97,939 research outputs found
Abschlußbericht des Forschungsvorhabens, gefördert von der Deutschen Bundesstiftung Umwelt, Osnabrück
No full textA model to predict the accuracy of measurements of legume N rhizodeposition using a split-root technique
No full textLegume N rhizodeposition is an important process for understanding the N turnover in legume-based cropping systems. Different N-15 labeling techniques have been developed to estimate the rhizodeposition of legume-derived N into the soil. However, it is not known how the N-15-based experiments have to be designed to achieve a defined degree of accuracy in measuring the amount of N derived from rhizodeposition (Ndfr). As a consequence therefore, a model for the split-root technique was developed on the basis of experimental data to (i) test the effects of various experimental conditions on soil N-15 enrichment, (ii) evaluate the accuracy of the measurements, and to (iii) deduce instructions for designing efficient experiments using N-15 techniques for quantifying legume N rhizodeposition. It turned out that the coefficient of disproportional N-15 distribution between non-N-15-fed roots grown in soil (Root(Soil)) and total plant biomass (D coefficient) is an indispensable component in the development of such a model for N-15-based split-root experiments. The model showed the coefficients of variation in measuring the Ndfr with regard to the analytical accuracy in determining not only the isotope composition of both the Root(Soil) and the soil, but also the N content of the soil itself. Suggestions for designing specific experimental conditions to achieve a high accuracy in quantifying Ndfr were deduced from the model for the split-root technique, particularly in the choice of the amount of soil N at the start of the experiment and the N-15 enrichment of the fertilizer being used. The coefficients of variation in measuring Ndfr are presented regarding the N-15 abundance of Root(Soil) and the quotient of the amount of Ndfr and soil N at the start of the experiment. (c) 2004 Elsevier Ltd. All rights reserved
Abschlußbericht des Forschungsvorhabens, gefördert von der Deutschen Bundesstiftung Umwelt, Osnabrück
No full textHow to calculate nitrogen rhizodeposition: a case study in estimating N rhizodeposition in the pea (Pisum sativum L.) and grasspea (Lathyrus sativus L.) using a continuous N-15 labelling split-root technique
No full textThe formulae used in studies with N-15 labelling techniques for estimating the N rhizodeposition (Ndfr) of legumes differ according to the background atom% N-15 values used to determine N-15 excess in the soil and roots grown in soil. Therefore, a continuous N-15 labelling splitroot experiment with pea (Pisum sativum L.) and grasspea (Lathyrus sativus L.) was undertaken and the relevant calculations were made to determine a valid method for calculating Ndfr. It is shown that a non-nodulated reference plant or a legume grown on soil without N-15 labelling are required components of experiments which aim to estimate legume-N rhizodeposition, if the N-15 abundance of the total soil N at the start of the experiment and that of the total plant available soil N are different. The standard formula was developed further to calculate Ndfr in a valid way. The impact of using different background atom% N-15 values on the results when estimating Ndfr are demonstrated according to the N-15 abundance of the roots grown in the soil. At physiological maturity, the rhizodeposition of N from roots grown in the soil was 19.8 mg N plant(-1) for pea and 14.1 mg N plant(-1) for grasspea, which is, respectively, equivalent to 10.5 and 9.2% of their total root and shoot N. (c) 2005 Elsevier Ltd. All rights reserved
Joshua Davis: Author of Spare Parts
No full textCitation: K-State First (2016). Joshua Davis: Author of Spare Parts [Flier]. Manhattan, Kansas: K-State First.Flyer advertising Joshua Davis's author talk at Kansas State University
Bodenfruchtbarkeit im Ackerbau: Markante Unterschiede zwischen ökologischer und konventioneller Bewirtschaftung vor allem bei Regenwürmern
No full textBodenfruchtbarkeit im Ackerbau: Markante Unterschiede zwischen ökologischer und konventioneller Bewirtschaftung vor allem bei Regenwürmern
No full textThe influence of long-term tillage systems on symbiotic N-2 fixation of pea (Pisum sativum L.) and red clover (Trifolium pratense L.)
