The temporal context for this analysis is a dramatic increase in the publication rate of original research articles within the journal World Development, against which several other trends stand out . First, there has been a decrease in the reliance on the term “development” to discuss the associated issues, with the per cent of articles that meet the selection criteria dropping from over 25% of the total published in 1973 to 17.0% in 1993 and 11.0% in 2013 . Second, the term has come to be used more rigorously over this period, such as is evidenced by a decrease in the occurrence of unclear and unrelated uses and an increase in the use of adjacent qualifiers . Third, this increasingly rigorous use is also increasingly specialized, with a decrease in the number of general categories referenced within each article . Fourth, a dramatic increase in the use of “development” within proper nouns and an increase in the use of qualifiers may indicate an increase in the official use of the term in related agencies and activities, and an increased formalization in the discussion of these official efforts . Finally, there has been a decrease in the use of “development” to refer to imminent processes and an increased focus on the perspectives found in the interdisciplinary discussions . This is also reflected in a decrease in the use of “developed” and “developing” to refer to societies,livestock fodder system which may have also been influenced by the criticism of Escobar and others .

Together, these trends appear to show a maturation of interdisciplinary discussions of “development” and perhaps the emergence of development studies as an integrative discipline in its own right, rather than simply a conversation among other existing disciplines. This transition from an interdisciplinary discussion to being considered a coherent discipline is not without precedent, and a recent striking example is the emergence of ecology in the twentieth century out of the confluence botany, zoology, soil science, and other natural science disciplines . This process likely requires increasing interest, coherence, and self-identity among the intellectual participants, along with some more formal recognition in the academic setting. The trends observed in this survey of World Development provide some evidence of the first requirement, and the increasing number of degrees offered in Development Studies, International Development, and related topics is This strategy of using a descriptive typology to analyse specific texts allows for such change to be monitored through the recognition of measurable patterns, an approach that compliments the more individual impressions of the participants. Recognition of these patterns might also help to intentionally direct this change, such as by offering new insights into the diverse ways in which “development” is used in practice and guidelines for how it might be most clearly used. For example, the use of adjacent qualifiers may not be as effective of a strategy in this interdisciplinary discussion as it is within the represented disciplines. This textual analysis found that each individual author was highly specific in their use of adjacent qualifiers, but that there was much less agreement among them. No author used the same qualifier of “development” in multiple specific categories, but as a group, 15 of the top 25 most common qualifiers were used in more than one of the four general categories, while nine of these were used in both immanent and intentional categories .

This suggests that while qualifiers of “development” can be useful for reducing some of the ambiguity surrounding a textual use of the term, they should be used with care in development studies, as they may also be disciplinary relics that demand their own semantic investigations. This self-reflective perspective on this emerging intellectual field may therefore be both an indication of and an influence on the development of development studies.The development of agriculture as a reliable, localized source of protein and other foodstuffs enabled civilization as we know it, including the scientific enterprise that now underpins it. Nitrogen is a crucial element of proteins and other essential biomolecules, and soil N availability is a key limiting factor for both natural and agricultural productivity in terrestrial ecosystems . Development of the Haber-Bosch process to convert atmospheric dinitrogen to ammonia in the early twentieth century gave rise to the N fertilizer industry. This synthetic N fertilizer, together with improved crop genetics and agronomy, fueled the Green Revolution that led to several-fold increases in crop productivity in many parts of the world, averting starvation for large numbers of people . Today, over 120 Tg of synthetic N fertilizer are used in agriculture each year . In 2010, total N inputs from synthetic N fertilizers, biological N fixation by leguminous crops, atmospheric deposition, and manure amounted to 174 Tg N, yet only 74 Tg N were captured in harvested products . Much of the remaining N is lost from agricultural land to the surrounding environment, where it damages sensitive ecosystems, reduces air quality, and contributes to climate change, with costs to biodiversity, fisheries, human health, and societal infrastructure .

