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Soil tillage is an agricultural practice that directly affects the global carbon cycle. Our study sought to assess the implications of adopting sunn hemp cover crops with different tillage practices on CO2 emissions for two soil types (clayey and sandy soil) cultivated with sugarcane in Brazil. The experimental design was a split‐plot with randomized blocks, with the main plots being with cover crop or fallow and sub‐plots being under conventional or minimum tillage. Our results indicate that during the first 50 days after soil tillage, the variation in soil CO2 emissions was stimulated by cover crop and soil tillage, while after that, it became dominated by the root respiration of sugarcane plants. We also found that over the first 97 days after the tillage, the clayey soil showed differences between minimum tillage with cover crop and fallow. Conversely, for sandy soil over the first 50 days following, there were differences between the tillage systems under cover cropping. Emissions from sugarcane rows were found to be greater than those from inter‐row positions. We concluded that soils under different textural classes had distinct patterns in terms of soil CO2 emissions. The correct quantification of CO2 emissions during the sugarcane renovation period should prioritize having a short assessment period (~50 days after soil tillage) as well as including measurements at row and inter‐row positions. [ABSTRACT FROM AUTHOR]

Abstract: This study aimed to evaluate variations in the seed bank within a 3-year temporal series in order to answer the following questions: 1) Does the seed bank''s species richness and seed density differ among climatic seasons and between years? 2) Are there differences in the richness and density of seed banks between the litter and mineral soil? 3) Can the seed bank''s species richness and seed density be explained by characteristics such as the previous year''s precipitation and soil depth (litter or mineral soil)? The samples were collected from litter and mineral soil (0–5 cm), in 210 sub-plots, during the dry and rainy seasons of each year (August 2005 through February 2008). Overall, 79 species were recorded. On average, 1 168, 304 and 302 seeds.m−2 were recorded in the seed bank during years I, II and III, respectively. This study showed that the Caatinga''s seed bank is rich in herbaceous species, yet species'' density and richness are low in the litter. Furthermore, about 43% of the variation in species richness and density was explained by soil depth (litter and mineral soil) and previous years'' rainfall. [Copyright &y& Elsevier]

A characterization of the process of organic agriculture production of Calendula officinalis L. in the State of Santa Catarina is presented, evidencing particularities and discrepancies contrasting to the models already described in specialized literature, by field visits, participative observations and interviews with a medicinal plant producer. The main particularities identified were the health in the agricultural family, demonstrated by the practice of organic culture, besides pest control and the handling of production. The main evidenced problems or divergences were: soil characteristics; period of the marigold planting and its following stages, such as transplanting and flowering. Aspects of the crop were conflicting as for the period of the day indicated for the procedure, as well as the absence of information from the producer about the existence of other government incentives to the agricultural section. It is recommended to the rural extensions and/or competent institutions to seek for guiding the organic producers of marigold to promote adequate practices for the cultivation of this medicinal species. [ABSTRACT FROM AUTHOR]

Continued use of the crop-livestock system in agricultural areas can promote changes in soil physical attributes, as well as affect the productivity of crops grown in rotation with pasture. The aim of this study was to evaluate the effects of methods of sowing and the interval between the withdrawal and desiccation of pasture on soil physical attributes, aboveground biomass of pasture and productivity of crops sown in succession. It was conducted an experiment in a rural property in Campos Novos, which uses the crop-livestok system, with the following treatments: two types of pasture seeding in autumn (direct seeding without and with subsequent soil harrowing), allocated in main plots, and four intervals of removing animals from the pasture before desiccation (removal of the animals at 28, 14 and 1 day before the desiccation and control, without grazing), allocated as subplots. It was determined the aboveground biomass of pasture, the soil physical attributes after desiccation of grassland and yield of soybeans and corn. The form of winter pasture seeding does not affect the soil physical attributes and crop productivity, while increasing the interval between the withdrawal and desiccation of winter pasture increases the production of the aboveground biomass of the pasture. [ABSTRACT FROM AUTHOR]

Agricultural efficiency (EA) is used as an indicator of the level of regional agricultural development, reflecting, by mean of the ratio between actual and achievable yields, the crop technology level. Based on that, the objective of this study was to evaluate the EA for soybean, corn and wheat crops in the state of Rio Grande do Sul, Brazil, between 1980 and 2008, identifying the main factors which conditioned it. EA was obtained by the relationship between the achievable yield (PA) and actual crop yield (PR). PR was obtained from the Brazilian Institute of Geography and Statistics (IBGE) data base. PA was obtained by estimating the potential yield (PPf) with the FAO Agroecological Zone method, penalized by the water deficit for each crop phase. Average EAs for corn, soybean and wheat crops were 54, 61 and 43%, respectively. On the contrary of the majority of location, in Santa Rosa, São Borja and Veranópolis EA values were negative for soybean crop. The main factors that contributed to the increase of EA, in the majority of the locations, were: change on the soil use and fertility; use of agricultural machinery; prices paid for commodities; investments in research and development; climatic risk zoning; and plant breeding. [ABSTRACT FROM AUTHOR]