No full textPea as a grain legume and red clover as a forage legume in the seeding year were cultivated in two long-term differentiated tillage systems on a loess soil in Germany. A continuous conventional tillage system (plow; CT) and a continuous minimum tillage system (rotary harrow; MT) were established in 1970. With pea and red clover dry matter accumulation and N parameters (N accumulation, Ndfa, N-harvest-index, N balance) were investigated in 1998 and 1999. Differences in the N-2 fixation of pea due to the tillage system could clearly be shown whereas grain yields and total N accumulation were equal in both tillage systems and years. In both years a significantly (P < 0.05) higher Ndfa in the MT system was found at least in the final harvest (maturity of pea): 1998/1999, 0.42/0.54 in CT, 0.62/0.75 in MT. The differences in N-2 fixation of pea may be explained by the delayed soil N supply in MT at the beginning of the vegetative period. Simplified N balances of pea were -18 and -25 kg N ha(-1) in CT and -5 and +1 kg N ha(-1) in MT for 1998 and 1999, respectively. Red clover showed no significant differences in the DM and N accumulation between both tillage systems but a year dependent effect caused by different stubble and root yields between the years was apparent. With red clover slightly, but also significantly (P < 0.05) increased Ndfa values were found in the MT system compared to the CT system with 0.55/0.62 in CT (1998/1999) and 0.64/0.71 in MT. However, the difference in Ndfa between the tillage systems (9 percentage points) was much smaller with red clover than with pea (20 and 21 percentage points in 1998 and 1999, respectively). Soil N uptake of red clover using the longer growing season reflected the more adjusted N supply in both long-term differentiated tillage systems, whereas pea in using only a short-term vegetative period reacted stronger to the lower N mineralization in the MT system in springtime
Steven Johnson Author Talk Poster
No full textK-State Book NetworkA poster advertising an author talk by Steven Johnson at Kansas State University on September 3, 2014. Steven Johnson's book "The Ghost Map" was the 2014-2015 common book
Estimation of symbiotic N2 fixation by a low-level, large-scale 15N application technique
No full textA modified approach is presented for the N-15 isotope dilution method to estimate the proportion of plant nitrogen derived from the atmosphere (Ndfa). This approach utilizes a low-level, large-scale application of N-15 enriched fertiliser. In a field study, pea (Pisum sativum L.) was cultivated in two long-term (since 1970) tillage systems (conventional: CT, minimum tillage: MT). Nitrogen (26 g NO3-N ha(-1) with 10 at.% N-15) was distributed with a conventional field sprayer to increase the plant available soil N-15 level up to the desired range of delta(15)N > 5parts per thousand. A formula for determining the desired amounts of N-15 application is presented and a model is introduced comparing the apparent Ndfa calculated by field data to the theoretically calculated true values of Ndfa. The model makes it possible to consider three basic factors: (i) the amount of plant available soil nitrogen, (ii) the distribution of N-15 enrichment in different soil layers and (iii) the soil N uptake proportions of the legume and the reference plant when the amount of applied N-15 fertilizer is the dependent variable. Errors in estimating Ndfa by the N-15 dilution method can be quantitatively determined with different soil N uptake patterns of legumes and reference plants at varying N-15 enrichment levels. The model shows that results obtained by using the low-level, large-scale N-15 enrichment technique produced a slightly smaller margin of error than did the addition of larger amounts of N-15 labelled fertilizer when N uptake patterns of the legume and the reference plant differ. The new technique offers distinct advantages, in that it is very practical and makes the enlargement of plots possible at low cost and with marginal effort. The results of the low-level enrichment field study were evaluated using the model as well as the results of an investigation on pea with moderate N-15 enrichment by liquid manure (isotope dilution method). (C) 2002 Elsevier Science Ltd. All rights reserved
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