Regional differences in phosphorus budgets in intensive soybean agriculture

Author Posting. © American Institute of Biological Sciences, 2013. This article is posted here by permission of University of California Press for personal use, not for redistribution. The definitive version was published in BioScience 63 (2013): 49-54, doi:10.1525/bio.2013.63.1.10.Fertilizer-intensive agriculture has been integral to increasing food production over the past half century but has been accompanied by environmental costs. We use case studies of phosphorus fertilizer use in the world’s most productive soybean-growing regions, Iowa (United States), Mato Grosso (Brazil), and Buenos Aires (Argentina), to examine influences of management and soil type on agriculture’s most prevalent phosphorusrelated environmental consequences: eutrophication and consumption of Earth’s finite phosphorus reserves. With increasing phosphorus inputs, achieving high yields on tropical soils with high phosphorus-binding capacity is becoming more common. This system has low eutrophication risks but increases demands on phosphorus supplies. In contrast, production in traditional breadbaskets, on soils with lower phosphorus-binding capacities, is being sustained with decreasing phosphorus inputs. However, in these regions, historical overuse of phosphorus may mean continued eutrophication risk even as pressures on phosphorus reserves diminish. We focus here on soybean production but illustrate how achieving sustainable agriculture involves an intricate optimization of local, regional, and global considerations.SP is supported by the Andrew Mellon Foundation, and CN and SHR’s work in Mato Grosso was funded by National Science Foundation grant no. NSF-DEB-0640661 and through collaboration with the Instituto de Pesquisa Ambiental da Amazonia

Cover Crops to Improve Soil Health in the North American Great Plains

Rotating cereal crops (e.g., wheat [Triticum aestivum L.] with a 10- to 21-mo summer fallow period [fallow]) is a common farming practice in dryland (rainfed) agricultural regions. Fallow is associated with several challenges including low precipitation storage efficiency, depletion of soil organic carbon (SOC), loss of soil fertility, little crop residue retention and soil erosion, and few control options for herbicide-resistant (HR) weeds. The inability to effectively control HR weeds poses a major challenge to maintaining soil and water conservation practices such as no-tillage, as some producers are considering tillage to control weeds. Cover crop (CC) integration into wheat-based production systems to replace portions of the fallow period provides an opportunity to increase SOC, improve soil fertility, suppress weeds, and increase profitability of dryland crop production, especially when CCs are used as forage. This forum paper used the North American Great Plains as a model region to review information on (a) challenges of dryland agriculture; (b) integrating CCs in dryland agriculture; (c) benefits, challenges, and limitations of CCs in dryland crop production; (d) management options for CC integration in dryland grain systems; and (e) recommendations for future research efforts

Eficiência de fungicidas para controle de giberela em trigo: resultados dos ensaios cooperativos - safra 2011.

O conjunto de ensaios instalados permitiu avaliar a eficiência de fungicidas no controle de giberela em diferentes níveis de ocorrência da doença. Considerando a variável composta índice de Giberela e os três locais de maior ocorrência de giberela (Castro - PR, Guarapuava - PR e Cruz Alta - RS) todos os fungicidas testados foram capazes de reduzir a ocorrência de giberela. Ainda considerando este conjunto de dados, a redução na ocorrência da doença implicou em maior manutenção da produtividade. Dada a interação observada entre tratamentos e ambiente, que levou a diferentes níveis de doença e de controle, e ainda considerando os dados de rendimento de grãos, não se pode concluir, neste primeiro ano de ensaios, que algum dos fungicidas utilizados seja indubitavelmente superior aos demais e com alta eficiência no controle de giberela do trigo.bitstream/item/72717/1/co-23-2012.pd

Comparison of Permanganate-Oxidizable Carbon and Mineralizable Carbon for Assessment of Organic Matter Stabilization and Mineralization

Permanganate-oxidizable C (POXC) and mineralizable C (as determined by short-term aerobic incubation of rewetted soil) are measures of active organic matter that may provide early indication of soil C stabilization and mineralization processes. To date, the relationship between these two promising active organic matter tests has not been comprehensively evaluated, and little is known about their functional role in the soil ecosystem. Here, we examined the relationship between POXC and mineralizable C across a wide range of soil types, management histories, and geographic locations across the United States (13 studies, 76 total sites; n = 1071) and the ability of POXC and mineralizable C to predict crop yield and total aboveground biomass. Results from this comparative analysis showed that POXC and mineralizable C are related (r2 = 0.15–0.80) but that the relationship was differentially influenced by management practices. Overall, POXC better reflected practices that promote organic matter accumulation or stabilization and therefore can be a useful indicator of long-term soil C sequestration. Conversely, mineralizable C better reflected practices that promote organic matter mineralization and therefore can be a useful indicator of short-term soil nutrient availability. Our results also show that both mineralizable C and POXC were better predictors of corn (Zea mays L.) grain yield, aboveground biomass, and tomato (Solanum lycopersicum L.) fruit yield than other soil C fractions evaluated here. Thus, the integrated use of POXC and mineralizable C can provide a complementary framework to assess the relative dynamics of soil C stabilization and nutrient mineralization functions in agroecosystems

Transition Pathways to Sustainable Agricultural Water Management: A Review of Integrated Modeling Approaches

Agricultural water management (AWM) is an interdisciplinary concern, cutting across traditional domains such as agronomy, climatology, geology, economics, and sociology. Each of these disciplines has developed numerous process-based and empirical models for AWM. However, models that simulate all major hydrologic, water quality, and crop growth processes in agricultural systems are still lacking. As computers become more powerful, more researchers are choosing to integrate existing models to account for these major processes rather than building new cross-disciplinary models. Model integration carries the hope that, as in a real system, the sum of the model will be greater than the parts. However, models based upon simplified and unrealistic assumptions of physical or empirical processes can generate misleading results which are not useful for informing policy. In this article, we use literature and case studies from the High Plains Aquifer and Southeastern United States regions to elucidate the challenges and opportunities associated with integrated modeling for AWM and recommend conditions in which to use integrated models. Additionally, we examine the potential contributions of integrated modeling to AWM — the actual practice of conserving water while maximizing productivity