G. K. Donagemma

Fósforo remanescente em argila e silte retirados de Latossolos após pré-tratamentos na análise textural

The presence of highly stable microaggregates can hamper soil dispersion in some Oxisols. These very clayey groupings may be not completely disaggregated by chemical and mechanical dispersion. Due to their size, the silt proportion of the soil is overestimated. A laboratory experiment was conducted to verify the use of the solution equilibrium P (SEP) to evaluate the response to particle size analysis pre-treatments in Oxisols. The treatments were arranged in a 7 x 22 factorial design, in randomized blocks with four replications. The factors were samples of seven Oxisols dispersed with 0.1 mol L-1 NaOH, with and without pre-treatment to remove organic matter (-OM) and poorly crystallized iron oxides (-Ox). SEP was determined in samples of the dispersed clay and silt fractions and in the silt fraction, after a second dispersion with 0.1 mol L-1 NaOH. It was observed that SEP is sensitive enough to identify differences between the treatments applied. This indicates the usefulness of SEP as an auxiliary determination in soil dispersion studies.

Distribuição do amônio, nitrato, potássio e fósforo em colunas de latossolos fertirrigadas

It is convenient to apply nutrients in fertigation at an appropriate depth, in order to locate those elements at a convenient place for plant uptake. So, an experiment was carried out under laboratory conditions using percolation columns, to establish the irrigation lamina fraction in which N (NH4+ e NO3-), K+, and H2PO4- doses must be applied as well as the optimum dose fractioning of these nutrients so as to locate their adequate depth and determine the distribution of fertigated NH4+, NO3-, K+, and H2PO4-. The treatments consisted of a 4 (1 + 7) factorial, using four Latosols from Minas Gerais (two dystrophic Red-Yellow, one dystroferric Red, and one dystrophic Red), a control (aplication of deionized water) and seven modes of application of 1 mmol dm-3 of NH4+, 1 mmol dm-3 of NO3- , 2 mmol dm-3 of K+ and 2 mmol dm-3 of H2PO4-. The irrigation lamina was divided into five equal fractions (F1 to F5) and the nutrient dose was applied whole (D), or fractioned two (D1/2) or three times (D1/3). Hence, nutrient application was performed according to the following scheme: F2D, F3D, F4D, F2D1/2F3D1/2 , F3D1/2F4D1/2 , F2D1/2F4D1/2 or F2D1/3F3D1/3 F4D1/3. Sub-samples were used to analyze NH4+, NO3-, K+ and H2PO4-, through the determination of the profile of distribution of these nutrients. Mobility was in the following order: NO3- > NH4+ > K+ > H2PO4-, on soils LVAd1, LVAd2 and LVd. For the soil LVdf, the order was: NH4+ > NO3- > K+ > H2PO4- . And the risk of contamination of groundwater caused by NO3-: LVAd1 > LVAd2 > LVdf > LVd. The amount of water added to the column, lower than half pore per volume, was not sufficient to displace H2PO4-beyond the first ring. Regarding the other ions studied, localization at a higher depth when applied as a single pulse, was verified with a higher pulse concentration (D > D1/2 > D1/3) and with a greater irrigation lamina following its application (F2D > F3D > F 4D and F2D1/2F3D1/2 > F3D1/2F4D1/2 ). The results shows that the differential mobility of (N-NNO3- e NH4+ ) and K+ would require a careful dosage of these nutrients in the solution to prevent nitrogen losses due to leaching, or excessively superficial localization of potassium. The extremely low mobility of H2PO4- shows that fertigation would not be an appropriate technique for incorporation of this mineral into soil for crop fertilization purposes.

Soil, water, and nutrient losses from management alternatives for degraded pasture in Brazilian Atlantic Rainforest biome

The objective of this study was to evaluate sediment, water and nutrient losses from different pasture managements in the Atlantic Rainforest biome. A field study was carried out in Alegre Espiríto Santo, Brazil, on a Xanthic Ferralsol cultivated with braquiaria (Brachiaria brizantha). The six pasture managements studied were: control (CON), chisel (CHI), fertilizer (FER), burned (BUR), plowing and harrowing (PH), and integrated crop-livestock (iCL). Runoff and sediment samples were collected and analyzed for calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P) and organic carbon contents. Soil physical attributes and above and below biomass were also evaluated. The results indicated that higher water loss was observed for iCL (129.90mm) and CON (123.25mm) managements, and the sediment losses were higher for CON (10.24tha-1) and BUR (5.20tha-1) managements when compared to the other managements. Majority of the nutrients losses occurred in dissolved fraction (99% of Ca, 99% of Mg, 96% of K, and 65% of P), whereas a significant fraction of organic carbon (80%) loss occurred in a particulate form. Except for P, other nutrients (Ca, Mg and K) and organic carbon losses were higher in coarse sediment compared to fine sediment. The greater losses of sediment, organic carbon, and nutrients were observed for CON followed by BUR management (p<0.05). Our findings indicated that the traditional pasture management adopted in the Atlantic Rainforest needs to be rethought and burned management should be avoided. Based on the water, soil, and nutrient losses from various practices, to reduce pasture degradation, farmers should adopt edaphic practices by applying lime and fertilize to improve pasture growth and soil cover, and reducing soil erosion in the hilly Brazilian Atlantic Rainforest biome.

