Soil Solution Nutrient Research Articles

Monitoring of soil EC for the prediction of soil nutrient regime under different soil water and organic matter contents

Smart farms and precision agriculture require automatic monitoring and supply of water and nutrients for crops, but sensors to monitor plant available nutrients in soil are not available. Soil electrical conductivity (EC) is related to nutrients in soil solution, which can be affected by soil organic matter, soil texture, temperature, and water content. Therefore, the objective of this study is to evaluate factors influencing soil EC sensor values by monitoring EC under different soil organic matter and water contents. Ten soil samples with various sand and clay contents, EC, pH, and organic matter contents were selected and saturated with water. Volumetric water content and EC of the soil were monitored while drying the soil. Humic acid and manure were added to soils in order to evaluate the effect of organic matter on soil EC. Soil EC values linearly increased with increasing water content at 10–25% which is favorable water content for plant growth. The EC increased when organic matter was added to soils, which was related to ions released from the organic matter. Soil EC calibration factor for soil water content increased when EC of the soil was high and organic matter was added. The sensor EC values in sandy loam and loam soils was related to the ion contents in pore water, and exchangeable ions in soil, respectively. Sensor EC values were highly correlated with organic matter and K contents in soil and can be used as an indicator for plant available nutrients in soil. Therefore, the sensor EC at optimal soil water content for plant growth can be used to monitor changes in plant available nutrients in soil.

Life in the dark: Impact of future winter warming scenarios on carbon and nitrogen cycling in Arctic soils

The high Arctic region is warming faster than other areas globally, with widespread decreases in snow cover and longer growing seasons. This is expected to greatly influence plant-microbial carbon (C) and nitrogen (N) cycling and thus ecosystem functioning, particularly when soils remain unfrozen during the dark winter period and no photosynthesis is possible. To better understand this response, we studied the effects of different winter warming scenarios on soil C and N dynamics. We collected intact soils cores from two contrasting biomes from Svalbard, namely a moss-dominated peat mire and purple saxifrage-dominated dry tundra heath. In the laboratory, we used an Arctic annual light regime and three contrasting winter temperature regimes to simulate a range of climate scenarios: (i) current climate in which the soils were frozen in winter and thawed in the summer, (ii) a year 2050 regime in which the soils were both frozen and thawed in winter, and (iii) a year 2100 regime in which the soils remained unfrozen during winter. We monitored greenhouse gas (GHG) emissions (CO2, CH4 and N2O) and nutrients in soil solution (DOC, NO3−, NH4+, P) over a one-year period. In the peat mire, warmer winters increased CO2 emissions due to increased microbial activity but had little effect on methane or N2O fluxes. Warmer winters also decreased dissolved organic carbon and nutrients in soil solution. In the dry tundra heath, warmer winters increased nitrate availability but did not greatly alter CO2, CH4 or N2O gas fluxes or other nutrients. Warming in the dry tundra health induced earlier spring flowering and shifts in vegetation composition. Overall, we present clear evidence that warmer winter conditions are likely to alter C and N cycling in Arctic soils, with implications for plant productivity and vegetation community composition.

Essential Role of Potassium in Apple and Its Implications for Management of Orchard Fertilization.

K (K) is of paramount importance for apple (Malus × domestica Borkh.), not only for tree growth and development but also for the size and quality of fruit yield. The apple plant’s demand for K varies, along with the progression of phenological phases, during the growing season. The K demand peaks during ripening of fruits featuring relatively high concentration of K comparable to that of the leaves. The mainstream method of apple tree K fertilization is through application of the fertilizer to the soils to improve K uptake by the roots. The bioavailability of K depends on assorted various factors, including pH, interaction with other nutrients in soil solution, temperature, and humidity. An important role in making the K from soil available for uptake by plants is played by plant growth-promoting microorganisms (PGPM), and the specific role of the PGPM is discussed. Advantages of fertigation (the combination of irrigation and fertilization) as an approach include allowing to balance application rate of K fertilizer against its variable demand by plants during the growing season. Excess K in the soil leads to competitive inhibition of calcium uptake by plants. The K-dependent deficiency of Ca leads to its predominant channeling to the leaves and hence to its decline in fruits. Consequently, the apple fruits affected by the K/Ca imbalance frequently develop physiological disorders in storage. This emphasizes the importance of the balanced K application, especially during the last months of the growing season, depending on the crop load and the actual K demand. The potential use of modern approaches to automated crop load estimation through machine vision for adjustment of K fertilization is underlined.

