|DE PAZ, JOSE|
Submitted to: Soil and Water Conservation Society
Publication Type: Book / Chapter
Publication Acceptance Date: 12/7/2007
Publication Date: 12/10/2010
Citation: Lavado, R., De Paz, J., Delgado, J.A., Rimski-Korsakov, H. 2010. Evaluation of best nitrogen management practices across regions of Argentina and Spain. p. 313-342. Delgado, J.A. and R.F. Follett (eds). Advances in Nitrogen Management for Water Quality. SWCS, Ankeny, IA.
Interpretive Summary: The nitrogen management problems in Argentina and Spain illustrate similar management problems, however they differ in the factors that cause the specific problems. With projected increases in N fertilizer inputs, we expect that the occurrence of NO3-N leaching events will increase in both countries. It is important to calibrate new tools, such as the NLEAP, to assess the changes in management to help the development of BMP that will increase NUE. The NLEAP model is a versatile tool that allows for the calculation of potential losses of NO3-N, making use of easily obtained or estimated inputs to run in any local conditions. In Spain, the screening analysis of the NLEAP model linked to a GIS system provides a useful tool that can quickly assess and estimate the potential NO3-N leaching at a regional scale. This tool can also be used to evaluate the NO3-N leaching from different management practices in a cost-effective way. We found that the N doses recommended by the GAP reduced the NO3-N leaching 35 percent compared with conventional management. A higher reduction is possible if the farmer uses some other fertilizer recommendation system or a detailed simulation model to optimize the management practices. The NLEAP model allowed us to conduct a more detailed analysis of N management and NUE for several crops. After a slight calibration, the model simulated water drainage and NO3-N leaching accurately. For Argentina, the NLEAP model is starting to be used to develop management strategies to improve the nitrogen fertilization efficiency, reducing the nitrate leaching risk, and increasing crop yield in the less developed areas in the Pampas region. Future uses of the model with GIS technology would be valuable to detect areas of high risk aquifer contamination, differences in soil properties, management, fertilization doses and application moments, complementary irrigation, crop rotation, and so on. There is potential to use NLEAP as a tool to assess changes in management to help develop BMP that will increase NUE across regions of international countries.
Technical Abstract: Argentina is a large country that covers an extensive area from middle South America to near the South Pole (Fig. 1). The grassland zones for Argentina range from arid zones in the northwest (with low potential for NO3-N leaching) to temperate grasslands in the middle of the country (with a high potential for NO3-N leaching). The Pampas region, extending across 55 Mha, is one of the largest temperate areas dedicated to cereal crops in the southern hemisphere. Fertilizer consumption across the Pampas increased exponentially in the last decade, from nearly no fertilizer used to 100 and 83 percent of the cropland area being fertilized for wheat and corn, respectively. About fifty percent of Spain’s land area is cultivated with two main agroecosystems: the humid Atlantic climate of Northern Spain and the remainder of the area with a dry Mediterranean climate. Since the average N fertilizer rates for these small grains and olive crops are 50 to 100 kg N ha-1, combined with a low, dry climate, the potential for NO3-N leaching across the area, planted in small grains and olives, is low. There are irrigated areas across the dry Mediterranean climate region such as vegetables (e.g. tomato, cauliflower, cabbage, artichoke, onion, lettuce, etc), fruits (melon), citrus (e.g. orange, mandarine, etc.), or tuber crops (e.g. potato, sugar beet etc.) that are heavily N fertilized with rates of 200 to 300 kg N ha-1, where the NO3-N leaching potential is higher. In Spain, the NO3-N content in groundwater has been correlated to land use with high N fertilizer rates. The NLEAP model was tested near the key south rolling Pampas towns of Alberti, Pergamino, and Salto. The simulated NO3-N values after harvest were correlated to measured residual soil NO3-N (p<0.001, R2=0.7944) with an intercept close to 0 and the slope at 1. The NLEAP model was an effective tool capable of simulating different soils and climate conditions in Argentina. The NLEAP model was used to estimate effects of nitrogen management practices on NO3-N leaching across 230 km2 located near the Valencia Mediterranean coast of Spain. In Spain, the screening analysis of the NLEAP model linked to a GIS system provides a useful tool that can quickly assess and estimate the potential NO3-N leaching at a regional scale. This tool can also be used to evaluate the NO3-N leaching from different management practices in a cost-effective way. There is the potential to use NLEAP as a tool to assess changes in management to help develop BMP that will increase NUE across regions of international countries.