Use Of Slow-release Fertilizers Research Articles

Effects of fertilizer management practices on yield-scaled ammonia emissions from croplands in China: A meta-analysis

China is the world’s largest emitter of gaseous ammonia (NH3), a compound carrying severe human health and ecosystem risks. Fertilizer N application is a major source of this atmospheric NH3. Although many studies have measured NH3 emissions from croplands in China, the effect of fertilizer management on yield-scaled NH3 emissions (i.e., NH3 intensity defined as NH3 emissions per unit crop yield) is not so clear. Thus, we performed a meta-analysis to quantify the effect of fertilizer management on NH3 emissions and NH3 intensity in China’s croplands. Results showed that the increases in NH3 emissions and NH3 intensity over a control were greater at high N rates (averaging 305kgNha−1) than at low and moderate N rates (average of 130 and 206kgNha−1, respectively), while crop yields stayed flat over this range. Rice had greater increases in NH3 emissions and NH3 intensity in response to inorganic N addition than other crops. The emission factor for NH3 was also higher for rice than other crops, and increased with increasing proportions of basal N and soil organic carbon and total N content. Relative to surface application, deep placement of fertilizer N significantly decreased NH3 emissions and NH3 intensity. Increasing the number of split applications of fertilizer N significantly reduced NH3 emissions and NH3 intensity. Organic manure amendments substituting for all or part of inorganic fertilizer N significantly mitigated NH3 emissions and led to a reduction in NH3 intensity but without statistical significance. The use of slow release fertilizers (SR) and urease inhibitors (UI) significantly reduced NH3 emissions and NH3 intensity, whereas application of nitrification inhibitors actually increased both. Overall, this meta-analysis demonstrates that appropriate fertilizer management practices such as reducing inorganic N rates, deep placement and split applications of fertilizer N, and using SR and UI can all reduce NH3 emissions and NH3 intensity in China’s croplands.

Nitrate and Nitrogen Oxides: Sources, Health Effects and Their Remediation.

Increased use of nitrogenous (N) fertilizers in agriculture has significantly altered the global N-cycle because they release nitrogenous gases of environmental concerns. The emission of nitrous oxide (N2O) contributes to the global greenhouse gas accumulation and the stratospheric ozone depletion. In addition, it causes nitrate leaching problem deteriorating ground water quality. The nitrate toxicity has been reported in a number of studies showing the health hazards like methemoglobinemia in infants and is a potent cause of cancer. Despite these evident negative environmental as well as health impacts, consumption of N fertilizer cannot be reduced in view of the food security for the teeming growing world population. Various agronomic and genetic modifications have been practiced to tackle this problem. Some agronomic techniques adopted include split application of N, use of slow-release fertilizers, nitrification inhibitors and encouraging the use of organic manure over chemical fertilizers. As a matter of fact, the use of chemical means to remediate nitrate from the environment is very difficult and costly. Particularly, removal of nitrate from water is difficult task because it is chemically non-reactive in dilute aqueous solutions. Hence, the use of biological means for nitrate remediation offers a promising strategy to minimize the ill effects of nitrates and nitrites. One of the important goals to reduce N-fertilizer application can be effectively achieved by choosing N-efficient genotypes. This will ensure the optimum uptake of applied N in a balanced manner and exploring the molecular mechanisms for their uptake as well as metabolism in assimilatory pathways. The objectives of this paper are to evaluate the interrelations which exist in the terrestrial ecosystems between the plant type and characteristics of nutrient uptake and analyze the global consumption and demand for fertilizer nitrogen in relation to cereal production, evaluate the various methods used to determine nitrogen use efficincy (NUE), determine NUE for the major cereals grown across large agroclimatic regions, determine the key factors that control NUE, and finally analyze various strategies available to improve the use efficiency of fertilizer nitrogen.

