Doses Of Gypsum Research Articles

Spatial variability of pores in oxidic latosol under a conservation management system with different gypsium doses

Soil structure is modify when subjected to the agricultural process, i.e., a new spatial organization of the pores system is formed, with relation to the physical quality of it. Thus the aim of this work was to visualize and quantify, through X-ray CT scan, the pores distribution in an oxidic Latosol submitted to a conservation management system with different gypsum doses. Three random trenches were dug lengthwise along the plant row in a very clayey gibbsitic dystrophic Red Latosol, subjected to the following gypsum levels: G0: absence of gypsum; G7: 7 Mg ha-1 and G28: 28 Mg ha-1 of additional gypsum, applied to the surface of the plant row. Undisturbed soil samples were collected in plexiglass tubes at depths of 0.20-0.34, 0.80-0.94 and 1.50-1.64 m after six years of coffee cultivation for quantification of 3D pores obtained by X-ray CT scan. The spatial variability of the soil structure was evaluated by semivariograms generated by 3D images in grayscale. Distribution of the detectable pore diameter was conducted by data mining. Statistical analyzes employed packages 'geoR' to semivariogram and 'randomForest' for data mining in R language. A greater spatial continuity of the pores occurred in the G7 at the three depths. The combined effects of the management system promoted a greater spatial variability of the soil structure in the G28 treatment. Based on geostatistical analyses, it can be infer that the adoption of the system under study promoted changes in the pore network in all directions (X, Y and Z), however with better pores continuity in the vertical direction(Z).

Yield of cotton/cowpea and sunflower/cowpea crop rotation systems during the reclamation process of a saline-sodic soil

The objective of this study was to evaluate the use of subsoiling, gypsum and organic matter associated with the cultivation of cotton, sunflower and cowpea in crop rotation, seeking the reclamation and use of a saline-sodic soil. The treatments were arranged in a randomized block design in split plots with four replications, during two crop cycles (2009/2010 and 2010/2011). The plots were formed by the treatments: T1. Subsoiling (S); T2. S + 20 Mg ha-1 of gypsum; T3. S + 40 Mg ha-1 of organic matter; T4. S + 10 Mg ha-1 of gypsum + 20 Mg ha-1 of organic matter; T5. S + 20 Mg ha-1 of gypsum + 40 Mg ha-1 of organic matter and the sub-plots consisted of the cotton-cowpea (C/CP) and sunflower-cowpea (S/CP) crop rotation. The use of gypsum and organic matter contributed to decrease the soil salinity and sodicity. Cotton was not affected by the treatments, while the sunflower crop was favored by the application of amendments only in the second production cycle. Higher yields of cowpea in T5 treatment, during the 2009/2010 cycle, are indicative that higher doses of gypsum and organic matter applied in this treatment accelerate the reclamation process. For other treatments with amendment application there was a beneficial effect for this crop only in the second cycle, when the values of productivity were similar to T5.

Gypsum effects on the spatial distribution of coffee roots and the pores system in oxidic Brazilian Latosol

The aim of this study was to jointly evaluate the root system and soil pore distribution in depth and their relation to the development of the coffee crop. Three trenches were dug at random, longitudinal to the plant row, in a very clayey oxidic Latosol (Oxisol), subject to the following dose of gypsum: G0: absence of additional gypsum; G7: 7Mgha−1; and G28: 28Mgha−1 of additional gypsum, both applied on the surface in the plant row. For the root system evaluation we used the crop profile method associated with 2D image analyzes, and subsequent elaboration of root variables maps. Soil pores system was quantified in 3D images, originated by X-ray CT scan, in undisturbed soil cores (0.06m diameter and 0.14m high) sampled at 0.20–0.34; 0.80–0.94; and 1.50–1.64m depth. Roots and pores were classified by diameter. The statistical inferences were performed in R language. The increasing doses of gypsum favored the development of fine roots efficient in water absorption, and the highest gypsum dose promoted the better spatial distribution of the root system and was more homogeneous in the vertical direction of the soil profile, with highlighting to G28. The highest pore number and volume occurs in the 0.20–0.34m structural layer, particularly pores with a diameter less than 2mm. This management system that employs high gypsum doses contributed beneficially to a new structural organization in all depth studied, and most meaningful at 0.20–0.34m depth, especially with the increase of pores and expertise of roots (smallest diameter: 1mm) contributing to better exploitation of the soil conditions by the coffee plant. Image analyses are an tool with high predictive power to evaluated soil pores and roots system without destruction of the soil structure.