Agronomic Bio-fortification of Rice and Maize with Iron and Zinc: A Review

Earlier, the agriculture system was oriented more towards achieving higher agronomic yields than the nutritional quality of food. Green revolution significantly enhanced the crop production primarily rice, wheat and maize production was boosted to meet the energy needs of growing population. As a consequence of the predominance of cereal-based staples that are fundamentally low in micronutrients, specifically Zn and Fe, more than 2 billion people worldwide suffer from an insidious type of deficiency known as micronutrient malnutrition. Just moderate amounts of micronutrient malnutrition can affect cognitive development, reduce disease resistance and increase the risk of women dying during childbirth. The approach to micronutrient fertilization has been shown to improve the yield and nutritional content of the staples. Agronomic biofortification provides an immediate and effective method to enhance accumulation of micronutrients especially Zn and Fe in cereals. An adequate amount of plant available micronutrients is a prime requisite to ensure adequate nutrient uptake. Most of the cereals are grown in soils deficit in Zn and under reduced conditions of rice ecosystem, its availability is decreased due to formation of less soluble Zn complexes with sulphate and carbonate. The form of fertilizer used, timing and method of application is critical for the enhancement of the grain quality of Zn and Fe. The effectiveness of agronomic biofortification can be enhanced by application of synthetic chelated micronutrient fertilizers and/or organic fertilizers fortified with micronutrients in combination with NPK ensuring proper nourishment of crops with adequate nutrient supply by slow release of nutrients in soil solution. Further, the response of foliar application has shown better results than soil application. Previous studies suggest that Zn fertilization not only enhances Zn concentration in grain but also improves the overall performance of maize crop. Agronomic biofortification of crops is advantageous in terms of accessibility, rapid result, ease in application and high sustainability.

Evaluating foliar nutrient concentration as an indicator of soil nutrients in reclaimed and natural forests in Alberta, Canada

ABSTRACT Foliar nutrient concentrations are commonly recommended as indicator for soil nutrient status in managed and wildland ecosystems. Using data from an oil sands mine reclamation site in Alberta, Canada, we evaluated whether trembling aspen (Populus tremuloides Michx.) foliar concentrations of macronutrients accurately represent soil solution and soil nutrient pools in both reclaimed and wildfire-impacted natural reference boreal forest ecosystems. Reclamation soils were upland-based forest soil (forest floor-mineral mix; FFMM) and lowland-based peat soil (peat-mineral mix; PMM) with and without fertilisation. Individual macronutrient concentrations differed among treatments in the soil nutrient pool, but differences decreased in the soil solution pool and disappeared in the foliar pool. Few significant correlations between foliar and belowground pools were observed, but foliar phosphorus was correlated to soil phosphorus in natural reference sites. Multivariate analyses showed reclaimed sites were different from reference sites across all nutrient pools. Again, few significant multivariate correlations between foliar and belowground nutrient pools were observed, except for the unfertilised forest floor-mineral mix site, where foliar nutrients were positively correlated with soil solution. Based on our findings, we suggest that trembling aspen foliar nutrient concentrations are not a consistently reliable indicator of soil and soil solution nutrients in reclaimed or natural ecosystems.

