Ha-1 Gypsum Research Articles

Pemulsaan dan Ameliorasi Tanah Salin untuk Pertumbuhan dan Hasil Kedelai

<p class="teks">ABSTRACT<br /><br />Most salt-affected agricultural land has low productivity such that suitable management is required to improve the productivity. Negative effect of salinity stress can be reduced by growing salt-tolerant cultivars and soil amelioration. The objective of the research was to identify effective ameliorant and effect of mulching in improving soybean growth and yield on saline soil. The research was conducted on saline soil in Lamongan District that has electrical conductivity (EC) of 11.39 dS m-1 during dry season 2016. Treatments consists of two factors that were arranged in split plot design, and replicated three times. The main plot was mulching, i.e. without mulching and mulching with 3.5 ton ha-1 rice straw. The subplots were six amelioration traits, namely without amelioration (control), 120 kg ha-1 K2O, 750 kg ha-1 S, 5 ton ha-1 gypsum, 5 ton ha-1 manure and combination of 5 ton ha-1 manure+1.5 ton ha-1 gypsum. The soybean seed used was K-13, a saline tolerant genotipe. The results showed that mulching reduced soil EC, increased K and Ca absorption, leaf chlorophyll index, improved growth and yield. Soil amelioration with K2O, sulphur, gypsum, or combination of manure+gypsum decreased soil EC and soil pH. Amelioration with gypsum increased the grain yield of 36.3%. <br /><br />Keywords: EC, leaf chlorophyl index, salinity stress, soil management <br /><br /></p>

The residual effect of gypsum on subsoil conditioning, nutrition and productivity of sugarcane crops

Although the benefits of gypsum for subsoil conditioning are known, there is still a lack of information regarding the duration of its effects on soil chemical attributes and sugarcane productivity. Therefore, the objective of this work was to evaluate the residual effect of gypsum doses on soil chemical attributes, root density and productivity in seven sugarcane crops (ratoon). The experiment was conducted in an experimental area located at Embrapa Cerrados, in Planaltina, DF, Brazil. The experimental design consisted of four gypsum doses (0, 0.5, 5 and 10 t ha-1) distributed in randomized blocks with four replications. Gypsum was applied only one time to the soil surface after sugarcane planting in July 2009. After 13 and 87 months of gypsum application under sugarcane cultivation, the soil was collected from layers up to 120 and 200 cm deep, respectively. For evaluation of the soil chemical attributes: sulfate (S-SO42-), calcium (Ca2+), magnesium (Mg2+) and aluminum saturation (m) were assessed. Also, the root dry mass density was evaluated after the first and seventh sugarcane crops, in September 2010 and 2016, respectively. Furthermore, the variables leaf macronutrient concentrations (N, P, K, S, Ca and Mg), stalk yield and total reducing sugars (TRS) were analyzed in all seven crops/ratoons (first is the main crop and other six are ratoons). The application of 5 t ha-1 gypsum increased SO42- and Ca2+ and reduced the aluminum saturation after 13 and 87 months, with higher intensities in the subsurface layers of the soil. As a consequence of this chemical conditioning of the subsurface soil layers, the root dry mass density was increased by 18 and 37% in the 0-120 and 0-200 layers, respectively, after the first (main) and seventh sugarcane crops (ratoons) in relation to the absence of gypsum application. Furthermore, treatments with 5 and 10 t ha-1 of gypsum increased the leaf contents of S, Ca and N in relation to treatments with 0 and 0.5 t ha-1 of gypsum. As a consequence of the increased root growth and better nutrition of sugarcane, the use of gypsum provided a long residual effect, observed in the increase of stalk and sugar yields.