Bio-chemical amelioration effects on physico-chemical dynamics of sodic soils under rice (Oryza sativa) –wheat (Triticum aestivum) cropping system

The effect of dhaincha (Sesbania aculeata) as first crop on physico-chemical dynamics and productivity of “B” class sodic soils was assessed on farmer’s field under rice-wheat cropping system to generate the knowledge of sodic soil management for increasing the soil and crop productivity for sustainable crop production in sodic soil environment. The experiment was laid out in randomized block design at ten sites having six treatment combinations of different doses of gypsum and green manuring with sesbania under two cropping sequences, i e sesbania-rice (Oryza sativa L.) -wheat (Triticum aestivum L.) and rice-wheat. Cultivation of sesbania with gypsum significantly decreased the surface soil pH from 9.3 to 8.6 and increased the hydraulic conductivity from 0.3 × 10-3 to 3.7 × 10-3 cm/hr and buildup of soil organic matter by increasing organic carbon content from 0.20 % to 0.22 % through growing of sesbania. Sesbania green manure also increased the available water content in the soil system, which enhanced soil moisture availability for longer period. As a result, rice crop yield increased by 16.2 % in sesbania-rice- wheat cropping system in comparison to rice–wheat cropping sequence because of synergistic effect of sesbania with gypsum. Consequently, residual effect of sesbania green manuring alone and in combination with gypsum significantly enhanced the wheat grain yield by 42.5 % and 72.5 % and 80% in T4, T5 and T6 treatments respectively during first year in sesbania–rice-wheat cropping sequence as compared to control. In consecutive second year, rice and wheat grain yields further enhanced by 8.1 % and 2.71% respectively, under sesbania –rice -wheat than that of rice –wheat cropping sequence. Under sesbania- rice- wheat and rice-wheat-sesbania cropping sequence, rice and wheat grain yield were similar. Hence, inclusion of Sesbania aculeata as green manure either before or after rice-wheat cropping sequence is equally better to improve the soil physical dynamics and crop productivity of ‘B’ class sodic soils in Indo-Gangetic region of Uttar Pradesh.

Effect of liquid humus and calcium sulphate on soil aggregation

An Ultic Haploxeralf soil collected from ridges built into the slopes of the Coastal Mountain Range of Central Chile was used in applications of humic and fulvic acids (HFA) extracted from sludge from sewage treatment plants, in combination with gypsum (CaSO4). A total of 12 treatments were applied by combining four doses of HFA (0, 20, 30 and 40 t ha-1) with three doses of gypsum (0, 1.2 and 6.0 t ha-1). The effect of these treatments was assessed using three indicators of the degree of soil aggregation: macroporosity (MA), bulk density (Da) and microinfiltration (MI). The experiment was set up in a laboratory using a completely randomised design (CRD). Factorial variance analysis was also performed using two factors: gypsum in three doses and HFA in four doses. For all three indicators, MA, Db and MI, it can be seen that there is interaction between the HFA treatments and the gypsum treatments in the studied soil. The macroporosity increased with HFA treatments with 20 or 30 t ha-1 (9%) and with gypsum of 1.2 t ha-1 plus 20 t ha-1 HFA (11%). It can also be seen that the gypsum treatments have no effect on Db when HFA is not applied. Microinfiltration is the variable that shows the greatest effects from the treatments applied. The results also clearly show that high amounts of HFA (40 t ha-1) and of gypsum (6.0 t ha-1) cancel out the differential effects and cause negative effects on the three indicators for the studied soils. The use of liquid humus and its combination with calcium sulphate (20/1.2 t ha-1) improves soil aggregation.

