Soil Compaction Curve of an Oxisol Under Sugarcane Planted After In-row Deep Tillage

ABSTRACT Soil tillage that maintains the productivity of sugarcane plantations, providing an area for the root development and without traffic on crop rows, has given rise to new technologies in rural areas. The purpose of this study was to evaluate the soil physical properties in two sugarcane plantations, one of which was prepared with deep tilling and the other with conventional tillage. The experiment was conducted in Lençóis Paulista, São Paulo State. Soil penetration resistance and relative density were analyzed. The cone index was lower in deep-tilled soil without traffic in all layers, than in deep-tilled soil with traffic and in conventional tillage. In both tillage treatments, the relative density values were acceptable in the 0.00-0.15 m soil layer, but considered detrimental for sugarcane development in the 0.15-0.30 and 0.30-0.45 m layers.

Process of fixation, imobilization and mineralization of ammonium in soil using N-15

The organic and inorganic forms of soil nitrogen and how they participate in the process of fixation, immobilization and mineralization of ammonium in soils were evaluated, after different periods of incubaton, utilizing two soils, a Lithic Haplustoll and a Typic Eutrorthox. The results obtained permit to suggest that : 1) The method for determination of the ammonium fixing capacity based on the extraction with 2N KC1, is considered to be subject to interferences of other soil fractions capable of retaining ammonium. 2) The increase in exchangeable ammonium content is related to the decrease in amino acids and hydrolyzable ammonium. 3) The immobilization and mineralization processes are still held under mil microbial. The forms more affected by this condition are amino acids and hydrolyzable ammonium.

Soil profile internal drainage for a central pivot fertigated coffee crop

Coffee cultivation via central-pivot fertigation can lead to fertilizer losses by soil profile internal drainage when water application is excessive and soils have low water retention and cation adsorption capacities. This study analyses the deep water losses from the top 1 m sandy soil layer of east Bahia, Brazil, cultivated with coffee at a high technology level (central-pivot fertigation), using above normal N fertilizer rates. The deep drainage (Q) estimation is made through the application of a climatologic water balance (CWB) program having as input direct measures of irrigation and rainfall, climatological data from weather stations, and measured soil water retention characteristics. The aim of the study is to contribute to the understanding of the hydric regime of coffee crops managed by central-pivot irrigation, analyzing three scenarios (Sc): i) rainfall only, ii) rainfall and irrigation full year, and iii) rainfall and irrigation dry season only. Annual Q values for the 2008/2009 agricultural year were: Sc i = 811.5 mm; Sc ii = 1010.5 mm; and Sc iii = 873.1 mm, so that the irrigation interruption in the wet season reduced Q by 15.7%, without the appearance of water deficit periods. Results show that the use of the CWB program is a convenient tool for the evaluation of Q under the cited conditions.

Soil CO2 efflux in central Amazonia: environmental and methodological effects

Soil respiration plays a significant role in the carbon cycle of Amazonian rainforests. Measurements of soil respiration have only been carried out in few places in the Amazon. This study investigated the effects of the method of ring insertion in the soil as well as of rainfall and spatial distribution on CO2 emission in the central Amazon region. The ring insertion effect increased the soil emission about 13-20% for sandy and loamy soils during the firsts 4-7 hours, respectively. After rainfall events below 2 mm, the soil respiration did not change, but for rainfall greater than 3 mm, after 2 hours there was a decrease in soil temperature and respiration of about 10-34% for the loamy and sand soils, with emissions returning to normal after around 15-18 hours. The size of the measurement areas and the spatial distribution of soil respiration were better estimated using the Shuttle Radar Topographic Mission (SRTM) data. The Campina reserve is a mosaic of bare soil, stunted heath forest-SHF and tall heath forest-THF. The estimated total average CO2 emissions from the area was 3.08±0.8 µmol CO2 m-2 s-1. The Cuieiras reserve is another mosaic of plateau, slope, Campinarana and riparian forests and the total average emission from the area was 3.82±0.76 µmol CO2 m-2 s-1. We also found that the main control factor of the soil respiration was soil temperature, with 90% explained by regression analysis. Automated soil respiration datasets are a good tool to improve the technique and increase the reliability of measurements to allow a better understanding of all possible factors driven by soil respiration processes.

