and K application rates. However, mean Leaf Area Index (LAI) reached a maximum value of 10.21 (P3K3) at 8 weeks after emergence (WAE) and then a decline to 5.37 (P0K3) at 10 WAE. K significantly affected LAI only at 2 and 6 WAE. Crop growth rate (CGR) and leaf area duration (D) significantly increased up to K1, whilst P did not. Both optimum total dry weight of 1,7221 kg ha(-1) (10 WAE) and seed yields of 5,169 kg ha(-1) were obtained from P0K1. Both P and K had no significant effect on 1000-seed weight. P did not affect brix value, whilst K significantly depressed this parameter. K had no significant effect on crude protein (CP), whilst P did. P had no significant effect on neutral detergent fibre (NDF), whilst K significantly did it. Both P and K had no significant effect on both acid detergent fibre (ADF) and ruminal dry matter degradability (DMD) of the sorghum plants.

Effects of Crop Residues of Sunflower (Helianthus annuus), Maize (Zea mays L.) and Soybean (Glycine max) on Growth and Seed Yields of Sunflower

This pot experiment was carried out at Suranaree Technology University Experimental Farm, Northeast Thailand to investigate effects of crop residues of sunflower, maize and soybean on total dry weight, top dry weight, plant height, root dry weight and seed yield of sunflower plants with the use of Korat soil series (Oxic Paleustults) during the rainy season (July-October) of the 2001. The experiment was laid in a split plot arranged in a Completely Randomized Design (CRD) with four replications where the crop residues of maize, sunflower and soybean were used as main plots. Whilst crop residues of roots, top growth and roots+top growth were used as subplots. The results showed that crop residues derived from roots of both sunflower and soybean plants had their significant inhibition effects of allelopathic substances on plant height, root dry weight, top growth dry weight and total dry weight plant(-1) of the sunflower plants than those derived from top growth of both crops alone (sunflower and soybean). Maize plant residues had no significant inhibition effect on growth of subsequent crop of sunflower.

Effects of Green Manures on Growth, Yield and Quality of Green Okra (Abelmoschus esculentus L.) Har Lium Cultivar

This green manure experiment with the use of okra crop as indicator plant was carried out at Mahasarakham University Experimental Farm, Mahasarakham province, Northeast Thailand during May to September 2005 to investigate four types of green manure legume crops on growth, yield and quality of edible fresh pods of okra crop when grown on Roi-Et soil series (Oxic Paleustults). The four types of green manure plants include Jack bean, Cowpea, Green gram, and Giant sensitive plant. The experiment consisted of five treatments, i.e., T1 (Control), T2 (Jack bean), T3 (Cowpea), T4 (Green gram) and T5 (Giant sensitive plant). The experiment was laid in a Completely Randomized Design (CRD) with four replications. The results showed that Roi-Et soil series (Oxic Paleustults) contained some considerable mean values of organic matter (1.64-1.66%) but soil available phosphorus and exchangeable potassium were relatively low, particularly potassium. Green manures of the four legume plants slightly improved soil property of the Roi-Et soil series (tested at the end of the experimental period). The most effective green manure on stem diameter, bushy diameter, leaf numbers plant(-1) and leaf area of the fifth leaf of the okra plants, in most cases, was found with Jack bean and Cowpea ranked the second. However, in most cases, Cowpea gave a similar effect as that of Green gram and Giant sensitive plant. Pod length and weight pod(-1), pod diameter and edible fresh pod yields (5941.86 kg ha(-1)) were highest with Jack bean green manure treatment (T2), whilst the rest, in most cases, were similar. Green manure treatments gave highly significant effect on total soluble solids of pods over the control treatment, whilst total acidity, fibre and pectin contents were unaffected by green manure treatments. Green manure of Jack bean was the best legume crop for green manure to be used in improving soil fertility, particularly for Roi-Et soil series (Oxic Paleustults).

Sugarcane yield prediction in degraded sandy soil amelioration

The relationship between soil properties and sugarcane growth parameters can be determined sugarcane yield of banding application in degraded Korat sandy soil series (Oxic Paleustults). The agronomic traits affecting cane yield can be arranged in descending order from tiller density, stool density, stalk length, germination and plant height, respectively. Cane yield (t ha−1) = −59.29 + 0.14 (tiller density) + 0.31 (stalk length); r2 = 0.90**. The soil properties affected to tiller density and stalk length were organic matter and available phosphorus. Hence, the factors should be collected for sugarcane yield prediction in degraded sandy soil amelioration were tiller density, stalk length, organic matter and available phosphorus which can reduce cost of data collection and soil analysis with high accuracy result.