Physiological, morphometric characteristics and yield of Origanum vulgare L. and Thymus vulgaris L. exposed to open-field and shade-enclosure

The aim of this research was to investigate the effect of two different production systems, open-field and shade-enclosure, and four gypsum doses, to find the best environmental option in terms of physiological, morphometric characteristics and with optimum yield in two crops, oregano and thyme in Baja California Sur, Mexico. One cultivar of oregano and one of thyme were grown in shade-enclosure and open-field environments and evaluated for photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll, leaf area, fresh and dry biomass and yield. The results showed significant differences between environmental conditions, crops and their interaction. Gypsum doses had no significant effect on any of the variables measured. For both species shade-enclosure variables measured were more favorable than open-field. In general, of the two crops, oregano performed better than thyme under shade-enclosure conditions, except for Chl a, b, total and leaf water potential which were higher in thyme.

Enxofre Disponível em Solo Cultivado com Cana-de-Açúcar Submetido a Doses de Gesso Mineral

The purpose of this work was to evaluate the levels of sulfur available in soil levels of gypsum.The experiment was conducted at the Experimental Station of sugar cane in Carpina (EECAC) from the Federal Rural University of Pernambuco (UFRPE), located in the city of Carpina FR. The experimental design was a randomized block consisting of 5 doses of mineral gypsum and 4 repetitions in a total of 20 experimental plots. At 10 months after the planting was held to the soil sampling, opening themselves to a profile in each plot. In each profile (20), with rings were held three soil samples (0.0 0.3 , 0.3 0.6 and 0.6 -0.9 m), respectively. The 60 samples after they have been put to dry and-drying, followed for analysis. Sulfur was extracted by monocalcium phosphate in water. It can be observed that in greater depths there was a greater extraction, with the exception of the second dose of gypsum in relation to the superficial layer. In the three depths to higher extraction of sulphate corresponded to higher dose of plaster.

Alterações físico-químicas e movimentação de íons em Latossolo gibbsítico sob doses de gesso

Com o objetivo de avaliar o efeito de doses de gesso no ponto de carga zero estimado (PCZ), na dinâmica do cálcio, magnésio, potássio e sulfato, e na retenção de água de um Latossolo Vermelho distroférrico gibbsítico, textura muito argilosa, realizou-se experimento em vasos, em casa de vegetação. Foram estudadas seis doses de gesso agrícola (correspondentes a 0, 3, 6, 9, 12 e 15 Mg ha-1) e duas condições de fornecimento de água, "sem veranico" e "com veranico" para a soja cultivada. Na coleta de solo para o experimento foram consideradas as camadas 0-0,2 m e 0,7-0,9 m representando os horizontes A e Bw respectivamente. Foram montados vasos com a sobreposição de dois tubos de PVC de 0,2 m de comprimento e 0,1 m de diâmetro interno, formando duas camadas: a superior, com material do horizonte A, corrigido com calcário dolomítico, e a inferior, com material do horizonte Bw, sem correção do pH; ambas na densidade de 1 kg dm-3. O PCZ foi alterado em função das doses de gesso. Houve aumento dos teores de Ca, também em resposta as doses de gesso. Não houve diferença nos teores de S na camada superficial, mas houve aumento na camada subsuperficial em resposta à dose de gesso. Constatou-se redução nos teores de Mg na camada superficial e elevação na camada subsuperficial, com o aumento das doses de gesso. Não houve variação nos teores de K e na retenção de água para as diferentes doses de gesso e regime de fornecimento de água.

Fluoride accumulation by plants grown in acid soils amended with flue gas desulphurisation gypsum

The application of flue gas desulphurisation (FGD) gypsum as an acid soil ameliorant was studied in order to establish the possible detrimental effects on plants and animals feeding on them caused by the high fluoride content in this by-product. A greenhouse experiment was conducted under controlled conditions to determine the F accumulation by two plant species (alfalfa ( Medicago sativa L.) and ryegrass ( Lolium perenne L.)) grown in acid soils amended with different FGD gypsum doses (0–10%). The F concentrations in plant aerial parts were comprised in the range 22–65 mg kg −1, and those in plant roots varied from 49 to 135 mg kg −1. The F contents in the above-ground plant tissues showed to decrease with the FGD gypsum application rate, whereas an inverse trend was manifested by plant roots. The increase in the soil content of soluble Ca as a result of the FGD gypsum addition seemed to play an important role in limiting the translocation of F to plant aerial parts.