Influência lunar sobre plantas hortícolas

The aim of this paper is the study of moon effects on ten different crops divided in four groups: 1) salad and cole crops (lettuce, endive, cabbage, cauliflower); 2) root crops (beet, carrot, radish, turnip); 3) bulb crops (onion); 4) solanaceous fruits (eggplant). The design of the experiment was randomized blocks, with four replications, the different treatments being the four phases of the moon. The analyses of variance are given in the work of Simão (1953) and the analises of the mean in tables 1 to 2. The main conclusions are: 1) No difference in production were found related to different moon phases, even it the crops supposed to be sensible to moon effects. 2) In a few cases, where some increase in production was observed, such increase could be atributed by other apents 3) The agents supposed to interfere with increase in production were temperature and photoperiodism, rather than moon phases. 4) The most sensible crops to low temperature, during the night, were: lettuce, endive, cauliflower, cabbage, carrots, turnips and radish. 5) The most sensible crops to both low temperature and photoperiodism were: onion and beet. 6) The moon phases supposed to have opposed effects, namely full-moon and half-moon, gave mixed results sometimes both giving the best yield simultaneously and sometimes giving the poorest crops. 7) As a final conclusion, no moon effects could be detectable in the present experiment.

Conservação do bambu

This paper brings to light new data on the absence of influence of lunar phases on the preservation of bamboo sticks. The author cut down for one and a half years (from - June 18, 1947 to December 30,1948) bamboos in every phase of the moon. With part of the sticks obtained a fence was built; the rest v/as kept under shelter. In the fence there were: 5 whole sticks with no preservative, 5 whole sticks with thanalith, 5 halved sticks with no preservative, 5 halved sticks with thanalith, all buried 10 centimeters in the soil. An equal number of the same types and in the same fence were kept upright 10 centimeters above the soil. Under shelter, in a shed, there was another group of sticks, 10 of each of the same four types. After 5 1/2 years no damage was observed in the fence for any treatment or any phase of the moon. On the other hand, for those bamboos kept under shelter the following numbers of perforated sticks were observed. Number of perforated sticks after 5 1/2 years Without Thanalith Thanalith Date of cutting Phase of the moon Whole Halved Whole Halved 8 - 25 - 47 Prime 0 3 0 0 9 - 29 - 47 Full 0 3 0 0 10 - 7 - 47 Wane 0 3 0 0 10 - 14 - 47 New 2 4 0 0 10 - 29 - 47 Full 0 5 0 0 11 - 6 - 47 Wane 3 3 0 0 11 - 13 - 47 New 0 1 0 0 4 - 1 - 43 Wane 3 5 0 0 8 - 27 - 48 Wane 1 3 0 0 10 - 10 - 48 Prime 1 3 0 0 Totals 10 36 0 0 So, among the 400 sticks kept under shelter, after 5 1/2 years, only 46 were perforated, all among those withe no preservative. No influence of lunar phase at cutting down of sticks seems to be present.

Influence of tree species on the herbaceous understory and soil chemical characteristics in a silvopastoral system in semi-arid northeastern Brazil

Studies from some semi-arid regions of the world have shown the beneficial effect of trees in silvopastoral systems, by promoting the formation of resource islands and increasing the sustainability of the system. No data are available in this respect for tree species of common occurrence in semi-arid Northeastern Brazil. In the present study, conducted in the summer of 1996, three tree species (Zyziphus joazeiro, Spondias tuberosa and Prosopis juliflora: ) found within Cenchrus ciliaris pastures were selected to evaluate differences on herbaceous understory and soil chemical characteristics between samples taken under the tree canopy and in open grass areas. Transects extending from the tree trunk to open grass areas were established, and soil (0-15 cm) and herbaceous understory (standing live biomass in 1 m² plots) samples were taken at 0, 25, 50, 100, 150 and 200% of the average canopy radius (average radius was 6.6 ± 0.5, 4.5 ± 0.5, and 5.3 ± 0.8 m for Z. joazeiro, P. juliflora, and S. tuberosa , respectively). Higher levels of soil C, N, P, Ca, Mg, K, and Na were found under the canopies of Z. joazeiro and P. juliflora: trees, as compared to open grass areas. Only soil Mg organic P were higher under the canopies of S. tuberosa trees, as compared to open grass areas. Herbaceous understory biomass was significantly lower under the canopy of S. tuberosa and P. juliflora trees (107 and 96 g m-2, respectively) relatively to open grass areas (145 and 194 g m-2). No herbaceous biomass differences were found between Z. joazeiro canopies and open grass areas (107 and 87 g m-2, respectively). Among the three tree species studied, Z. joazeiro was the one that presented the greatest potential for use in a silvopastoral system at the study site, since it had a larger nutrient stock in the soil without negatively affecting herbaceous understory biomass, relatively to open grass areas.