MORTALIDADE, CRESCIMENTO E SOLUÇÃO DO SOLO EM EUCALIPTO COM APLICAÇÃO DE FERTILIZANTE DE LIBERAÇÃO LENTA

RESUMO A fertilização é uma das maneiras para aumentar a produtividade e a utilização de fertilizantes de liberação lenta pode ser vantajosa, permitindo a assimilação dos nutrientes à medida que as plantas crescem. O objetivo deste trabalho foi avaliar o efeito da utilização de fertilizante de liberação lenta no crescimento inicial de um plantio de Eucalyptus urophylla x E.grandis, visando reduzir o número de fertilizações de cobertura. O delineamento experimental foi o de blocos ao acaso, com quatro tratamentos fornecendo as mesmas quantidades de nutrientes, porém variando o parcelamento e a fonte do fertilizante: T1-Fertilizante convencional com aplicação parcelada; T2-Fertilizante convencional com aplicação em dose única aos três meses; T3-Fertilizante de liberação lenta no plantio; e T4-Fertilizante de liberação lenta aos três meses. Foram avaliadas as seguintes características: mortalidade, altura, DAP, volume de madeira, teores foliares dos macronutrientes e de N e K na solução do solo. A mortalidade média foi de 4%, altura de 8,5 m, DAP de 7,5 cm e volume de 24 m3.ha-1, aos 18 meses de idade, não diferindo entre os tratamentos. Apenas o teor foliar de K diferiu entre os tratamentos, sendo a menor concentração com a aplicação parcelada do fertilizante. A aplicação do fertilizante de liberação lenta aos três meses proporcionou os menores teores na solução do solo. A aplicação parcelada dos nutrientes não resultou em ganho de produtividade ou benefícios nutricionais. O uso de fertilizantes de liberação lenta possibilita a redução do número de fertilizações de cobertura, sem o risco de lixiviação dos nutrientes.

English

In this paper the preparation of chitosan nanoparticles was carried out using methacrylic acid (MAA) and studied by both ultraviolet (UV)- visible transmission spectrophotometry and transmission electron microscopy (TEM). Nanoparticles with sizes as small as 17 to 25 nm were achieved. The obtained nanoparticles had a homogeneous morphology showing a quite uniform particles size distribution with a spherical shape. The solution was pH-sensitive, due to swelling and aggregation of the nanoparticles. The use of slow release fertilizer has become a new trend to save fertilizer consumption and to reduce environmental pollution. In this work, chitosan (CS) nanoparticles were obtained for the loading of NPK fertilizers. The stability of the CS-PMAA colloidal suspension was higher with the addition of nitrogen and potassium than with the addition of phosphorus, due to the higher anion charge from the calcium phosphate than the anion charges from the potassium chloride and urea. The mean diameter increase of the CS-PMAA nanoparticles in suspension with the addition of different compounds was P > K > N which indicates that the elements are being aggregated and loaded on the surface of the chitosan nanoparticles. Key words: Nanoparticles formation, chitosan, fertilizers, nanosolution.

Fertilizaçao de liberação lenta no crescimento de mudas de paricá em viveiro

The use of slow release fertilizer (SRF) can contribute to obtain better seedlings before an industry accustomed to the use of commercial fertilizers. This work aimed to evaluate doses of SRF on the growth of parica tree seedlings and to compare the cost of conventional fertilizer use in relation to the cost involved in producing with SRF. The experimental design was completely randomized with 6 treatments and 4 replications of 40 plants, with one control and the other treatments with the addition of different doses of SRF per m³ of substrate used for seedlings production . After 81 days of sowing, it was analyzed total height, stem diameter, shoot fresh and dry weights, root dry weight, total biomass and maximum level of technical efficiency. Parica tree seedlings responded positively to the use of SRF, presenting best results in parameters at doses ranging from 8.65 to 12.07 kg m -3 compared to control without SRF. Acquisition costs were higher when compared to conventional fertilization, requiring an economical and forestry analysis to infer on the feasibility of its use in the production and establishment of stands.

Alternativas para adubação de porta-enxertos de abacateiro 'quintal' e seu efeito no pegamento de enxertia