Produtividade de cana-de-açúcar com a utilização de doses e fontes de gesso em um latossolo no estado de Pernambuco

This work is about the answers of yield on the first cut of the sugar cane (plant cane), using the varieties SP79-1011 on an Oxisol red-yellow (Latossolo vermelho-amarelo in Portuguese), by the application of gypsum doses. Establishing a study that uses two gypsum sources, here called Mineral Gypsum (MG/ GM in Portuguese) and Recycled Gypsum (RG/GR in Portuguese). The study was lead in a experimental area, implanted on the Usina Cucau’s agricultural field, in Rio Formoso City – PE. Beside the weight after the cut of each plot with the respective treatment, was valued the percentage of fiber the amount of TSR - Total Sugars Recovered (ATR in Portuguese) and Tons of Pol per Hectare (TPH), by technological analysis of the cane produced, permitting a quantitative and qualitative valuation of raw material (sugar cane). In relation of (about) the weight per plot, the witness (zero gypsum) presented a major value followed by the dose 2 for both treatments (GM and GR). The major dose of GR resulted on a major tenor of fiber, and the doses 1 and 2 of GM together with the witness showed the major tenors sub-sequent. The doses 1 of GM and dose 4 of GR had the best answers about ATR and the dose 2 of GM and dose 4 of GR best answers about TPH.

PRODUTIVIDADE DE CANA-DE-AÇÚCAR COM A UTILIZAÇÃO DE DOSES E FONTES DE GESSO EM UM LATOSSOLO NO ESTADO DE PERNAMBUCO

This work is about the answers of yield on the first cut of the sugar cane (plant cane), using the varieties SP79-1011 on an Oxisol red-yellow (Latossolo vermelho-amarelo in Portuguese), by the application of gypsum doses. Establishing a study that uses two gypsum sources, here called Mineral Gypsum (MG/ GM in Portuguese) and Recycled Gypsum (RG/GR in Portuguese). The study was lead in a experimental area, implanted on the Usina Cucau’s agricultural field, in Rio Formoso City – PE. Beside the weight after the cut of each plot with the respective treatment, was valued the percentage of fiber the amount of TSR - Total Sugars Recovered (ATR in Portuguese) and Tons of Pol per Hectare (TPH), by technological analysis of the cane produced, permitting a quantitative and qualitative valuation of raw material (sugar cane). In relation of (about) the weight per plot, the witness (zero gypsum) presented a major value followed by the dose 2 for both treatments (GM and GR). The major dose of GR resulted on a major tenor of fiber, and the doses 1 and 2 of GM together with the witness showed the major tenors sub-sequent. The doses 1 of GM and dose 4 of GR had the best answers about ATR and the dose 2 of GM and dose 4 of GR best answers about TPH.

Fitorremediação de solo salino s ódico por Atriplex nummularia e gesso de jazida

Atriplex nummularia apresenta-se como alternativa de uso na recuperação de solos salino-sódicos, podendo servir como suporte forrageiro e como folhagem na floricultura e paisagismo. Com o objetivo de avaliar o potencial desta halófita na fitorremediação de solo salino-sódico sob irrigação com águas salinas e verificar o potencial do gesso como potencializador da fitoextração de Na, realizou-se um experimento em casa de vegetação, em esquema fatorial 2 x 3, sendo dois tratamentos com gesso de jazida(ausência, e aplicação de 50 % da dose recomendada pela necessidade de gesso) e três classes de água para irrigação (C1 = 175 μS cm-1; C2 = 500 μS cm-1e C3 = 1500 μS cm-1). Foram realizadas avaliações dos teores de Na, no solo e na planta, aos 40, 70, 100 e 130 dias do transplantio da A. nummularia. O gesso proporcionou ganho médio de 96 % na matéria seca de raiz. O teor de Na nas folhas foi significativo a partir da terceira época avaliada com valores de 90,1 e 109,7 g kg-1, para 100 e 130 dias após o transplantio, respectivamente. Este efeito foi aumentado em 30 % com a aplicação de gesso. O teor de Na+ no solo foi menor em média 31 e 26 %, com e sem gesso, respectivamente, a partir de 100 dias após o transplantio. Com base nas condições estudadas, pode-se concluir que a Atriplex nummularia comportou-se como planta hiperacumuladora de Na, com potencial de uso na fitoextração deste elemento no solo. O uso do gesso de jazida promoveu o aumento da capacidade de extração de Na do solo pela planta, podendo ser usado como potencializador da fitoextração. A irrigação da A. nummularia para uso de fitorremediação pode ser feita com águas salinas na faixa de 175 a 1500 μS cm-1.

