Graziela Moraes de Cesare Barbosa

Physical properties of dystrophic Red Latosol (Oxisol) under different agricultural uses

Obtaining information about soil properties under different agricultural uses to plan soil management is very important with a view to sustainability in the different agricultural systems. The aim of this study was to evaluate changes in certain indicators of the physical quality of a dystrophic Red Latosol (Oxisol) under different agricultural uses. The study was conducted in an agricultural area located in northern Parana State. Dystrophic Red Latosol samples were taken from four sites featuring different types of land use typical of the region: pasture of Brachiaria decumbens (P); sugarcane (CN); annual crops under no-tillage (CAPD); and native forest (permanent conservation area) (control (C)). For each land use, 20 completely randomized, disturbed and undisturbed soil samples were collected from the 0– 20 cm soil layer, to determine soil texture, volume of water-dispersible clay, soil flocculation (FD), particle density, quantity of organic matter (OM), soil bulk density (Ds), soil macroporosity (Ma) and microporosity (Mi), total soil porosity (TSP), mean geometric diameter of soil aggregates (MGD), and penetration resistance (PR). The results showed differences in OM, FD, MGD, Ds, PR, and Ma between the control (soil under forest) and the areas used for agriculture (P, CN and CAPD). The soils of the lowest physical quality were those used for CN and CAPD, although only the former presented a Ma level very close to that representing unfavorable conditions for plant growth. For the purposes of this study, the physical properties studied were found to perform well as indicators of soil quality.

EFEITO RESIDUAL DO LODO DE ESGOTO NAPRODUTIVIDADE DO MILHO SAFRINHA

Among the possibilities of final disposal of sewage sludge, agricultural recycling has become one of the most widely used in several developed countries, and is considered the most appropriate in technical, economical and environmental terms. This study aimed at evaluating the sewage sludge residual effect on off-season corn yield on an Eutroferric Red Latossol (Oxisol). The field experiment was in a randomized block design with three replications, with treatments consisting of increasing doses of sewage sludge (0, 6, 12, 24 and 36 t ha-1, on a dry weight basis), applied in the two previous cropping seasons.. The residual effect of the application of lime-stabilized sewage sludge increased the yield of off-season corn; the grain yield under a rate of 36 t ha-1 was statistically higher than those under 6 and 12 t ha-1.

Efeito da escarificação na condutividade hidráulica saturada de um Latossolo Vermelho sob plantio direto

Intensive soil cultivation in tropical and subtropical regions is only viable within the context of the sustainable agriculture that ensures appropriated technologies that assures productive efficiency without soil degradation. The present in situ study was carried out to determine the effect of the soil scarification in the saturated hydraulic conductivity in a dystrophic Red Latosol (Oxisol) under no-tillage systems for 20 years. The results showed that the study of hydraulic conductivity in the soil under no-tillage system was significantly affected in 1.45 10-5m s-1 after soil scarification, but a year later this gain was greatly reduced for 0.48 10-5m s-1.

Propriedades físicas de solo e crescimento de batata-doce em diferentes sistemas de preparo

Trabalhos sobre preparo reduzido em solos cultivados com raizes e tuberculos sao escassos e controversos. Assim, este trabalho teve por objetivo avaliar o impacto de sistemas de preparo em propriedades fisicas de um Argissolo Vermelho-Amarelo e no crescimento de raizes tuberosas de batata-doce. Para avaliacao das propriedades fisicas do solo, foi instalado experimento em blocos ao acaso, esquema de parcelas subdivididas. As parcelas corresponderam aos tratamentos: preparo convencional, com confeccao de leiras, e preparo reduzido, com manutencao de palhada superficial e as subparcelas, as epocas de coleta: 120 e 180 dias apos o plantio (DAP) da cultura de batata-doce. Foram avaliados os atributos fisicos densidade do solo, porosidade total, macro e microporosidade, resistencia do solo a penetracao e umidade gravimetrica do solo. Para avaliacao do crescimento de raizes tuberosas de batata-doce, montou-se experimento em que as parcelas corresponderam as formas de manejo do solo, e as subparcelas as quatro epocas de colheita: 90, 120, 150 e 180 DAP. Avaliaram-se as relacoes comprimento/diâmetro e massa fresca individual/comprimento de raizes tuberosas. O preparo convencional do solo com confeccao de leiras, em oposicao ao preparo reduzido, promoveu menores valores de densidade do solo, resistencia do solo a penetracao e microporosidade, maiores valores de porosidade total e macroporosidade; proporcionou menor manutencao de agua na camada superior do solo (0-0,15 m); e permitiu maior crescimento vertical de raizes tuberosas de plantas de batata-doce.

