Dynamics of potassium leaching on a hillslope grassland soil

There have been only a few studies of potassium (K) losses from grassland systems, and little is known about their dynamics, especially in relation to nitrogen (N) management. A study was performed during the autumn and winter of 1999 and 2000 to understand the effects of N and drainage on the dynamics of K leaching on a hillslope grassland soil in southwestern England. Two N application rates were studied (0 and 280 kg N ha(-1) yr(-1)), both with and without the drainage. Treatments receiving N also received farmyard manure (FM). Higher total K losses and K concentrations in the leachates were found in the N + FM treatments (150 and 185% higher than in 0 N treatments), which were related to K additions in the FM. Drainage reduced K losses by 35% because of an increase in dry matter production and a reduction in overland and preferential flow. The pattern of change in K concentration in the leachates was associated with preferential flow at the beginning of the drainage season and with matrix flow later in winter, and was best described by a double exponential curve. Rainfall intensity and the autumn application of FM were the main determinants of K losses by leaching. The study provided new insights into the relationships between soil hydrology, rainfall, and K leaching and its implications for grassland systems.

Factors affecting potassium leaching in different soils

A set of lysimeter based experiments was carried out during 2000/01 to evaluate the impact of soil type and grassland management on potassium (K) leaching. The effects of (1) four soil textures (sand, loam, loam over chalk and clay), (2) grazing and cutting (with farmyard manure application), and (3) K applied as inorganic fertilizer, dairy slurry or a mixture of both sources were tested. Total K losses in the clay soil were more than twice those in the sand soil (13 and 6 kg K ha(-1), respectively) because of the development of preferential flow in the clay soil. They were also greater in the cut treatment than in the grazed treatment (82 and 51 kg K ha(-1), respectively; P less than or equal to0.01), associated with a 63% increase of K concentration in the leachates from the former (6.7 +/- 0.28 and 4.1 +/- 0.22 mg K L-1 for cut and grazed, respectively; P less than or equal to0.01) because of the K input from the farmyard manure. The source of fertilizer did not affect total K losses or the average K concentration in the leachates (P >0.05), but it changed the pattern of these over time.

Prediction leaching of potassium using the convective-dispersive and the convective log-normal transfer function models

There is increasing concern about soil enrichment with K+ and subsequent potential losses following long-term application of poor quality water to agricultural land. Different models are increasingly being used for predicting or analyzing water flow and chemical transport in soils and groundwater. The convective-dispersive equation (CDE) and the convective log-normal transfer function (CLT) models were fitted to the potassium (K+) leaching data. The CDE and CLT models produced equivalent goodness of fit. Simulated breakthrough curves for a range of CaCl2 concentration based on parameters of 15 mmol l(-1) CaCl2 were characterised by an early peak position associated with higher K+ concentration as the CaCl2 concentration used in leaching experiments decreased. In another method, the parameters estimated from 15 mmol l(-1) CaCl2 solution were used for all other CaCl2 concentrations, and the best value of retardation factor (R) was optimised for each data set. A better prediction was found. With decreasing CaCl2 concentration the value of R is required to be more than that measured (except for 10 mmol l(-1) CaCl2), if the estimated parameters of 15 mmol l(-1) CaCl2 are used. The two models suffer from the fact that they need to be calibrated against a data set, and some of their parameters are not measurable and cannot be determined independently.

Potassium Leaching as Affected by Soil Texture and Residual Fertilization in Tropical Soils

Potassium (K) leaching is affected by soil texture and available K, among other factors. In this experiment, effects of soil texture and K availability on K distribution were studied in the presence of roots, with no excess water. Soils from two 6-year field experiments on a sandy clay loam and a clay soil fertilized yearly with 0, 60, 120, and 180 kg ha-1 of K2O were accommodated in pots that received 90 kg ha-1 of K2O. Soybean was grown up to its full bloom (R2). Under field conditions, K leaching below the arable layer increased with K rates, but the effect was less noticeable in the clay soil. Potassium leaching in a sandy clay loam soil was related to soil K contents from prior fertilizations. With no excess water, in the presence of soybean roots, K distribution in the profile was significant in the lighter textured soil but was not apparent on the heavier textured soil.

