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The state of Rio Grande do Sul has about 20% of the total area as lowland soils, suitable for flooded rice (Oryza sativa). In order to mitigate damage caused by rice monoculture, new crops such as sorghum (Sorghum bicolor) and soybean (Glycine max) have been cultivated in these areas. With different qualities of crop residues, it is expected a change in soil organic matter (SOM) dynamics and consequently, nitrogen (N) availability. The objective of this study was to evaluate the influence of rice, soybean and sorghum crop residues on the N present in physical fractions of SOM of two lowland soils, using labeled 15N technique, under incubation for 180 days in aerobic condition and more 180 days in anaerobic condition. At 30, 180 and 360 days of incubation the remaining N of the plant residues and N destination from the residues in both soils were quantified in the physical fractions of SOM >250 µm, 250-53 µm and <53 µm. The soil with higher amount of clay+silt received a larger quantity of 15N from residues, while flooding of the soil after 180 days caused a loss of N added to the soil by the soybean and sorghum residues. In general, larger amounts of 15N were reported in the fraction <53 µm, associated with clay minerals, throughout the incubation period. These N losses should be considered in N fertilization for the following crops in rotation with flooded rice. [ABSTRACT FROM AUTHOR]

Rhizospheric carbon resulting from root exudation is one of the substrates used by the soil microbiota, and reflects methane (CH4) emissions in anoxic environments such as irrigated rice cultivation. With the increase of the photosynthetic capacity of the plant in the reproductive period, there is greater accumulation of biomass which, in turn, increases the rate of root exudation. However, genotypic variations in the physiological aspects of rice plants may be related to the amount of root exudates. Ten cultivars of irrigated rice were evaluated for the exudation rate of total organic carbon (EXRToc), shoot dry matter (SDM), and physiological variables related to photosynthesis during the full flowering (blooming) period. Two experiments were conducted in the greenhouse of the Department of Soils of the UFSM (University of Santa Maria, Santa Maria, RS, Brazil) in a completely randomized experimental design. The cultivars presented significant differences in EXRToc, SDM, and all physiological variables as well as positive and significant correlations between EXRToc and physiological variables. Early cultivars were more inefficient in the physiological variables reflecting reduced values of EXRToc and SDM whereas medium-cycle cultivars were more efficient with larger EXRToc and SDM reflections. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

The chlorophyll meter and the color chart have been applied to monitor nitrogen fertilization in different crops, based on the assumption that there is a correlation between their readings and the nitrogen content (N) in the plant tissue. This research aims at assessing the use of the chlorophyll meter and the color chart to estimate the N content in leaves of flooded rice plants. Two experiments installed at a Albaqualf (Planossolo Háplico) were used, the first using five N doses (0, 50, 80, 120 and 160kg ha-1 as urea) and the cultivar 'IRGA 417', and the second with six flooded rice cultivars of different cycles ('BRIRGA 409', 'BR-IRGA 410', 'IRGA 417', 'IRGA 421', 'EPAGRI 108' and 'HÍBRIDO 2') with one only N dose. Assessments with the chlorophyll meter and the color chart were carried out on leaves of rice at different growth stages. Along with the readings, leaves were sampled and the leaf N content was determined. When the N doses varied, there was a meaningful correlation between the readings from the chlorophyll meter and the color chart with the leaf N content, regardless the assessment period. When the cultivars varied, the chlorophyll meter readings correlated with the N content (r=0.78, P<0.05) but not with the color chart (r=0.25ns). The chlorophyll meter and the color chart were efficient to estimate the N content when a particular cultivar was used, however, the color chart presents higher dependence of the accurate evaluator's interpretation as well as a narrower range of scales, making it often harder to find the best color setting. When different rice cultivars are used, only the chlorophyll meter is sensitive to estimate the leaf N content. [ABSTRACT FROM AUTHOR]

The no-tillage system success relies on higher addition of different types of crop residues to the soil, each one with specific decomposition kinetics which drives the net mineralization and immobilization of the nitrogen (N) in the soil. This manuscript had as objective to evaluate the decomposition rate and N released from winter cover crops residues under different above ground biomass input to the soil. The experiment was carried out in the experimental area of the Soil Department at Federal University of Santa Maria, in random complete block design, with three replications, during 2003/04 and 2004/05. The decomposition and the N released from black oat, oil radish and hairy vetch residues were investigated using mesh bags of decomposition containing fitomass equivalent to 3, 6 and 9 Mg of dry matter ha-1 placed in plots with 80 m2 with the same level of crop residues used in the mesh bags. They were collected at 7, 14, 28, 42, 63, 84, 113 and 141 days after cover crops management. The amount of residues input did not influence the decomposition rate. However, the N mineralization and immobilization processes were affected by the level of residues input and they were driven by C/N ratio. The larger decomposition residues rate and higher N release followed the order: vetch, radish oil and black oat. The C/N ratio drives the size of labil and recalcitrant compartiments of cover crops fitomass. [ABSTRACT FROM AUTHOR]

