LTREB: Long-term Consequences of Biochemical and Biogeochemical Changes in the Horseshoe Bend Agroecosystem, Athens, GA.

了解许多土壤过程，包括有机质的积累和土壤团聚体的形成，需要在十年的时间段进行研究。自1978年以来，在格鲁吉亚的马蹄弯曲（HSB）农业生态系统中，在重复的试验样地中研究了土壤有机质和土壤动物的动态。分析表明，试验处理（免耕和传统耕作制度）继续分歧。必须将实验再持续六年，以便能够预测我们操纵的长期后果。因此，在HSB的免耕和常规耕作地块的土壤过程的持续LTREB研究提出了一些显着的变化。新的研究集中在两个相关的领域：1）在1997年以来实施的轮作中，对C3途径植物土壤有机质逐渐增加的基础进行长期测量。2）在我们的主要地块内的子地块中，跟踪夏季种植Bt（和非Bt）棉花的Bt蛋白的生产，积累，归宿和生态效应。土壤团聚体大小的变化可能影响Bt毒素及其分解产物在土壤中的固定。已经表明，在HSB的免耕管理系统产生了越来越多的代表性的土壤大团聚体相比，在我们的传统耕作地块的大团聚体显著减少。一些短期研究（见项目说明中的参考文献）未能发现作物残留物中的Bt对非目标土壤动物造成的有害变化。对此有三种可能的解释：a）不存在有害影响，B）短期实验不能充分预测重复暴露于Bt残留物的长期后果，以及c）影响取决于土壤的性质，如团聚体大小。能够区分这些可能性似乎是谨慎的，HSB的长期种植将允许这种情况发生。

0214946ColemanUnderstanding many soil processes, including the accumulation of organic matter andthe formation of soil aggregates, requires research that is conducted over decadal timeperiods. The dynamics of soil organic matter and soil fauna at the Horseshoe Bend(HSB) agroecosystem site in Georgia have been studied in replicated experimentalplots since 1978. Analyses indicate that the experimental treatments (no-tillage andconventional-tillage regimes) are continuing to diverge. It is essential to continue theexperiments for an additional six years, to enable prediction of what the long-termconsequences of our manipulations will be. Consequently, a continuation of ongoingLTREB research on soil processes in no-till and conventional till plots at HSB is proposed, withsome significant changes. The new research focuses on two related areas:1) long-term measurements of the gradually-increasing base of soil organic matter fromC3-pathway plants, in crop rotations that have been in effect since 1997.2) following the production, accumulation, fate and ecological effects of the Bt proteinsfrom the summer planting of Bt (and non-Bt) cotton in subplots within our main plots.The relationship between these focal areas is simple. The variation in the size of soilaggregates may influence the sequestration of Bt toxins, and their breakdown products,within soils. It has already been shown that no-tillage management systems at HSBgenerate an increasing representation of soil macroaggregates in comparison to themarkedly reduced macroaggregates in our conventional tillage plots. Therefore, it ishypothesized that no-tillage systems will sequester more Bt-related products than willconventional-tillage plots.Several short-term studies (see references in Project Description) have failed to detectdeleterious changes in non-target soil fauna as a result of Bt in crop residues. Thereare three possible explanations for this: a) that no deleterious effects exist, b) that short-term experiments do not adequately predict the long-term consequences of repeatedexposure to Bt residues, and c) that effects are contingent upon properties of the soilsuch as aggregate size. It would seem prudent to be able to distinguish among thesepossibilities and the long-term plantings at HSB will allow that to occur.