Gypsum, Soil Scarification and Succession Planting as Alternatives to Mitigate Compaction of Dystrophic Red-Yellow Latosol

Understanding and quantifying the impact of soil management and use on its physical properties are essential to the development of sustainable agricultural systems. Thus, the aim of this study was to assess the effect of agricultural gypsum, soil scarification and succession planting on the physical attributes of dystrophic red-yellow latosol in Porto Velho, Rondônia state (RO), Brazil. The treatments used were absence and application of 2000 kg ha-1 of gypsum, absence and use of soil scarification, and three types of crop succession: SF (soybean/fallow), SMF (soybean/maize/fallow) and SMBF (soybean/maize/brachiaria/fallow). A randomized block design was used on eight blocks, for a 2 × 2 × 3 factorial arrangement. Soil parameters assessed were macroporosity, microporosity, total porosity, soil density, moisture content and penetration resistance. Data normality was assessed using the Shapiro-Wilk test. The data were submitted to analysis of variance and means were compared by the Scott-Knott test at 5% probability. The highest macroporosity and total porosity values were recorded in treatments with gypsum application and soil scarification. Penetration resistance was lower in the SMBF and SMF crop successions. There was no treatment effect on the soil density.

Efecto del yeso sobre las características químicas de un Oxisol de la Orinoquia colombiana cultivado con lima ácida Tahití

La lima acida Tahití [Citrus latifolia (Yu Tanaka) Tanaka] es una de las especies de cítricos con potencial de producción para consumo interno y exportación en los llanos Orientales de Colombia. Con el propósito de evaluar los efectos del uso de yeso agrícola sobre las propiedades químicas, absorción de nutrientes y producción de frutos de lima Tahití, se realizó un experimento en un suelo Oxisol de terraza alta del Piedemonte Llanero. Los tratamientos consistieron de cinco niveles de yeso (0,5 - 1,0 - 1,5 - 2,0 y 2,5 t ha-1). Se utilizó un diseño de BCA con 4 repeticiones. La producción de fruto fue evaluada durante cinco años consecutivos y al sexto año se realizó el análisis químico del suelo y análisis foliar. Se encontró un efecto positivo sobre el aumento en el contenido y la distribución de Ca, Mg, y S en el perfil del suelo, disminución de la acidez intercambiable y aumento del pH con las aplicaciones crecientes de yeso agrícola. Las aplicaciones de yeso aumentaron la absorción de Ca y S y redujeron los niveles foliares de N, K, Mg y Zn, sin alterar la productividad del cultivo. La mayor producción acumulada de frutos (141,41 t ha-1) fue obtenido con la aplicación de 2,5 t ha-1 de yeso. Se demostró los efectos positivos del yeso agrícola en la distribución de bases en el suelo, en la reducción de la acidez y el incremento de pH en profundidad, mejorando la productividad de lima Tahití.

Management of peanut (Arachis hypogaea L.) diseases through nutrient supplements

Crop responses to mineral nutrients may be conducive or adverse to diseases, depending on disease type, severity, crop species, and cultivars. Therefore, an experiment was conducted to measure the effect of nutrient doses on to peanut diseases. The treatments were quite effective to manage the peanut diseases in kharif (Kh) as well as in rabi-summer (RS). All the treatments, applied however significantly reduced the soil borne as well as foliar fungal disease in comparison to control (without any external supply of nutrients). In kharif severity of ELS, LLS and Rust was (6.9) (4.4) and (6.2), respectively while it was highest in control (T7) and the per cent disease incidence of soil borne disease viz. aflaroot, collar rot and stem rot observed (2.5, 3.9 and 13.2 respectively) in T1 while it was (4.5, 5.7 and 16.8 respectively) in control (T7). In rabi stem rot incidence (21.3%) was recorded in control while it was lowest (9.7%) in the treatment T3 (25:50:0 NPK + 500 kg gypsum ha-1 + 2.5 kg zinc ha-1). The pod and haulm yield was recorded for effectiveness of different treatment on yield and found that the treatment T1 (25:50:0 NPK + 500 kg Gypsum+ 2.5 kg zinc+ 1 kg Boron) significantly increased the yield up to 40.5%. In both season T1 (25:50:0 NPK + 500 kg Gypsum+ 2.5 kg zinc + 1 kg Boron) reduces the disease severity significantly.

