Innovations for improving productivity and nutrient use efficiency: No-Till grain cropping systems of South America

DÍAZ-ZORITA, MARTÍN

Philadelphia, PA. USA

Congreso; 18th Worl Congress of Soil Science; 2006

International Union of Soil Science

South America is a vast region with large differences in extensive agricultural production systems depending on diverse climate and soil conditions that vary among its ecological regions. Most of the agricultural land is located towards the East of the continent lying on tropical, subtropical and temperate regions. For most of the countries within this area, the cultivated land and the total crop productivity have increased since the last 2 decades. The purpose of this article is to summarize and to discuss nutrient management for extensive no-tillage (NT) crop production systems in South America. The use of nutrients for extensive annual crop production in South America follows the increasing requirements because of the agricultural expansion towards new lands (ex. Cerrado region in Brazil), the replacement of pasture rotated lands (ex. Pampas region in Argentina and Uruguay), or the improvement in soybean [Glycine max (L.) Merrill], wheat (Triticum aestivum L.) and corn (Zea mays L.) grain yields in almost all the region. Because most of the recommendation practices are based on crop sufficiency criteria, fertilization practices are unsatisfactory for soil nutrient balances in the region and the reduction in soil extractable nutrients is a common issue in all the production systems. Adoption of NT has sharply increased since the 90´s and, currently, it is the dominant crop and soil management practice in almost all the region. This production system contributes to the reduction in soil erosion process, soil organic matter conservation, and the improvement in soil water storage and availability, and it induces changes in soil-plant nutrient dynamics. In general, crop yields under NT practices are more stable than under tilled systems with greater efficiency in the use of nutrients. Under NT, most of the fertilization and liming treatments are broadcasted or placed in a shallow layer and the nutrient cycling has been improved because of the use of intensive cropping practices replacing uncovered fallows. As a consequence the nutrients lost by soil erosion and leaching has been decreased in last two decades. However, the challenge is a better understanding of the complexity of nutrient dynamics under NT for improving the ity of these systems in environmental and crop production conditions of South America. Trabajo presentado como conferencia