Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2006
Publication Date: 4/18/2006
Citation: Delgado, J.A., Shaffer, M.J., Hu, C., Lavado, R., Wong, J.C., Joosse, P., Li, X., Rimski-Korsakov, H., Follett, R.F., Colon, W., Sotomayor, D. 2006. A decade if cgange in nutrient management: a new nitrogen index. Journal of Soil and Water Conservation. J. Soil and Water Conservation. 61:62!-71A.
Interpretive Summary: Nutrient management is a key to continue feeding increasing worldwide population and to conserve soil and water quality. Delgado and Lemunyon (2006) defined Nutrient Management as the science and art directed to link soil, crop, weather and hydrologic factors with cultural, irrigation and soil and water conservation practices to achieve the goals of optimizing nutrient use efficiency, yields, crop quality, and economic returns, while reducing off-site transport of nutrients that may impact the environment. Nutrient managers confront the difficult task of making management decisions that can increase the use efficiency of one element, but simultaneously reduce the efficiency of a second nutrient, increasing its losses. This dilemma in nutrient management was clearly pointed out by Sharpley et al. (1999, 2001) when they reported that if manure applications were based on crop N needs and manure N content, soil P concentrations will be built up to excessive levels, increasing the potential for off-site transport of P. The also pointed out as an example that minimum tillage practices that can reduce off-site transport of phosphorous can potentially contribute to higher nitrate-nitrogen leaching. There is a need to provide nutrient managers across worldwide agroecosystems with management tools that can quickly assess how the effects of management decisions impact the availability of multiple nutrients. We are proposing that our new Nitrogen Index tool version 1.0 can be easily coupled to already established P Indexes, helping to synchronize the simultaneously evaluations of N and P. We also propose that our Nitrogen Index version 1.0 is flexible and can potentially be coupled to other salinity, potassium, erosion, or micronutrient indexes in the future.
Technical Abstract: Our Nitrogen Index Version 1.0 has a large number of drop-down menus, facilitating the use of a series of scenarios. Although qualitative in rankings, our Nitrogen Index is based on quantitative Nitrogen balances, keeping tacks of inputs and outputs and soil nitrogen dynamics for the entered scenarios on an annual basis. Although preliminary analysis shows that the Nitrogen Index Version 1.0 has the capability to assess the effect of management practices across different agroecosystems in the USA and internationally, there is also the need to continue testing and evaluating the Nitrogen Index potential. There are some limitations and the index is not very sensitive to sudden changes driven by a sudden event (e.g. a high precipitation event). The effect of these events will depend on the amount of rain and or texture of the soils. Similarly these events can also trigger denitrification events that cannot be assessed with the index. In general the index is capable of assessing effects of management practices on N transport use efficiencies and losses, but we need to continue assessing capabilities and limitations of the Nitrogen Index. We propose that this is a good tool that can be used by managers to evaluate N and P jointly and that there is the continuing need to celebrate joint symposiums where scientists and conservation practitioners can come together with other interested members and the general public to present recent advances in soil and water conservation and nutrient management.