|MATTOS, JR, D|
Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2003
Publication Date: 6/1/2004
Citation: Alva, A.K., Paramasivam, S., Fares, A., Delgado, J.A., Mattos, Jr, D., Sajwan, K. 2004. Nitrogen and irrigation management practices to improve nitrogen uptake efficiency and minimize leaching losses in soils under citrus. Journal of Crop Improvement. 15:421-470.
Technical Abstract: Nitrogen is a key component of economic viability and sustainability of worldwide agroecosystems. Most agricultural systems have significant spatial and temporal variability that make N management difficult. Since N is such a dynamic and mobile element, management is also affected by irrigation and unpredictable rain events. Nitrogne uptake efficiency for different crop production systems worldwide range from 33 to 55 percent. Thus increasing NUE is a great challenge for nutrient managers who want to maximize yields, and decrease N losses to the environment. There is the need to continue developing new tools and methods to quickly assess N status and to improve N management at regional, field, zone, and site specific levels. Significant advances have been made during the last two decades that are contributing to improve N management and reduce N losses. Further improvements in N management will need to be made within the context of N cycle and N budgets. There are no simple solutions; nutrient managers must consider viable solutions that account for regional and local variability in crops, weather, and soils. There are several universal principles and tools that can be applied to improve N management and increase NUE. New technology is also being developed that will help to increase the accuracy of N needs and N status, and identify hot spots and sensitive areas. Applying N close to the time of greater demand in multiple applications has demonstrated significant benefits in different geographical regions and for different crops. Crop rotations, especially of shallower and deeper rooted crops, can be used as tool to increase the NUE of shallow rooted systems and to reduce N applications. Rotations that incorporate NO3-N scavenger crops and legumes are also universal tools that can be used to increase NUE. Another universal concept is the application of irrigation scheduling in phase with crop water needs. It is important to know at each site the soil water holding capacities, the evapotranspiration rate and precipitation. Evapotranspiration models and expert systems could be used to improve irrigation scheduling, and may need to be calibrated in different production systems based on soil water holding capacity. This chapter emphasizes the need to follow a holistic approach that considers water and N management for a given cropping system and soil condition. We need to follow best water management practices (BMP) that facilitate retention of N in the soil profile, within the rooting zone. Rotation of a deep rooted crop following a shallow rooted crop provides benefit of scavenging N from the deeper soil layers. Rotations have additional benefits such as reduction of disease and weed problems that will increase yields thus leading to greater NUE. Use of simulation models to assess sensitive areas of the fields is also a BMP option. New technologies will facilitate the application of these universal principles at a site specific level. The use of remote sensing, and development of management zones will contribute to increase NUE for precise conservation of water quality, reducing N losses from sensitive areas of the field. The calibration, use and development of quick techniques to determine N status will also contribute to increase NUE. Although there is the need to continue developing BMP to improve NUE, maximize yields, product quality and economic returns to farmers, there are universal principles and new technology that can contribute to improve NUE of irrigated system, while reducing the N losses to the environment.