Soil management and application of agricultural gypsum in a Planosol for soybean cultivation

ABSTRACT: This study investigated the effects of soil management systems, tillage, and application of gypsum agricultural to soil, on soybean development in lowland areas. The experiment was carried out on an Alfisol in a randomized complete block design in a factorial arrangement. The two soil tillage practices were without deep tillage and with deep tillage. Gypsum treatments were no gypsum application, 500kg of gypsum ha-1, 1000kg of gypsum ha-1, and 1500kg of gypsum ha-1. Deep tillage resulted in less soil resistance to root penetration during ryegrass cultivation during the soybean offseason, 11 months after applying the management treatments, resulting in higher dry mass of ryegrass in the offseason and higher soybean yield in the following year.

Effect of Plant Spacing and Fertilizer Management on the Yield Performance of BRRI dhan39 under Old Brahmaputra Floodplain Soil

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, Bangladesh from June to December 2015 to investigate the effect of spacing and fertilizer management on the yield of transplanted Aman rice cv. BRRI dhan39. The experiment comprised of five spacings viz. 25 × 5 cm, 25 × 10 cm, 25 × 15 cm, 25 × 20 cm, 25 × 25 cm and four fertilizer schedules viz. no manure and no fertilizer (control), recommended dose of inorganic fertilizer (80-60-40 kg N, P2 O5 , K2 O ha-1, respectively + 60 kg ha-1 gypsum + 10 kg ha-1 ZnSO4 ), 75% recommended dose of inorganic fertilizer + cow dung at 5 t ha-1, 75% recommended dose of inorganic fertilizer + poultry manure @ 2.5 t ha-1. The experiment was laid out in a Randomized Complete Block Design with three replications. Plant height (104.60 cm), number of total tillers hill-1 (11.03), panicle length (22.25 cm), grains panicle-1 (109.00) and grain yield (4.42 t ha-1) were found to be the highest in 25 × 15 cm spacing. Regarding nutrient management, 75% recommended dose of inorganic fertilizers + cow dung at 5 t ha-1 superseded other treatments in terms of plant height (107.50 cm), number of total tillers hill-1 (10.40), number of effective tillers hill-1 (7.68), panicle length (22.26 cm), grains panicle-1 (111.70) and grain yield (4.14 t ha-1). The control treatment (no manures and no fertilizers) gave the lowest values for all these parameters. The highest grain yield (4.57 t ha-1) was found in 25 × 15 cm spacing combined with 75% recommended dose of inorganic fertilizers + cow dung at 5 t ha-1 and the lowest grain yield (2.50 t ha-1) was found in 25 × 5 cm spacing combined with control (no manures and fertilizers). Therefore, 25 × 15 cm spacing combined with 75% recommended dose of inorganic fertilizers + cow dung at 5 t ha-1 appeared as the promising practice in transplant Aman rice cv. BRRI dhan39 cultivation.

Chemical properties of an Oxisol after gypsum application

Gypsum utilization is a critical practice in agriculture because of the high solubility and consequent relative neutralization of subsurface toxic aluminum. However, it has been observed that in most cases, gypsum is being randomly utilized without scientifically established parameters or even the need to use it as a soil amendment at all. The objective of this study was to evaluate the chemical composition and electrical conductivity of an Oxisol’s saturation extract under different gypsum doses (0, 1.0, 2.0, 4.0, and 8.0 Mg ha-1). This experiment was conducted in a greenhouse environment. Soil columns (V = 1.57 dm3) were filled with sifted (2 mm) soil collected from the upper layer (0-20 cm). The experimental design adopted was completely randomized with five repetitions. The treatments consisted of a 5 × 2 factorial through five gypsum doses (0.0, 1.0, 2.0, 4.0, and 8.0 Mg ha-1 of gypsum consisting of 224.1 g kg-1 S, 314.8 g kg-1 CaO, and 7 g kg-1 P2O5) and two depth evaluations (0-10 and 10-20 cm). After the treatments, soil from both 0-10 cm and 10-20 cm layers was removed from the columns, sifted once (2 mm), and subjected to vacuum extraction to assess the saturation extract. The data acquired was processed and submitted to variance analysis (when due) and adjusted to regression equations when statistically relevant. Significant increases were observed for Ca, Mg, K, P, and S, although Al, Si, and pH presented no statistically significant difference. The electrical conductivity value of this soil in particular is directly related to the gypsum dose.

