Nitrogen fertilizer leaching from cropped and irrigated sandy soil in Central Turkey

Abstract

Summary Pollution of ground water caused by excessive and uncontrolled use of nitrogen fertilizer is worrying. A recent example of such pollution has been observed in an agricultural basin in the province of Nevsehir, Turkey, where up to 900 kg ha−1 nitrogen fertilizer is used for growing potatoes in sandy soils under irrigation. Using nitrogen fertilizer in amounts that guarantee large yields without polluting ground water is essential. We present results of field experiments and numerical simulations involving 15N‐labelled nitrogen fertilizer leaching. In the field, we monitored the movement of water and the distributions of nitrogen species within the soil–water–plant continuum. The detailed dynamics of the nitrogen cycle within the system were simulated. Simulations included calibration and validation of the nitrogen version of the LEACHM model (LEACHN, version 3) and long‐term applications of the model. The model’s predictions of nitrogen fluxes under long‐term use of fertilizer and irrigation were analysed. Nearly half of the applied ammonium‐N was converted to nitrate‐N during the growing season. With increasing additions of N the rate of plant uptake declined, while leaching increased significantly, and the fraction of nitrogen remaining in the soil profile increased only moderately. In long‐term applications, a significant fraction of the applied fertilizer tended to accumulate after the first year in soil as the residual nitrogen not taken up by the crop. Accumulated residual nitrogen is converted to nitrate‐N and leached rapidly from the soil profile during the wet season following the harvest. To reduce leaching of the residual nitrate, the rates, frequencies and timings of fertilizer application and irrigation must be scheduled in accordance with the plant growth periods and the hydraulic regime of the soil.

Nitrate leaching reduced with Dynamic‐Adaptive nitrogen management under contrasting soils and tillage

“…It was originally developed from two models, the soil hydrology-biogeochemistry LEACHN model (Hutson, 2010), and a maize N uptake, growth and yield model (Sinclair & Muchow, 1995). These were previously validated in various studies (e.g., Jabro, Toth, Dou, Fox, & Fritton, 1995;Sinclair & Muchow, 1995;Unlu, Ozenirler, & Yurteri, 1999;Sogbedji et al, 2001a;Jabro, Jabro, & Fox, 2006). Later developments of Adapt-N were validated against leached N and water drainage measurements (Sogbedji, van Es, Hutson, & Geohring, 2001b, as well as a complete set of leached N, soil N, gaseous N losses, and crop yield for fields in both New York and Minnesota .…”

Dynamic Model Improves Agronomic and Environmental Outcomes for Maize Nitrogen Management over Static Approach

“…The PNM model itself is a combination of (i) the LEACHN model (Hutson and Wagenet,1995;Hutson, 2003), which simulates the soil hydrology and biogeochemistry, and (ii) a maize N uptake, growth, and yield model (Sinclair and Muchow, 1995). These two components of the PNM model were validated previously in multiple studies (e.g., Khakural and Robert, 1993;Jabro et al, 1995;Sinclair and Muchow, 1995;Unlu et al, 1999;Jabro et al, 2006). The PNM model and the constituent LEACHN model were extensively validated against leached N and water drainage measurements in previous New York-based studies on a range of soil types, providing reasonable confidence to simulated N-loss estimates in this study.…”

Forest management and soil respiration: Implications for carbon sequestration

“…Soil acidification and degradation problems may arise from the air emissions originating from industrial facilities such as thermal power plants, petroleum refineries, and petrochemical industries and have become a serious environmental concern (Unlu et al 1999). Increased soil acidity is generally linked with a decrease of SOM decomposition (Alexander 1980;Jenkinson 1981), although the extent of the decrease varies with the nature of the organic materials (Abrahamsen et al 1977;Baath et al 1980).…”