O abacate é uma fruta de alta expressividade no cenário frutícola brasileiro. Dos fatores limitantes na expansão racional dessa frutífera, destaca-se a dificuldade de obtenção de mudas de alta qualidade. O objetivo deste trabalho foi avaliar a obtenção de porta-enxertos de abacateiro 'Quintal', em condições de telado, com o uso de fertilizante de liberação lenta e solução nutritiva, com diferentes doses de N, P e K. O experimento foi instalado e conduzido no Setor de Fruticultura do Departamento de Agricultura da Universidade Federal de Lavras-MG, de maio a outubro de 2009. O delineamento utilizado foi em blocos casualizados, em esquema fatorial 2X4 (duas fontes de fertilizantes e quatro doses) com um tratamento adicional (controle), com quatro repetições, sendo a parcela experimental composta de dez plantas. Os tratamentos consistiram em quatro doses de fertilizante de liberação lenta 15-10-10 (N-P2O5-K2O), nas dosagens 4; 8; 16 e 24 kg m-3 de solo usado como substrato e quatro doses de solução nutritiva, sendo o NPK aplicado numa mistura de ureia, nitrato de potássio e monoamônio fosfato, na mesma proporção do outro fertilizante. As plantas foram enxertadas, utilizando-se como copa da cultivar Fortuna. As características do porta-enxerto avaliadas foram: altura (cm), diâmetro (mm), matéria seca das folhas, raízes e caule (g), teor de N, P e K nas folhas (mg kg-1) e porcentagem de pegamento da enxertia (%). Houve interação significativa entre os fatores para a altura, diâmetro, matéria seca das folhas, raízes, caule e porcentagem de pegamento da enxertia. O uso de fertilizante de liberação lenta propiciou maior crescimento e desenvolvimento dos porta-enxertos de abacateiro cultivar Quintal comparado à solução nutritiva. Doses acima de 4 kg m-3 de fertilizante de liberação lenta e solução nutritiva não produziram efeito positivo na formação de porta-enxertos de abacateiro 'Quintal'.

Ammonium nitrate-impregnated woodchips: a slow-release nitrogen fertilizer for plants

Different types of fertilizers are widely used throughout the world for successful crop production. Chemical fertilizers have some adverse effects on the environment if used indiscriminately and are a major source of soil and water pollution. To minimize environmental pollution, use of slow-release fertilizer (SRF) in agricultural practices is an important and effective method. Different materials have been used so far to formulate SRF, but SRF from wood is a unique technique which reflects a new dimension of wood use. In this aspect, present study was designed to develop a slow-release nitrogen fertilizer using three kinds of woodchips: Japanese red pine (Pinus densiflora S. et Z.), eunsasi poplar (Populus tomentiglandulosa T. Lee), and konara oak (Quercus serrata Thunb.). Fertilizers were prepared from woodchips after full-cell treated with a saturated solution (2140 g/l at 25°C) of ammonium nitrate (NH4NO3). The morphology of woodchip fertilizer was investigated by using a field-emission electron microscope (FE-SEM) equipped with an energy-dispersive X-ray (EDX) spectrometer to locate NH4NO3 in woodchips. Deposition of nitrogen in the cell lumen was verified by FE-SEM. Deposition inside the cell wall was confirmed by EDX mapping. This study also evaluated the release pattern of nitrogen from impregnated woodchips in distilled water for 768 h and found that nitrogen was released from poplar, pine, and oak in a slow-release pattern. The encapsulated nutrient in the void volume of wood facilitated the slow release. The above findings confirm that woodchip fertilizers can be used as a slow-release nitrogen source for plants.

Use of zeolite in maize (Zea mays) cultivation on nitrogen, potassium and phosphorus uptake and use efficiency.

Concerns about unbalanced use of fertilizers leading to environmental pollution have been globally expressed. As a result, studies on how to use efficient methods to reduce nutrient applications at the same time increasing or maintaining crop yield, reducing nutrient losses and improving nutrient use efficiency are imperative. Nutrient loss due to leaching, volatilization and fixation upon fertilizer application to soils may be reduced through the use of slow-release fertilizers. A pot study was conducted to investigate if the use of inorganic fertilizers together with zeolite will improve nitrogen (N), phosphorus (P) and potassium (K) uptake and efficiency in maize (Zea mays) cultivation on Nyalau series (Typic Paleudalts). Maize hybrid no. 5 variety was used as test crop. Treatments evaluated were: (i) Unfertilized condition (T1), (ii) normal N, P and K application (7.4 g urea + 11.3 g Christmas Island rock phosphate (CIRP) + 3.8 g muriate of potash (MOP)) (T2), (iii) 135 g zeolite + 5.92 g urea+9.0 g CIRP + 3.0 g MOP (T3), (iv) 270 g zeolite + 4.44 g urea + 6.8 g CIRP + 2.3 g MOP (T4), (v) 405 g zeolite+3.0 g urea+4.5 g CIRP+1.5 g MOP (T5) and (vi) 540 g zeolite + 1.5 g urea + 2.3 g CIRP + 0.8 g MOP (T6). The effect of T2, T3, T4, T5 and T6 on soil N, P and Mg at harvest was not significantly different compared with T1. However, treatments with zeolite significantly increased K and Ca contents of soil compared to T1. Irrespective of treatment, dry matter production was not different. However, nutrient concentrations determined in plant tissues were clearly affected by the addition of zeolite. N, P and K uptake varied significantly but T6 significantly affected N, P and K use efficiency. The use of inorganic fertilizers mixed with zeolite remarkably increased N, P and K uptake, and their use efficiency in leaves, stem and roots. The use of zeolite could be beneficial with respect to nutrient retention in soil and their use efficiency.