Caracterização, potencial agrícola e perspectivas de manejo de solos leves no Brasil

Light soils occupy 8% of the Brazilian territory and are especially expressive in the new and last agricultural frontier in Brazil: the Matopiba region – in the states of Maranhão, Tocantins, Piauí, and Bahia –, where they represent 20% of the area. These soils fit into the textural classes of sand and loamy sand or sandy loam, down to 0.75-m soil depth or deeper, and they are mainly represented by Neossolos Quartzarênicos (Quartzipsamments) and, partly, by Latossolos (Oxisols) and Argissolos (Ultisols). The understanding of soil functioning depends on the establishment of distinguishing criteria for: organic matter dynamics; content and mineralogy of the clay fraction; coarse sand and total sand contents, in relation to those of fine sand; mean diameter of the sand fraction; and water retention capacity. These criteria can contribute for the zoning and for the conservation and fertility management of light soils, as well as for the estimation of their agricultural potential. Integrated production systems, such as crop-livestock and crop-livestock-forestry integration, besides no-tillage with crop rotation, mixed forestry planting with legumes, and the use of green manure and cover crops are relevant for the proper management of these soils. The objective of this review was to characterize light soils and to highlight the main challenges regarding their agricultural potential and their conservation and fertility managements, in face of the expansion and consolidation of the new Brazilian agricultural frontier.

Soil carbon stock in silvopastoral system, pasture and sugarcaneculture

espanolLa conversion de sistemas naturales en tierras agricolas es uno de los principales factores responsables por la reduccion de la reserva de C en el suelo y el aumento de la liberacion de C-CO2-1, 3494 Mg ha-1 y 1964 Mg ha-1 para las areas con cana de azucar, sistema silvopastoril y pastizal, respectivamente. El manejo de lafertilizacion y de la cosecha de cana de azucar en la region de Gobernador Valadares es eficiente en el incremento de las reservas de C en el suelo, siendo incluso superior que las reservas encontradas en el fragmento florestal, y el area silvopastoril presenta mayor potencial para el almacenamiento de C en los estratos superficiales (0-10 cm y 10-20 cm) comparado con las areas de pastoreo continuo. EnglishThe conversion of natural system in tillage agriculture areas is largely responsible for the reduction of Organic Carbon stock (OC-stock) in the soil and increases C-CO2 atmospheric release in tropical countries. The objective of this study was to evaluate the impacts of different situations of soil uses (silvopastoral, pasture and sugarcane) in OC-stocks of Utilsols in the regions of Vale do Rio Doce in the state of Minas Gerais. It was determined contents of total soil organic carbon (SOC) and soil bulk density (Bd) in different situations studied. The use of anthropic soil is promoting the increase of the soil Bd due to the deployment of cultures being preformed mechanically, therefore the systems provided higher content of SOC and consequently increased the OC-stock. The highest content of SOC was found in the area with sugarcane. The studied situations provided increase in the OC-stock in depth 0-10 cm, of 5,397 Mg ha-1, 3,494 Mg ha-1 and 1,964 Mg ha-1 for sugarcane, silvopastoral system and pasture. The management of fertilization and harvesting of sugarcane in the region of the city Governador Valadares is efficient in increasing the OC-stock, including being greater than the secondaryforest, and the silvopastoral site shows a greater potential in carbon stocking in the surface layers (0-10 cm and 10-20 cm) compared to continuous grazing areas.