Influence of Gypsum Amendment on Methane Emission from Paddy Soil Affected by Saline Irrigation Water

To investigate the influence of gypsum application on methane (CH4) emission from paddy rice soil affected by saline irrigation water, two pot experiments with the rice cultivation were conducted. In pot experiment (I), salinity levels 30 mMNaCl (S30) and 90 mMNaCl (S90), that showed maximum and minimum CH4 production in an incubation experiment, respectively, were selected and studied without and with application of 1 Mg gypsum ha-1(G1). In pot experiment (II), CH4 emission was investigated under different rates of gypsum application: 1 (G1), 2.5 (G2.5) and 5 (G5) Mg gypsum ha-1 under a non-saline and saline condition of 25 mMNaCl (S25). In experiment (I), the smallest CH4 emission was observed in S90. Methane emission in S30 was not significantly different with the non-saline control. The addition of gypsum showed significant lower CH4 emission in saline and non-saline treatments compared with non-saline control. In experiment (II), the CH4 emissions in the saline treatments were not significantly different to the non-saline treatments except S25-G5. However, our work has shown that gypsum can lower CH4 emissions under saline and non-saline conditions. Thus, gypsum can be used as a CH4 mitigation option in non-saline as well as in saline conditions.

Foliar tissue, grain yield and economic return by surface application of gypsum and different number of soybean plants in precision seed drill

The gypsum has elevated calcium and sulfur in the soil, and there are reports of increased grain yield of soybean with reduced number of plants, being necessary in conjunction with economic return on investment. This study investigated the effect of application superficial of gypsum and different numbers of plants in precision seed drill in the nutritional aspect of the leaf tissue, grain yield of soybean cultivated in clayey Rhodic Hapludox and economic return on investment. Used in the experiment was a randomized block design in scheme tracks (4 × 4), with four doses of gypsum (0, 800, 1600 and 2400 kg ha-1) applied at the V4 stage of soybean Vmax RR (SYN 7059RR) and four variations in the number of plants (12, 14, 16 and 18 plants per meter), with four replications. Samples of leaf tissue were collected in the flowering stage of soybean in the 2011/2012 crop, and then determined the levels of Ca, Mg, K, P, S, Cu, Zn, Mn and Fe. At maturity the yield assessment was performed. The number of plants per meter with precision seed drill and superficial application of gypsum at the V4 stage do not affect the content of macro-and micronutrients leaf tissue of soybean cultivar SYN 7059RR. The application of gypsum at the V4 stage and reducing the number of plants per meter statistically do not affect the grain yield. Recommend lower number of plant (12 plants m-1) on soybean cultivar for SYN 7059RR. The economic returns using higher amount of seed (14, 16 and 18 plants m-1) is -283, -260 and -271% with investment of US$ 13.76, 29.24 and 44.72. Use of gypsum focused costs to only two cultures (soybeans and wheat) during the crop season provides residual soil of 104.43 kg ha-1 of S. Application 800 kg ha-1 gypsum provides US$ 14.56 profit with 44% economic return to payment half investment (US$ 33.32). Key words: No-till, fertilization, plant population, seeding rate, investment return

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.

