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1. Effect of Ammonium to Nitrate Rations of Fertilizers Applied at Various Times Throughout the Growing Season on Yield and Nitrogen Concentrationof CornA number of recent investigations have produced evidenm that the ionic form of N taken up by roots affects the growth of plants. While soil- plants generally take up rest of their N as nitrate, there is evidence that increasing the relative proportion of ammonium in the culture (or soil) solution can enhance growth and yield. Owing to difficulties in prevent* the rapid miaxbial conversion of ammonium to nitrate in soil, this response has nat been well demnstrated in a field situation. The objective... |
2. Yield and N Concentraions of Corn with Different N Sources Applied at Different timesA number of recent investigations have produced evidence that the ionic form of N taken up by roots affects the growth of plants. While soil- grown plants generally take up most of their N as nitrate, there is evidence that increasing the relative proportion of ammonium in the culture (or soil) solution can enhance growth and yield. Owing to difficulties in preventing the rapid microbial conversion of ammonium to nitrate in soil, this response has not been well demonstrated in a field situation.... |
3. On-Farm Nitrogen Fertilizer DemonstrationsThe Magdoff Pre-Sidedress Nitrate Test (PSNT) has been successful 1y used in the Northeast and humid parts of Midwest to improve N fertilizer recommendations. A modified version of the Magdoff PSNT was evaluated in 1989 and 1990 in Michigan. Fifty-three large scale on-farm corn N demonstrations were carried out. Two rates of N (a reduced rate and a high rate) were rep1 icated 3 to 6 times in each field. Forty-six sites showed no significant (p=.05) yield reduction due to the reduce N rate. Forty-nine... |
4. A Smorgasbord of Preliminary Results from Field Trials in OntarioField scale trials may be established to support lo cal needs, but the results seldom reach a wider audience. This paper summarizes two recent fiel d studies by staff of the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) on fertilizer use in soybeans and corn. A study of starter fertilizer response in soybeans found that yield responses to fertilizer tended to be relatively small, and seldom large enough to cove r the cost of the added fertilizer. A second study of ammonia volatilization... |
5. Active-Optical Reflectance Sensing Evaluated for Red and Red-Edge Waveband SensitivityUncertainty exists with corn (Zea mays L.) N management due to year-to-year variation in crop N need, soil N supply, and N loss from leaching, volatilization, and denitrification. Active-optical reflectance sensing (AORS) has proven effective in some fields for generating N fertilizer recommendations that improve N use efficiency. However, various sensors utilize different wavebands of light to calculate N fertilizer recommendations making it difficult to know which waveband is most sensitive... G. Bean, N. Kitchen, J. Camberato, R. Ferguson, F. Fernandez, D. Franzen, C. Laboski, E. Nafziger, J. Sawyer, P. Scharf, J. Schepers, J. Shanahan |