Nitrogen Cycling in an Irrigated Wheat System in Sonora, Mexico: Measurements and Modeling

Abstract

An improved version of an ecosystem nitrogen cycling model (NLOSS) is described, tested, and used to analyze nitrogen cycling in the Yaqui Valley, Sonora, Mexico. In addition to previously described modules in NLOSS that simulate soil water and solute fluxes, soil evaporation, soil energy balance, and denitrification, modules were added to estimate crop growth, soil carbon cycling, urea hydrolysis, and nitrification. We first tested the model against season-long measurements of soil NO 3 -, NO 2 -, and NH 4 + aqueous concentrations; NO and N 2 O soil effluxes; and crop biomass accumulation in three fertilizer treatments. We used NLOSS to test the sensitivity of wheat production, NO 3 -losses, and trace-gas emissions to fertilizer application rate. With the model, we compared the typical farmer's fertilization of 250 kg N ha -1 with five other fertilization scenarios, ranging from 110 to 220 kg N ha -1 . The typical farmer's practice produced higher wheat yield than the lower fertilization treatments. However, the increase in yield per increase in kg N applied decreased with increasing fertilizer addition as a result of higher leaching losses, higher residual N, and higher trace-gas emissions. In addition, with respect to the lowest fertilization treatment, the highest fertilization treatment resulted in an 11% decrease, a 10% increase, and a 157% increase in N 2 , N 2 O, and NO emissions, respectively, and a 41% increase in leached NO 3 -+ NO 2 -. These results demonstrate that a small decrease in fertilizer application rate can increase N-use efficiency for wheat growth, while reducing leaching losses and emissions of harmful trace gas fluxes.

Use of the new Nitrogen Index tier zero to assess the effects of nitrogen fertilizer on N2O emissions from cropping systems in Mexico

“…The weather, precipitation, irrigation, soil conditions, crop type (wheat, maize, bean (Phaseolus vulgaris L.), and yield information were also entered. Table 1 has some of the study information that was entered into the tool assessment, and detailed information about these studies can be found in Christensen et al (2006), Riley et al (2001), Grajeda-Cabrera et al (2004), Limon-Ortega et al (2008 and Govaerts et al (2006). The studies were used to assess the capability of the tool to estimate aboveground crop N uptake, system N use efficiency and N 2 O emissions.…”

The value of seasonal forecasts for irrigated, supplementary irrigated, and rainfed wheat cropping systems in northwest Mexico

“…The price of water is often subsidized in irrigated systems, and farmers in these systems often apply an excessive amount of N to guarantee a high yield (Christensen et al 2006;Lobell and Ortiz-Monasterio 2006;Lobell et al 2004). This approach is different from rainfed farmers of Australia.…”

“…Farmers in irrigated regions do not follow this type of risk-averse behavior as strongly as under rainfed conditions. Rather, irrigation farmers tend to over-fertilize to guarantee the highest achievable yields using fertilizer subsidies (Christensen et al 2006;Lobell and Ortiz-Monasterio 2006;Lobell et al 2004). For that reason, in the FIS we assumed farmers optimized the N fertilizer application in situations where the net returns equal zero.…”

15N Fertilizer recovery in different tillage–straw systems on a Vertisol in north‐west Mexico

“…The Yaqui Valley in north‐western Mexico represents one of the world's largest wheat‐growing systems under irrigation and has conditions similar to the Indian and Pakistani Punjab and the Nile Valley in Egypt. Nitrogen application is indispensable in intensive, irrigated cropping systems, but the application of mineral N fertilizer is often inefficient, leading to a N use efficiency (NUE) of only 31% in the Yaqui Valley (Ortiz‐Monasterio & Raun, ) with high N leaching losses and medium gaseous N losses in farmers’ fields (Christensen, Riley, & Ortiz‐Monasterio, ; Grahmann, Verhulst, Palomino, et al., ). Under gravity irrigated conditions in this area, CA is implemented by using permanent beds (PB) with residue retention, which have the potential to reduce soil degradation and moisture loss, enhance nutrient cycling, decrease greenhouse gas emissions and increase farm sustainability (Verhulst et al., ; Dendooven et al., ).…”