Potassium leaching from millet straw as affected by rainfall and potassium rates

Pearl millet (Penisetum glaucum) is an interesting species to be used as cover crop in tropical areas, showing a high ability in potassium uptake. Potassium (K) is not linked to organic compounds in the plant, and can easily be released from decaying straw becoming available for subsequent crops. This experiment evaluated K leaching from millet straw grown under potassium rates (0, 100, 200, and 300 mg dm-3), and submitted to five levels of simulated rain (5, 10, 20, 40, and 80 mm). Plants were grown in soil filled pots in a greenhouse. On the 50th day after emergence, the plants were desiccated with glyphosate. Artificial rain was applied over the straw. Potassium deficiency speeds up millet dehydration after herbicide application and increases lightly rain water retention in the straw. The amount of K leached right after plant desiccation is correlated with the residue nutrient content and can be as high as 64 kg ha-1 considering a mulch of 8 t ha -1. Although well-nourished millet plants release considerable amounts of K with the first rains, a large percentage of the nutrient is still retained in the straw. Copyright © Taylor & Francis, Inc.

Implications of burial alterations on luminescence dating of archaeological ceramics

Recent mineralogical studies on archaeological pottery samples report significant variations in alkali metal concentrations due to environmental alterations during burial. Here we examine the effects of potassium (K) leaching on luminescence dating. The effect on the estimation of the dose rate is studied by considering four models of leaching (exponential, linear, early and late) and their impact on fine- and coarse-grain dating are calculated. The modeling approaches are applied to two cases of pottery in which evidence for alteration was found. Additionally, TL dating performed on pottery of one of the studied cases, indicates the importance of leaching effects on absolute dating measurements.

Lixiviação de potássio da palha de espécies de cobertura de solo de acordo com a quantidade de chuva aplicada

Os restos vegetais deixados na superfície do solo em sistemas de semeadura direta, além de proteger o solo da erosão, constituem considerável reserva de nutrientes que podem ser disponibilizados para a cultura principal, subseqüente. Avaliou-se a lixiviação de K da palha de seis espécies vegetais com potencial de uso como plantas para cobertura do solo de acordo com a quantidade de chuva recebida após o manejo. Milheto (Pennisetum americanum, var. BN-2), sorgo de guiné (Sorghum vulgare), aveia preta (Avena strigosa), triticale (Triticum secale), crotalária juncea (Crotalaria juncea) e braquiária (Brachiaria decumbens) foram cultivados em vasos com terra, em casa de vegetação, em Botucatu (SP). Aos 45 dias da emergência, as plantas foram cortadas na altura do colo, secas em estufa e submetidas a chuvas simuladas de 4,4, 8,7, 17,4, 34,9 e 69,8 mm, considerando uma quantidade de palha equivalente a 8,0 t ha-1. A máxima retenção de água pela palha corresponde a uma lâmina de até 3,0 mm, independentemente da espécie, praticamente não ocorrendo lixiviação do potássio com chuvas da ordem de 5 mm. A máxima liberação de K por unidade de chuva ocorre com lâminas de até 20 mm, decrescendo a partir deste ponto. A quantidade de K liberado da palha logo após o manejo depende da espécie vegetal, não ultrapassando, no entanto, 24 kg ha-1 com chuvas da ordem de 70 mm, apresentando correlação positiva com a concentração do nutriente no tecido vegetal. O triticale e a aveia são mais eficientes na ciclagem do potássio.

Lixiviação de potássio no solo de acordo com suas doses aplicadas sobre palha de milheto