A preliminary study of the incorparation of NPK fertilizer into chitosan nanoparticles

The use of slow release fertilizer has become a new trend to save fertilizer consumption and to minimize envi- ronmental pollution. Due to its polymeric cationic, biodegradable, bioabsorbable, and bactericidal characteristics, chitosan (CS) nanoparticle is an interesting material for use in controlled release systems. However, there are no attempts to explore the potential of chitosan nanoparticles as controlled release for NPK fertilizers. In this work chitosan nanoparticles were obtained by polymerizing methacrylic acid for the incorporation of NPK fertilizers. The interaction and stability of chitosan nanoparticle suspensions containing nitrogen (N), phosphorus (P) and potassium (K) were evaluated by FTIR spectroscopy, particle size analysis and zeta-potential. The FTIR results indicated the existence of electrostatic interactions between chi- tosan nanoparticles and the elements N, P and K. The stability of the CS-PMAA colloidal suspension was higher with the addition of nitrogen and potassium than with the addition of phosphorus, due to the higher anion charge from the calcium phosphate than the anion charges from the potassium chloride and urea. The mean diameter increase of the CS-PMAA nanoparticles in suspension with the addition of different compounds indicated that the elements are being aggregated on the surface of the chitosan nanoparticles.

Release Mechanisms for Slow- and Controlled-release Fertilizers and Strategies for Their Use in Vegetable Production

Fertilizer material costs, particularly nitrogen (N), have increased substantially over the past 5 years. Increased costs, along with increased awareness of the impact of fertilizer leaching on the environment in humid regions, have increased interest in use of slow-release fertilizer (SRF) or controlled-release fertilizer (CRF) materials. The goals of SRF and CRF use are that no nutrient should be limiting for crop uptake, there should be improved nutrient uptake efficiency, and nutrient-leaching potential should be reduced. These considerations are particularly important for crops grown on sandy soils with relatively low nutrient and water holding capacities. Release rates of biodegradable, or slow-release materials, such urea formaldehyde, isobutylidene diurea, and methylene urea are proportional to soil microbial activity and are therefore soil temperature dependent. These materials are N sources and depend on soil biological activity, thus, soil temperature during specific crop growth phenology must be considered and release may be delayed by soil fumigation. Whereas CRFs depend on diffusion through coatings and not biodegradation, both are soil moisture and temperature dependent. Examples of coated materials are sulfur-coated urea, polymer-coated urea, and polymer/sulfur-coated urea. The advantage of these materials is that leachable fertilizer elements other than N can be incorporated within the coating. However, this comes at an increased cost. The use of any single or combination of these materials depends on time of year, the length of crop cycle and crop nutrient demand patterns, and the use of soil fumigants.

Release Mechanisms for Slow- and Controlled-release Fertilizers and Strategies for Their Use in Vegetable Production

Fertilizer material costs, particularly nitrogen (N), have increased substantially over the past 5 years. Increased costs, along with increased awareness of the impact of fertilizer leaching on the environment in humid regions, have increased interest in use of slow-release fertilizer (SRF) or controlled-release fertilizer (CRF) materials. The goals of SRF and CRF use are that no nutrient should be limiting for crop uptake, there should be improved nutrient uptake efficiency, and nutrient-leaching potential should be reduced. These considerations are particularly important for crops grown on sandy soils with relatively low nutrient and water holding capacities. Release rates of biodegradable, or slow-release materials, such urea formaldehyde, isobutylidene diurea, and methylene urea are proportional to soil microbial activity and are therefore soil temperature dependent. These materials are N sources and depend on soil biological activity, thus, soil temperature during specific crop growth phenology must be considered and release may be delayed by soil fumigation. Whereas CRFs depend on diffusion through coatings and not biodegradation, both are soil moisture and temperature dependent. Examples of coated materials are sulfur-coated urea, polymer-coated urea, and polymer/sulfur-coated urea. The advantage of these materials is that leachable fertilizer elements other than N can be incorporated within the coating. However, this comes at an increased cost. The use of any single or combination of these materials depends on time of year, the length of crop cycle and crop nutrient demand patterns, and the use of soil fumigants.