Soil fertility, nutrition and yield of maize and barley with gypsum application on soil surface in no-till

Annual crop yield and nutrition have shown differentiated responses to modifications in soil chemical properties brought about by gypsum application. The aim of this study was to evaluate the effect of gypsum application rates on the chemical properties of a Latossolo Bruno (Clayey Oxisol), as well as on the nutrition and yield of a maize-barley succession under no-till. The experiment was set up in November 2009 in Guarapuava, Parana, Brazil, applying gypsum rates of 0.0, 1.5, 3.0, 4.5, and 6.0 Mg ha-1 to the soil surface upon sowing maize, with crop succession of barley. Gypsum application decreased the levels of Al3+ and Mg2+ in the 0.0-0.1 m layer and increased soil pH in the layers from 0.2-0.6 m depth. Gypsum application has increased the levels of Ca2+ in all soil layers up to 0.6 m, and the levels of S-SO4(2-) up to 0.8 m. In both crops, the leaf concentrations of Ca and S were increased while Mg concentrations have decreased as a function of gypsum rates. There was also an effect of gypsum rates on grain yield, with a quadratic response of maize and a linear increase for barley. Yield increases were up to 11 and 12 % in relation to control for the maximum technical efficiency (MTE) rates of 3.8 and 6.0 Mg ha-1 of gypsum, respectively. Gypsum application improved soil fertility in the profile, especially in the subsurface, as well as plant nutrition, increasing the yields of maize and barley.

Impact of Applying Calcium on Yield and Visual Quality of Groundnut(Arachis hypogaea L.)

Recently, Department of Agriculture (DOA), Sri Lanka had developed four new varieties namely, Thissa, Indi, Walawa and Tikiri. Groundnut is cultivated in the dry and intermediate zones of Sri Lanka mainly under rain fed in October season and, in paddy lands under irrigation in April season. Low yields and the poor quality kernels are the major constraints to cultivation of Groundnut (Arachis hypogaea L.) in Sri Lanka. Groundnut is usually grown in well-drained soils with a pH of 6.5. Inadequate and unbalanced supply of nutrients may be one of the reasons for low yields in acidic and sandy soils. Farmers in Dambulla and Maspotha, apply 60-350 kg ha-1 of Gypsum for their cultivations and obtained a yield of 2000-2500 kg ha-1. Therefore, this study was conducted to find out the effect of Calcium using Gypsum on the yield and quality of Groundnut in Maspotha divisional secretariat area of Kurunegala district, in the intermediate zone of Sri Lanka. Soil pH and EC were measured to determine the acidity and salinity levels. The field experiment was conducted during the October seasons 2011/2012 and 2012/2013. Randomized Complete Block Design was used with four treatments (0, 125, 175, 250 kg ha-1 of Gypsum) and three replicates. The crop management practices were done according to the standard procedures. The nut yield, number of pegs per plant, kernel and shell weight of fifty pegs per plot, dry weight of fifty seeds were measured. The seed quality and filling of seeds in each treatment were also evaluated. The results revealed that with application of 250 kg ha-1 of Gypsum increased the soil pH from 4.1 to 5.0 and increase the mean pod dry weight per plot of 40 plants, from 578 to 835 g with better quality kernels.

Modalities for soil preparation and gypsum application in ultisol: stem productivity of sugarcane

The study was conducted in an area of expansion of sugarcane at Vale do Paraná factory in Suzanápolis city - São Paulo (SP), in Brazil, in the northwestern region of the State of São Paulo. It was used the sugarcane variety RB92-5345, 1.5m of spacing between rows, in an Ultisol. The study aimed to evaluate the productivity of sugarcane and first ratoon and some soil chemical attributes in function of soil tillage and application or not of gypsum. The experimental design was randomized blocks with six treatments, in a factorial 3x2 and six replicates, the main treatments were soil tillage with three equipments, moldboard plow, chisel plow, and heavy harrow, and two secondary treatments with application of 1 t ha-1of gypsum and no gypsum. After each harvest of cane, the soil was characterized as to its fertility indicators in layers of 0.0-0.15; 0.15-0.30 and 0.30-0.45m. Differences in values of soil chemical attributes due to the methods of preparation occurred in the sugarcane did not last until the harvest of the 1st ratoon cane, and also did not influence the crop productivity. The gypsum application resulted in higher values of total recoverable sugar (TRS) and the productivity of tons of stems per hectare (TSH) to sugarcane and 1st ratoon cane, respectively, confirming the initial hypothesis.

