Food production requires application of fertilizers containing phosphorus, nitrogen and potassium on agricultural fields in order to sustain crop yields. However modern agriculture is dependent on phosphorus derived from phosphate rock, which is a non-renewable resource and current global reserves may be depleted in 50–100 years. While phosphorus demand is projected to increase, the expected global peak in phosphorus production is predicted to occur around 2030. The exact timing of peak phosphorus production might be disputed, however it is widely acknowledged within the fertilizer industry that the quality of remaining phosphate rock is decreasing and production costs are increasing. Yet future access to phosphorus receives little or no international attention. This paper puts forward the case for including long-term phosphorus scarcity on the priority agenda for global food security. Opportunities for recovering phosphorus and reducing demand are also addressed together with institutional challenges.

/pdf/the-story-of-phosphorus-global-food-security-and-food-for-189ky5hvd6.pdf

The story of phosphorus: Global food security and food for thought

Our understanding of plant mineral nutrition comes largely from studies of herbaceous crops that evolved from ruderal species characteristic of nutri­ ent-rich disturbed sites (52). With the development of agriculture, these ancestral species were bred for greater productivity and reproductive output at high nutrient levels where there was little selective advantage in efficient nutrient use. This paper briefly reviews the nature of crop responses to nutrient stress and compares these responses to those of species that have evolved under more natural conditions, particularly in low-nutrient envi­ ronments. I draw primarily upon nutritional studies of nitrogen and phos­ phorus because these elements most commonly limit plant growth and because their role in controlling plant growth and metabolism is most clearly understood (51). Other more specific aspects of nutritional plant ecology not discussed here include ammonium/nitrate nutrition (79), cal­ cicole/calcifuge nutrition (51,88), heavy metal tolerance (4), and serpentine ecology (133).

The Mineral Nutrition of Wild Plants

The nitrogen content of a plant is only one of the many plant characteristics that are vitally important to herbivores. However, because of its central role in all metabolic processes as well as in cellular structure and genetic coding, nitrogen is a critical element in the growth of all organisms. Supplementary N often elicits enhanced health, growth, reproduction, and survival in many organisms. This suggests that N is a limiting factor. Since N makes up a large portion of the earth's atmosphere (about 78%), the problem is not an absolute but a relative shortage-that is, a scarcity of usable or metaboliza­ ble N during critical growth periods (159, 328). Plants encounter shortages of inorganic nitrogen (nitrate and/or ammonium ions); animals experience shortages of organic nitrogen (specific proteins and/or amino acids). This article reviews and examines the evidence (a) that N is scarce and perhaps a limiting nutrient for many herbivores, and (b) that in response to this selection pressure, many herbivores have evolved specific behavioral, morphological, physiological, and other adaptations to cope with and uti­ lize the ambient N levels of their normal haunts. McNeill & Southwood (201) and White (328) have also reviewed these general questions. There­ fore, this review explores additional evidence and further develops the fundamental arguments. The review is organized into three major divisions. The first focuses on important sources of variation in plant N (seasonal and ontogenetic trends, different tissues and species, etc) because such variation may be the basis

Herbivory in relation to plant nitrogen content

Since the 1900s, the link between soil biotic activity, soil organic matter (SOM) decomposition and stabilization, and soil aggregate dynamics has been recognized and intensively been studied. By 1950, many studies had, mostly qualitatively, investigated the influence of the five major factors (i.e. soil fauna, microorganisms, roots, inorganics and physical processes) on this link. After 1950, four theoretical mile-stones related to this subject were realized. The first one was when Emerson [Nature 183 (1959) 538] proposed a model of a soil crumb consisting of domains of oriented clay and quartz particles. Next, Edwards and Bremner [J. Soil Sci. 18 (1967) 64] formulated a theory in which the solid-phase reaction between clay minerals, polyvalent cations and SOM is the main process leading to microaggregate formation. Based on this concept, Tisdall and Oades [J. Soil Sci. 62 (1982) 141] coined the aggregate hierarchy concept describing a spatial scale dependence of mechanisms involved in micro- and macroaggregate formation. Oades [Plant Soil 76 (1984) 319] suggested a small, but very important, modification to the aggregate hierarchy concept by theorizing the formation of microaggregates within macroaggregates. Recent research on aggregate formation and SOM stabilization extensively corroborate this modification and use it as the base for furthering the understanding of SOM dynamics. The major outcomes of adopting this modification are: (1) microaggregates, rather than macroaggregates protect SOM in the long term; and (2) macroaggregate turnover is a crucial process influencing the stabilization of SOM. Reviewing the progress made over the last 50 years in this area of research reveals that still very few studies are quantitative and/or consider interactive effects between the five factors. The quantification of these relationships is clearly needed to improve our ability to predict changes in soil ecosystems due to management and global change. This quantification can greatly benefit from viewing aggregates as dynamic rather than static entities and relating aggregate measurements with 2D and 3D quantitative spatial information.

