65 research outputs found
Green and animal manure use in organic field crop systems
Dual-use cover/green manure (CGM) crops and animal manure are used to supply nitrogen (N) and phosphorus (P) to organically grown field crops. A comprehensive review of previous research was conducted to identify how CGM crops and animal manure have been used to meet N and P needs of organic field crops, and to identify knowledge gaps to direct future research efforts. Results indicate that: (a) CGM crops are used to provide N to subsequent cash crops in rotations; (b) CGM-supplied N generally can meet field crop needs in warm, humid regions but is insufficient for organic grain crops grown in cool and sub-humid regions; (c) adoption of conservation tillage practices can create or exacerbate N deficiencies; (d) excess N and P can result where animal manures are accessible if application rates are not carefully managed; and (e) integrating animal grazing into organic field crop systems has potential benefits but is generally not practiced. Work is needed to better understand the mechanisms governing the release of N by CGM crops to subsequent cash crops, and the legacy effects of animal manure applications in cool and sub-humid regions. The benefits and synergies that can occur by combining targeted animal grazing and CGMs on soil N, P, and other nutrients should be investigated. Improved communication and networking among researchers can aid efforts to solve soil fertility challenges faced by organic farmers when growing field crops in North America and elsewhere
Effect of host–guest complex formation on the fluorescence of 6-methoxy-1-methyl-quinolinium cation with 4-sulfonatocalix[4]arene: utilization as a fluorescent probe for the study of difenzoquat binding
Niche differentiation and plasticity in soil phosphorus acquisition among co-occurring plants
How species coexist despite competing for the same resources that are in limited supply is central to our understanding of the controls on biodiversity. Resource partitioning may facilitate coexistence, as co-occurring species use different sources of the same limiting resource. In plant communities, however, direct evidence for partitioning of the commonly limiting nutrient, phosphorus (P), has remained scarce due to the challenges of quantifying P acquisition from its different chemical forms present in soil. To address this, we used 33P to directly trace P uptake from DNA, orthophosphate and calcium phosphate into monocultures and mixed communities of plants growing in grassland soil. We show that co-occurring plants acquire P from these important organic and mineral sources in different proportions, and that differences in P source use are consistent with the species’ root adaptations for P acquisition. Furthermore, the net benefit arising from niche plasticity (the gain in P uptake for a species in a mixed community compared to monoculture) correlates with species abundance in the wild, suggesting that niche plasticity for P is a driver of community structure. This evidence for P resource partitioning and niche plasticity may explain the high levels of biodiversity frequently found in P-limited ecosystems worldwide
Effects of Poultry Manure Application on Phosphorus in Soil and Tile Drain Water Under a Corn-Soybean Rotation
Influence of Addition Order and Contact Time on Thorium(IV) Retention by Hematite in the Presence of Humic Acids
Forest Resource Islands in a Sub-tropical Marsh: Soil–Site Relationships in Everglades Hardwood Hammocks
Il dubbio sulla fotografia: Brecht, Bachmann, Handke.
Tre scrittori si interrogano sulle implicazioni politiche ed etiche della fotografia: Bertolt Brecht - Ingeborg Bachmann - Peter Handke. Dalla domanda  se la fotografia possa fare altra cosa che "rifornire" i media  che port\uf2 Brecht a comporre il suo Abic\uec della guerra, ai dubbi su voyeurismo e indiscrezione del giornalismo politico nel racconto bachmanniano Tre sentieri per il lago, fino alla critica radicale del procedere dei mass-media negli scritti di viaggio nell'Ex-Jugoslavia di Peter Handke, la fotografia non smette di suscitare una perplessit\ue0 molto produttiva
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