NITRATE CONTENT OF GREENHOUSE TOMATOES

Nitrate accumulation in plants is subject of concern for human health. Tomatoes are usually low in nitrate content. However, the effects of nutrition are straightforward on nitrate accumulation, especially when crops are grown in soilless systems. Because the mineral composition of tomatoes depends on the amount and type of nutrients taken from the growth medium it is necessary to adopt appropriate nutrient management practices (use of slow-release fertilizers, split applications, combining of radicular and foliar fertilization) which help to supply nutrients in quantities adequate to just meet crop demand and minimize losses, thus increasing the nutrient use efficiency. The study was carried out to determine the effects of fertilization and system of culture on nitrate content of greenhouse tomatoes fruit and had three experimental factors: 1. system of culture: soil and organic substrate (made from 80% peat and 20% long duration follow soil + well decomposed manure); 2. basic soil fertilization with two treatments (simple doze and double doze); 3. additional fertilization consisted of radicular and radicular + foliar treatments. Cronos F1 was used as biological material. The quantity of absorbed nitrogen and the way in which it is utilized in plant metabolism, mainly with respect to the nitrate accumulation in fruit, influence vegetables quality. However, both these factors are better managed in hydroponics, since in the small volume of rooting medium the nutrient supply is more efficiently controlled through the composition of the nutrient solution. In this experiment the recorded values of nitrates content of fruit were situated under normal accepted limits and varied between 49.87 mg/kg and 83.44 mg/kg, even if they were a little bigger in case of organic substrate culture than in soil culture. Potassium has major roles in production of proteins, thereby decreasing nitrate within the plant. Ruiz (2002), in case of cucumber, reported a positive effect of higher K fertilisation on uptake, translocation and reduction of nitrate in fruit compared with the lowest K rate. In this experiment nitrate ratios in the fruit decreased in case of variants with double doze basic fertilization (Multicote IV 12:0:43) and foliar fertilization (Ferticare 10:5:26) as response to high K rate of used fertilizers. Vitamin C is a health-promoting factor with antioxidant properties. It has been reported that the vitamin C content in the fruit is influenced by K supply. Vitamin C is very efficient at preventing the conversion of nitrate to nitrite in plant tissue and within the human body (Hill, 1991). High vitamin C contents were recorded in case of organic substrate culture (19.42–24.28 mg/100 g fresh matter) and vitamin C content increased in case of foliar fertilization both for soil culture and for organic substrate culture.

Options for reducing the negative effects of nitrogen in agriculture

After addition to farms by fertilizer, crop residues, biological fixation and animal excreta, nitrogen can be lost through gaseous emission, runoff and leaching to contaminate the atmosphere and water bodies, and cause adverse health effects. The efficiency of fertilizer nitrogen can be increased and losses reduced, by matching supply with crop demand, optimizing split application schemes, changing the form to suit the conditions, and use of slow-release fertilizers and inhibitors. In addition, agronomic practices such as higher plant densities, weed and pest control and balanced fertilization with other nutrients can also increase efficiency of nitrogen use. Efficiency of use by animals can be increased by diet manipulation. Feeding dairy cattle low degradable protein and high starch diets, and grazing sheep and cattle on grasses high in water soluble carbohydrate result in less nitrogen excretion in urine and reduced ammonia volatilization.

Use of slow-release fertilizer and biopolymers for stimulating hydrocarbon biodegradation in oil-contaminated beach sediments

Nutrient concentration and hydrocarbon bioavailability are key factors affecting biodegradation rates of oil in contaminated beach sediments. The effect of a slow-release fertilizer, Osmocote, as well as two biopolymers, chitin and chitosan, on the bioremediation of oil-spiked beach sediments was investigated using an open irrigation system over a 56-day period under laboratory conditions. Osmocote was effective in sustaining a high level of nutrients in leached sediments, as well as elevated levels of microbial activity and rates of hydrocarbon biodegradation. Chitin was more biodegradable than chitosan and gradually released nitrogen into the sediment. The addition of chitin or chitosan to the Osmocote amended sediments enhanced biodegradation rates of the alkanes relative to the presence of Osmocote alone, where chitosan was more effective than chitin due to its greater oil sorption capacity. Furthermore, chitosan significantly enhanced the biodegradation rates of all target polycyclic aromatic hydrocarbons.