Soil nematode communities were studied in four differents crop systems at the Integrated System of Agroecological Production. Soil samples were collected at four-month intervals during one year, with three replications for each location. Nematode communities were measured by the following parameters: family richness, Shannon-Weaner′s index, Simpson′s index, trophic diversity (T) and dominance index (Ig). These data were submitted to ANOVA statistical analysis at 5% level of Tukey′s test. The population of bacterivores and herbivore nematodes was high in all areas. Omnivores were found in lower abundance in all systems. The highest diversity of nematode families was found on pasture. In forests, the values of richness and abundance were always lower but constant in time, suggesting an ecosystem of higher stability. Soil management induced the proliferation of bacterivores usually associated with higher decomposition rates of organic matter. Herbivores and bacterivores were dominant in all systems, suggesting it is important to have high root (for pasture) or high decomposition rates (for horticulture system). The relative distribution of trophic groups of soil nematodes proved to be a good way to determine the level of perturbation of ecosystems. [ABSTRACT FROM AUTHOR]

Copyright of Agricultural Research in the Tropics / Pesquisa Agropecuária Tropical is the property of Pesquisa Agropecuaria Tropical and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of this work was to determine nutrients growth and accumulation in coriander and rocket crops. The experiments were carried out in an experimental area of the Federal Rural University of the Semiarid, in Mossoro, Rio Grande do Norte, Brazil, in a soil classified as Red-Yellow Oxisol. The experimental design used was in completely randomized blocks, with four replications. Treatments consisted of plant harvesting times, which were 20, 25, 30, 35 and 40 days after sowing (DAS) for coriander, and 15, 20, 25 and 30 DAS for the rocket crop. The maximum dry mass accumulation (921.25 mg plant-1) for coriander took place 40 DAS, and for rocket (3622.8 mg plant-1) 30 DAS. The highest nutrients demands took place from 30 to 35 DAS for coriander and from 25 to 30 DAS for the rocket crop. The highest demand for Ca in the rocket crop took place between 15 to 20 DAS. [ABSTRACT FROM AUTHOR]

Copyright of Agricultural Research in the Tropics / Pesquisa Agropecuária Tropical is the property of Pesquisa Agropecuaria Tropical and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Amazonas State is the largest state in Brazil and mainly covered by tropical forest. Because of the importance of the tropical forest in maintaining soil health and a clean environment, conservation of the Amazon forest is a national priority. However, sustainable agriculture development is necessary in the state for the welfare of the local population. Maintaining soil fertility at an adequate level is an important component of sustainable farming. Very little information is available about soil fertility of Amazonas State. The objective of the present study was to evaluate chemical soil properties of Amazonas State of Brazil. Results include chemical properties of 3,340 samples, covering 62 municipalities of the state collected at 0-20 cm deep during 30 years (1975-2005). Chemical properties [phosphorus (P), potassium (K) extracted with Mehlich 1, calcium (Ca), magnesium (Mg), aluminum (Al) extracted with potassium chloride (KCl) 1.0 mol L-1, potential acidity (H + Al) extracted with calcium acetate, and base saturation] presented great variation, except cation exchange capacity (CEC) and pH (water). Most of the soil samples were characterized as having high acidity; medium level of organic-matter content; low levels of P, K, Ca, and Mg; and high levels of Al and H + Al. Overall, base saturation was less than 20%, a value considered very low for most of annual crops. Soils from upland areas were more acidic and have poor fertility compared with lowland soils. To maintain sustainability of cropping systems, use of an adequate level of liming and chemical fertilizers are necessary on these soils. [ABSTRACT FROM AUTHOR]

The quantitative analysis with different types of indicators is crucial in determining the sustainability of crop succession. This study aimed to appraise that in tilled plain areas. The research was carried out in Pelotas, RS, Brazil at Embrapa Clima Temperado research area. The treatments consisted of successions of winter and spring-summer crops species for five years, followed by two years of fallow and three years of rice cropping. The spring-summer crops were corn and soybean, besides rice; the winter crops were cereals, leguminous pastures, mixtures species, turnip and native grass species. Seeding was performed either by no-till (NT) or conventional (CT). The experiment was planned in a split-plot randomized blocks design with three replications, where the summer crops occupied the plots, while the winter's species were allocated to the subplots. The parameters measured were transformed into index to standardize the variables, each one in relation to the better measurement behavior, and arranged in four categories of analysis: (a) Agronomics indices (dry weight and grain yield); (b) Environmental indicators (soil fertility); (c) Energy Indicators (gain and energy efficiency); d) Economic Indicators (profitability and gross value of production). Through harmonic average rates calculated for each indicator, comparisons to the crop succession were then performed, and its sustainability inferred. Analyses of contrasts between the crop successions were accomplished too. The results provided the following conclusions: (a) All crop succession which had maize participation had a higher index sustainability; (b) the crops successions S1 [Cereals x soybean x rice(NT)] and S4 [Turnip x soybean x rice(NT)] had, respectively, the highest and the lowest sustainability among the ones with the soybean crop participation; (c) S5 [Native grass x soybean x rice(CT)] showed the lowest sustainability level, (d) S8 [Species mixtures x corn x rice(NT)] presented the best distribution and balance between the different classes of sustainability considered; (e) S10 [Native grass x corn x rice(CT)] has the worst performance, regarding the sustainability of the one's which included maize; (f) the NT system gives greater sustainability to the crop succession. [ABSTRACT FROM AUTHOR]

The article presents data collected from a family farm in southern Brazil, which indicate that almost three decades of no-tillage farming practices have the ability to restore soil organic carbon (SOC) to near native levels. It says that the no-till practice was implemented in 1983, although crop rotation sequence remains in operation. The observation supports the idea that SOC can be restored and that the no-tillage system also favored soil conservation by ameliorating soil erosion.