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Title: A new nitrogen index for assessment of nitrogen management practices of Andean Mountain cropping systems of Ecuador

Author
item ESCUDERO, LUIS - National Institute For Agricultural Research (INIAP)
item Delgado, Jorge
item MONAR, CARLOS - Bolivar State University
item VALVERDE, FRANKLIN - National Institute For Agricultural Research (INIAP)
item BARRERA, VICTOR - National Institute For Agricultural Research (INIAP)
item ALWANG, JEFF - Virginia Polytechnic Institution & State University

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2014
Publication Date: 5/24/2014
Citation: Escudero, L., Delgado, J.A., Monar, C., Valverde, F., Barrera, V., Alwang, J. 2014. A new nitrogen index for assessment of nitrogen management practices of Andean Mountain cropping systems of Ecuador. Soil Science. 179:130-140.

Interpretive Summary: Using nitrogen fertilizer to maximize yields in minimum tillage systems that minimize the potential for soil erosion for off-site transport of agrochemicals, will be key to developing cropping systems that can adapt to a changing climate. The scientific literature lacks studies that have validated tools that can be used to quickly assess the effects of nitrogen management practices on nitrogen uptake, nitrogen use efficiency, and the potential risk of nitrogen losses to the environment in high-altitude mountain systems. Additional information is needed to improve nitrogen management and sustainability in these high-altitude cropping systems. This is the first study of the application of a Nitrogen Index for high-altitude mountain systems. The Ecuador Nitrogen Index was able to assess nitrogen uptake, nitrogen use efficiency, and the potential risk of nitrogen losses to the environment (P < 0.05). The measured data and Nitrogen Index assessment strongly suggest that the split applications of nitrogen at planting, V6, and V9 can contribute to much higher nitrogen use efficiency and lower nitrate leaching. The corn crop significantly responded to nitrogen fertilizer inputs, doubling the yields at 120 and 140 kg N ha-1. Our study suggests that 120 kg N ha-1 applied at planting, V6, and V9, could be a good practice that minimizes nitrogen losses to the environment, especially under minimum tillage systems. We also found that the efficiency of the system is also affected by the rate of precipitation, and at precipitation rates of > 900 mm the nitrate leaching potential increases. The validation of the tool’s estimates for crop uptake and nitrogen use efficiency has been conducted for mountain systems for the first time. More studies like this, where user-friendly tools are used to help provide additional management information, are needed. Additional studies are needed to evaluate the tools and the effects of these practices on the sustainability of the system. We are conducting further studies where the effects of management practices on the sustainability of the system is being monitored.

Technical Abstract: Corn (Zea mays L.) is the most important crop for food security in several regions of Ecuador. Small farmers are using nitrogen (N) fertilizer without technical advice based on soil, crop and climatological data. The scientific literature lacks studies where tools are validated that can be used to quickly assess the effects of nitrogen management practices on nitrogen uptake, nitrogen use efficiency, and the risk of nitrogen losses to the environment in high-altitude mountain systems. A study was conducted to test the response of corn to fertilizer application and to test the potential use of the Nitrogen Index and sustainability index to assess the nitrogen dynamics of the system. The responses to nitrogen fertilizer application were tested across six mountain sites in the Bolivar province of Ecuador, where the INIAP-111 variety was planted in farmers’ fields. What makes this study unique is that we conducted fertilizer studies at each site with minimum tillage, traditional farming practices, and a control treatment of zero nitrogen fertilizer, and we also used a new Nitrogen Index tool that was developed for Ecuador. This study was conducted under conservation agriculture with minimum tillage. Corn significantly responded to nitrogen fertilizer application with an average increase of 67 kg ha-1 corn grain per every 1 kg of N ha-1 applied. The nitrogen use efficiency in the system was reduced with higher nitrogen rate, and nitrogen leaching increased with nitrogen fertilizer application, especially for the areas with precipitation above 900 mm. The sites with precipitation < 900 mm had minimal nitrate leaching (< 10 kg NO3-N ha-1) for loam and clay loam soils. The sustainability index indicates that conservation agriculture is a sustainable system in these high-altitude regions of Ecuador. The Nitrogen Index was able to quickly assess the effects of nitrogen management practices on nitrogen uptake, nitrogen use efficiencies, and the potential risk of nitrogen losses to the environment (P < 0.05). The Nitrogen Index has the potential to be used in extension programs, and as an aid to talk to local farmers and improve the technical evaluation of best management practices in these high-altitude mountain systems.