Resposta do alho (Allium sativum L.) à aplicação de gesso agrícola, esterco de curral e bórax

This paper had the objective to evaluate the use of gypsum, stable manure and borax in the yield garlic, cateto roxo cultivar. The experiment was conducted in an alluvial soil, at Epamig Experimental Farm, in Sao Sebastiao do Paraiso (MG), in a design of randomized blocks, in the (4x2x2) factorial scheme, with three replications. Four gypsum doses (G0 = 0; G1 = 500; G2 = 1,000 and G3 = 2,000 kg ha -1 ), two stable manure doses (E0 = 0 and E1 = 20t ha -1 ) and two borax doses (B0 = 0 and B1 = 15 kg ha -1 ) were evaluated, using gypsum only in 1994 and the other treatments in 1994 and 1995. The garlic bulbs were harvested and stored for 20 days, being obtained the total and commercial weight of bulbs, according to size classification; for each rate, the medium diameter in weight (MDW) was also calculated. In the treatment that received stable manure, gypsum interfered negatively in the garlic yield, in the year of application (1994), with residual effect on the subsequent year (1995). It affected the decomposion processes of the stable manure, reflecting in B liberation. The maximum yields were obtained in the absence of the treatments in 1994 (7,347 kg ha -1 ) and in the presence stable manure and borax, for the zero dose of gypsum, in the year of 1995 (7359 kg ha -1 ). The medium diameter in weight of bulbs (MDW), for 1994 wasn’t affected significantly by the treatments. However to 1995, there was a highly significant effect of the stable manure. In its presence and absence MDW was of 36.2 mm and 35.0 mm, respectively. The gypsum use generally presented negative effects in garlic yield, interfering in B dynamics; howerer the use of stable manure attenuated these effects without eliminating them. In 1995, stable manure provided a larger amount in bulbs weight in the classes with larger diameter, interfering positively in their classification

Atributos químicos e físicos de um Latossolo sendo influenciados pelo manejo do solo e efeito da gessagem

The objective of this work was to evaluate the gypsum residual effect and two tillage systems as for their chemical and physical attributes in a red dystroferric Latossol (Hapludox). The experiment was carried out in 2004/2005 on the experimental field of the Federal University of Mato Grosso do Sul - UFMS, in Dourados, State of Mato Grosso do Sul. The experimental design was in randomized blocks in sub-subdivided plots with four replications. Main plots consisted of two tillage system (no tillage and conventional tillage). The subdivided plots were gypsum doses (0 and 2000 kg ha-1) and sub-subdivided plots, the depths. The following parameters were estimated: pH in CaCl2, P, Ca+2, Mg+2, K+, Al+3, H++Al+3, aluminum saturation, base saturation, bases sum, cation exchange capability, particle density, soil bulk density, soil total porosity. The interaction between tillage system and gypsum dose was significant for soil density and total porosity, with an increase in the soil density and a reduction in the total porosity in combination with no tillage and 2000 kg ha-1 of gypsum. The tillage system and gypsum effect did not affect the chemical attributes, except for the P drift which was bigger in no tillage system than in conventional tillage.

