Drivers of spatio-temporal changes in paddy soil pH in Jiangxi Province, China from 1980 to 2010.

The spatio-temporal distribution soil pH is critical for understanding the productivity and long-term sustainability of our agri-ecosystem. This study quantified the spatio-temporal distribution of paddy soil pH in Jiangxi province, China, and the potential driver of the change between 1980 and 2010. Data from the Soil Survey Information of Jiangxi province (1980s) and Jiangxi Soil Testing and Fertilizer Recommendation study (2010s) were collected and categorized into six pH ranges from strongly-acidic to strongly-alkaline with unit pH differences. Changes were calculated from the maps developed using the Pedological Knowledge base for 1980s data (without geolocation) and geostatistical methods for the 2010s data (geolocated). An overall 0.6-unit decrease and a major shift of soil pH from weakly-acidic (54% → 18%) to acidic (35% → 74%) was observed over the province in a scattered fashion with concentration in the central part and the Poyang Lake area. About half of the area under paddy cultivation went through acidification by at least one pH unit and 7% by at least 2 pH units, while 40% of the area remained unchanged. Excessive fertilizer application and acid-rain intensity contributed to the acidification. Thus, a more knowledge-based and comprehensive fertilizer management should be adopted to make paddy production sustainable in the province.

A chronology of human understanding of the nitrogen cycle.

Nitrogen over the ages! It was discovered in the eighteenth century. The following century, its importance in agriculture was documented and the basic components of its cycle were elucidated. In the twentieth century, a process to provide an inexhaustible supply of reactive N (Nr; all N species except N2) for agricultural, industrial and military uses was invented. This discovery and the extensive burning of fossil fuels meant that by the beginning of the twenty-first century, anthropogenic sources of newly created Nr were two to three times that of natural terrestrial sources. This caused a fundamental change in the nitrogen cycle; for the first time, there was the potential for enough food to sustain growing populations and changing dietary patterns. However, most Nr created by humans is lost to the environment, resulting in a cascade of negative earth systems impacts-including enhanced acid rain, smog, eutrophication, greenhouse effect and stratospheric ozone depletion, with associated impacts on human and ecosystem health. The impacts continue and will be magnified, as Nr is lost to the environment at an even greater rate. Thus, the challenge for the current century is how to optimize the uses of N while minimizing the negative impacts.

Private initiatives, public support, and war practices: development of fertilisers in Russia.

The scarcity of experiments with fertilisers, the poor domestic industry, and high prices for imported products made Russia lag far behind the leading agrarian countries in the research and use of fertilisers. The first experiments on fertilisers were connected mostly with the private estates of Russian nobility. Things began to change slowly by the turn of the twentieth century, when the Ministry of Agriculture launched a policy of agricultural science promotion, including the development of agricultural chemistry. It was the outbreak of World War I that created a powerful stimulus for fertiliser research in Russia. A specific Russian "symbiosis" emerged between military industry and agricultural chemistry. The numerous factories of explosives set up ad hoc produced vast amounts of waste products; modified, they could serve as fertilisers. In 1915, the Public Committee for Support of Fertilisers was organised. Eventually, this committee gave birth to the Institute of Fertilisers, the first institute founded by the Bolshevik government. Thus, the project of "chemicalisation of agriculture," usually described as a revolutionary endeavour, was firmly rooted in World War I.

Norman Borlaug: the man I worked with and knew.

Much has been written about Norman Borlaug the agricultural scientist and humanitarian whose achievements are recognized with many accolades; to add to those writings is a difficult task. This brief paper is an attempt to provide a personal perspective on Norman Borlaug that can come only from someone who has worked closely with him throughout his professional life. I have endeavored to recollect my early impressions of working with Borlaug as a wheat breeder in Mexico and to highlight his innovative approach to wheat breeding, as well as his views on global population and food security, fertilizers, organic agriculture, biotechnology, and conventional academia. His work ethic was instrumental in his vision for the international agricultural system as an instrument of change in the world. His spirit serves as a reminder to future agricultural scientists that the battle must be vigorously engaged and can be won.