Uniformity distribution index of ammonium, nitrate, potassium and phosphorus in fertigated Oxisols

Fertigation if conducted inadequately may cause soil salinization and consequently leaching of nutrients can pollute ground water. An index is proposed to determine the uniformity of distribution of ammonium, nitrate, potassium and phosphorus in columns of fertigated Oxisols, which relates the highest content of the nutrient in a column segment with the mean nutrient content in the experimental unit. The higher the index value, the more irregular is the nutrient distribution. This index was calculated based on laboratory data evaluated in a 4 x (1 + 6) factorial design including four Oxisols of Minas Gerais (two distrophic Red-Yellow, one dystroferric Red and one dystrophic Red oxisol), one control (application of deionized water) and six application modes of application of 1 mmolc of N-NH4+, 1 mmolc N-NO3-, 2 mmolc K and 2 mmolc dm-3 P. The coefficient of variation was calculated for the content of each nutrient along the columns. The ratio between the mean and the highest nutrient content was computed as well, considering the soil and the treatment. It was inferred that the ratio mean/highest content is an adequate index of uniformity of nutrient distribution to evaluate the movement of major mobile ions such as nitrate, ammonium and potassium in the soil. The coefficient of variation is less appropriate to show the uniformity of nutrient distribution.Fertigation if conducted inadequately may cause soil salinization and consequently leaching of nutrients can pollute ground water. An index is proposed to determine the uniformity of distribution of ammonium, nitrate, potassium and phosphorus in columns of fertigated Oxisols, which relates the highest content of the nutrient in a column segment with the mean nutrient content in the experimental unit. The higher the index value, the more irregular is the nutrient distribution. This index was calculated based on laboratory data evaluated in a 4 x (1 + 6) factorial design including four Oxisols of Minas Gerais (two distrophic Red-Yellow, one dystroferric Red and one dystrophic Red oxisol), one control (application of deionized water) and six application modes of application of 1 mmolc of N-NH4, 1 mmolc N-NO3, 2 mmolc K and 2 mmolc dm-3 P. The coefficient of variation was calculated for the content of each nutrient along the columns. The ratio between the mean and the highest nutrient content was computed as well, considering the soil and the treatment. It was inferred that the ratio mean/highest content is an adequate index of uniformity of nutrient distribution to evaluate the movement of major mobile ions such as nitrate, ammonium and potassium in the soil. The coefficient of variation is less appropriate to show the uniformity of nutrient distribution.

Soil and Water Management for Ecosystem Services Provision in Agricultural Landscapes: The Challenge of Monitoring

Soil and water conservation management includes practices that help to preserve the quality of soil, water, and biodiversity, to promote sustainable agriculture and to provide ecosystem services (ES). In the state of Rio de Janeiro, some agriculture conservation practices such as minimal tillage, crop rotation, agroforestry systems, rotational grazing, and fallow can contribute to value and provide ES and also increase productivity and income of the family farmers. However, it is necessary to identify the impacts of these practices on the provision of ES, and monitoring is an important means of analysis. This chapter presents a review of studies on the conservation management practices in the state of Rio de Janeiro and their impacts on ES. Moreover, it highlights aspects to be considered in monitoring of ecosystem service indicators. The main challenges of the monitoring approach include participatory efforts and multidisciplinary criteria used at appropriate scales in order to provide adequate and useful answers to society.

CARBON STOCKS IN MINED AREA RECLAIMED BY LEGUMINOUS TREES AND SLUDGE

Few studies have been carried out on aboveground (or belowground) and soil/substrate C accumulation in severely degraded areas, such as mined areas. The present study was developed in order to find a recovery strategy for a mined area and characterize its potential for C sequestration by planting two nitrogen-fixing Brazilian tree species (Mimosa caesalpiniifolia Benth and M. bimucronata (DC.) O. Kuntze). Sewage sludge was included in the experimental design. An experiment under randomized block condition and 2 x 5 factorial design with four replications were defined and carried out, in Rio de Janeiro State, Brazil. The treatments consisted of a combination of both tree species and five sewage sludge doses (0, 2.85; 5.70; 11.40 and 22.80 Mg ha-1). M. caesalpiniifolia grows better (p<0.05) in reclaimed areas than M. bimucronata, even though neither the height nor the basal area of both species responded to the sludge application. Carbon stock in the tree trunks differ between species (27.3 and 14.3 Mg ha-1, for M. caesalpinifolia and M. bimucronata, respectively), and was influenced by the doses of sewage sludge, whereas the soil carbon stock (0-10 cm) did not differ between species and doses (12.0 and 12.2 Mg ha-1, for M. caesalpiniifolia and M. bimucronata, respectively). Soil fertility in the degraded site was found to be improved by legume trees six years after planting, with a small influence of the sewage sludge level. Mined areas recovered with legume trees can sequestrate significant amounts of C both in aboveground biomass and soil in a short period of time.