Soil Solution Aluminum, and Nutrient and Aluminum Uptake in Hibiscus Sabdariffa Under Nitrogen and Phosphorous Fertilizers

ABSTRACTThe result of intensive agriculture in cities is the decline in crop yields and depletion of the resource base. The aims of this study were to assess effects of nitrogen (N) or phosphorus (P) fertilization on bioavailable aluminum (Al) and their contribution on Al and nutrient uptake in Hibiscus sabdariffa. A pot experiment was led to supply a tropical soil with N and P fertilizers. P amendment decreased Al in soil solution, not N amendment. Fertilizers had effects on Al and nutrient uptake in roots and leaves of Hibiscus sabdariffa. The results also showed that the uptake of Al and nutrients depends on Al in soil solution or N supply or P supply. Only P uptake in roots and leaves was explained by combined effects of a nutrient supply × exchangeable Al. Furthermore, P supply does not limit the translocation of Al in shoots of plants in acid soils.

Arsenic uptake, accumulation and toxicity in rice plants: Possible remedies for its detoxification: A review.

Arsenic (As) is a toxic metalloid. Serious concerns have been raised in literature owing to its potential toxicity towards living beings. The metalloid causes various water- and food-borne diseases. Among food crops, rice contains the highest concentrations of As. Consuming As-contaminated rice results in serious health issues. Arsenic concentration in rice is governed by various factors in the rhizosphere such as availability and concentration of various mineral nutrients (iron, phosphate, sulfur and silicon) in soil solution, soil oxidation/reduction status, inter-conversion between organic and inorganic As compounds. Agronomic and civil engineering methods can be adopted to decrease As accumulation in rice. Agronomic methods such as improving soil porosity/aeration by irrigation management or creating the conditions favorable for As-precipitate formation, and decreasing As uptake and translocation by adding a inorganic nutrients that compete with As are easy and cost effective techniques at field scale. This review focuses on the factors regulating and competing As in soil-plant system and As accumulation in rice grains. Therefore, it is suggested that judicious use of water, management of soil, antagonistic effects of various inorganic plant-nutrients to As should be considered in rice cultivated areas to mitigate the building up of As in human food chain and with minimum negative impact to the environment.

Soil solution nutrient monitoring as a guide to more efficient fertigation in commercial almond production

Soil solution nutrient monitoring as a guide to more efficient fertigation in commercial almond production

Nutrient Dynamics in Soil Solution and Wheat Response after Biomass Ash Amendments

Among the possible methods for biomass ash (BA) utilization, land application represents an important nutrient‐saving approach of BA management. The land application of BA results in an increase of soil pH, but in contrast to conventional liming, ash application on agricultural land can supply additional nutrients to soil, such as K, Mg, or P. However, due to the complex mineral phase composition of ashes, release of nutrients from the ash matrix into soil solution is not well understood. In the presented pot experiment, two agricultural soils were amended using two common types of BA (wood and straw ash) at rate 1% (w/w). During the vegetation period of spring wheat (Triticum aestivum L.), soil solution was sampled and monitored for the concentrations of Ca, K, Mg, and P. Subsequently, yield and nutrient uptake of wheat were determined. The effect of ash application on the investigated parameters differed substantially between the tested soils. Positive yield responses were found in soil with higher N content. Straw ash application increased concentrations of all monitored nutrients in soil solution but simultaneously increased plant uptake of K and P only. Wood ash increased concentrations of Ca and Mg in solution, while its effect on nutrient uptake strongly differed between soils. Generally, higher relative increases of nutrients in soil solution were surprisingly found in soil with higher pH and higher cation exchange capacity (CEC). Factors influencing dynamics of ash‐contained nutrients in soil solution are discussed. Nutrient leaching from straw and wood ash matrix in soil‐plant conditions is investigated. The influence of ashes on yield and nutrient uptake differed substantially depending on types of ash and soil. Highly soluble K‐compounds in straw ash revealed by X‐ray powder diffraction. Straw ash is a much more efficient P source than wood ash.

