Search

Recycling of crop straws has been practiced in every conventional agriculture. The increase in the yield of crop straws annually has given rise to a series of serious environmental problems for leaving them to decay or burning on the field surfaces after the harvest. In order to solve these recycling problems of resource wastes during the utilization of crop straws, an experimental study was conducted on the properties and performance of water-retaining concurrently slow-release straw-based cellulose fertilizers, further to discuss their production cost and applicability to the modern agriculture. In this study, the aqueous solution of nitric acid was used to extract the required cellulose from corn straws. A novel semi-interpenetrating polymer networks (semi-IPNs) superabsorbent resin with slow-release fertilizers (MS-CPPC) were prepared through solution polymerization based on corn straw cellulose polymer and linear polyvinyl alcohol copolymer (PVA-APP). Ammonium polyphosphate (APP) was also introduced to supply the nutrients of nitrogen and phosphorus. The design of orthogonal test has been used to optimize the fabrication parameters of the obtained products, as well as the water absorbency of MS-CPPC and the slow-release performance of nutrients in water and soil. The prepared products were also characterized using scanning electron microscopy, flourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermos-gravimetric analysis. The experimental results indicated that acrylic acid (AA) acrylamide(AAm) were grafted onto the chain of corn straw cellulose, and PVA-APP was also involved by semi-interpenetrating with them in the synthesis process of fertilizers. This finding demonstrated that the formation of semi-interpenetrating networks can greatly improve the stability of raw materials. Orthogonal experiments showed that the MS to the acrylic acid mass ratio of 1:6, the MBA to MS mass ratio of 20:1, the initiator to MS mass ratio of 5:1, the PVA-APP to MS mass ratio of 5:2.The fertilizer based on the semi-IPNs superabsorbent resin (SAR) showed excellent water absorbency with the water absorption of 443.2 g/g, while significantly reduced the leaching losses of fertilizers in comparison to traditional fertilizers. Therefore, the application of this products would provide an effective way to solve the leaching loss of fertilizers that often occurred in agricultural fields. The results from the infiltration test showed that MS-CPPC that applied in soil could enhance water absorbency during the infiltration, and effectively inhibit the formation of the soil crust during the rainfall due to the increase in the infiltration rate of soil water. The accumulated release rates of nitrogen and phosphorus in distilled water for one day and 30 days were 14.69%, 13.01% and 67.11%, 55.74%, respectively, indicating the sustained release of nutrients. The release behavior of MS-CPPC was also in good agreement with the National standard on sustained-release fertilizers (GB/T 23348-2009), confirming excellent property of slow release in soil. The slow release behavior of the products can attributed that to a porous structure of the semi-interpenetrating polymer networks, which can restrict the diffusion rate of water molecules into the hydrogel network to delayed dissolution of the encapsulated fertilizer. In the Korsmeyer-Peppas model, the release patterns of nitrogen and phosphorus in the MS-CPPC both follow Fick diffusion and polymer chain relaxation according to the n value. The superabsorbent resin with straw-based cellulose fertilizers become therefore expected to share the combined properties of water-retaining and slow-release, further to provide reducing the production costing while promoting comprehensive utilization of crop straws. [ABSTRACT FROM AUTHOR]

Recent discoveries of polyhalite (K2SO4.MgSO4.2CaSO4.2H2O) in the UK provide an alternative to conventional fertilizer sources. This work investigated the interaction of polyhalite, commercially known as POLY4, with soil using leaching columns. Different physical forms of polyhalite (powder, crushed rock and granules) were compared to potassium chloride (KCl) for the movement of potassium, calcium, magnesium and sulphur (as sulphate) through the soil profile using 19.7 L of water, equivalent to 4,500 mm rainfall. The nutrients from polyhalite were found to be available at 30 cm depth, with calcium showing signs of interacting with the soil clay particles to release cationic nutrients. Polyhalite granules showed the greatest release of sulphate, magnesium and calcium as a proportion of the additional nutrient with 127%, 71% and 102%, respectively leached. For potassium, all forms of polyhalite had greater release than KCl (powder = 58%; granules = 86%; crushed rock = 57% and KCl 16%). Nutrients from polyhalite and those mobilized from soil interactions are present in soil solution indicating availability for plant growth. [ABSTRACT FROM AUTHOR]