A presença de palha na superfície do solo influi na ciclagem do K do sistema de produção e pode alterar as propriedades químicas do solo, com possíveis reflexos na lixiviação do nutriente. No presente trabalho, foi avaliada a lixiviação de K no perfil de um solo submetido a 30 mm de chuva simulada, de acordo com doses de K aplicadas a lanço, na presença e ausência de palha de milheto na superfície do solo. O milheto foi cultivado por 55 dias em condições controladas. A seguir, foi cortado à altura do colo, em pedaços de 3 a 5 cm e colocado sobre o solo, em vasos de PVC com 20 cm de diâmetro, em quantidade equivalente a 8 t ha-1 do material seco. Sobre a palha foi aplicado cloreto de K, correspondente às doses de 0, 40, 80, 120 e 160 kg ha-1. A seguir, os vasos foram submetidos à chuva simulada equivalente a 30 mm. A palha foi coletada e analisada quanto aos teores de K, assim como o solo foi amostrado nas profundidades de 0-2, 2-4, 4-8, 8-12 e 12-20 cm de profundidade para análise de K trocável. A chuva de 30 mm foi necessária e suficiente para carrear para o solo o fertilizante potássico aplicado sobre a palha. A intensidade de lixiviação do K no perfil do solo foi proporcional à dose aplicada, de modo que uma chuva de 30 mm lixiviou o nutriente até a camada de 8-12 cm de profundidade, quando o solo estava descoberto. A presença de palha de milheto na superfície do solo aumentou a quantidade de K levada até à superfície do solo pela chuva, mas diminuiu a intensidade de lixiviação do nutriente.

Potássio no solo em conseqüência da adubação sobre a palha de milheto e chuva simulada

O objetivo deste trabalho foi avaliar a lixiviação de potássio (K), no solo, e sua presença nas formas trocável e não trocável, em conseqüência da aplicação de chuva simulada e adubação potássica sobre palha de milheto, na superfície do solo. Vasos com terra e palha de milheto na superfície (quantidade equivalente a 8 t ha-1) receberam ou não adubação potássica, na dose de 150 kg ha-1 de K2O, na forma de KCl, aplicados sobre a palha. Na seqüência, foram aplicadas lâminas de água de 0 a 50 mm. O solo foi analisado em diversas profundidades, quanto aos teores de K trocável e não trocável. A palha do milheto revelou-se fonte importante de K, que é lixiviado até 4 cm de profundidade por chuvas superiores a 30 mm. A lixiviação de K, em profundidade no solo, é proporcional à chuva aplicada; entretanto, uma chuva de 50 mm não carreia o nutriente para profundidades superiores a 8 cm. A passagem de K trocável para não trocável é rápida, conforme atestado pelo conteúdo de K não trocável na camada de solo abaixo de 4 cm.

Phosphorus and potassium budget in the soil-plant system in crop rotations under no-till

Soil management and crop rotations can affect P and K budget in soil, decreasing losses, and increasing fertilizer use efficiency. The P and K budget in the soil-plant system at depths up to 60. cm was studied for different soil managements and crop rotations under no-till for three years in Botucatu, São Paulo, Brazil. The investigated crop rotations were: triticale (X Triticosecale) and sunflower (Helianthus annuus) cropped in autumn-winter; pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor), and Sunn hemp (Crotalaria juncea) were grown in the spring, as well as an additional treatment with chiseling followed by a fallow period; and soybean (Glycini max, L., Merril) was cropped in the summer. Each year triticale and sunflower were grown in plots and pearl millet, forage sorghum, Sunn hemp and of chisel/fallow in sub-plots. The triticale/millet rotation led to the largest decrease in available P within the 0-0.60. m layer of the soil profile and the largest K increase within the 0-0.05. m layer. Potassium mobility in the soil profile and the increases in the available K content in the 0.40-0.60. m layer were independent of the management system. Crop rotations with or without chiseling are not effective in preventing soil P losses. There is considerable K leaching below 0.60. m, but chiseling and the use of high K accumulating plants as triticale results in lower K losses. © 2012 Elsevier B.V.

Lixiviação de bases em função da calagem, adubação nitrogenada e resíduos vegetais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Coffee processing residues as a soil potassium amendment

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Resposta do cafeeiro arábica ao magnésio em solos fertilizados com altas doses de potássio