Biomassa microbiana e produção de C-CO2 e N mineral de um podzólico vermelho-escuro submetido a diferentes sistemas de manejo: Microbial biomass and C-CO2 and mineral nitrogen production in paleudult soil cultivated under different management systems

Os sistemas de manejo, com diferenças no revolvimento do solo e na composição dos resíduos vegetais, alteram as propriedades biológicas do solo, com reflexos na qualidade do solo e na produtividade das culturas. Com vistas em medir estas alterações nas propriedades biológicas do solo, a biomassa e a atividade microbiana foram avaliadas em um Podzólico Vermelho-Escuro, em Eldorado do Sul (RS), utilizando diferentes preparos (convencional, reduzido e plantio direto) e dois sistemas de sucessões de culturas (aveia preta + vica/milho + caupi e aveia/milho). As avaliações foram realizadas em quatro épocas, durante 12 meses, e em duas profundidades (0-5 e 5-15 cm). O carbono da biomassa microbiana foi analisado pelo método de fumigação-incubação, e a atividade microbiana, pela produção de C-CO2 e N mineral, após 60 dias de incubação. As diferenças na biomassa e na atividade microbiana, entre os sistemas de manejo, foram mais pronunciadas na camada de 0-5 cm. Nesta camada de solo, observaram-se os maiores valores de biomassa e de atividade nos preparos conservacionistas e no sistema aveia + vica/milho + caupi. Dentre as variáveis estudadas, a mineralização de N mostrou-se a mais sensível aos manejos, à profundidade e à época de amostragem.

Variability of apparently homogeneous soilscapes in São Paulo state, Brazil: II. quality of soil maps

The quality of semi-detailed (scale 1:100.000) soil maps and the utility of a taxonomically based legend were assessed by studying 33 apparently homogeneous fields with strongly weathered soils in two regions in São Paulo State: Araras and Assis. An independent data set of 395 auger sites was used to determine purity of soil mapping units and analysis of variance within and between mapping units and soil classification units. Twenty three soil profiles were studied in detail. The studied soil maps have a high purity for some legend criteria, such as B horizon type (> 90%) and soil texture class (> 80%). The purity for the "trophic character" (eutrophic, dystrophic, allic) was only 55% in Assis. It was 88% in Araras, where many soil units had been mapped as associations. In both regions, the base status of clay-textured soils was generally better than suggested by the maps. Analysis of variance showed that mapping was successful for "durable" soil characteristics such as clay content (> 80% of variance explained) and cation exchange capacity (≥ 50% of variance explained) of 0-20 and 60-80 cm layers. For soil characteristics that are easily modified by management, such as base saturation of the 0-20 cm layer, the maps had explained very little (< 15%) of the total variance in the study areas. Intermediate results were obtained for base saturation of the 60-80 cm layer (56% in Assis; 42% in Araras). Variance explained by taxonomic groupings that formed the basis for the legend of the soil maps was similar to, often even smaller than, variance explained by mapping units. The conclusion is that map boundaries have been very carefully located, but descriptions of mapping units could be improved. In future mappings, this could possibly be done at low cost by (a) bulk sampling to remove short range variation and enhance visualization of spatial patterns at distances > 100 m; (b) taking advantage of correlations between easily measured soil characteristics and chemical soil properties and, (c) unbending the link between legend criteria and a taxonomic system. The maps are well suited to obtain an impression of land suitability for high-input farming. Additional field work and data on former land use/management are necessary for the evaluation of chemical properties of surface horizons.

State-space approach to evaluate the relation between soil physical and chemical properties

The state-space approach is used to evaluate the relation between soil physical and chemical properties in an area cultivated with sugarcane. The experiment was carried out on a Rhodic Kandiudalf in Piracicaba, State of São Paulo, Brazil. Sugarcane was planted on an area of 0.21 ha i.e., in 15 rows 100 m long, spaced 1.4 m. Soil water content, soil organic matter, clay content and aggregate stability were sampled along a transect of 84 points, meter by meter. The state-space approach is used to evaluate how the soil water content is affected by itself and by soil organic matter, clay content, and aggregate stability of neighboring locations, in different combinations, aiming to contribute to a better understanding of the relation among these variables in the soil. Results show that soil water contents were successfully estimated by this approach. Best performances were found when the estimate of soil water content at locations i was related to soil water content, clay content and aggregate stability at locations i-1. Results also indicate that this state-space model using all series describes the soil water content better than any equivalent multiple regression equation.