Effectiveness of Sulphuric Acid and Gypsum for the Reclamation of a Calcareous Saline‐Sodic Soil Under Four Crop Rotations

AbstractAs a low‐cost strategy, the cultivation of certain salt‐tolerant crop species on calcareous saline‐sodic soils, i.e. phytoreclamation, has enjoyed great attention in recent years. A lysimeter study was carried out to evaluate whether a phytoreclamation approach alone, or in combination with some booster dose of either gypsum or sulphuric acid, is sufficient to reclaim a calcareous, moderately saline‐sodic soil. Four crop rotations, rice (Oryza sativa L.)–wheat (Triticum aestivum L.)–sesbania (Sesbania aculeata L.); rice–berseem (Trifolium alexandrinum L.); Kallar grass (Leptochloa fusca L.)–alfalfa (Medicago sativa L.) and sesbania–berseem were tested against three treatments: (T1) control, (T2) sulphuric acid application 25 % of soil gypsum requirement (SGR), and (T3) application of gypsum 25 % SGR. To decrease the sodium adsorption ratio of the saline‐sodic soil well below the threshold level, especially from deeper depth, a booster dose of gypsum or sulphuric acid 25 % SGR was quite effective. Rice–berseem and Kallar grass–alfalfa rotations were more promising in combination with inorganic amendments than the rest of the rotations. The study also suggests that better yields of wheat and rice crops can be obtained with the application of inorganic amendments like gypsum or sulphuric acid. However, Kallar grass yield was somewhat suppressed with these amendments.

Relative efficiency of sources of sulfur at varying rate of its application to wheat and rapeseed

Field experiments were conducted during the winter season of 2002 – 2003 on wheat and rapeseed at the Indian Agricultural Research Institute, New Delhi, to compare Cosavet, a new sulfur material, with elemental sulfur and gypsum at varying rates of their application. The results of these experiments indicated that both wheat and mustard responded to sulfur significantly. Cosavet increased the yield over control by 0.4 – 1.3 t ha−1 in wheat and 0.2 – 0.5 t ha−1 in rapeseed, whereas elemental sulfur and gypsum increased the yield over control by 0.4 – 1.9 t ha−1 in wheat and 0.3 – 0.4 t ha−1 in rapeseed. Cosavet was most effective at 10 – 20 kg S ha−1, whereas elemental sulfur and gypsum at 40 – 60 kg S ha−1. The economic optimum dose (EOD) of Cosavet, elemental sulfur and gypsum for wheat was 20, 38 and 45 kg S ha−1, respectively, and response at EOD was 79, 32 and 38 kg grain kg−1 S, respectively. Similarly for rapeseed the EOD of Cosavet, elemental sulfur and gypsum was 10, 41 and 37 kg S ha−1, respectively, and response at EOD was 30, 7 and 11 kg grain kg−1 S, respectively. These results, thus, indicate that Cosavet was more effective than elemental sulfur and gypsum for both wheat and rapeseed.

Mapping of groundwater quality in the Turonian aquifer of Oum Er-Rabia Basin, Morocco: a case study

This study takes the groundwater of the Moroccan limestone aquifer of Oum Er-Rabia as an example of statistical and cartographical approaches in water resources management. Statistical analyses based on frequency distribution and PCA methods revealed the homogeneity of waters with the existence of abnormal points and have helped to assess correlations between the studied variables. The mapping approach illustrated that waters are influenced by the lithology of the surrounding rocks and are of Ca–Mg–HCO3, Ca–Mg–Cl–SO4, and mixed types according to the Piper classification. The quality of water is of high to medium, north of the basin, but it is of medium to bad, NE and south, due to excessive contents of chloride, sulfate and nitrate. According to the US Salinity Laboratory classification, water used for irrigation in the eastern and the southern parts of the basin should take into consideration the drainage conditions, the nature of plants and the addition of gypsum doses.

Influence of fertilisers, host factors and storage conditions in relation to disease severity: a case study of black mould rot of onion

Aspergillus niger was found to be the predominant pathogen associated with black mould rot of onion during storage. Market survey for the assessment of spoilage caused by the fungus recorded a loss of 2.9% to 12.09% during the period from June 1998 to February 1999. Application of higher doses of calcium in the form of gypsum (400 kg/ha) and lower dose of nitrogen in the form of urea (50 kg/ha) to the field and advancing the harvest of onion bulbs by fifteen days significantly reduced the spoilage of bulbs during storage. An inverse relationship existed between neck length of the bulbs and spoilage at storage. Bulb rotting was noticed when the storage temperature was between 30 °C and 40 °C and the relative humidity was above 80%. Further, A. niger infection caused reduction in pungency of onion bulbs which was more pronounced at grade 4 than grade 1. The culture filtrates of Aspergillus niger and Aspergillus flavus isolated from onion as well as the extracts from onion bulbs infected with the above fungi were free from aflatoxin contamination.