Soil acidification is caused by a number of factors including acidic precipitation and the deposition from the atmosphere of acidifying gases or particles, such as sulphur dioxide, ammonia and nitric acid. The most important causes of soil acidification on agricultural land, however, are the application of ammonium-based fertilizers and urea, elemental S fertilizer and the growth of legumes. Acidification causes the loss of base cations, an increase in aluminium saturation and a decline in crop yields; severe acidification can cause nonreversible clay mineral dissolution and a reduction in cation exchange capacity, accompanied by structural deterioration. Soil acidity is ameliorated by applying lime or other acid-neutralizing materials. 'Liming' also reduces N2O emissions, but this is more than offset by CO2 emissions from the lime as it neutralizes acidity. Because crop plants vary in their tolerance to acidity and plant nutrients have different optimal pH ranges, target soil pH values in the UK are set at 6.5 (5.8 in peaty soils) for cropped land and 6.0 (5.3 in peaty soils) for grassland. Agricultural lime products can be sold as ' EC Fertiliser Liming Materials' but, although vital for soil quality and agricultural production, liming tends to be strongly influenced by the economics of farming. Consequently, much less lime is being applied in the UK than required, and many arable and grassland soils are below optimum pH. [ABSTRACT FROM AUTHOR]

Upland hay meadows conforming to MG3 in the National Vegetation Classification of the UK are a rare habitat in Britain and are largely confined to upland valleys in northern England. Agricultural intensification, particularly ploughing and reseeding and a shift from hay-making to silage production over the last 50 years, has resulted in large losses of species-rich upland hay meadows. Remaining species-rich meadows have been the focus of much nature conservation effort resulting in many of the species-rich sites being protected by statutory designations or through voluntary agri-environment scheme agreements. Research and monitoring has tended to confirm that species richness is maximized by management involving spring and autumn grazing, a mid-July hay cut, no inorganic fertilizer and possibly low levels of farmyard manure. Deviations from this regime result in a loss of species richness. Restoration of semi-improved grassland to swards resembling species-rich MG3 also requires a similar regime but is also dependent on the introduction of seed of appropriate species. The role of Rhinanthus minor as a tool for manipulating meadow biodiversity during restoration management is discussed. Suggestions for future research are outlined. [ABSTRACT FROM AUTHOR]

Discusses the restoration of coastal shingle vegetation and the effects of substrate composition on the establishment of container-grown plants. Use of container-grown plants in restoring shingle beach vegetation was investigated at Sizewell, Suffolk, UK, where the vegetation had been destroyed by the construction of a power station; Six vegetation species selected to counter erosion and assist the development of a more complex and natural community; Use of container-grown plants to establish shingle vegetation.

Nitrate leaching is the process whereby the nitrate (NO 3 ) anion moves downwards in the soil profile with soil water. Nitrate leaching is commonly associated with chemical nitrogen (N) fertilizers used in agriculture. Nitrate leaching from different sources and contamination of surface and groundwater is a global phenomenon that has prompted social and political pressure to reduce nitrate leaching and contamination of water bodies. This bibliometric study analyzed global trends in nitrate leaching research. The results showed a rising interest in the last decades in this topic; given the growth tendency over the last years, it was envisaged that the importance on nitrate leaching research will continue increasing in the future. Knowledge on nitrate leaching was mostly disseminated through scientific publications (90% of total documents recovered), both as journal articles and reviews, classified in the Scopus database in the Agricultural, Biological and Environmental Sciences areas. Most publications dealt with soil nitrogen losses from agroecosystems and farmlands and the associated impact on the environment; they were published in journals with a focus on the influence of anthropogenic and soil-crop-animal systems in the environment, and on how such changes in the environment impact agroecosystems. Most documents published on nitrate leaching were indisputably from the United States, followed by China, the United Kingdom and Germany. An analysis of the main keywords showed an overall dominance of the soil nitrogen cycle, fertilizer use in agriculture and water quality aspects. The evolution of main crop species involved in nitrate leaching research showed a rising relevance of research conducted with maize, wheat and grasses from 1990 onwards. The most productive institutions in terms of number of documents dealing with nitrate leaching research, h-index and total citations, were located in the United States, China and the Netherlands. The United States Department of Agriculture stood out, followed by the Chinese Academy of Sciences and Wageningen University and Research. There were clusters of institutions with intercontinental interaction, on nitrate leaching research, between institutions from Europe, Asia and South and North America. Overall, this study has highlighted, from a bibliometric perspective, the rising concern on nitrate leaching. Progress in this field has been made particularly on the impact of the soil-plant-animal system on the environment and agroecosystems, and on fundamental and applied aspects of plant-soil interactions with an emphasis in cropping systems.- ) anion moves downwards in the soil profile with soil water. Nitrate leaching is commonly associated with chemical nitrogen (N) fertilizers used in agriculture. Nitrate leaching from different sources and contamination of surface and groundwater is a global phenomenon that has prompted social and political pressure to reduce nitrate leaching and contamination of water bodies. This bibliometric study analyzed global trends in nitrate leaching research. The results showed a rising interest in the last decades in this topic; given the growth tendency over the last years, it was envisaged that the importance on nitrate leaching research will continue increasing in the future. Knowledge on nitrate leaching was mostly disseminated through scientific publications (90% of total documents recovered), both as journal articles and reviews, classified in the Scopus database in the Agricultural, Biological and Environmental Sciences areas. Most publications dealt with soil nitrogen losses from agroecosystems and farmlands and the associated impact on the environment; they were published in journals with a focus on the influence of anthropogenic and soil-crop-animal systems in the environment, and on how such changes in the environment impact agroecosystems. Most documents published on nitrate leaching were indisputably from the United States, followed by China, the United Kingdom and Germany. An analysis of the main keywords showed an overall dominance of the soil nitrogen cycle, fertilizer use in agriculture and water quality aspects. The evolution of main crop species involved in nitrate leaching research showed a rising relevance of research conducted with maize, wheat and grasses from 1990 onwards. The most productive institutions in terms of number of documents dealing with nitrate leaching research, h-index and total citations, were located in the United States, China and the Netherlands. The United States Department of Agriculture stood out, followed by the Chinese Academy of Sciences and Wageningen University and Research. There were clusters of institutions with intercontinental interaction, on nitrate leaching research, between institutions from Europe, Asia and South and North America. Overall, this study has highlighted, from a bibliometric perspective, the rising concern on nitrate leaching. Progress in this field has been made particularly on the impact of the soil-plant-animal system on the environment and agroecosystems, and on fundamental and applied aspects of plant-soil interactions with an emphasis in cropping systems., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Limited supplies of naturally occurring phosphorus (P) resources andtheir decreasing purity, coupled with legislative pressure on water service companies to remove P from both their effluent and waste streams, has focused considerable attention on recycling P recovered fromdomestic wastewater in existing P markets. In the context of the fertiliser industry there may be a number opportunities to substitute fertilisers based on P recovered as struvtite for existing fertiliser products. An economic and environmental evaluation of such substitution opportunities suggests that providing high struvite recovery rates can be achieved in relatively simple process configurations, and recovered materials are distributed to satisfy regional demand, they may offer the most effective economic and environmental use of resources. [ABSTRACT FROM AUTHOR]

