אסיף מאגר המחקר החקלאי

Ecological and agricultural aspects of nitrogen balance in perennial pasture irrigated with municipal effluents

Year:

1979

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Volume :

11

Co-Authors:

Kipnis, T., Agric. Res. Organ., Volcani Cent., Bet-Dagan, Israel
Feigin, A., Agric. Res. Organ., Volcani Cent., Bet-Dagan, Israel
Dovrat, A., Agric. Res. Organ., Volcani Cent., Bet-Dagan, Israel
Levanon, D., Agric. Res. Organ., Volcani Cent., Bet-Dagan, Israel

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Abstract:

Nitrogen requirement of Rhodes grass, its response to various N sources, as well as the availability of N originating from secondary municipal wastewater, its use as an alternative to N fertilizer and the N balance of the soil-plant system were studied in pot and field experiments. Sand culture experiments showed that for dry matter production, NH4-N and NO3-N were equally efficient. Physiological criteria for determining the N requirement based on the critical NO3-N value of shoots and nitrate reductase activity were defined. The above mentioned nitrogen-response data, as well as the shallow root system, formed the basis for examining and adapting a suitable irrigation regime for use with municipal effluents. The idea was to reduce pollution hazards by increasing the absorption of nitrogen from effluents by frequent irrigation (at least twice a week) in order to obtain an optimal moisture status in the upper soil layers. As a result, the amount of nitrate available for leaching would be reduced, and, the cost of nitrogen fertilizer which accounts for approximately 45% of production costs, could be saved. Increasing irrigation frequency raised yields and nitrogen uptake and decreased nitrogen loss from the soil-plant system. Low nitrate levels found below the root system together with a decrease in O2 concentration of soil atmosphere indicate indirectly, that denitrification is responsible for the disappearance of nitrate which leached to lower layers, from where its uptake is unlikely. We suggest that the management procedure described in this experiment greatly reduces the hazard of nitrate pollution and that Rhodes grass is a crop which lends itself to irrigation with effluents, both from the agricultural and ecological points of view.

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