COMPORTAMENTO DE BRACATINGA (Mimosa scabrella) E SESBÂNIA (Sesbania sesban) EM ÁREAS DEGRADADAS PELA DISPOSIÇÃO DE RESÍDUOS PROVENIENTES DO PROCESSAMENTO DA BAUXITA

O retorno de horizontes superficiais do solo para áreas degradadas por atividade de disposição de resíduos tem sido prática rotineira e largamente utilizada. Para algumas empresas, no entanto, essa operação tem representado cerca de 70 a 80% dos custos finais de recuperação de áreas mineradas. O presente trabalho teve como objetivo avaliar a contribuição de duas espécies leguminosas na colonização inicial de um solo degradado pela disposição de resíduo de bauxita pós processamento, em Poços de Caldas-MG. O plantio foi efetuado em Janeiro de 1999, utilizando-se leguminosas Mimosa scabrella e Sesbania sesban. Adotou-se o espaçamento de 2,0 x 1,5m, e o delineamento estatístico foi o de blocos casualizados no esquema fatorial (3 x 4 x 2),
 sendo três doses de gesso diferentes, quatro espessuras de camada de solo superficial colocada sobre o resíduo e duas espécies vegetais. Foram feitas 4 repetições, com 5
 plantas cada. Realizaram-se medições da altura total e o cálculo da taxa de mortalidade. Os resultados mostraram que o resíduo apresenta propriedades semelhantes a um solo
 salino-sódico, com altos valores para o pH e condutividade elétrica. Registrou-se ainda que as doses de gesso, as espessuras das camadas e as espécies influenciaram
 significativamente nos valores médios obtidos para as variáveis. Verificou-se a relação inversamente proporcional entre a taxa de mortalidade e os fatores dose de gesso e
 espessura da camada de solo colocado. Observou-se que doses crescentes de gesso e a espessura da camada de solo acarretaram decréscimo da taxa de mortalidade para as
 espécies. Para todas as variáveis estudadas, a sesbânia apresentou melhores resultados do que a bracatinga.

Combined effect of reduced dose of gypsum and salt tolerant varieties of rice (Oryza sativa) and wheat (Triticum aestivum) on rice-wheat cropping system in sodic soils

A field experiment was conducted at Lucknow in Uttar Pradesh during 2001-2002 to 2003-04 on a fine loamy, mixed, hyperthermic, sodic soil having high pH, low electrical conductivity, high exchangeable sodium percentage and very low water permeability to find out the combined effect of reduced dose of gypsum and salt tolerant variet- ies of rice ( Oryza sativa L.) and wheat ( Tr iticum aestivum L. emend. Fiori & Paol.) on productivity of rice - wheat cropping system in sodic soil. This study revealed that application of gypsum @ 25% gypsum requirement (G.R.) and growing of salt tolerant varieties of rice CSR 13 and wheat KRL 19 significantly increased the yield attributes and yields of these crops in the system over control treatment as well as 15% G.R. So much so it was at par with 50% G.R. with non- salt tolerant varieties. The magnitude of combined effect of reduced dose of gypsum and salt tolerant varieties was reflected as 17 and 8.2% increase in grain yield over their counterpart varieties. Interaction between gypsum levels and salt-tolerant varieties on grain yields indicated that gypsum @ 25% G.R. with sodicity tolerant varieties in rice-wheat cropping system could save about 43% of the total initial expenditure for the recla- mation of sodic soils over the recommended dose of gypsum (50% G.R.) with non-sodicity tolerant traditional high yielding varieties. Thus, for low-cost effective technology, treating the sodic soils with reduced dose of gypsum (25% G.R.) and growing salt tolerant varieties of rice 'CSR 13' and wheat 'KRL 19' proved highly economical and sustainable technology for resource scarce situations.