Research conducted in the MAFF Nitrate Programme has been used to formulate new and improved guidelines on the efficient use of manure nitrogen (N). In order to reduce nitrate leaching losses, manures containing large amounts of available N (i.e. slurries and poultry manures) should not be applied to free-draining soils in the period from autumn to early winter. Also, for efficient nutrient utilization manure application rates should be consistent with agronomic requirements (up to 250 kg total N ha-1 yr-1). Existing farm machinery was shown to be capable of applying manures evenly to grassland and arable stubbles, but required an accurate estimate of application rate and the careful matching of spreading widths. To provide growers with detailed guidance on the fertilizer N replacement value ofmanures the computer-based decision support system MANNER (MANure Nitrogen Evaluation Routine) has been developed. The much improved understanding of manure N losses and availability has been summarized in a series of 'Managing Livestock Manures' booklets, the MAFF Fertilizer Recommendation booklet and the Codes of Good Agricultural Practice. [ABSTRACT FROM AUTHOR]

The large input of research effort on aspects of nitrate leaching over the last two decades has produced many innovative scientific and practical results. The MAFF Nitrate Programme has enabled considerableprogress to be made in unravelling much of the complexity of the grassland nitrogen (N) cycle, and identifying gaps as essential first stages in providing improved managements for N in grassland systems. From a practical standpoint, there have been key outputs which have allowed the identification of options for policy, and which should allowgrassland farmers to increase the efficiency of N use throughout their farming system and thereby improve the sustainability of their enterprises. As well as quantifying N transformations, transfers and losses, other important outcomes have been the development of user-friendly models of N cycling (NCYCLE and variants) and an easy to use field kit to determine mineral N in pasture soils. The use of modeling toproduce fertilizer recommendations with a Decision Support System and of new approaches developed within the Programme, in particular system synthesis desk studies, and 'farmlet' investigations to determinethe consequences of modifying N flows and losses, have allowed us toproduce solutions to satisfy the dual aims of meeting environmental and economic production targets. [ABSTRACT FROM AUTHOR]