Soil water storage in an upland forest after selective logging in Central Amazonia

Soil water storage of Central Amazonian soil profiles in upland forest plots subjected to selective logging (in average, 8 trees or 34, 3 m³ of timber per hectare were removed) was measured in four layers, down to a depth of 70 cm. The study lasted 27-months and was divided in two phases: measurements were carried out nearly every week during the first 15 months; in the following year, five intensive periods of measurements were performed. Five damage levels were compared: (a) control (undisturbed forest plot); (b) centre of the clearing/gap; (c) edge of the gap; (d) edge of the remaining forest; and (e) remaining forest. The lowest values for water storage were found in the control (296 ± 19.1 mm), while the highest were observed (333 ± 25.8 mm) in the centre of the gap, during the dry period. In the older gaps (7.5-8.5 year old), soil water storage was similar to the remaining and the control forest, indicating a recovery of hydric soil properties to nearly the levels prior to selective logging.

Nitrogen application timing and soil inorganic nitrogen dynamics under no-till oat/maize sequential cropping

The timing of N application to maize is a key factor to be considered in no-till oat/maize sequential cropping. This study aimed to evaluate the influence of pre-planting, planting and sidedress N application on oat residue decomposition, on soil N immobilisation and remineralisation and on N uptake by maize plants in no-till oat/maize sequential cropping. Undisturbed soil cores of 10 and 20 cm diameter were collected from the 0-15 cm layer of a no-till Red Latossol, when the oat cover crop was in the milk-grain stage. Two greenhouse experiments were conducted simultaneously. Experiment A, established in the 10 cm diameter cores and without plant cultivation, was used to asses N dynamics in soil and oat residues. Experiment B, established in the 20 cm diameter cores and with maize cultivation, was used to assess plant growth and N uptake. An amount of 6.0 Mg ha-1 dry matter of oat residues was spread on the surface of the cores. A rate of 90 kg N ha-1 applied as ammonium sulphate in both experiments was split in pre-planting, planting and sidedress applications as follows: (a) 00-00-00 (control), (b) 90-00-00 (pre-planting application, 20 days before planting), (c) 00-90-00 (planting application), (d) 00-30-60 (split in a planting and a sidedress application 31 days after emergence), (e) 00-00-00* (control, without oat residue) and (f) 90-00-00* (pre-planting application, without oat residue). The N concentration and N content in oat residues were not affected during decomposition by N fertilisation. Most of the fertiliser NH4+-N was converted into NO3--N within 20 days after application. A significant decrease in NO3--N contents in the 0-4 cm layer was observed in all treatments between 40 and 60 days after the oat residue placement on the soil surface, suggesting the occurrence of N immobilisation in this period. Considering that most of the inorganic N was converted into NO3- and that no immobilisation of the pre planting fertiliser N occurred at the time of its application, it was possible to conclude that pre-planting applied N was prone to losses by leaching. On the other hand, with split N applications, maize plants showed N deficiency symptoms before sidedress application. Two indications for fertiliser-N management in no-till oat/maize sequential cropping could be suggested: (a) in case of split application, the sidedress should be earlier than 30 days after emergence, and (b) if integral application is preferred to save field operations, this should be done at planting.

Qualidade do solo avaliada pelo "Soil Quality Kit Test" em dois experimentos de longa duração no Rio Grande do Sul

A avaliação da qualidade do solo (QS) é importante estratégia no planejamento agrícola, possibilitando a identificação e o aprimoramento de sistemas de manejo com características de alta produtividade e de preservação ambiental. O presente estudo foi realizado em dois experimentos de longa duração (10 e 15 anos) conduzidos no Sul do Brasil e teve por objetivo avaliar o efeito de sistemas de manejo na QS, utilizando um kit de análise expedita de qualidade de solo (KQS), desenvolvido pelo Instituto de Qualidade do Solo-USDA-ARS. A eficiência desse kit foi avaliada pela comparação com os métodos tradicionais utilizados na ciência do solo. Nas duas áreas experimentais investigou-se um total de 12 tratamentos, os quais englobaram sistemas de preparo com diferentes intensidades de revolvimento do solo (preparo convencional, preparo reduzido e plantio direto) e sistemas de culturas com ampla faixa de adição de resíduos vegetais ao solo, além da aplicação de doses anuais de N-uréia, variando de 0 a 144 kg ha-1. Em cada base experimental uma área sob campo natural foi avaliada, servindo como referência da condição do solo na ausência de interferência antrópica. Como indicadores de QS, foram avaliados infiltração de água, respiração do solo, densidade do solo, teor de nitrato+nitrito (N-NO3- + N-NO2-), estabilidade de agregados em água e pH. De maneira geral, os coeficientes de correlação entre os métodos do KQS e os métodos tradicionais foram elevados, sendo o mais alto para o indicador pH (r = 0,98) e o menor para o indicador infiltração de água no solo (r = 0,42). Os tratamentos selecionados foram teoricamente ordenados em ordem crescente de QS, a qual foi reproduzida de forma eficiente pelo índice de estoque de carbono (IEC), calculado pela razão entre o estoque de C orgânico do solo, na camada de 0-5 cm, de cada tratamento e o estoque de C orgânico no solo sob campo natural. Os indicadores estabilidade de agregados, N-NO3- + N-NO2- e respiração do solo foram os mais eficientes em discriminar a QS. O KQS foi eficiente em avaliar a QS dos tratamentos nas duas áreas experimentais. Os níveis mais elevados de QS foram alcançados nos tratamentos com plantio direto e consórcio de gramíneas e leguminosas tropicais, devido à cobertura do solo e às elevadas adições de C e N via resíduos culturais.