Soil N and salinity leaching after the autumn irrigation and its impact on groundwater in Hetao Irrigation District, China

Soil water and salinity are crucial factors influencing crop production in arid regions. An autumn irrigation system employing the application of a large volume of water (2200–2600 m 3 ha −1) is being developed in the Hetao Irrigation District of China, since the 1980s with the goal to reduce salinity levels in the root zone and increase the water availability for the following spring crops. However, the autumn irrigation can cause significant quantities of NO 3 − to leach from the plant root zone into the groundwater. In this study, we investigated the changes in soil water content, NO 3–N and salinity within a 150 cm deep soil profile in four different types of farmlands: spring wheat (F W), maize (F M), spring wheat–maize inter-planting (F W–M) and sunflower (F S). Our results showed that (1) salt losses mainly occurred in the upper 60 cm of the soil and in the upper 40 cm for NO 3–N; (2) the highest losses of salt and NO 3–N could be observed in F W, whereas the lowest losses were found in F W–M. NO 3–N concentration, pH and electrical conductivity (EC) in the groundwater were also monitored before and after the autumn irrigation. We found that the autumn irrigation caused the groundwater concentration of NO 3–N to increase from 1.73 to 21.6 mg L −1, thereby, exceeding the standards of the World Health Organization (WHO). Our results suggest that extensive development of inter-planting tillage might be a viable measure to reduce groundwater pollution, and that the application of optimized minimum amounts of water and nitrogen to meet realistic yield goals, as well as the timely application of N fertilizers and the use of slow release fertilizers can be viable measures to minimize nitrate leaching.

Crescimento e composição mineral de mudas de eucalipto cultivadas sob condições de diferentes fontes de fertilizantes

The objective of this work was to evaluate the effects of different fertilizers on the growth and mineral composition of eucalyptus seedlings. Three species of eucalyptus (E. saligna, E. grandis and E. citriodora), nine fertilizers (differing in composition and solubility - rate of nutrient liberation: high and low liberation), and 4 replications were used in this study. The eucalyptus seedlings were cultivated into plastic tubes (50cm3) with commercial substratum, under controlled conditions of illumination and irrigation, during a period of 6 months. Results showed that the use of slow release fertilizers resulted in a larger accumulation of nutrients in the shoot part of the eucalyptus seedlings, except for phosphorus and potassium, that the high contents values were noticed for E. citriodora. For E. saligna and E. citriodora, the utilization of micro nutrients and foliar fertilization did not result in a significantly increase in dry mass production of eucalyptus seedlings

EFFECT OF FERTILIZERS ON FRUIT QUALITY OF PROCESSING TOMATOES

Fertilizer research trials were conducted in tomato fields in Central California to determine the impact of slow release fertilizer on fruit quality and yield of processing tomatoes. Quality parameters evaluated were soluble solids content, color of a blended juice sample and total yield. Tomato yield was affected by soil type, type of fertilizer and variety used. Soluble solids content was affected by the different environmental or growing conditions in which the trials were conducted. Level of soil nutrition, type of fertilizer and cultural management of the tomato crop seem to have played a significant role on fruit quality and production. Slow release nitrogen fertilizer in combination with a potassium source fertilizer had a significant effect increasing soluble solids content (°Brix) in one of the sites. Furthermore, the addition of potassium + humic acid increased soluble solids in marginal tomato fields (poor soil types with low levels of residual nutrients). Yield response was similar to °Brix increases. Small yield differences were observed in what is considered good soils (deep sandy loam-class 1 soils). Poor to marginal fields, however, responded better to both yield and soluble solids which could benefit from the use of slow release fertilizers and justify their higher price over conventional fertilizers.