The effect of nitrogen (N) fertilization levels was assessed by the industrial yield, the incidence of chalky and white belly grains as well as protein and amylose content of IRGA 422CL cultivar polished grains. The experiment was consisted with N levels applied in coverage using urea as a N source. The first application (0, 40, 63, 80 and 120kg ha-1 of N) was carried out on a main plot (10x5m) and the second application (0, 25, 50 and 75kg ha-1 of N) on a subplot (2,5x5m). Therefore, 20 treatments were obtained varying from 0 to 195kg ha-1 of N applied during cultivation. The nitrogen levels presented a positive quadratic influence on the yield of whole grains (R2 =0.75) and a negative influence on the percentage of broken grains (R2 =-0.89), not demonstrating significant effects on the percentage of rice hulls + bran. The nitrogen levels influenced protein content in a positive linear way (R2 =0.81) and amylose content in a negative linear way (R2 =-0.66), in IRGA 422CL cultivar flood-irrigated polished grains. [ABSTRACT FROM AUTHOR]

Nitrogen doses and timing of topdressing application affects the sensibility of rice plants to low temperature in reproductive stage. For these reasons it were installed two experiments with the objective of determining the effect of nitrogen topdressing application doses and timing on the susceptibility of rice plants to low temperature in the reproductive phase. The experiments were sowed in 2007/08 growing season in a greenhouse at Instituto Nacional de Investigação Agropecuária (INIA), INIA Treinta y Tres, Uruguay, with INIA Olimar cultivar. In both experiments, a factorial experiment was carried out in a completely randomized design, with four replications (factor A: stages or rates of N application and factor B: temperature treatment, with or without cold). In the experiment 1 the treatments of factor A were N application of 30 kg ha-1 in V4, V5, V6, V7, V8, R0, R1+4 days and an untreated check without N in topdressing. In experiment 2, the factor A was doses of N: 0, 23, 46 and 69kg ha-1 in V4 stage and the same levels of N in R0 stage plus a check without N in topdressing. The plants were treated with 12.5 C during seven hours for four nights when the collar of the flag leaf was at the same height of the previous leaf. The following aspects were evaluated: grain yield; spikelet sterility; SPAD index at three, ten and sixteen days of low temperature treatment; number of panicles per plot and weight of 1000 grains. Spikelet sterility was not affected by the application of N in different stages or doses, by cold treatment or their interaction, but the cold treatment affected temporally the SPAD index with delaying panicle emerge. It is not necessary to modify the N applications for this variety in Uruguay. [ABSTRACT FROM AUTHOR]

The rate and method of lime application modify soil chemical attributes, but the re-acidification process after liming remains poorly understood in the long-term. This study aimed to assess the long-term effect of surface and incorporated liming on shifting soil use from native grassland of South Brazilian Campos to no-tillage system (NTS) for grain production in a highly acidic sandy-loam Ultisol. In 1994, an experiment in a randomized block with split plot design and four replications was installed in Southern Brazil. The main plot consisted of lime application method (surface or incorporation by soil tillage), while the subplots were lime rates (0.0, 2.0, 8.5 and 17.0 Mg ha −1 ), corresponding, approximately, to 0, 1/8, 1/2, and 1 fold the recommended dose to rise soil pH to 6.0 in the 0–20 cm soil layer. The 2 Mg ha ‒1 treatment had reapplication every two years until soil accumulated 8 Mg ha ‒1 of lime. In October 2006 and 2012 (i.e., 12 and 18 years after lime application), soil samples were collected at every centimeter from 1 to 10 cm depth, every 2.5 cm from 10 to 25 cm, every 5 cm from 25 to 50 cm and 50 to 60 cm. The chemical attributes related to soil acidity were evaluated. Even after 18 years of lime application, the re-acidification process recovered only 50% of the exchangeable Al and 30% of the potential acidity compared to native soil. Lime incorporation before NTS adoption proved to be more rapid and efficient to mitigate soil acidity than surface liming, and it is suitable for correction of deep-layered soil acidity in the soil profile. Surface lime application induced a lower alkalinization front in the soil profile, and even after 18 years there was no neutralization of total exchangeable Al in the 10–20 cm layer. [ABSTRACT FROM AUTHOR]