Doses de gesso em cafeeiro: influência nos teores de cálcio, magnésio, potássio e ph na solução de um latossolo vermelho distrófico

O desbalanço entre Ca2+, Mg2+ e K+ no solo como consequência das aplicações elevadas de gesso deve-se às relações de tamanho (raio iônico) e densidades de cargas (relação carga/raio) de cada espécie iônica. Quanto maior a densidade de carga, mais intensa será a ligação iônica do cátion com íons de cargas opostas como OH- e SO4-2. Dessa maneira, o uso excessivo de gesso agrícola, sem considerar o balanço de cargas das partículas do solo; o equilíbrio iônico; e a CTC podem resultar em expressiva lixiviação ao longo do perfil do solo. O objetivo deste estudo foi avaliar o efeito de elevadas doses de gesso (0, 7 e 56 t ha-1) nos teores de Ca2+, Mg2+, K+ e pH na solução de um Latossolo Vermelho distrófico cultivado com cafeeiro, obtida pelo método adaptado do extrato aquoso. O solo foi amostrado nas profundidades de 0,15-0,25; 0,35-0,45; 0,75-0,85; 1,15-1,25 e 2,35-2,45 m na linha de plantio, em quatro tratamentos: G-0 - gesso no preparo (aplicação ocorreu em setembro de 2008, distribuído a lanço, na quantidade de 2 t ha-1) e sem gesso na linha de plantio; G-7 - gesso adicionado durante a preparação do solo (2 t ha-1), na mesma condição do G-0 e 7,0 t ha-1 de gesso na linha de plantio; G-56 - gesso adicionado durante a preparação do solo (2 t ha-1), na mesma condição do G-0 e 56 t ha-1 de gesso na linha de plantio (nessas parcelas experimentais as entrelinhas de plantio foram cobertas com braquiária); e CV-7: ausência de braquiária na entrelinha, com gesso no preparo e 7 t ha-1 de gesso na linha, com três repetições distribuídas em blocos ao acaso, totalizando 60 amostras. Após 16 meses da adição de gesso, observou-se redução do pH na solução do solo nas profundidades de 0,15-0,25; 0,35-0,45 e 0,75-0,85 m. A aplicação de gesso agrícola foi eficiente na melhoria do ambiente radicular no subsolo, aumentou a concentração de Mg2+ e Ca2+ na solução do solo, mas reduziu o K+ em profundidade, a partir de 0,85 m. Os teores de Ca2+ e Mg2+ trocáveis na solução do solo estiveram acima do nível crítico; entretanto, os teores de K+ trocável se mantiveram na faixa do valor crítico, indicado para o desenvolvimento da cultura.

Morphology and stability of aggregates of an Oxisol according to tillage system and gypsum application

Morphological characterization and aggregate stability is an important factor in evaluating management systems. The aim of this paper is to evaluate the stability and morphology of the aggregates of a dystrophic Oxisol managed with no-tillage and conventional tillage with and without the residual action of gypsum. The experimental design was randomized blocks arranged in split-split plot, where the treatments were two soil management systems (plots) with 0 and 2000 kg ha-1 of gypsum (subplots) and five depths (0-0.05, 0.05-0.10, 0.10-0.15, 0.15-0.20 and 0.20-0.30 m) as the subsubplots, with four replications. The aggregate morphology was determined through images and later evaluated by the Quantporo software. Stability was determined by the wet method. The results showed that the no-tillage system, with or without gypsum residual effect, provided the aggregates with the largest geometric diameters. The combination of no-tillage system and the gypsum residual effect provided rougher aggregates.