NITROGEN LEACHING FROM FOREST SOIL CORES AFTER AMENDING ORGANIC RECYCLING PRODUCTS AND FERTILIZERS

Many alpine forests are severely depleted of nutrients by extensive logging and by grazing of cattle and wildlife. Fertilization may be a remedy, but nitrate leaching may pose problems for the groundwater. However, use of slow-release fertilizers may avoid this problem, whilst improving the Ca, Mg, K, and P status of these soils. Intact soil cores (11 cm diameter, 40 cm depth) from a mixed forest and a Norway spruce stand in the Northern Calcareous Alps of Austria were used in a laboratory experiment to study the effects of adding organic fertilizers and recycling products on patterns of nitrate and ammonium release. The amended (corresponding to 300 kg N ha−1) and control cores were incubated for 29 weeks at 15°C. Soil water (retrieved 5 cm below the soil surface) and leachate were analysed for nitrate and ammonium in regular intervals. After the incubation, soil microbial biomass, basal respiration and nitrogen mineralization were determined. Some of the organic fertilizers, especially those that had undergone composting processes (compost of organic waste, compost of bark+sewage sludge, compost of sawdust+sewage sludge, Biovin®) and Biosol®, caused only minor increases of nitrate and ammonium in the soil water and leachate. Others, like uncomposted sewage sludge products (Primafert® and sewage sludge+shale), resulted in elevated (up to 150 mg nitrate-N l−1) nitrate concentrations in the soil water and in the leachate. Fertilization with N-rich fertilizers (Biosol®, Primafert®, sewage sludge+shale) resulted in significant decreases in microbial biomass and basal respiration at the end of the 6-month incubation. Microbial biomass and basal respiration were not affected by the other organic fertilizers.

Nitrogen Leaching From Forest Soil Cores After Amending Organic Recycling Products and Fertilizers

Many alpine forests are severely depleted of nutrients by extensive logging and by grazing of cattle and wildlife. Fertilization may be a remedy, but nitrate leaching may pose problems for the groundwater. However, use of slow-release fertilizers may avoid this problem, whilst improving the Ca, Mg, K, and P status of these soils. Intact soil cores (11 cm diameter, 40 cm depth) from a mixed forest and a Norway spruce stand in the Northern Calcareous Alps of Austria were used in a laboratory experiment to study the effects of adding organic fertilizers and recycling products on patterns of nitrate and ammonium release. The amended (correspondmg to 300 kg N ha-1) and control cores were incubated for 29 weeks at 15°C. Soil water (retrieved 5 cm below the soil surface) and leachate were analysed for nitrate and ammonium in regular intervals. After the incubation, soil microbial biomass, basal respiration and nitrogen mineralization were determined. Some of the organic fertilizers, especially those that had undergone composting processes (compost of organic waste, compost of bark + sewage sludge, compost of sawdust + sewage sludge, Biovin®) and Biosol®, caused only minor increases of nitrate and ammonium in the soil water and leachate. Others, like uncomposted sewage sludge products (Primafert® and sewage sludge + shale), resulted in elevated (up to 150 mg nitrate-N 1 1) nitrate concentrations in the soil water and in the leachate. Fertilization with N-rich fertilizers (Biosol®, Primafert®, sewage sludge + shale) resulted in significant decreases in microbial biomass and basal respiration at the end of the 6-month incubation. Microbial biomass and basal respiration were not affected by the other organic fertilizers. © 1997 ISWA

Strategies to reduce gaseous emissions of nitrogen from irrigated agriculture

Fertilizer nitrogen (N) is not used efficiently in irrigation agriculture because much of the N applied is lost from the plant-soil system by emission of gaseous compounds to the atmosphere. Nitrogen may be emitted by ammonia volatilization, and as nitrous oxide, nitric oxide and dinitrogen during nitrification, biological denitrification and chemodenitrification. Nitrogen emitted to the atmosphere as ammonia may be returned to the biosphere and recycled thus adding to the nitrous oxide and nitric oxide burden in the atmosphere. Thus ammonia volatilization needs to be controlled as well as nitrification-denitrification to limit emission of nitrogen oxides. Many approaches have been suggested for controlling losses of fertilizer N including optimal use of fertilizer form, rate and method of application, matching N supply with demand, supplying fertilizer in the irrigation water, applying fertilizer to the plant rather than the soil, and use of slow-release fertilizers. While these techniques have the potential to increase the effectiveness of the applied N none of them have a large impact on gaseous loss of N. However, the results of recent experiments in tropical and temperate regions with flooded rice, and irrigated cotton, wheat and maize show that use of newly developed urease and nitrification inhibitors has the capacity to prevent loss of N and increase the yield of crops.