An 11-year competition experiment among combinations of six prairie perennial plant species showed that resource competition theory generally predicted the long-term outcome of competition. We grew each species in replicated monocultures to determine its requirements for soil nitrate (R*) and light (I*). In six pairwise combinations, the species with the lower R* and I* excluded its competitor,...

Nitrogen management continues to be diffi cult due to transformations of nitrogen fertilizers that are possible when applied to soil and the uncertainties of weather (Cabrera et al., 2008). Nitrogen (N) fertilizer in the form of urea is subject to ammonia volatilization through the activity of the urease enzyme found ubiquitously in soil (Kissel et al., 2008). Nitrate fertilizer is subject to l...

This study examines the effects of land use and slope angle on runoff, soil loss and nitrogen loss from hillslopes of the Loess Plateau in China. Farmland, wasteland and four forest treatments (sea buckthornþ poplar, immature sea buckthorn, mature sea buckthorn, and immature Chinese pine) were the types of land use that were compared. The results showed that July was the critical period for run...

Unpublished studies in the files of the Pineapple Research Institute of Hawaii indicate that under present cultural conditions the .pineapp1e plant displays superior performance with a foliar applied combination of ammonium and nitrate nitrogen than with either form of nitrogen alone. The studies presented here were undertaken to evaluate ammonium nitrate as a nitrogen source under different so...

J. M. H. Knops,* K. L. Bradley and D. A. Wedin School of Biological Sciences, School of Natural Resource Sciences, University of Nebraska, 348 Manter Hall, Lincoln, NE 68588, USA. *Correspondence: E-mail: [email protected] Abstract Plant species are hypothesized to impact ecosystem nitrogen cycling in two distinctly different ways. First, differences in nitrogen use efficiency can lead to positiv...

Increased fertilizer input in agricultural systems during the last few decades has resulted in large yield increases, but also in environmental problems. We used data from published papers and a soil testing and fertilization project in Shaanxi province during the years 2005 to 2009 to analyze chemical fertilizer inputs and yields of wheat (Triticum aestivum L.) and maize (Zea mays L.) on the f...

Nitrogen fixation (C(2)H(2) reduction) by algae in flooded soil was limited by interactions within the algal community. Nitrogen fixation by either indigenous algae or Tolypothrix tenuis was reduced severalfold by a dense suspension of the green alga Nephrocytium sp. Similarly, interactions between the nitrogen-fixing alga (cyanobacterium) Aulosira 68 and natural densities of indigenous algae l...

amounts involved are much smaller. The amount of boron in the 7-ton potato crop (if determined) would have been about 0.2 pound. In the case of boron (and to a lesser degree the other micronutrients) if the soil contains excessive amounts, toxic quantities are absorbed by plants and growth is restricted. The need for a reasonable balance in amounts of available nutrients in the soil has been po...

nitrogen and soil water were studied in loblolly pine (Pinus taeda L.) seedlings grown in monoculture and in competition with sweetgum (Liquidambar styraciflua L.) or crab grass (Digitaria spp.). Rhizotron cells were maintained at high soil water availability (approximately −0.1 MPa) or subjected to three dry-down cycles to low soil water availability (approximately −1.0 MPa), over two growing ...