Soil Solution Nutrient Availability, Nutritional Status and Yield of Corn Grown in a Typic Hapludox under Twelve Years of Pig Slurry Fertilizations

Nutrient content in soil solution may vary in response to the applied amount of pig slurry (PS). Thus, the aim of this research was to evaluate the nutrient content in soil solution and its relationship to nutritional status and yield of corn under 12 years of annual fertilization with increasing doses of PS, soluble mineral fertilizer (MF) and PS combined with MF. The experiment was conducted under field conditions in a Latossolo Vermelho Distroferrico (Typic Hapludox). The treatments consisted of pig slurry at annual rates of 50 and 100 m3 ha-1 (PS50 and PS100), soluble mineral fertilizer (MF), and pig slurry at a rate of 25 m3 ha-1 complemented with mineral fertilizer (PS25 + MF), distributed in a randomized block design. Soil solution was sampled at two depths, 0.40 and 0.80 m, on six dates after the fertilizer applications. The nitrate (NO−3-N) and K levels in the soil solution were measured 40, 108 and 135 days after the last application of fertilizer (DAAF), being subsequently correlated with corn yield. PS50 provide contents of NO−3-N, P and K to the soil solution similar to those supplied by MF or PS25+MF. The critical limit of 10 mg L-1 NO−3-N in the soil solution was exceeded on 108, 135 and 230 DAAF, at rates of 100 and 50 m3 ha1 of PS and on 230 DAAF when using MF.

Nutrientes no solo e na solução do solo na citricultura fertirrigada por gotejamento

A analise da solucao do solo vem mostrando-se um metodo promissor de diagnostico da fertilidade de solo, principalmente em sistemas de fertirrigacao. O objetivo deste estudo foi avaliar o comportamento dos nutrientes no solo e na solucao do solo, quando fornecidas cinco doses de N, P2O5 e K2O (0; 25; 50; 100 e 200% da dose recomendada) via fertirrigacao. O experimento foi conduzido por tres safras em laranjeiras Valencia enxertadas sobre citrumelo Swingle. O solo e a solucao do solo foram coletados ao final do periodo de fertirrigacao de cada safra. As doses de N, P2O5 e K2O aplicadas proporcionaram reducao nos valores de pH do solo e da solucao do solo, porem a variacao dos valores de pH da solucao do solo foi 3,5 vezes maior que a observada no solo. Para o P, esta variacao ficou em torno de 65 vezes e, para o K, foi maior que 100 vezes. Os teores de P e K apresentaram comportamento semelhante no solo e na solucao do solo, com valores de correlacao de 0,87 e 0,97, respectivamente, e ambos os teores de P e K aumentaram em funcao das doses de fertilizantes. Os resultados sugerem que a analise da solucao do solo pode ser utilizada como ferramenta para estimar os valores de pH, P, K, Mn e Zn no solo, e tambem para determinar a disponibilidade de nitrogenio em sistemas de fertirrigacao na citricultura.

A New Architecture in Greenhouse Soil Solution Monitoring System Based on ZigBee Protocol

Nowadays in the greenhouse monitoring system, there are some shortages: a. the concentration of nutrients (such as N, P plasma) in soil solution as a greenhouse environment parameter is often overlooked; b. small ZigBee system can’t meet the needs of real-time data storage and remote monitoring. Basing on the situation, this paper designs a new architecture in greenhouse soil solution monitoring system based on ZigBee protocol. The architecture has several small sub-networks. Each of these subnets forms an Ad-hoc network by ZigBee protocol. And nodes in the sub-network can real-time monitor the soil solution concentrations of greenhouse and send data to the coordinator after carrying out data cleaning. The coordinator will send real-time data to a PC monitoring machine and the Cloud. Using PC monitoring machine staff can monitor greenhouse crop conditions. And by utilizing mobile devices access to the Cloud, customers can also monitor soil solution concentration. The experimental results show that the system is stable, real-time and accurate

