Antônio Faganello

Distribution of phosphorus fractions in a Brazilian Oxisol under different tillage systems

Abstract Changes in residue management resulting from adoption of conservation tillage systems have the potential to alter the concentration and distribution of phosphorus (P) in the soil surface. The objective of this study was to determine the effect of methods of tillage management on the distribution and concentration of organic and inorganic forms of soil P near the soil surface (0–10 cm depth) for an Oxisol in southern Brazil. The tillage systems included zero tillage (ZT) (seeding directly onto the standing stubble of the previous crop), minimum tillage (MT) (seeding the crop after chisel plowing to 15-cm depth and disk harrowing to 7.5 cm), or conventional tillage (CT) (seeding after disk plowing to 20-cm depth with nearly total soil inversion plus two disk harrowings to 10-cm depth). After a period of five years, reducing tillage through adoption of MT or ZT practices increased total P in the surface 10 cm by 15% when compared to CT. Although there were no differences in amounts of total P between MT and ZT systems, under ZT management larger amounts of labile organic and inorganic forms of P accumulated close to the soil surface, followed by a reduction below the 6-cm depth. Under MT, the labile organic and inorganic forms of P were uniformly distributed within the surface 10 cm of soil. The accumulation of high levels of labile P near the soil surface under ZT followed a distribution pattern similar to the accumulation of organic residues in the soil. This would help explain why other workers have found increased P uptake by crops grown under ZT, and why more available P can be extracted by common soil testing methods from the surface 7 to 10 cm of soils under ZT than under CT management.

Persistência dos efeitos da escarificação sobre a compactação de Nitossolo sob plantio direto em região subtropical úmida

O objetivo deste trabalho foi avaliar a persistencia dos efeitos da escarificacao sobre a compactacao de Nitossolo Vermelho, manejado sob plantio direto (PD), na regiao subtropical umida do Brasil. O experimento foi realizado em blocos ao acaso, com quatro repeticoes e seis tratamentos, constituidos pelo tempo de manutencao do solo sob PD apos escarificacao: PD continuo por 24 meses apos escarificacao, realizada em setembro de 2009; PD continuo por 18 meses apos escarificacao, realizada em marco de 2010; PD continuo por 12 meses apos escarificacao, realizada em setembro de 2010; PD continuo por seis meses apos escarificacao, realizada em marco de 2011; plantio realizado em solo recem escarificado, em setembro de 2011; e PD continuo e sem escarificacao (testemunha). As especies cultivadas na area foram: milho, safra 2009/2010; trigo, em 2010; soja, safra 2010/2011; centeio, em 2011; e milho, safra 2011/2012. Os efeitos dos tratamentos foram avaliados a partir de parâmetros fisicos do solo e de parâmetros morfologicos e produtivos da cultura do milho, na safra 2011/2012. A escarificacao do Nitossolo sob plantio direto, em regiao de clima subtropical umido, nao aumenta a produtividade de graos de milho, e os seus efeitos sobre a estrutura do solo nao persistem por mais de 18 meses.

Efeito de semeadora com haste sulcadora para ação profunda em solo manejado com plantio direto

The adoption of no-till in the humid subtropical region of Brazil based on only two precepts of conservation agriculture, soil disturbance restricted to the crop row and crop residue maintained as soil cover, has led to stratification of soil chemical properties in the 0-20 cm soil layer and physical degradation of the subsurface layer (from approximately the 5-20 cm depth), which may make for lower yields during short term droughts. The aim of this study was to evaluate the residual effect of a seed drill/fertilizer applicator equipped with fixed shanks, set at four different depths, for the sowing of maize (Zea mays L.), in mitigation of chemical and physical problems in a Latossolo Vermelho distrofico humico (Rhodic Hapludox) under no-till for more than ten years. The treatments were: T1 = shank extremity at 5 cm depth; T2 = shank extremity at 10 cm depth; T3 = shank extremity at 15 cm depth; and T4 = shank extremity at 17 cm depth. The crop profile method was used to evaluate soil physical properties (bulk density, total porosity, macroporosity, and soil resistance to penetration) at eight and ten months after sowing the maize. The chemical properties (pH in water; available P and K; exchangeable Ca, Mg, and Al; potential acidity; and organic matter) were evaluated in layers every 2.5 cm from the 0-22.5 cm depth. The seed drill/fertilizer applicator equipped with fixed shanks for ripping the soil was able to mitigate soil physical and chemical problems, both at eight and 12 months after sowing.

Resistência à penetração e rendimento da soja após intervenção mecânica em latossolo vermelho sob plantio direto