A history of research on the link between (micro)aggregates, soil biota, and soil organic matter dynamics

The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

/pdf/the-environmental-protection-agency-3gx4opzrjm.pdf

The Environmental Protection Agency

Effects of experimental acidification and liming on soil organisms and decomposition in a Scots pine forest

The Flow of Phosphorus in Food Production and Consumption : Linköping, Sweden, 1870-2000

Energetical significance of the annelids and arthropods in a Swedish grassland soil

Series of pots containing Scots pine seedlings and a humus-sand mixture were watered twice weekly for 398 d with different nutrient solutions (control treatment with complete plant nutrient solution less nitrogen; glucose addition; nitrogen addition; glucose and nitrogen addition). Analyses were made of organic and nitrogen contents in the substrate, plant weights and nitrogen contents, nitrogen fixation and respiration rates, abundance, biomass and in some cases species composition of different soil organism populations. The growth rate of pine seedlings was lowest in series supplied with glucose, which is most easily explained by a deficiency of nitrogen due to microbial immobilization. The fungi and yeast were stimulated by addition of an easily available carbon source whereas the bacteria needed both nitrogen and carbon to maintain high biomass. A positive correlation between fungal feeding soil organisms and amount of fungal mycelium was found while a more complex situation prevailed with regard to bacterial numbers and bacterial feeding nematodes. The systems are evaluated in relation to the different treatments and compared with the field situation. (Less)

Effect of nitrogen and carbon supply on the development of soil organism populations and pine seedlings - microcosm experiment

The aim of this study was to quantify the diffuse emissionsduring use of metal containing goods in the capital of Sweden,Stockholm. The following metals were studied: Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), Mercury (Hg), Nickel (Ni) and Zinc (Zn).A major part of the metals are found in a protected environmentwhere degrading processes like corrosion are most limited. However, during the lifetime of some goods the metal release to the environment is significant. The quantitatively most dominant emissions were found for Cu and Zn. The tap water system and roofs/fronts (Cu) represent goods with large exposedareas but with relatively small release rates per unit. In contrast, brake linings, aerial lines and electrical grounding (Cu) and tyres, brake linings and chemicals (Zn) are allgoods with high release rates but mostly limited exposed stocks.High yearly emissions are also found for Pb, ammunition andsinkers dominate the calculated emissions totally. For Cr and Ni, stainless steel represent the major part of the stocks, butcorrosion was estimated to give only a minor contribution to the emissions. Potential emission sources, i.e. stabilisers,pigments and plated goods dominate the exposed Cd stock. Theseemissions were not quantified due to lack of data. Hg is currently phased out, but one major source of emission, i.e. the use of amalgam, will be continuously significant for several decades. The importance of the traffic sector is obvious. The emissionsfrom brake linings (Cu, Zn and Pb), tyres (Zn, Pb, Cr and Ni)and asphalt wear (Cu, Zn, Cr, Ni and Pb) are all of large importance for the total emission from respectively metal.

https://www.miljobarometern.stockholm.se/content/docs/mg/sorme2001b.pdf

Ulrik Lohm

Papers

Effects of experimental acidification and liming on soil organisms and decomposition in a Scots pine forest

The Flow of Phosphorus in Food Production and Consumption : Linköping, Sweden, 1870-2000

Energetical significance of the annelids and arthropods in a Swedish grassland soil

Effect of nitrogen and carbon supply on the development of soil organism populations and pine seedlings - microcosm experiment

GOODS IN THE ANTHROPOSPHERE AS A METAL EMISSION SOURCE A Case Study of Stockholm, Sweden