Nutrientes na seiva de plantas cítricas fertirrigadas

A análise de nutrientes na seiva vem destacando-se como ferramenta sensível no estudo do estado nutricional de plantas perenes, sendo útil também na avaliação da disponibilidade de nutrientes no solo para as plantas. Este experimento foi conduzido com o objetivo de avaliar a concentração de nutrientes na seiva de duas variedades de laranja, quando fornecidas cinco doses de N, P2O5 e K2O via fertirrigação. A seiva foi extraída mensalmente do ramo da brotação nova com éter etílico, durante duas safras consecutivas. Para compreender a dinâmica dos nutrientes na seiva, também foram feitas, simultaneamente, análises de folha e de solução do solo. Os valores de pH na seiva mantiveram-se constantes, em torno de 5,5, independentemente dos tratamentos. A análise da seiva mostrou-se sensível às variações da adubação, pois as concentrações de N e K na seiva aumentaram conforme as doses de nutrientes aplicadas e correlacionaram-se de forma positiva com os valores desses nutrientes na folha e na solução do solo. Alta concentração de K foi observada na seiva, em torno de 4,0 g L-1, sendo esta maior que todos os outros nutrientes analisados. Observou-se diferença significativa no teor de N-NO3 entre as duas variedades de copa estudadas: a variedade de copa Hamlin, de ciclo precoce, apresentou concentração na seiva cerca de 20% superior à variedade Valência, que é de ciclo tardio. Os resultados sugerem que a análise da seiva pode ser empregada como ferramenta auxiliar na avaliação do estado nutricional de plantas cítricas.

UJI EFEKTIVITAS PUPUK PETROKALIMAS TERHADAP PRODUKSI KENTANG DI KLEDUNG KABUPATEN TEMANGGUNG

Potato (Solanum tuberosum L.) is one of the important vegetable crops in Indonesia. Potato production has grown rapidly over the past decade, and now Indonesia has become the largest potato producing country in Southeast Asia. This commodity is a commodity to be developed given the potential prospective market absorption continues to increase. According to data from the 2009 level of consumption of vegetables magnitude 37.94 kg / capita / year. The use of artificial fertilizers to increase crop yields but reduce the negative impacts of soil fertility. To overcome this needed technology that could save the use of agrochemicals to maintain soil fertility, improve product quality, and increase farmers' income. Fertilizing is an effort to maintain and preserve the balance of nutrients in soil solution through the input of nutrients from fertilizers, to support the potato crop production optimization. Effectiveness and efficiency of fertilization was influenced by the type of fertilizer, how, time, dose, and frequency of application. The purpose of the assessment to determine the effectiveness of fertilizer dosage Petrokalimas on growth and yield potato. So the expected output is data and information level of effectiveness Kalimas fertilizer on potatoes, which can ultimately balanced fertilization technology available information on the use of fertilizers Kalimas potatoes. Testing the use of fertilizer on potato Petrokalimas held in the village Kledung, Kledung District, County Waterford, which is planted in mid March 2008 and harvested in mid-June 2008. Research in the design using a randomized block design (RAK), each treatment was repeated 3 times. In this study, comparing several dosages of Petrokalimas (3 kinds of doses), the standard fertilizer, and control (fertilizer with a custom farmer). The parameters observed included agronomic data and economic analysis. The assessment indicated that availability of P2O5 and K2O on the location of the study is high, but low N availability. In potato plants, the use of fertilizers as a source of K2O Kalimas Petro results are not significantly different from that recommended the use of KCl. Increased use of fertilizer on crop Potato Petro Kalimas than 300 kg / ha up to a dose of 500 kg / ha, the value of R / C increase correlated positively with fertilizer pningkatan Kalimas Petro. Results of financial analysis on the most profitable potato crop is the use of fertilizer 200 kg / ha Urea + 500 kg / ha ZA + 300 kg / ha SP36 + 200 kg / ha ZK Petro Kalimas with the R / C ratio of 2.25