Living lawns, dying waters: The suburban boom, nitrogenous fertilizers, and the nonpoint source pollution dilemma.

The March 1963 issue of Consumer Bulletin included a four-page article titled "How to grow a better lawn", the lead paragraph of which assured readers that "one does not have to be an expert or spend large sums of money to have a good lawn. It is necessary, however, to follow certain established practices in the construction and maintenance of any lawn." These two assertions may have struck readers, as I suspect they would strike lawngrowers today, as somewhat contradictory. Given the list of established practices that followed--"the construction of the lawn base, with proper grading, drainage, and preparation of the seedbed; selection of the type of grass and spreading of the seed; and maintenance, including fertilizing, mowing, and control of weeds"--it is difficult to imagine how the homeowner could have accomplished all of this without large sums of money or expertise. In fact, building lawns in the manner described by Consumer Bulletin required tremendous amounts of both. Recognizing these established practices in lawn construction and maintenance as a technological system allows us to better understand the persistence of this grassy landscape in America.

Sociopolitical crisis and the reconstruction of sustainable periurban agriculture in Abidjan, Côte d'Ivoire.

This article examines the effects of the post-2002 sociopolitical crisis in Abidjan, Côte d'Ivoire, on urban and peri-urban agriculture. Based on the case study of Abidjan, it argues for a conceptualization of sustainability that includes social as well as environmental dimensions and focuses on coping strategies of producers and merchants. In Abidjan, these strategies included internal migration within the city and its periphery, the use of organic fertilizers, and changes in market structure. The study illustrates how such strategies allowed producers to continue to supply produce to the market, despite the difficulties of war.

Guatemala's green revolution: synthetic fertilizer, public health, and economic autonomy in the Mayan highland.

Despite extensive literature both supporting and critiquing the Green Revolution, surprisingly little attention has been paid to synthetic fertilizers' health and environmental effects or indigenous farmers' perspectives. The introduction of agrochemicals in the mid-twentieth century was a watershed event for many Mayan farmers in Guatemala. While some Maya hailed synthetic fertilizers' immediate effectiveness as a relief from famines and migrant labor, other lamented the long-term deterioration of their public health, soil quality, and economic autonomy. Since the rising cost of agrochemicals compelled Maya to return to plantation labor in the 1970s, synthetic fertilizers simply shifted, rather than alleviated, Mayan dependency on the cash economy. By highlighting Mayan farmers' historical narratives and delineating the relationship between agricultural science and postwar geopolitics, the constraints on agriculturists' agency become clear. In the end, politics, more than technology or agricultural performance, influenced guatemala's shift toward the Green Revolution.

Historical changes in the concentrations of selenium in soil and wheat grain from the Broadbalk experiment over the last 160 years.

Selenium (Se) intake has decreased substantially in the UK population since 1970s. To investigate whether Se concentration in wheat grain has changed as a result of yield improvement or environmental changes, we analyzed archived wheat grain from the Broadbalk Wheat Experiment at Rothamsted, England, which has been run continuously for over 160 years. Wheat grain and soil samples were selected from plots receiving different fertilizer or manure treatments. Grain Se concentration varied from 11 to 236 ng g(-1), with a mean and median of 44 and 32 ng g(-1), respectively. Grain samples from the unfertilized control plot had significantly higher concentrations of Se than those from fertilized or manured plots; the latter received various amounts of S and also had higher grain yield. No significant trends in grain Se concentrations were detected in the fertilized or manured plots, in spite of a dramatic increase in grain yield since the introduction of modern short-straw cultivars in the mid 1960s. In the control plot, grain samples had higher Se concentrations in the periods before 1920 or after 1970 than those during 1920-1970. This temporal pattern mirrored that of SO(2) emissions and atmospheric S deposition. Soil Se concentrations showed an increasing trend in all plots over 160 years. The results show that the Se concentration of wheat grain from the Broadbalk experiment was influenced by S inputs from fertilizers and atmospheric deposition, and that improving grain yield through plant breeding has not resulted in a significant decrease in grain Se concentration in the fertilized plots.

