Ion exchange resins-based NO 3-fluxes displayed high spatial variability, therefore a large number of repetitions was necessary. PB-straw burned had highest residual soil NO 3-N after crop harvest. Soil NO 3-N concentrations were significantly affected by sampling date and depth. For maize, overall leaching losses were highest for PB-straw retained (81.9 kg ha −1 season −1 NO 3-N), followed by 75.6 kg ha −1 season −1 NO 3-N for CTB-straw incorporated and 47.7 kg ha −1 season −1 NO 3-N for PB-straw burned. NO 3-N leaching for wheat was 51.1 kg ha −1 season −1 NO 3-N in CTB-straw incorporated, 60.8 kg ha −1 season −1 NO 3-N in PB-straw retained and only 46 kg ha −1 season −1 NO 3-N in PB-straw burned. Tillage-straw treatment did not significantly affect NO 3-N leaching in wheat, but it did in maize.
Leaching losses were higher with maize than with wheat cultivation (68.2 and 53.5 kg ha −1 season −1 NO 3-N P = 0.25). Ion exchange resin samplers were installed at 90 cm depth in a consecutive crop rotation of wheat ( Triticum durum L.) and maize ( Zea mays L.) for 6 and 5 months, respectively (from first pre-plant fertilization to harvest). Tillage-straw treatments were conventionally tilled beds with incorporated crop residue (CTB-straw incorporated), permanent beds with crop residue retained at the surface (PB-straw retained) and permanent beds with residue burning (PB-straw burned). To this end data were collected in 2013/2014 from a tillage experiment established in 2005 as a randomized complete block design with two replications and three subplots on a Hyposodic Vertisol. This study aimed at estimating NO 3-N leaching losses for three tillage-straw management systems in the intensely cropped Yaqui Valley, Northern Mexico using ion exchange resin samplers. Nitrate (NO 3-N) leaching from agricultural soils can lead to substantial losses of fertilizer nitrogen (N) and cause considerable contamination of aquatic ecosystems and groundwater.