Model Estimates of Nutrient Uptake by Red Spruce Respond to Soil Temperature

A better understanding of the mechanisms that control nutrient acquisition in the context of plant and ecosystem responses to climate change is needed. Mechanistic nutrient uptake models provide a means to investigate some of the impacts of temperature change on soil nutrient supply and root uptake kinetics through the simulation of key soil and plant processes. The NST 3.0 model, in combination with literature values on plant and soil parameters from a red spruce (Picea rubens L.) site in the southern Appalachians, was used to conduct a series of model simulations focused on the combined effects of changes to the maximal rate of nutrient influx at high concentrations (Imax), root growth rate (k), concentration of nutrient occurring in the soil solution (Cli), and the ability of the soil solid phase to buffer changes to the soil solution nutrient concentration (b). Previous research has indicated that these four parameters are responsive to changes in root zone temperature. Simulated uptake of NH4 increased by a factor of up to 2.6 in response to increases in soil temperature of 1°C to 5°C. The model also projected an increase in P uptake coupled with up to an 80% reduction in solution P concentration in response to a 1°C -5°C increase over a 147-d simulation period. These hypothetical changes, if validated, have interesting implications for plant growth and competition and point to a need for additional studies to better define the impacts of soil temperature on soil nutrient supply and root uptake.

Speciation of Aluminum in Solution of an Acidic Sandy Soil Amended with Organic Composts

The effects of organic amendments (10 and 50 g/kg soil of yard waste, yard + municipal waste, GreenEdge, and synthetic humic acid) on soil chemical properties related to aluminum (Al) phytotoxicity and nutrient availability were evaluated. Compost amendment increased Mehlich 3–extractable calcium (Ca), magnesium (Mg), phosphorus (P), and potassium (K) in the soil by 3.5–260 times. No significant effect of composts on total Al in solution was observed. Organic amendments increased solution pH and decreased the activities of phytotoxic Al species to less than the critical levels, as a result of the formation of aluminate and humic acid–Al complexes. Low‐molecular‐weight organic acids were not effective in forming complexes with Al. Application of composts increased the concentrations of most nutrients in soil solution, suggesting a potential for ameliorating subsoil, but care must be taken to avoid nitrogen (N) and P leaching. Amending composts to acidic soils appears a useful strategy for diminishing Al phytotoxicity potential and improving soil fertility.

In Situ Monitoring of Soil Solution Nitrate: Proof of Concept

A lack of in situ instrumentation limits continuous monitoring of contaminants and plant nutrients in soil solution to evaluate environmental and agricultural management practices. We developed a prototype soil solution monitoring technique to measure long‐term in situ NO3−–N concentration, consisting of an in situ stainless steel (SS) porous cup, with real time concentration measurements using an ion selective electrode and an ultraviolet fiber‐optic sensor. The measurement technique does not require soil solution extraction, but is based on in situ soil solution equilibration by diffusion between the porous cup and the surrounding medium. The technique was tested on a NO3−–N solution with two different SS collection cups. Analytical solutions evaluated solute diffusion coefficients, as controlled by a variety of experimental conditions. The principles of operation were developed for diffusion in a liquid solution and a saturated sand, illustrating the potential application in a soil environment.

Deepened snow alters soil microbial nutrient limitations in arctic birch hummock tundra

