Efficient use of nitrogen on crop land in the Northeast efficientuseofni00bark Year: 1980 Efficient Use of Nitrogen AIR 29 NH, DUST RUNOFF EROSION LEACHING CLAY AND ORGANIC COMPLEXES Figure 20. The Nitrogen Cycle. or to predict the contribution of soils to the N de- mands of a crop. Some laboratory procedures appear promising, but calibration of these procedures in the field with crop demands is lacking. More data must be obtained from research under farm conditions and at numerous sites before laboratory evaluations of the N status of soil can be correlated to field conditions. He
Efficient use of nitrogen on crop land in the Northeast efficientuseofni00bark Year: 1980 Efficient Use of Nitrogen AIR 29 NH, DUST RUNOFF EROSION LEACHING CLAY AND ORGANIC COMPLEXES Figure 20. The Nitrogen Cycle. or to predict the contribution of soils to the N de- mands of a crop. Some laboratory procedures appear promising, but calibration of these procedures in the field with crop demands is lacking. More data must be obtained from research under farm conditions and at numerous sites before laboratory evaluations of the N status of soil can be correlated to field conditions. Heretofore, time and expense has limited these investigations; how- ever, increased support of this research may now be justified by the rising costs of N fertilizers and by the necessity to improve the efficiency of N use. The concern for the effects of N on our environ- ment is another factor pressing for efficient use of N in agriculture. The recovery by a crop of only half of the applied N is a frequently cited statistic. There- fore, some of the fertilizer N is said to be a source of environmental pollution. Research is underway in the Northeast that indicates that the fraction of fer- tilizer N recovered by a crop under good manage- ment practices may approach 90. Ammonia volatilization from urea and other am- moniacal fertilizers is likely to result from poor man- agement. Research is needed to develop procedures to diminish these losses. The leaching of nitrates into ground water and the movement of nitrate into drinking and recreational waters has been a long-term environmental concern. Agriculture has frequently been accused of being a source of nitrates found in these waters, although leaching losses from applied fertilizers have been dif- ficult to verify. On the other hand, agriculturists have had difficulty in inventorying and accounting for all of the N applied to the soil. Investigations on the movement of N in the soil and on the conversion of N into soil organic
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