Wednesday, November 15, 2006 - 8:20 AM

Optimizing Nitrogen Management under Rainfed Agriculture.

Upendra Singh1, Paul Wilkens2, Sanjay Patil3, and Mustapha Naimi1. (1) IFDC, PO Box 2040, Muscle Shoals, AL 35662, (2) Intl. Fertilizer Development Ctr., IFDC, PO Box 2040, Muscle Shoals, AL 35662, (3) Indira Gandhi Agricultural Univ, Raipur, India

The constraints faced by rainfed farmers are far more complex than those faced by their irrigated counterparts. Rainfed agriculture is characterized by high production risks associated with rainfall amount and distribution. Fluctuations in prices of inputs and produce further enhance the risks faced by rainfed farmers. These biophysical and socioeconomic factors are responsible to a large extent for the low agricultural productivity—less than 20% compared to irrigated agriculture. Farmers are aware of nitrogen needs of crops, but they also know of: (1) lack of crop response when other factors are limiting, (2) high N losses associated with leaching, denitrification, and volatilization, (3) poor residual value of applied N fertilizers, (4) cost of N fertilizers, and (5) limited availability of organic N sources, particularly under unfavorable rainfall conditions. A truly dynamic and site-specific N management considers the variations associated with weather and prices and the past and current management and production objectives of a farmer.  Decision support systems (DSS) comprised of a natural resource database, soil-crop simulation models, and economic evaluators integrate knowledge about soil, climate, crops, and management and offer options for making site- and season-specific management recommendations.   
In this presentation through field validation trials and the application of DSS, we will illustrate how N management decisions are influenced by weather (rainfall and temperature) and the management options that are available to farmers to reduce risks and improve productivity. Such options include crops, varieties, optimum planting windows, crop rotation, and integrated N management with options to choose different sources (mineral fertilizers, organic material, or the combination of both). Examples of N model applications from Morocco, Uganda, and India are presented.