O aumento das doses de potássio (K) para atender a demanda nutricional desse nutriente em cafezais produtivos induz a deficiência de Mg. Esta pesquisa foi realizada com o objetivo de compreender como a classe de solo interfere na interação entre esses nutrientes (K e Mg), de maneira que a aplicação de alta dose de K não afete a nutrição da planta em relação ao Mg. Dois experimentos foram conduzidos em duas classes de solo: Latossolo, com textura muito argilosa, em Machado-MG, e Argissolo, com textura media sobre argilosa, em Monte Santo de Minas-MG. Adotou-se delineamento fatorial com três doses de K (110, 260 e 390 kg ha-1 K2O) x cinco doses de Mg (0, 81, 162, 324 e 405 kg ha-1 MgO), com três repetições. No Argissolo, a lixiviação de K impediu a redução da concentração foliar de Mg, independentemente da dose de K. No Latossolo, a concentração de Mg foliar variou com a dose de K, e apresentou ajuste quadrático. A concentração foliar de Mg aumentou linearmente com a dose desse nutriente, independentemente da classe de solo e da dose de K.

Leaching of nutrients from a sugarcane crop growing on an Ultisol in Brazil

Leaching is disadvantageous, both for economical and environmental reasons since it may decrease the ecosystem productivity and may also contribute to the contamination of surface and ground water. The objective of this paper was to quantify the loss of nitrogen and sulfur by leaching, at the depth of 0.9 m, in an Ultisol in Sao Paulo State (Brazil) with high permeability, Cultivated with sugarcane during the agricultural cycle of crop plant. The following ions were evaluated: nitrite, nitrate, ammonium, and sulfate. Calcium, magnesium, potassium, and phosphate were also evaluated at the same depth. The sugarcane was planted and fertilized in the furrows with 120 log ha(-1) of N-urea. In order to find out the fate of N-fertilizer, four microplots with (15)N-enriched fertilizer were installed. Input and output of the considered ions at the depth of 0.9 m were quantified from the flux density of water and the concentration of the elements in the soil solution at this soil depth: tensiometers, soil water retention curve and soil solution extractors were used for this quantification. The internal drainage was 205 mm of water, with a total loss of 18 kg ha(-1) of N and 10 kg ha(-1) of S. The percentage of N in the soil solution derived from the fertilizer (%NSSDF) was 1.34, resulting in only 25 g ha(-1) of N fertilizer loss by leaching during all agricultural cycle. Under the experimental conditions of this crop plant, that is, high demand of nutrients and high incorporation of crop residues, the leached N represented 15% of applied N and S leaching were not considerable; the higher amount of leached N was native nitrogen and a minor quantity from N fertilizer; and the leached amount of Ca, Mg, K and P did not exceed the applications performed in the crop by lime and fertilization. (C) 2009 Elsevier B.V. All rights reserved.

Increasing the efficiency of solute leaching: impacts of flow interruption with drainage of the "preferential flow paths"

Most soils contain preferential flow paths that can impact on solute mobility. Solutes can move rapidly down the preferential flow paths with high pore-water velocities, but can be held in the less permeable region of the soil matrix with low pore-water velocities, thereby reducing the efficiency of leaching. In this study, we conducted leaching experiments with interruption of the flow and drainage of the main flow paths to assess the efficiency of this type of leaching. We compared our experimental results to a simple analytical model, which predicts the influence of the variations in concentration gradients within a single spherical aggregate (SSA) surrounded by preferential flow paths on leaching. We used large (length: 300 mm, diameter: 216 mm) undisturbed field soil cores from two contrasting soil types. To carry out intermittent leaching experiments, the field soil cores were first saturated with tracer solution (CaBr2), and background solution (CaCl2) was applied to mimic a leaching event. The cores were then drained at 25- to 30-cm suction to empty the main flow paths to mimic a dry period during which solutes could redistribute within the undrained region. We also conducted continuous leaching experiments to assess the impact of the dry periods on the efficiency of leaching. The flow interruptions with drainage enhanced leaching by 10-20% for our soils, which was consistent with the model's prediction, given an optimised equivalent aggregate radius for each soil. This parameter quantifies the time scales that characterise diffusion within the undrained region of the soil, and allows us to calculate the duration of the leaching events and interruption periods that would lead to more efficient leaching. Application of these methodologies will aid development of strategies for improving management of chemicals in soils, needed in managing salts in soils, in improving fertiliser efficiency, and in reclaiming contaminated soils. (C) 2000 Elsevier Science B.V. All rights reserved.