Residual Effects of Applied Chemical Fertilisers on Growth andSeed Yields of Sunflower (Helianthus annuus cv. High Sun 33) After the Harvests of Initial Main Crops of Maize (Zea mays L.), Soybean (Glycine max L.) and Sunflower (Helianthus annuus)

The experiments consisted of two locations, i.e., the first one was carried out on a growers's upland area at Saraburi Province, Central Plane region of Thailand with the use of Chatturat soil series (Typic Haplustalfs, fine, mixed) and the second experiment was carried out at Suranaree Technology university Experimental Farm, Suranaree Technology University Northeast Thailand with the use of Korat soil series (Oxic Paleustults). The experiments aimed to investigate the effect of residual effects of applied chemical fertilisers on growth and seed yields of sunflower (Helianthus annuus) after the harvests of initial main crops of maize, soybean and sunflower. The experiments consisted of four cultural methods being practiced by growers in both regions. For Methods 1 and 2, each had four fertiliser treatments; Method 3 consisted of two fertiliser treatments and Method 4 was used as a control treatment. The results showed that soil pH, organic matter and nutrients of Korat soil series were most suited soil conditions for growth of sunflower plants, whilst that of Chatturat soil series at Saraburi province was an alkaline soil with a mean value of soil pH of 7.8. Chatturat soil series, in most cases, gave higher amounts of seed yields (1,943.75 kg ha(-1)) than Korat soil series. Residual effects of applied chemical fertilisers to main crops of soybean gave better growth and seed yields of sunflower plants and it is considered to be the first choice. The use of sunflower and maize as main crops gave a second choice for subsequent crop of sunflower.

Effect of Chemical Paclobutrazol on Growth, Yield and Quality of Okra (Abelmoschus esculentus L.) Har Lium Cultivar in Northeast Thailand

This investigation was carried out at Mahasarakham University Experimental Farm, Mahasarakham University, Northeast Thailand in the late rainy season of the 2003 to 2004 with the use of Roi-Et soil series (Oxic Paleustults). The experiment aims to search for more information on the effect of different rates of chemical Paclobutrazol (PBZ) application on growth, yield and quality of edible okra pods. A Randomised Complete Block Design (RCDB) with four replications was used for the experiment. The experiments consisted of five treatments, i.e., 0 (T1), 4000 (T2), 8000 (T3), 12,000 (T4) and 16,000 ppm ha(-1) (T5) of chemical PBZ. The results showed that an increase in PBZ application rate highly decreased plant height, harvesting age and significantly decreased leaf area of the fifth leaf but highly increased pod length, fresh weight/pod and fresh pod yield ha(-1) of the okra plants. PBZ had no significant effect on stem diameter and diameter of pods of the okra plants. Total soluble solid, fibre content, titratable acid, vitamin C and pectin contents in pods were not affected by chemical PBZ application. Pod yield highly increased with an increase in rate of PBZ application. The highest edible pod yield reached a value of 4501 kg ha(-1) for the highest rate of PBZ application (T5).

Effect of organic and clay material amendment on physical properties of degraded sandy soil for sugarcane production

Degraded sandy soil in Northeast of Thailand is a main problem for crop production due to low water holding capacity, low organic matter, low cation exchange capacity and poor soil fertility. The present experiment was established to identify the type and rate of amending materials for improving physical soil properties in Korat soil serie (Kt, Oxic Paleustults) at Kuchinarai district, Kalasin province. The trial was done with completely randomized design with 4 replications and planted with K 88–92 variety. Soil samples were collected in 0–30 cm and 30–60 cm depths before land preparation and at harvest with undisturbed and composite disturbed samples. It was found (1) cattle manure @ 25 tons/ha decreased bulk density in both soil depth (P<0.01), aggregate stability did not differ and increased clay particle content at 0–30 cm depth (P<0.05). (2) Filter cake @ 50 tons/ha, bagasse @ 12.5 tons/ha, clay soil @ 25 tons/ha, conventional chemical fertilizer and control treatments showed non significant effect on bulk density, aggregate stability and particle size distribution. (3) Application of clay soil @ 50 tons/ha did not significantly change the soil bulk density and particle size distribution but significantly increased aggregate stability at 30–60 cm depth (P<0.01). (4) Application of clay soil @ 75 tons/ha significantly decreased bulk density in both soil depths (P<0.01) but showed no significant effect on aggregate stability and particle size distribution. We recommended that the most appropriate methods to improve soil for cane production was through application of cattle manure @ 25 tons/ha or clay soil @ 50 and @ 75 tons/ha.

Environmental influences on nitrogen transformation of different quality tree litter under submerged and aerobic conditions

Trees in farming systems can improve fertility of soils through mineralization of N in their litter. This study was to determine the quality parameters (i.e., chemical composition) of organic residues that are associated with N mineralization in soils under submerged and aerobic conditions, and to demonstrate that aeration conditions should be taken into account in categorization of organic residues as N sources in farming systems. Incubation experiments were conducted in Aeric Paleaquult soil under submerged and Oxic Paleustult soil under aerobic conditions. Treatments included litter and some fresh materials from trees as well as rice straw available in farming systems of Northeast Thailand. S. grandiflora and L. leucocephala (32 g kg−1 N) had the highest net N mineralization in both conditions. Some lower-quality (< 20 g kg−1 N) residues did exhibit low net N mineralization during the 16-week period under submerged conditions, but displayed almost no net N mineralization in aerobic conditions. Under submerged conditions, their net N mineralization was higher and more rapid. The nitrogen content of the residues was the most important factor controlling N mineralization under both conditions. Polyphenols exerted the highest negative influence on N mineralization in aerobic conditions, but exhibited no negative effect in submerged conditions. In categorizing organic residues for their effective use in soil fertility management, soil aeration conditions, as well as other environmental factors, should be taken into consideration in addition to residue quality.