Arable crops in the UK make a large contribution to nitrate leachingby virtue of the land area they cover (>4.5 million ha). By contrasthorticultural crops occupy only a small area (< 0.2 million ha) but can leach very large amounts of nitrogen. The application of nitrogenfertilizer to arable and horticultural crops is very cost-effective,stimulating its use. MAFF's Nitrate Research Programme for arable and horticultural crops aims to reduce nitrate leaching and maintain productive farming through Best Management Practice. The Programme has led to the development and testing of methods to measure nitrate leaching, the identification of 'leaky' crops, soils and practices, and strategies to optimize the use of fertilizer nitrogen. Data have been used to construct and test models of nitrate leaching, which in turn have been used to evaluate the leakiness of potential rotations. Current best practice to minimize nitrate leaching requires measures to improve the efficiency of nitrogen use by crops, combined with measures to protect soil nitrogen from leaching during the late autumn to spring drainage period. This involves consideration of many factors: anappropriate crop variety must be chosen; a green cover must be maintained for as much of the year as is practicable; crops should be drilled early; fertilizer requirements should be calculated using a recommendation system and allowing for soil mineral nitrogen and any manures applied; fertilizers should be spread evenly with a properly calibrated spreader, perhaps using split applications; starter fertilizersand banding of fertilizers should be used where appropriate to reduce losses from vegetables; pest and disease infestation must be minimized; any irrigation must be applied carefully with scheduling. Research is now moving on to study whole farm systems and the interactions between losses of nitrogen and other pollutants to the environment with the aim of minimizing total environmental impact. [ABSTRACT FROM AUTHOR]

Emissions of N2O were measured from different agricultural systems in SE Scotland. N2O emissions increased temporarily after fertilization of arable crops, cultivation of bare soil, ploughing up of grassland and incorporation of arable and horticulturalcrop residues, but the effect was short-lived. Most of the emission occurred during the first two weeks, returning to 'background' levelsafter 30-40 days. The highest flux was from N-rich lettuce residues,1100 g N2O-N ha-1 being emitted over the first14 days after incorporation by rotary tillage. The magnitude and pattern of emissions was strongly influenced by rainfall, soil mineral N, cultivation technique and CN ratio of the residue. Comparatively large emissions were measured after incorporation of material with low CN ratios. Management practices are recommended that would increase N-use efficiency and reduce N2O emissions from agriculturalsoils. [ABSTRACT FROM AUTHOR]

The effect of increasing rates of nitrogen (N) fertilizer on the yield response of 3 or 4 consecutive winter cereal crops after ploughingout grass was investigated at six field sites on commercial farms inEngland and Wales. Amounts of N required for an economically optimumyield (> 3 kg of grain for each kg of fertilizer N applied) ranged from 0 to 265 kg ha-1 and were dependent on soil N supply, but not on crop yield. Optimum N rates were large (mean 197 kg N ha-1) at three sites: two sites where cereals followed 2-year grass leys receiving low N inputs (<200 kg N ha )), and at one site where a cut and grazed 4-year ley had received c. 315 kg N ha of fertilizer N annually. At the other three sites where 4 and 5-year grass leys had received large regular amounts of organic manures (20-30 t orm3 ha-1) plus fertilizer N (c. 300 kg ha-1 each year), optimum N rates were low (mean 93 kg N ha-1) and consistently over-estimated by the farmer by an average of107 kg N ha-1. Optimum N rates generally increased in successive years after ploughing as the N supply from the soil declined.Determination of soil C:N ratio and mineral N (NO3N + NH4N) to 90 cm depth in autumn were helpful in assessing fertilizer N need. The results suggest there is scope to improve current fertilizer recommendations for cereals after grass by removing crop yield as a determinant and including an assessment of soil mineralizable N during the growing season. [ABSTRACT FROM AUTHOR]

The effect of rate and timing of autumn/winter straw incorporation on the immobilization of spring applied N-fertilizer are studied. The immobilization of 15N-labeled fertilizer by straw was determined in pot trials with a sandy loam soil (Wick series) collected from two field experiments. In experiment 1, straw was incorporated atfour different rates in the autumn; experiment 2 had a fixed rate ofstraw (7.5 t/ha) incorporated at monthly intervals from September toMarch. Immobilization in spring was not enhanced when only stubble was incorporated in autumn. However, autumn incorporation of 7.5 t/ha straw resulted in a significant increase in the immobilization of spring-applied N, equivalent to 10 kg/ha; when 15 t/ha straw was incorporated, immobilization increased to 18 kg/ha. The enhancement of immobilization, immediately following fertilizer application, was dependent on the extent of straw decomposition prior to N application. Thus immobilization was related to cumulative thermal time (day deg. C above 0 deg. C; Tsum between the date of straw incorporation and fertilizer application). Straw which had been incorporated for Tsum > 1200 no longer caused appreciable immobilization of spring fertilizer. [ABSTRACT FROM AUTHOR]