Produtividade da cultura da batata-doce em diferentes sistemas de preparo do solo

Studies about reduced tillage in soil cultivated with roots and tubers are rare and controversial. This study aimed to assess and compare the sweet potato tuberous roots yield in an alfisol type soil managed with conventional tillage (plowing followed by leveling and making mounds) and reduced tillage with straw on the soil surface (cultivated only along the rows). The experimental design was in randomized blocks in split-plot scheme. The principal plots corresponded to conventional tillage (with mounds) and reduced tillage, and the subplots to four collect periods: 90, 120, 150 and 180 days after planting. The characteristics evaluated were: total and commercial yields, numbers of total and commercial tuberous roots, and commercial tuberous roots individual fresh mass. Sweet potato crop had total and commercial tuberous roots yields around 68 and 75% higher in conventional tillage, respectively, than in reduced tillage. This response was caused by the high numbers of total and commercial roots in soil under conventional tillage. There was no difference between the soil management on tuberous roots individual fresh mass. As conclusion, the conventional tillage is better to the sweet potato crop.

Chemical and Microbiological Attributes of Soil Under Different Management With Application of Swine Wastewater

We evaluated the effects of biannual surface applications of swine wastewater (SWW) for 11 years, on chemical and microbiological attributes of a clay-textured soil under no-tillage (NT) or conventional tillage (CT) in Palotina, Parana, Brazil. The treatments consisted of SWW doses (split into autumn-winter/spring-summer seasons) totaling 30, 60, 90 or 120 m3 ha-1 year-1, and a control without application, under CT or NT soil managements (SM). The experimental design was in randomized blocks with a split-plot arrangement and four replications, with SM in the plots and the doses of SWW in the subplots. After 11 years of applications of SWW, soil samples were taken at 0-10, 10-20, 20-40, and 40-60 cm of depth by the end of the winter cover crop, 44 days after the second biannual application. The treatments had only minor effects on the assessed chemical and microbiological soil properties. Available P and NO3--N increased with the doses of SWW at the two upper soil layers, whereas NT decreased NO3--N at 10-20 cm and increased P at 0-10 cm. Zn2+ also increased with the doses of SWW, irrespectively the SM. NT increased the microbial biomass C (MBC) at 0-10 cm and 10-20 cm of soil depth, and the microbial quotient (qMic) at 0-10 cm. SM and SWW did not change the densities of heterotrophic bacteria, fungi, nitrite-oxidizers or ammonifiers at any soil depth. SM had single effects on organic C, MBC and qMic, whereas SWW had single effect only on Zn2+. Only available P and NO3--N were affected by both SM and SWW. The principal component analysis for chemical and microbiological attributes showed distinct groupings between CT and NT, and SWW rates at 0-10 cm and 10-20 cm of soil depths, the most influenced soil layers.

Soil aggregation and carbon stabilization in burn and no-burn sugarcane management systems

Retaining sugarcane straw over the soil after harvesting can improve soil structure and increase soil carbon stabilization, mainly in macroaggregates. We evaluated the carbon content in the aggregate classes in areas under burn and no-burn (adopted for five years) sugarcane management systems, focusing on the superficial layer (0.00-0.20 m). The experiment was carried in an Oxisol and the treatments consisted in burnt sugarcane, manual harvest; burnt sugarcane, mechanized harvest; and no-burn, mechanized harvest. The retention of sugarcane straw on the soil surface is justified by the increase in carbon content and carbon stock in the surface layer (0.00-0.20 m) by restructuring of the soil, even though it cannot match the structure of the soil under native forest. Our results suggest that in no-burn management the carbon not occluded inside aggregates was important to increase carbon stabilization in soil and that more attention should be given to macroaggregates 2.00-8.00 mm present in this management system, that showed higher carbon content and was responsible for increase of the geometric and weight diameter, increasing the erosion resistance in the long term in relation to burn systems.

Application of Landfill Leachate Improves Wheat Nutrition and Yield but Has Minor Effects on Soil Properties

Landfill leachates, which are potential pollutants, may also carry significant amounts of nutrients that can be recycled by plants. We assessed the nutritional status and yield of wheat ( L.) and properties of a Rhodic Kandiudult soil (depths of 0-10, 10-20, 20-40, and 40-60 cm) after 11 applications of landfill leachate over 4 yr. In the last application, wheat received 0, 32.7, 65.4, 98.1, or 130.8 m ha (875 mg L of nitrogen, N) of leachate and a positive control (90 kg ha of N as urea) 15 d after sowing. Urea increased nitrate (>160 mg kg) in the topsoil (down to 40 cm), whereas landfill leachate increased nitrate (>60 mg kg) only at 40 to 60 cm with the highest dose, suggesting leaching. Urea-treated soil had less negative ΔpH, which might have led to greater retention of nitrate in the topsoil. Sodium (0.02-0.26 cmol Na kg), potassium (0.18-0.82 cmol K kg), and electrical conductivity (0.05-0.14 dS m) all increased with leachate dosage. Treatments did not affect resistance to penetration and clay dispersion. Basal respiration increased with leachate dosage, whereas dehydrogenase activity decreased, suggesting effects on soil microbial metabolism. Microbial biomass and soil enzyme activities were not affected by addition of leachate. Nitrogen nutrition (15.1-22.7 g N kg in flag leaves) and grain yield (1381-2378 kg grain ha) increased with leachate dosage so that the highest dose gave results similar to those for urea-treated plants (2563 kg grain ha). Landfill leachate showed strong potential as source of N for wheat but caused none, or transient, effects on soil properties. However, nitrate from leachate was more leachable than nitrate from urea.