The Southern Grasslands or Pampa biome covers 176,496 km 2 (2.07%) of the Brazilian territory, concentrated in the southernmost state with 63% covered by this biome. When adding Uruguay and Argentina, the biome area reaches 750,000 km 2 . Rangelands are being substituted by crops and commercial eucalyptus, with potential impacts on ecological and hydrological response of watersheds and river basins. Studies of isotopic natural abundance may be used to understand vegetation dynamics in the past. We evaluated the natural abundance of 13 C in soil profiles (ten soil layers down to 1.40 m) at different positions of the landscape, in order to associate it with the vegetation dynamics in the studied environment. Two grassland areas and a forest area in the Pampa region of southern Brazil were sampled. Isotopic signature δ 13 C in the soil profile of the two grassland areas was dissimilar: one area is in the range of C4 plant formation, and the other followed the same trend up to the first 1.00 m but from this depth on δ 13 C is in an intermediate range, which could have occurred due to the influence of C3 and C4 plants. Forest vegetation presents a clear change of predominant vegetation in a more-recent past period. Characteristic values of soil formed by C3 photosynthetic cycle plants are predominant in surface layers, whereas those of C4 plants predominate in deeper soil layers. Our hypothesis that soil classes, texture, and position in landscape are related to the presence/absence of riparian forest, as evaluated by the 13 C isotopic abundance in soils from these sites, is accepted. Quantification of isotopic natural abundance allowed verifying changes in vegetation based on photosynthetic types predominant in the environments of grassland and native forests of the Pampa biome, and may provide information to manage this ecosystem. [ABSTRACT FROM AUTHOR]

It has become possible to evaluate the conversion of soil organic matter (SOM) in pastures and arboreal crops due to the difference between the photosynthetic cycles of Eucalyptus (C3) and most grasses (C4). The auto analyzer method coupled to the IRMS (Isotope Ratio Mass Spectrometer) in the present study evaluated the 13C content in soil profiles of Eucalyptus plantations of different ages (2, 10 and 21 years), in natural regeneration areas and natural grazing fields, and estimated the SOM conversion of each crop type of. The initial management of all sampled areas was natural pasture. The following profile layers were evaluated: 0-5, 5-10, 10-20, 20-30, 30-40, 40-50, 50-70 and 70-90cm, and the contribution of Eucalyptus biomass over the years of farming was estimated in the SOM conversion process. After 2 years of planting Eucalyptus, the beginning of pasture carbon conversion process occurred in the surface layer (0-5cm). Ten years after planting, the process of converting organic matter by arboreal crops reached the layers up to 20cm. After 21 years of planting and in natural regeneration areas, the entire profile has already been changed by planting Eucalyptus and native tree species. [ABSTRACT FROM AUTHOR]

Both soil phosphorus (P) and soil acidity are the key factors in soil fertility management and often limits crop production in subtropical agriculture. The objective of this study was to evaluate the response of lime and different P rates on sugarcane variety and their interactive effect on the sugar cane borer attack. A three factorial experiment containing, two sugarcane varieties i. e., (SP81-3250 and RB-956911); with and without application of agricultural lime (3.5 t ha-1) and four P rates i. e., (0, 20, 40 and 60 kg P2O5 ha-1) was carried out at the research field area of Federal University of Santa Maria, RS, Brazil during 2011-12. It assessed a) sugarcane stalk length, b) stem diameter; c) number of internodes, d) number of stalk ha-1, e) stalk yield, f) °Brix and g) Intensity of infestation Index. Results indicated that, the stalk yields of RB-956911 and SP81-3250 was 106.6 and 139.8 Mg ha-1, respectively. The °Brix was between 18.60% and 18.00%, respectively. The Intensity of infestation Index was 2.76% for the RB-956911 and 3.65% for the SP81-3250. The lime application showed significant results only on the borer attack. Phosphorus application increased the sugarcane yield from 105.9 Mg ha-1 to 136.5 Mg ha-1 with 60 kg of P2O5 ha-1. The application of phosphorus increased sugarcane productivity but it does not contribute which increase the borer attack. [ABSTRACT FROM AUTHOR]

Urea is the main source of N used in agriculture, but has large losses in irrigated rice. The objective of this study was to evaluate the efficiency of N sources alternative to urea for use by rice applied at different stages of plant development through the quantification of N-NH3 and agronomic parameters. The experiment was conducted in the field in the agricultural years 2007/08 and 2008/09. The experimental design was randomized blocks with four replications. The treatments consisted of different N sources applied at seeding, tillering and at the stage of floral differentiation: control without N, urea, urea + urease inhibitor, two sources of liquid N (N-28 and N-30) ammonium sulfate and urea + sulfur. In both seasons, the volatilization of N-NH3 at seeding was almost negligible, whereas in the V4 stage, the source that was less volatilized was the ammonium sulfate. Yield response varied among years, probably due to the availability of N in the soil and climatic aspects. When economically advantageous, the use of urease inhibitor and ammonium sulfate provide yields similar to urea supply. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which the editors discuss the importance of herbicide leaching soil, research on Collectotrichum species, and urban migration in Turkey.