Nitrogen use in the United States from 1961-2000 and potential future trends.

Nitrogen inputs to the US from human activity doubled between 1961 and 1997, with most of the increase in the 1960s and 1970s. The largest increase was in use of inorganic N fertilizer, but emissions of NOx from fossil-fuel combustion also increased substantially. In 1961, N fixation in agricultural systems was the largest single source of reactive N in the US. By 1997, even though N fixation had increased, fertilizer use and NOx emissions had increased more rapidly and were both larger inputs. In both 1961 and 1997, two thirds of reactive N inputs were denitrified or stored in soils and biota, while one third was exported. The largest export was in riverine flux to coastal oceans, followed by export in food and feeds, and atmospheric advection to the oceans. The consumption of meat protein is a major driver behind N use in agriculture in the US Without change in diet or agricultural practices, fertilizer use will increase over next 30 years, and fluxes to coastal oceans may increase by another 30%. However, substantial reductions are possible.

Estimated historical and current nitrogen balances for Illinois.

The Midwest has large riverine exports of nitrogen (N), with the largest flux per unit area to the Mississippi River system coming from Iowa and Illinois. We used historic and current data to estimate N inputs, outputs, and transformations for Illinois where human activity (principally agriculture and associated landscape drainage) have had a dominant impact. Presently, approximately 800,000 Mg of N is added each year as fertilizer and another 420,000 Mg is biologically fixed, primarily by soybean (Glycine max L. Merr.). These annual inputs are greater than exports in grain, which results in surplus N throughout the landscape. Rivers within the state export approximately 50% of this surplus N, mostly as nitrate, and the remainder appears to be denitrified or temporarily incorporated into the soil organic matter pool. The magnitude of N losses for 1880, 1910, 1950, and 1990 are compared. Initial cultivation of the prairies released large quantities of N (approximately 500,000 Mg N year(-1)), and resulted in riverine N transport during the late 19th century that appears to have been on the same order of magnitude as contemporary N losses. Riverine flux was estimated to have been at a minimum in about 1950, due to diminished net mineralization and low fertilizer inputs. Residual fertilizer N from corn (Zea mays L.), biological N fixed by soybean, short-circuiting of soil water through artificial drainage, and decreased cropping-system diversity appear to be the primary sources for current N export.

Use and misuse of nitrogen in agriculture: the German story.

Nitrogen (N) fertilization in agriculture has been discussed controversially in Germany for almost two centuries. The agronomist Carl Sprengel, who published his theory on the mineral nutrition of plants in 1828, advocated the use of mineral N fertilizers. Chemist Justus von Liebig, on the other hand, vehemently denied around 1850 the need for N fertilization. Although it soon became evident that Sprengel was right and Liebig was wrong, not much synthetic N fertilizer was used in German agriculture until around 1915, when the Haber-Bosch technique enabled the commercial production of NH3. The use of N fertilizers since then has grown, especially since 1950. To increase agricultural productivity, German governments have promoted, directly and indirectly, the use of N in crop and in animal production. Unfortunately, it was overlooked that N surpluses in agriculture increased rapidly; around 1980 they amounted yearly to more than 100 kg ha(-1). The extensive use of N in agriculture is causing environmental damage and is contributing substantially to the external costs of present agriculture. The main N compounds that affect the environment are N2O, NH3, and NO3. These compounds are considered to contribute one third to the external costs of agriculture. Additionally, the high rate of human intake of animal proteins and lipids has adversely affected the health of the country's population. Fundamental corrections in German farm policy appear inevitable.