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Title: Phosphorus availability and leaching losses in annual and perennial cropping systems in an upper US Midwest landscape
Excessive phosphorus (P) applications to croplands can contribute to eutrophication of surface waters through surface runoff and subsurface (leaching) losses. We analyzed leaching losses of total dissolved P (TDP)More>>
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  1. Abstract Excessive phosphorus (P) applications to croplands can contribute to eutrophication of surface waters through surface runoff and subsurface (leaching) losses. We analyzed leaching losses of total dissolved P (TDP) from no-till corn, hybrid poplar ( Populus nigra X P. maximowiczii ), switchgrass ( Panicum virgatum ), miscanthus ( Miscanthus giganteus ), native grasses, and restored prairie, all planted in 2008 on former cropland in Michigan, USA. All crops except corn (13 kg P ha −1  year −1 ) were grown without P fertilization. Biomass was harvested at the end of each growing season except for poplar. Soil water at 1.2 m depth was sampled weekly to biweekly for TDP determination during March–November 2009–2016 using tension lysimeters. Soil test P (0–25 cm depth) was measured every autumn. Soil water TDP concentrations were usually below levels where eutrophication of surface waters is frequently observed (> 0.02 mg L −1 ) but often higher than in deep groundwater or nearby streams and lakes. Rates of P leaching, estimated from measured concentrations and modeled drainage, did not differ statistically among cropping systems across years; 7-year cropping system means ranged from 0.035 to 0.072 kg P ha −1  year −1 with large interannual variation. Leached P was positively related to STP, which decreased over themore »7 years in all systems. These results indicate that both P-fertilized and unfertilized cropping systems may leach legacy P from past cropland management.« less
  2. Abstract
    Dataset Abstract This dataset includes information about the LTER main site treatments, agronomic practices carried out on the treatments and approved site use requests. Most long-term hypotheses associated with the KBS LTER site are being tested within the context of the main cropping systems study. This study was established on a 48 ha area on which a series of 7 different cropping systems were established in spring 1988, each replicated in one of 6 ha blocks. An eighth never-tilled successional treatment, is located 200 m off-site, replicated as four 0.06 ha plots. Cropping systems include the following treatments: T1. Conventional: standard chemical input corn/soybean/wheat rotation conventionally tilled (corn/soybean prior to 1992) T2. No-till: standard chemical input corn/soybean/wheat rotation no-tilled (corn/soybean prior to 1992) T3. Reduced input: low chemical input corn/soybean/wheat rotation conventionally tilled (ridge till prior to 1994) T4. Biologically based: zero chemical input corn/soybean wheat rotation conventionally tilled (ridge till prior to 1994) T5. Poplar: Populus clones on short-rotation (6-7 year) harvest cycle T6. Alfalfa: continuous alfalfa, replanted every 6-7 years (converted to switchgrass in 2018) T7. Early successional community: historically tilled soil T8. Mown grassland community: never-tilled soil. For specific crops in a given year see theMore>>
  3. At two sites in the North Central USA (Michigan (KBS) and Wisconsin (ARL)), we evaluated the effect of N fertilization on the yield and quality of five perennial bioenergy feedstock cropping systems: (1) switchgrass (Panicum virgatum L.), (2) giant miscanthus (Miscanthus × giganteus), (3) a native grass mixture (5 species), (4) an early successional field (volunteer herbaceous species), and (5) a restored prairie (18 species). In a randomized complete block design with 5 replicates and 2 split plots, N was applied at 0 and 56 kg ha−1 to split plots for each cropping system from 2010 to 2016. No yield response to N was detected in switchgrass at either location in any year. Giant miscanthus exhibited a positive yield response to N at both sites (11% at KBS and 83% at ARL). Nitrogen fertilizer addition significantly reduced glucose (KBS 12.9 and 13.8 g kg−1 year−1, ARL 11.2 and 9.7 g kg−1 year−1) in the native grass mix and restored prairie systems respectively. Nitrogen fertilizer also reduced xylose at KBS in the switchgrasss, native grass mix, and restored prairie (4.9, 7.5, and 5.0 g kg−1 year−1). At ARL, N fertilization reduced xylose levels in switchgrass, giant miscanthus, and restored prairie (7.4,more »6.8, and 6.2 g kg−1 year−1) and increased xylose levels in the early successional system (5.0 g kg−1 year−1).« less
  4. Abstract

    Expanding biofuel production is expected to accelerate the conversion of unmanaged marginal lands to meet biomass feedstock needs. Greenhouse gas production during conversion jeopardizes the ensuing climate benefits, but most research to date has focused only on conversion to annual crops and only following tillage. Here we report the global warming impact of converting USDA Conservation Reserve Program (CRP) grasslands to three types of bioenergy crops using no‐till (NT) vs. conventional tillage (CT). We established replicated NT and CT plots in three CRP fields planted to continuous corn, switchgrass, or restored prairie. For the 2 yr following an initial soybean year in all fields, we found that, on average, NT conversion reduced nitrous oxide (N2O) emissions by 50% and CO2emissions by 20% compared with CT conversion. Differences were higher in Year 1 than in Year 2 in the continuous corn field, and in the two perennial systems the differences disappeared after Year 1. In all fields net CO2emissions (as measured by eddy covariance) were positive for the first 2 yr following CT establishment, but following NT establishment net CO2emissions were close to zero or negative, indicating net C sequestration. Overall, NT improved the global warming impact of biofuel cropmore »establishment following CRP conversion by over 20‐fold compared with CT (−6.01 Mg CO2e ha−1 yr−1for NT vs. −0.25 Mg CO2e ha−1 yr−1for CT, on average). We also found that Intergovernmental Panel on Climate Change estimates of N2O emissions (as measured by static chambers) greatly underestimated actual emissions for converted fields regardless of tillage. Policies should encourage adoption of NT for converting marginal grasslands to perennial bioenergy crops to reduce C debt and maximize climate benefits.

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  5. Abstract
    Dataset Abstract A spatial variability study conducted across the LTER Main Site area (45 ha) at KBS prior to dividing the site into 1-ha experimental plots. During the 1988 growing season a stratified unaligned sampling scheme was used to collect 400-600 geo-referenced samples across the site (uniformly planted to a single variety of soybeans) for: geomorphological characteristics (microtopography, soil horizon depths, bulk density, texture); soil chemical characteristics (pH, NO3, NH4, total C, total N, moisture, inorganic P, trace metals); soil biological characteristics (N mineralization potentials, microbial biomass C, microbial biomass N, fungal/bacterial ratios, nematodes and other soil invertebrates; seed bank size); plant weed species abundance, weed biomass at peak standing crop); and insect characteristics (major pest and predator species). Most soil samples were taken before crop emergence, plant phenology samples were taken throughout the growing season, biomass samples were taken at physiological maturity, and insect samples were taken continuously. Dried soil and plant samples are archived for potential future analysis. original data source