Nitrogen losses, uptake and abundance of ammonia oxidizers in soil under mineral and organo-mineral fertilization regimes

A Poultry Litter-Derived Organomineral Phosphate Fertilizer Has Higher Agronomic Effectiveness Than Conventional Phosphate Fertilizer Applied to Field-Grown Maize and Soybean

Inadequate disposal of poultry litter (PL) may promote eutrophication of water bodies due to its high nutrient content, including phosphorus (P). Thus, recycling P from PL to produce organomineral fertilizer (OMF), reduces the dependence on finite mineral P reserves, and also reduces P losses from soil. In this context, a field experiment was carried out to assess the agronomic effectiveness of a granular PL-derived OMF applied to maize and soybean in a highly weathered tropical soil. OMF was compared to single superphosphate (SSP) at five P rates between 0 and 70 kg ha−1. The shoot dry weight (SDW) and grain yields of soybean and maize were affected by P rates; however, no difference between OMF and SSP was found. A similar trend was observed for soil P and P uptake. The leaf P content and soil pH were not affected by either P sources or P rates. Although there was no difference between OMF and SSP on the crop yields, OMF had the highest relative agronomic effectiveness based on the SDW. These results show that the production of granular OMF from PL is a viable alternative to conventional P fertilizers and reduces the dependence of mineral P reserves.

Seasonal Patterns of Dominant Microbes Involved in Central Nutrient Cycles in the Subsurface

Microbial communities play a key role for central biogeochemical cycles in the subsurface. Little is known about whether short-term seasonal drought and rewetting events influence the dominant microbes involved in C- and N-cycles. Here, we applied metaproteomics at different subsurface sites in winter, summer and autumn from surface litter layer, seepage water at increasing subsoil depths and remote located groundwater from two wells within the Hainich Critical Zone Exploratory, Germany. We observed changes in the dominance of microbial families at subsurface sampling sites with increasing distances, i.e., Microcoleaceae dominated in topsoil seepage, while Candidatus Brocadiaceae dominated at deeper and more distant groundwater wells. Nitrifying bacteria showed a shift in dominance from drought to rewetting events from summer by Nitrosomandaceae to autumn by Candidatus Brocadiaceae. We further observed that the reductive pentose phosphate pathway was a prominent CO2-fixation strategy, dominated by Woeseiaceae in wet early winter, which decreased under drought conditions and changed to a dominance of Sphingobacteriaceae under rewetting conditions. This study shows that increasing subsurface sites and rewetting event after drought alter the dominances of key subsurface microbes. This helps to predict the consequences of annual seasonal dynamics on the nutrient cycling microbes that contribute to ecosystem functioning.

Homogenizing and diversifying effects of intensive agricultural land-use on plant species beta diversity in Central Europe - A call to adapt our conservation measures

The prevention of biodiversity loss in agricultural landscapes to protect ecosystem stability and functions is of major importance to stabilize overall diversity. Intense agriculture leads to a loss in species richness and homogenization of species pools, but the processes behind are poorly understood due to a lack of systematic case studies: The specific impacts by agriculture in contrast to other land-use creating open habitat are not studied as such landscapes hardly exist in temperate regions. Applying systematic grids, we compared the plant species distribution at the landscape scale between an active military training areas in Europe and an adjacent rather intensively used agricultural landscape. As the study areas differ mainly in the type of disturbance regime (agricultural vs. non-agricultural), differences in species pattern can be traced back more or less directly to the management. Species trait analyses and multiple measures of beta diversity were applied to differentiate between species similarities between plots, distance-decay, or nestedness. Contrary to our expectation, overall beta diversity in the agricultural area was not reduced but increased under agricultural. This was probably the result of species nestedness due to fragmentation. The natural process of increasing dissimilarity with distance (distance-decay) was suppressed by intense agricultural land-use, generalist and long-distance dispersers gained importance, while rare species lost continuity. There are two independent processes that need to be addressed separately to halt biodiversity loss in agricultural land. There is a need to conserve semi-natural open habitat patches of diverse size to favor poor dispersers and specialist species. At the same time, we stress the importance of mediating biotic homogenization caused by the decrease of distance-decay: The spread of long-distance dispersers in agricultural fields may be acceptable, however, optimized fertilizer input and erosion control are needed to stop the homogenization of environmental gradients due to nitrogen input into semi-natural habitat.