The supplementation of nitrogen can be increased by the use of nitrogen-fixing, diazotrophic bacteria such as Azospirillum brasilense. These bacteria can act to promote plant growth in various plant species, including corn (Zea mays L.). However, there is a need to understand the behavior of these bacteria in different agricultural systems. The objective of this study was to evaluate the effect on the growth and yield of corn inoculated with A. brasilense, and to identify the type of farming system which benefited most from the use of A. brasilense-based inoculants. The experiment conducted over two corn crop seasons was arranged in a 6 × 2 factorial scheme, consisting of six farming systems and the presence or absence of inoculation with the bacteria A. brasilense. The farming systems were derived from a long-term experiment with different fertilization systems that has been conducted since 1984. Among these systems, there were three conventional systems (CNT1: conventional no-till without fertilizer; CNT2: conventional no-till with 150 kg ha−1 of mineral fertilizer + 50 kg ha−1 of urea; CNT3: conventional no-till with 300 kg ha−1 of mineral fertilizer + 100 kg ha−1 of urea), and three organic systems (ONT1: organic no-till with 40 m3 ha−1 of organic compost; ONT2: organic no-till with 20 m3 ha−1 of organic compost; ONT3: organic no-till with 40 m3 ha−1 of organic compost and intercropped with Canavalia ensiformis). Although the Azospirillum population in the soil before planting was the same for all six systems, the count in the rhizospheric soil was higher in the organic systems, and there was no increase in that count due to inoculation. In this study, the only difference observed was within the CNT1 system, between the inoculated (CNT1-I) and uninoculated (CNT1-NI) treatments. In this system, inoculation resulted in an increase in plant height, in addition to higher concentrations of foliar N and P, and a higher plant survival rate, which culminated in higher yield. Corn inoculated with A. brasilense in the CNT1-I treatment showed a significant increase in yield—2839 kg ha−1 higher than that recorded for CNT1-NI. This study shows that, in the conventional low input treatment CNT1-I, inoculation with A. brasilense resulted in an increase in corn growth and yield.

The principal objections to the proposition that organic agriculture can contribute significantly to the global food supply are low yields and insufficient quantities of organically acceptable fertilizers. We evaluated the universality of both claims. For the first claim, we compared yields of organic versus conventional or low-intensive food production for a global dataset of 293 examples and estimated the average yield ratio (organic:non-organic) of different food categories for the developed and the developing world. For most food categories, the average yield ratio was slightly <1.0 for studies in the developed world and >1.0 for studies in the developing world. With the average yield ratios, we modeled the global food supply that could be grown organically on the current agricultural land base. Model estimates indicate that organic methods could produce enough food on a global per capita basis to sustain the current human population, and potentially an even larger population, without increasing the agricultural land base. We also evaluated the amount of nitrogen potentially available from fixation by leguminous cover crops used as fertilizer. Data from temperate and tropical agroecosystems suggest that leguminous cover crops could fix enough nitrogen to replace the amount of synthetic fertilizer currently in use. These results indicate that organic agriculture has the potential to contribute quite substantially to the global food supply, while reducing the detrimental environmental impacts of conventional agriculture. Evaluation and review of this paper have raised important issues about crop rotations under organic versus conventional agriculture and the reliability of grey-literature sources. An ongoing dialogue on these subjects can be found in the Forum editorial of this issue.

Control of agricultural policymaking by the “agricultural establishment” has been challenged by a wide range of interests concerned with the externalities of modern industrialized agriculture. An “externalities/alternatives” or “ex/al” coalition appears to be an emerging force in agricultural policy debates. We surveyed three alternative agriculture groups, three conventional agriculture groups, and a statewide sample of farmers to learn whether each category forms a distinct, unified interest group whose perspectives on agricultural policy diverge substantially from the others'. There is considerable similarity among the alternative agriculture groups and among the conventional agriculture groups, the differences between them being much greater than the differences within each category. The statewide farmer sample is generally intermediate between the two sets of interest groups, but is closer to the conventional perspective on most issues.

This paper analyzes some of the potential problems that can be anticipated in putting a sustainable system together on an operating farm, and proposes a few of the principle practices and management strategies required for making such systems work.

Conventional agriculture is increasingly criticized as being too concentrated in ownership; too reliant on technology, petroleum-based inputs, and credit; too specialized and ecologically unsound; and too dependent on government subsidies. Alternative agriculture is offered by many as an alternative, and we discuss the possible impacts of its widespread adoption on farm income, yields, regions, labor, trade, environmental quality, and farm structure. The profitability of alternative agriculture is also examined - in so doing, a distinction is made between the adoption of low-input practices and a more holistic alternative agricultural system.