Anthropogenic reactive-N compounds are readily assimilated by plants and other organisms, and have doubled the flux of N in the global N cycle, taking us beyond what is considered a safe operating space for humanity . The United Nations Environment Programme has identified excessive reactive N as one of five emerging threats facing the planet , such that the fourth UN Environment Assembly adopted a resolution on “Sustainable N management.” Fertilizer N is a “double-edged sword” that ensures food security for much of humanity, while having enormous negative impacts on the environment and human health . Globally, it is also the single largest source of nitrous oxide , a potent and long-lived greenhouse gas that has increased by 0.8 parts per billion per annum from 300 ppb in 1980 to 332 ppb in 2020 . Thus, in many agricultural systems too much N is used and there is a need to rein-in the amounts of N fertilizer used to reduce environmental pollution. In contrast, in regions such as the sub-Saharan Africa, limited access to N fertilizer results in poor crop yields and food insecurity , requiring increased N inputs from either biological or industrial sources. Overall, cropping systems worldwide would benefit from practices that increase agricultural N use efficiency while sustaining or building soil organic matter and soil fertility. Nitrogen use efficiency is an umbrella term to broadly compare agronomic, physiological, and environmental effects of N use in agroecosystems. At least 18 numerical permutations of NUE appear in the literature , which highlights that there is no standard definition. Three NUE terms are widely used to quantify efficiency: partial factor productivity , defined as the ratio of yield to N inputs from fertilizer, BNF, crop residues, manure, and atmospheric deposition ; N removal efficiency, defined as the ratio of harvested plant N to N inputs; and N utilization efficiency ,hydroponic nft gully defined as the ratio of yield to plant N. Other terms such as system NUE and N surplus or balance have also proved useful for assessing environmental and production outcomes. We focus on N removal efficiency as it is amongst the easiest to measure and calculate from data available from many crop species and countries. This definition of NUE allows for global comparisons, trend analysis, identification and diffusion of best practices, and provides the impetus for this article. The average NUE of cropping systems has been estimated to be only 42% globally , and further losses of N occur along the food chain before it is consumed. Boosting NUE is one of four major areas of intervention identified to reduce N losses to the environment; the other three are dietary shifts toward more plant-based foods in high-income countries, reductions in food loss and waste, and reduced bio-fuel production from human-edible foods . Here, we focus on opportunities to increase NUE by improving technologies and agricultural management strategies for high-input and low-input cropping systems. Globally, NUE for major crops averaged between 30% and 50% from 1970 to 2010 .

While NUE improved significantly in parts of Europe and the USA from 1980 to 2010 due to increases in productivity for a given N rate or coupled with decreases in N use , it decreased in many developing countries, notably China and India, from 1960 to 2014 due to increases in N fertilizer use exceeding N harvest rates . Trends of NUE in other regions with low yields and low N fertilization rates have been inconsistent, such as in many countries in sub-Saharan Africa . The NUE of cropping systems ranges from as little as 14% for fruits and vegetables, because they are relatively low-protein but high-value foods , to as high as 80% for legumes, as exemplified by soybean . Most of the N assimilated by legumes is derived from BNF by symbiotic bacteria within plant root nodules, and much of this N is transferred eventually to harvested grains rather than lost to the surrounding environment . Cereal NUE falls between these extremes, with the three primary cereals, wheat, rice, and maize, exhibiting global averages of 42%, 39%, and 46% NUE, respectively, in 2010. Because cereal production accounts for approximately half of all N fertilizer use and half of all agricultural N pollution, it represents a high priority target for NUE improvement. For individual cropping systems, NUE varies widely, and highly mechanized, broad-acre, precision agriculture generally achieves higher NUE than some small-holder farms in countries such as China and India that are over-supplied with highly-subsidized synthetic N fertilizer . Thus, there are opportunities to increase NUE in many agricultural systems by applying up-to-date best practices with appropriate support from social, economic, and environmental policies . The view of soil as principally a support medium for plants, rather than a complex bio-geochemical system driven by soil biota, dominates soil management decisions in agronomic practice globally. To a large extent, the success of the Green Revolution is based on new technologies that provide, via inputs external to the system, ecological services traditionally supplied by soil—N supply among them . The result has been an agricultural enterprise that often values soil largely as a porous media that supports plants and drains excess rainfall, ignoring its crucial role in nutrient cycle regulation. Agricultural N flows are illustrated in Figure 1, in which nitrogen inputs enter the system through synthetic fertilizer, biological nitrogen fixation, manure, or atmospheric deposition. This nitrogen, in various chemical forms, enters the soil N cycle with pools and fluxes from soil organic matter, microbes, and dissolved N molecules in soil water. This N is utilized by the plant for growth and seed production, and some amount is harvested with the agricultural product and removed from the system. Less than 50% of the N taken up by most cereal crops is derived from N inputs from that planting season, a percentage unchanged from the 1930s to 2010 . The remaining N is derived from soil organic matter, crop residues or residual inorganic N present in the system, itself the product of soil biota partially consuming plant inputs dating from last year to past millennia. Soil organic N is a significant contributor to plant nutrition, satisfying much of the plant N demand . Even high-yielding soybean can derive a significant amount of its N from the soil , particularly where high amounts of residual inorganic N limit BNF. Although soil N mineralization can provide sufficient N to support the N demands of modern cropping systems in some individual years , over the long-term, it is apparent from using simple mass balance calculations that a highly productive maize crop with an annual grain yield of 16 Mg ha−1 removes ∼184 kg N ha−1 or ∼3.68 Mg N over 20 years of cropping. The N stores of many highly productive, rainfed arable soils can be as high as 10 Mg N ha−1 . Thus, continuous cropping has the potential to remove, within 20 years, 1/3 of the N in the original soil organic N stock, demonstrating the potential for rapid soil organic matter depletion and the consequent dependence of cropping systems on external N sources in order to mitigate such risks . This is why ’zero budget natural farming’, as promoted by the Indian government and some international agencies, carries a serious risk of long-term soil nutrient mining and soil health decline .