Compaction negatively affects a number of soil properties, e.g., resistance to root penetration and water and nutrient availability to plants, restricting the photosynthetic rate, shoot growth and consequently, the yield. When soil compaction becomes limiting to crop development, mitigation measures must be adopted. The purpose of this study was to evaluate the residual effect of mechanical soil plowing and chiseling, by a seeder with soil breakers (disks and disks plus short ripper) as mitigation practice of the soil compaction under no-tillage (NT), on soil penetration resistance and soybean yield. In 2001, a study was conducted in Coxilha, in northern Rio Grande do Sul, on an Oxisol, in an area with a sequence of NT management. In this field, every year a treatment of mechanical soil decompression was applied, consisting of plowing and chiseling the soil under NT, before sowing the summer crop, reassuming the NT management after this intervention. The experimental design consisted of randomized blocks in a split-plot design with three replications. The treatments consisted of a combination of 13 systems of soil management in the main plots and two seed drill devices in the subplots. Thus, the management systems were evaluated by the control, represented by the uninterrupted maintenance of NT for 16 years, six NT management periods (7.5, 6.5, 5.5, 4.5, 3.5, and 2.5 years) after one intervention with mechanical disc plow + disc harrow (A) and the same six NT management periods after one mechanical intervention with chiseling (E). The levels in the subplots consisted of the action of a no-till seeder equipped with double discs reaching a depth of 7 cm and a seeder equipped with double disks + short ripper reaching a depth of 13 cm. Results indicated that the mitigating effect on compaction and on the improvement of soil structure of the mechanical intervention in soil under consolidated NT consisting of soil chiseling or plowing is short-lived, with a residual effect of up to two and a half years for penetration resistance. The use of a no-till seeder drill equipped with short ripper + disc seeder has potential for mitigation of soil compaction, by reducing mechanical penetration resistance in the 7-15 cm layer. Nevertheless, the residual effect of mechanical intervention for soil decompaction and the adoption of different devices for fertilizer application in the plant furrow were not effective in altering the soybean yield in the 2008/2009 growing season.

Vertical mulching como prática conservacionista para manejo de enxurrada em sistema plantio direto

In regions of temperate and subtropical humid climate in Brazil, below the parallel of 24° latitude South, the rainfall characteristics potentially exceed the soil water infiltration rate and produce runoff, at any time of the year, independent of soil use and management system. The additional conservational practices have not been fully adopted in the no-tillage system as it would be required to control the erosion potential due to the soil conditions of these regions. Runoff results in chemically enriched sediments, which poses environmental risks, besides causing economical losses in the agriculture production system. The objective of this study was to evaluate the efficiency of vertical mulching as a conservation practice to restrict runoff in areas under no-tillage system, by evaluating the sediment enrichment rate based on double soil sampling in fields with presence and absence of the practice of vertical mulching. The double sampling covered representative soils of each plantation and the respective sediments generated by hydric erosion. Soil pH in water, SMP index, available P, exchangeable K, Ca, Mg and Al, and organic matter were determined, and the total and base saturation and cation exchange capacity in each sample were calculated. Results indicate that the conservation practice of vertical mulching reduces the degree of chemical enrichment of the sediments and mainly prevents the transport of these sediments away from plantations, minimizing economical losses and environmental risks. The no tillage system, without complementary conservation practices to control runoff, does therefore not represent a soil conservation practice capable of preventing environmental degradation.

Duração das alterações em propriedades físico-hídricas de Latossolo argiloso decorrentes da escarificação mecânica

The objective of this work was to determine the duration of the effects of soil decompaction, by mechanical chiseling, through physical and hydraulic indicators of a clayey Oxisol under no-tillage (NT). The treatments consisted of months (0, 6, 12, 18, 24, 30, and 36) after chiseling under NT and of a control treatment without chiseling under NT during 27 years. The following variables were evaluated: penetration resistance, infiltration rate, bulk density and relative density, pore size distribution, and saturated hydraulic conductivity. The duration of the effects of mechanical chiseling varied according to the evaluated soil property, lasting six months for bulk density and relative density, total porosity, and macroporosity; 18 months for penetration resistance; and 24 months for hydraulic conductivity and infiltration rate. Soil properties related to water transport, such as hydraulic conductivity and steady infiltration rate, maintain the effect of mechanical chiseling for a longer time and, therefore, are more suitable to measure the duration of mechanical decompaction.

Métodos de manejo de aveia preta para evitar sua ressurgência como planta daninha em trigo

Black oat is an important winter cover crop in south Brazilian. However, it is a weed problem in cool season grain crops as well as ryegrass. Two trials in a randomized complete block design were conducted at Embrapa Trigo in Passo Fundo, Rio Grande do Sul state. This research aimed to study different oat management methods applied on black oat at anthesis and milk stage to avoid it becoming a weed plant in wheat cropped after soybean. The plot area was 60m2. Nine treatments were tested, in both trials: spray herbicide; roll plus herbicide; hay harvest; silage harvest; mowing; grinding, silage; rolling; disking; and grain harvesting. The average total biomass at anthesis was 5,016kg DM ha-1 and at milk stage was 6,050kg DM ha-1. Soybean cropped in the summer season yield 2,080kg ha-1 and it was not affected by black oat treatments. During the second year, the wheat plots sprayed herbicide before planting yielded 2,472kg ha-1 and spike density of 355m-2, however plots without herbicide yielded 836kg ha-1 and had 225 spikes m-2. On black oat milk stage managements the yield average was 1,733kg ha-1 and 334 spikes m-2, on sprayed herbicide plots before planting. In opposite, the plots without herbicide, wheat plants were completely dominated by resurgent black oat plants, due to managements applied during previous winter. Mechanical management methods applied only in black oat development stages allowed seeds germination during winter crops cycle. This problem is avoided spraying herbicide before oat anthesis, because after that any management method tested was unsuccessful to control oat after the following winter crops, so is necessary to spray herbicide before seeding winter cash crops.