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Nitrogen‐15 Tracers Combined with Tensio‐Neutronic Method to Estimate the Nitrogen Balance of Irrigated Maize
Author(s) -
Normand Béatrice,
Vachaud Georges,
Recous Sylvie,
Kengni Lucas,
Garino Bernard
Publication year - 1997
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1997.03615995006100050031x
Subject(s) - environmental science , fertilizer , leaching (pedology) , water balance , irrigation , intercropping , agronomy , soil water , hydrology (agriculture) , soil science , geology , geotechnical engineering , biology
In response to a very high increase of groundwater NO − 3 pollution, largely connected with intensive agricultural practices, a long‐term experimentation has been set up close to Grenoble, France, with the following aims: first to characterize the response of maize ( Zea mays L.), a predominant crop in the area, to fertilization, and second to quantify the N balance during and after the crop cycle. This study relates to results concerning the second issue; experiments were conducted on irrigated maize in 1991, 1992, and 1993 on the Experimental Farm at La Côte Saint‐André, France, in the heart of one of the most important agricultural zones between the French Alps and the Rhone Valley. The dynamics of soil and fertilizer N (NO − 3 transport and N balance during cropping and intercropping periods) were continuously monitored using 15 N isotopic tracing and the tensio‐neutronic method (i.e., continual measurement of soil water balance using a neutron moisture meter and tensiometers), together with porous suction cups installed at 0.3‐, 0.5‐, and 0.8‐m depths. Water drainage and leaching of NO − 3 ‐N, with a partition between that derived from fertilizer and that produced by soil mineralization, were thus obtained during and after the crop cycle. The balance of the labeled fertilizer at harvest was also determined by conventional soil coring and plant sampling. The two methods were used successfully during the 3 yr in which there were different climatic conditions and different fertilizer application rates. The results show that the traditional fertilizer input in the area (260 kg N ha −1 ) could be reduced nearly 30% without any substantial loss in grain yield but with a considerable reduction of nonpoint source pollution due to NO − 3 leaching. It is also shown that with the combined use of the two methods, it is possible to characterize separately fertilizer‐N uptake, fertilizer‐N leaching, and N immobilization and to estimate N‐gaseous losses.