Impact of Excess Water on N Loss

Experience in 1993 as well as many other years has clearly shown that unpredictable, but frequently occurring heavy rains will result in significant N loss through denitrification or leaching. In those years, farmers and their advisers often wonder how much loss has occurred and whether or not it would be beneficial to apply more N late in the season. In order to answer that question, one needs to first be able to predict a) how much of the applied N was present as N03-N, b) what portion of that N was lost, and c) whether or not it would be profitable to apply supplemental N late in the season. Over the last 12-15 years, a series of studies have been conducted in Illinois and Iowa with the ultimate goal of finding techniques to use in predicting the consequences of N loss

Management of Urea Containing Fertilizers

Direct application of urea containing fertilizers (dry urea and UAN solutions) has increased markedly over the past two decades throughout Illinois, Iowa, and Minnesota (Fig.l). They now account for about 35% of the total N market (Fig.2). In that same time period, ammonium nitrate has decreased from 10 to less than 1 percent and anhydrous ammonia from approximately 80 to 65 percent of the market in Iowa, Illinois, and Indiana

The Structure of Alkali Halide Dimers: A Critical Test of Ionic Models and New Ab Initio Results

In semiempirical ionic models a number of adjustable parameters have to be fitted to experimental data of either monomer molecules or crystals. This leads to strong correlations between these constants and prevents a unique test and a clear physical interpretation of the fit parameters. Moreover, it is not clear whether these constants remain unchanged when the model is applied to dimers or larger clusters. It is shown that these correlations can be substantially reduced when reliable information about dimers is available from experiments or ab initio calculations. Starting with Dunham coefficients of the monomer potential determined from microwave measurements, we have calculated the monomer to dimer bond expansion and the bond angle without any additional adjustable parameter. Assuming that the overlap repulsion between nearest neighbors remains unchanged, the bond expansion is mainly determined by the simple Coulomb repulsion between equally charged ions and depends only very little on the effective ion polarizabilities. Deviation of the bond angle from 90° sensitively tests the difference of effective polarizabilities of the two ions. A comparison with previously available data and new ab initio MP2 results presented here for the heavy‐atom containing dimers shows that bond angles can be modeled reasonably well with Seitz–Ruffa corrected Pauling polarizabilities while calculated bond expansions are much too long. This shows that changes of the overlap repulsion term must be considered for reliable predictions of the structure of dimers and larger clusters

Nitrogen Fertilizer Management to Reduce Water Pollution Potential

published or submitted for publicationis peer reviewedOpe

Crop Responses to AmiSorb in the North Central Region

Originally used to prevent scale in boilers, carpramid or thermal polyaspartate (copoly[(3-carboxypropionamide)( 2-carboxylmethyl) acetamide)] was brought to agriculture under the trade names AmiSorb and Magnet. It claimed to increase nutrient uptake through artificially increasing the volume of soil occupied by roots through increased root branching and root hair development. Under controlled hydroponic or greenhouse conditions, the use of carpramid increased nutrient uptake, some yield determining factors such as wheat tillering and in some cases, crop yield. Extensive field testing from 1996 to 1998 under various nutrient regimes, placements, forms, and timings resulted in very inconsistent performance. Averaged across all experiments for which data were available, small yield increases were observed for corn (+1.75 bushels/acre), soybean (+0.63 bushel/acre), wheat (+1.07 bushels/acre), and grain sorghum (+0.32 bushel/acre), but at best only about one-fourth of the experiments (27 percent for corn and wheat) showed statistically significant yield increases. Across all crops, only three experiments showed an economic advantage to using carpramid. An attempt was made to better define the conditions when responses were observed but no clear pattern emerged that would allow improved probability of predicting a positive response.https://lib.dr.iastate.edu/extension_pubs/1225/thumbnail.jp

Alkalilimnicola ehrlichii sp. nov., a novel, arsenite-oxidizing haloalkaliphilic gammaproteobacterium capable of chemoautotrophic or heterotrophic growth with nitrate or oxygen as the electron acceptor

A facultative chemoautotrophic bacterium, strain MLHE-1T, was isolated from Mono Lake, an alkaline hypersaline soda lake in California, USA. Cells of strain MLHE-1T were Gram-negative, short motile rods that grew with inorganic electron donors (arsenite, hydrogen, sulfide or thiosulfate) coupled with the reduction of nitrate to nitrite. No aerobic growth was attained with arsenite or sulfide, but hydrogen sustained both aerobic and anaerobic growth. No growth occurred when nitrite or nitrous oxide was substituted for nitrate. Heterotrophic growth was observed under aerobic and anaerobic (nitrate) conditions. Cells of strain MLHE-1T could oxidize but not grow on CO, while CH4 neither supported growth nor was it oxidized. When grown chemoautotrophically, strain MLHE-1T assimilated inorganic carbon via the Calvin-Benson-Bassham reductive pentose phosphate pathway, with the activity of ribulose 1,5-bisphosphate carboxylase (RuBisCO) functioning optimally at 0.1 M NaCl and at pH 7.3. Strain MLHE-1T grew over broad ranges of pH (7.3-10.0; optimum, 9.3), salinity (115-190 g l-1; optimum 30 g l-1) and temperature (113-40 °C; optimum, 30 °C). Phylogenetic analysis of 16S rRNA gene sequences placed strain MLHE-1T in the class Gammaproteobacteria (family Ectothiorhodospiraceae) and most closely related to Alkalispirillum mobile (98.5%) and Alkalilimnicola halodurans (98.6%), although none of these three haloalkaliphilic micro-organisms were capable of photoautotrophic growth and only strain MLHE-1T was able to oxidize As(III). On the basis of physiological characteristics and DNA-DNA hybridization data, it is suggested that strain MLHE-1T represents a novel species within the genus Alkalilimnicola for which the name Alkalilimnicola ehrlichii is proposed. The type strain is MLHE-1T (=DSM 17681T =ATCC BAA-1101T). Aspects of the annotated full genome of Alkalilimnicola ehrlichii are discussed in the light of its physiology. © 2007 IUMS

Erratum: The Structure of Alkali Halide Dimers: A Critical Test of Ionic Models and New Ab Initio Results

It has come to our attention that some of the ab initio results presented are incorrect due to errors in the Cs and C1 basis sets, and a small error in the binding energy of Rb2F2. The corrected results are presented below for the species that were affected, modifying the results in Table III of the original paper. Only those values which are different from the results of the original Table III are included. Note that some of these results are used for comparison with the ionic models in later tables. In addition, some HF data quoted in Tables V and VI is affected, and the correct values are given in Table II. All the changes in quoted values are small and none of the conclusions drawn in the article are affected, nor are the comparisons with the ionic models significantly affected. However, the error in the C1 basis is what gave rise to the anomalously short M–Cl bond lengths, and the results presented here lead to longer bonds, in somewhat poorer agreement with the experimental results for Cl containing species