Crop sequences in no-tillage system: effects on soil fertility and soybean, maize and rice yield

Decomposing crop residues in no-tillage system can alter soil chemical properties, which may consequently influence the productivity of succession crops. The objective of this study was to evaluate soil chemical properties and soybean, maize and rice yield, grown in the summer, after winter crops in a no-tillage system. The experiment was carried out in Jaboticabal, SP, Brazil (21 ° 15 ' 22 '' S; 48 ° 18 ' 58 '' W) on a Red Latosol (Oxisol), in a completely randomized block design, in strip plots with three replications. The treatments consisted of four summer crop sequences (maize monocrop, soybean monocrop, soybean/maize rotation and rice/bean/cotton rotation) combined with seven winter crops (maize, sunflower, oilseed radish, pearl millet, pigeon pea, grain sorghum and sunn hemp). The experiment began in September 2002. After the winter crops in the 2005/2006 growing season and before the sowing of summer crops in the 2006/2007 season, soil samples were collected in the layers 0-2.5; 2.5-5.0; 5-10; 10-20; and 20-30 cm. Organic matter, pH, P, K+, Ca2+, Mg2+, and H + Al were determined in each soil sample. In the summer soybean/maize rotation and in maize the organic matter contents and P levels were lower, in the layers 0-10 cm and 0-20 cm, respectively. Summer rice/bean/cotton rotation increased soil K levels at 0-10 cm depth when sunn hemp and oilseed radish had previously been grown in the winter, and in the 0-2.5 cm layer for millet. Sunn hemp, millet, oilseed radish and sorghum grown in the winter increased organic matter contents in the soil down to 30 cm. Higher P levels were found at the depths 0-2.5 cm and 0-5 cm, respectively, when sunn hemp and oilseed radish were grown in the winter. Highest grain yields for soybean in monoculture were obtained in succession to winter oilseed radish and sunn hemp and in rotation with maize, after oilseed radish, sunn hemp and millet. Maize yields were highest in succession to winter oilseed radish, millet and pigeon pea. Rice yields were lowest when grown after sorghum.

Correction of soil acidity in the subsurface of an oxisol with sandy loam texture under no-tillage

In Rio Grande do Sul State (RS), Southern Brazil, aluminum saturation in many areas under no-till system is high and base saturation low in the 0.10-0.20 m layer (subsurface), which may reduce the grain yield of annual crops. The objective of this study was to evaluate if the occurrence of high aluminum saturation and low base saturation in the subsurface, under a no-till system, represents a restrictive environment for crop production, as well as to evaluate forms of lime incorporation for soil acidity correction in the subsurface. For this purpose, an experiment was carried out with soybean (2005/2006), corn (2006/2007), wheat (2007) and soybean (2007/2008) crops, in a Rhodic Hapludox (USDA, 1999) with sandy loam texture, under no-till for four years in the county of Tupanciretã (RS). The six treatments were: no-tillage with and without lime, plowing with and without lime, and chiseling with and without lime. The values of pH-H2O, aluminum saturation and base saturation were evaluated 24 months after treatment application in the layers 0-0.05; 0.05-0.10; 0.10-0.15; 0.15-0.20 and 0.20-0.30 m. The yields of soybean (2005/2006), corn (2006/2007), wheat (2007) and soybean (2007/2008) were evaluated. Soil acidity in the subsurface did not affect crop yield when the acidity in the layer from 0-0.10 m was at levels for which lime application is not recommended, according to CQFSRS/SC (2004). Lime incorporation through plowing was the most efficient way of correcting acidity at deeper levels.