Análise econômica do processo de recuperação de um solo sódico no Perímetro Irrigado Curu-Pentecoste, CE

A pesquisa teve como objetivo analisar, com base nos indicadores de rentabilidade da análise de investimento, a viabilidade econômica do processo de recuperação de um solo sódico no Perímetro Irrigado Curu-Pentecoste-CE. O delineamento experimental foi em blocos inteiramente casualizados com cinco tratamentos e cinco repetições. Os tratamentos de recuperação foram: T0: testemunha; T1: 40 t ha-1 de matéria orgânica (M.O); T2: 20 t ha-1 de gesso; T3: 20 t ha-1 gesso + 40 t ha-1 M.O.; T4: 10 t ha-1 gesso + 20 t ha-1 M.O. A análise dos indicadores de rentabilidade foi realizada de forma "ex-ante" e "ex-post", considerando-se os custos e/ou investimentos na recuperação do solo sódico e instalação futura de um sistema de drenagem subterrânea. O cultivo do feijão-de-corda contribuiu com apenas 12% do processo de recuperação do solo sódico. Do ponto de vista estritamente financeiro e na alternativa da aplicação de um único melhorador, o gesso se apresentou como a alternativa mais atrativa. O processo de recuperação apresentou viabilidade econômica a uma taxa de juros de 12% ao ano, porém, considerando-se que o "payback" foi de nove anos, há a necessidade da criação de uma linha de crédito subsidiada, destinada a agricultores familiares como forma de incorporar, ao processo produtivo, as extensas áreas de solos degradados por sódio.

Lime and gypsum to improve root depth of orange crop in an Ultisol of the Coastal Tablelands

Coastal Tableland is a landscape unit in the North East of Brazil in which the main soils are Ultisols. In these soils, a compacted layer denominated "cohesive horizon" occurs and root growth is limited by it. An experiment with five treatments and six replications was set up in order to study how liming and gypsum could improve root depth of orange (Citrus sinensis L. Osbeck) crop in an Ultisol in which a compacted layer was found at 0.3 m. Treatments were: A - No liming and no gypsum; B - Liming to achieve 60% base saturation; C - B + 1 t of gypsum ha-1 ; D - B + 2 t of gypsum ha-1 and E - B + 3 t of gypsum ha-1. Gypsum increased calcium and sulfate in the cohesive horizon. Surface application of lime and gypsum did not cause changes in soil density and total porosity in the cohesive horizon. An improvement of root length was observed at the cohesive horizon.

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.

POLYACRYLAMIDE SOIL AMENDMENT EFFECTS ON RUNOFF AND SEDIMENT YIELD ON STEEP SLOPES: PART I. SIMULATED RAINFALL CONDITIONS

Steep slopes consisting of disturbed soil are very often found in construction, landfill, and surface miningsituations. Although legislation and economics dictate that vegetative cover be established on these slopes as rapidly aspossible, the occurrence of large rainfall events during critical periods of vegetation establishment can frequently causeextensive soil loss. Sediment generated from erosion can impair offsite water quality, and onsite damages to the erodedregion can be so extensive that expensive earthmoving, regrading, reseeding, and remulching may be necessary. We evaluatedthe effectiveness of two soil treatments for reducing runoff and soil loss from a silt loam topsoil placed on a constructed 32%slope. The three treatments were an untreated control, 80 kg ha1 anionic polyacrylamide (PAM) applied as a liquid spray,and 80 kg ha1 PAM as a liquid spray combined with a dry granular application of 5 Mg ha1 of gypsum. Replicated plotswere subjected to a range of rainfall intensities under a programmable rainfall simulator, and resulting runoff and sedimentloss were measured. In the first event of 69 mm h1 uniform rainfall applied for one hour to initially dry soil, the PAM andPAM with gypsum treatments significantly reduced runoff by almost 90% and sediment yield by 99%, compared to the control.Total runoff through a series of simulated rainfall events was reduced by 40% to 52%, and sediment loss was reduced by 83%to 91% for the plots treated with PAM and PAM plus gypsum, respectively. These results indicate that the use of PAM aloneor in combination with gypsum can significantly reduce runoff and soil loss from large storm events, and may be acosteffective approach to protect the soil during critical periods of vegetation establishment, particularly for disturbed soilson steep slopes.