An Improvement of Yasothon Soil Fertility (Oxic Paleustults) Using Municipal Fermented Organic Compost and Panicum maximum TD 58 Grass

An Improvement of Yasothon Soil Fertility (Oxic Paleustults) Using Municipal Fermented Organic Compost and Panicum maximum TD 58 Grass

Soil organic matter and nitrogen transformation mediated by plant residues of different qualities in sandy acid upland and paddy soils

Organic matter management is believed to solve many of the chemical and physical problems of coarse-textured, low fertility soils of Northeast Thailand. We tested the influence of different plant residues available in this area on soil C and N dynamics in upland (Oxic Paleustult) and lowland (Aeric Paleaquult) soils. Residues included groundnut (upland) or Sesbania rostrata stover (lowland), rice straw, Tamarindus indica and Dipterocarpus tuber-culatus leaves applied at 10 t ha −1 (dry matter). For the former three residues additional application rates of 20 t ha −1 were included as well as a mixture (50:50) of groundnut Sesbania — rice straw treatment. Groundnut stover and Sesbania had C/N ratios <28:1 and low lignin, and polyphenol contents whereas rice straw had the highest C/N ratio of 79:1. Dipterocarp and tamarind leaves were characterized by high lignin (>17%) and polyphenol (>4.5%) contents. These latter residues, despite slow decomposition, apparently resulted in only moderate soil C (<1 mm) build-up after one year due to the fact that a large proportion of their residues remained in particulate form (>1 mm). Thus the mixture of groundnut/ Sesbania with straw was among those residue treatments that led to the highest soil C (<1 mm) buildup under both upland and lowland conditions. Groundnut stover under upland condition resulted in immediate net N mineralisation but also an early decline in soil mineral N presumably due to leaching. By mixing groundnut or Sesbania with rice straw with a high C/N ratio residue N mineralisation could be delayed and prolonged, improving potentially the synchrony of N release and plant demand. Additions of dipterocarp and tamarind resulted in an initial N immobilization phase and net mineral N release remained low thereafter. Dynamics of microbial biomass N were closely related to N mineralisation and immobilization cycles in both upland and lowland experiments. Residue N concentration was the most significant factor controlling N release in both systems. While extractable polyphenols exhibited a significant influence on N release in upland conditions their effect was not evident in the lowland.

Rainy Season Soybean (Glycine max L.) as Influenced by Nitrogen and Potassium Fertilisers Grown on Oxic Paleustults Soil in Northeast Thailand

Rainy Season Soybean (Glycine max L.) as Influenced by Nitrogen and Potassium Fertilisers Grown on Oxic Paleustults Soil in Northeast Thailand

Effects of Dolomite on Growth and Seed Yields of Soybeans (Glycine max L.) Grown on Oxic Paleustult Soil in Northeast Thailand

Effects of Dolomite on Growth and Seed Yields of Soybeans (Glycine max L.) Grown on Oxic Paleustult Soil in Northeast Thailand

Tillage-Induced Spatial Distribution of Surface Crusts on a Sandy Paleustult from Togo

The spatial distribution of crusts in coarse-textured soils and the processes affecting it are poorly documented, despite the potential impact of crusts on water infiltration. This study addresses the influence of tillage-induced microrelief on the morphology and spatial distribution of surface crusts in an Oxic Paleustult from southern Togo (West Africa). Replicate 1-m2 plots were exposed to 217 mm of natural rainfall during a 6-wk period, during which the surface topography was measured three times. Subsequently, 24 undisturbed crust samples were used for micromorphological analysis. The crusts exhibited a range of morphologies but were nevertheless adequately mapped and characterized according to two main types. Type 1 crusts (=runoff crusts) showed several superposed clay bands, 100 to 500 mm thick, buried within a micromass-depleted sand layer 5 12 mm thick. Type 2 crusts (=erosion crusts) had an exposed clay band a few tenths of a millimeter thick. The spatial distribution of crusts at the time of sampling appeared better correlated with the initial than with the final microtopography of the plots. These findings suggest that crust distribution should be regarded as history dependent and that erosion and deposition processes largely governed the development of the crusts. This latter aspect is in agreement with the recent crust genesis model of Valentin and Bresson, as is the fact that clay bands in our plots were laterally continuous at all observational scales 50.1 m. Other mechanisms proposed in the literature for the development of clay bands did not seem able to account adequately for the observed pattern.