Microbial activity in the long arctic cold season is low but cumulatively important. In particular, the size of the microbial biomass and soil solution nutrient pool at the end of winter may control the quantity of nutrients available to plants in the following spring. Microbial starvation and lysis as a result of increasingly severe soluble carbon (C) shortages over winter has been hypothesized as a potential mechanism for microbial nutrient release at thaw. These C shortages may be exacerbated by the warmer temperatures and increased winter precipitation that are consistently predicted for a large part of the low Arctic. In particular, warmer soil temperatures due to deeper snow may increase wintertime microbial activity and organic matter decomposition over the winter, potentially resulting in enhanced nutrient availability to plants in the following growing season. In this study, we investigated nutrient limitations to soil microbial growth and activity in late winter under ambient and experimentally deepened snow (∼0.3 and 1 m respectively) in birch hummock tundra within the Canadian low Arctic. We hypothesized that the build-up of moderately deeper snow over winter would exacerbate soluble C-limitation to microbial growth and activity and increase soluble N accumulation, and thus stimulate the growth of bacteria relative to fungi. We measured the in situ response of the soil microbial biomass and soil soluble pools in control and snow-fenced plots at the end of winter, and then incubated soils from these plots with added C, nitrogen (N) and phosphorus (P) (at 0–15 °C) to characterize nutrient limitations to microbial growth and activity. In late winter, deepened snow increased the microbial pool of N, yet decreased soil pools of dissolved organic N and C, and decreased bacterial counts. Fungal mass and hyphal lengths did not change, but remained dominant under both ambient and deepened snow. Deepened snow exacerbated the soluble C-limitation to microbial growth and reduced the P-limitation for microbial respiration. Fungal mass and hyphal length responses to nutrient addition were larger than the bacterial mass or abundance responses and fungi from under deepened snow responded more than those from under ambient snow, indicating a different potential structural and physiological response to substrate availability for these two soil microbial communities. Our results indicate that deeper snow may increase microbial nutrient pools and can alter the physiological functioning of the soil microbial community in late winter, suggesting that microbial N release and its availability to plants during spring thaw may be enhanced.

Doses de N e K no tomateiro sob estresse salino: II. Crescimento e partição de matéria seca

A presença de certos nutrientes na solução do solo pode estimular o crescimento de plantas quando cultivadas sob estresse salino. Desenvolveu-se um estudo para avaliar a resposta do tomateiro, híbrido Facundo, a diferentes doses de N e K, sob irrigação com água salina. O trabalho foi desenvolvido em um ambiente protegido e os tratamentos se compunham da combinação de três doses de N (7,5; 15,0 e 22,5 g por planta) e três doses de K (8, 16 e 24 gK2O por planta) aplicados via fertirrigação por gotejamento, no esquema fatorial 3 x 3, com cinco repetições sendo que, à água de irrigação, também foram adicionados os sais cloreto de sódio e cloreto de cálcio para obtenção de condutividade elétrica da água de 9,5 dS m-1. A altura, o diâmetro da haste, a área foliar e o número de dias para o florescimento, não foram afetados pelas doses de N e K, havendo efeito das doses de K para matéria seca de haste+cachos e matéria seca total dentro das doses mais baixas de N. Concluiu-se que a aplicação de doses elevadas de N e K não contribuiu para o aumento da tolerância do tomateiro à salinidade.

Relationships among forest age, composition and elemental dynamics of Adirondack northern hardwood forests1

We conducted a biogeochemical analysis of four Adirondack northern hardwood forests (two old-growth and two maturing second-growth) to elucidate correlations among stand age, site conditions and several nutrient cycling processes. One each of the old-growth and maturing forests were located on base-rich sites, while the other two were on base-poor sites. At each site we analyzed soil solution chemistry and estimated nutrient flux rates; measured annual litter production, and nutrient and lignin content; measured annual N mineralization and nitrification rates; and characterized herb- and canopy-layer vegetation, and coarse woody debris volumes. Vascular plant communities of the two base-rich sites were dominated by several rich-site indicator species, while such indicators were lacking at the base-poor sites. Tree basal areas and annual litter production did not differ among the study sites, but the old-growth stands contained 3-fold more coarse woody debris than the maturing stands. Foliar litter N concentrations did not differ among the study sites, but foliar litter from the base-rich sites had higher Ca2 and lower lignin concentrations than the base-poor sites. Differences in foliar litter quality among the sites were due, in part, to intraspecific variation in litter chemistry. There were no consistent differences between the old-growth and maturing stands in soil solution nutrient concentrations or fluxes. Soil solution H concentrations were higher and Ca:Al ratios lower at the two base-poor sites. Annual, net N mineralization rates did not differ among the sites, but net nitrification rates in the organic soil horizons at the rich old-growth site were more than twice those at the other sites. High levels of net nitrification and N leaching were observed only in the base-rich old-growth site. Our data suggest that net forest nutrient retention may be a function of interacting mechanisms associated with forest developmental stage, community composition and site conditions.