Influence of mineral nutrition on denitrification on plants in nutrient solution culture

Abstract

In solution culture experiments with spring wheat the effect of nitrogen sources, single nutrient deficiency and oxygen supply of the nutrient solution on denitrification was studied by means of the acetylene inhibition method. No denitrification was observed with ammonium nutrition, while denitrification was almost equally high with nitrate and a mixture of nitrate and ammonium nutrition. Discontinuing potassium for 7 and 14 days increased denitrification. Discontinuation of P for 14 days also increased total denitrification, whereas no difference from the complete nutrient solution was observed in Fe deficiency. Denitrification remained at a very low level, when Mg supply was discontinued. Denitrification potential of excised roots was high in K deficiency. It was also high at the beginning of Fe deficiency, whereas P and Mg deficiency had no effect on denitrification potential as compared to roots in complete nutrient solution. The differences in total denitrification are due to the effects of individual nutrient deficiency on root growth, root respiration and denitrification potential.

Suppression of Root Pathogens of Tomato by Rhizobia,Pseudomonas aeruginosa, and Mineral Fertilizers

“…Similarly, potassium and nitrogen are known to suppress some root-infecting fungi (Huber, 1980(Huber, , 1991Huber and Arny, 1985;Huber and Watson, 1974). Potassium deficiency increases root exudation (van Rheinbaben and Trolldenier, 1983), which in turn results in an increase in rhizospheric microorganisms, including pathogens. Urea used alone or with composted manure decreased populations of plant parasitic nematodes and increased populations of predatory and free-living nematodes in soil (Akhtar, 1998).…”