Excessive use of N fertilizers in agriculture often leads to NO 3 − accumulation in the unsaturated zone and to groundwater pollution. There is uncertainty regarding the variability in fertilizer transport and uptake efficiency due to the lack of studies based on continuous nondestructive measurements in unsaturated soils. In this study, we analyzed solute dynamics across the unsaturated zone underlying cultivated agricultural fields. Commercial crop rotations under four treatments, comprising two N fertilization regimes and two irrigation water salinity levels, were conducted in loess soil in the semiarid climate of the northern Negev Desert, Israel. The impact of the various treatments on water and solute dynamics below the root zone was monitored by a vadose zone monitoring system. The patterns of variations in soil water content and solute concentrations were analyzed using nonnegative tensor factorization. We found that irrigating using higher salinity water resulted in the earlier arrival of wetting fronts to the deeper layers and increased NO 3 − concentrations relative to the lower salinity treatments. Surprisingly, this effect was only seen in the deeper soil levels, whereas there was no significant difference in the arrival times and concentrations in the upper soil layers. Possible mechanisms are suggested and discussed. Abbreviations: CPD, canonical polyadic decomposition; FTDR, flexible time domain reflectometer; PSD, particle size distribution; VMS, vadose zone monitoring system; VSP, vadose zone pore water sampling port. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Summary Unraveling the long-term behavior of the geomagnetic field is crucial for understanding the dynamics of the deep Earth. Yet, obtaining an accurate measure of geomagnetic paleosecular variations (PSV) is difficult, partly because of tectonically induced rotations that overprint the original paleomagnetic signal. We present a detailed paleomagnetic investigation based on 99 sampling sites collected from the 119 to 112.6 Ma Ramon Volcanics exposed near the dormant Ramon Fault, southern Israel. These volcanic rocks were emplaced at equatorial paleolatitudes during the beginning of the Cretaceous Normal Superchron (CNS; 123.4-83.6 Ma), during which there were no polarity reversals. Structurally corrected remanence directions consistently vary across the investigated area, whereby the sites found near a sharp bend of the Ramon Fault are clockwise rotated, whereas the other sites show no obvious rotational pattern. Elasto-plastic modeling suggests that the rotations were induced by up to 1.5 km of dextral horizontal slip accommodated by the fault, consistent with previous geological and geophysical estimations. Considering the remanence directions obtained from sites that were not influenced by the fault, we calculated an SB value of $13.3_{ - 1.3}^{ + {{1.9}}^o}$ (95% confidence, 46 sites), which corresponds to previous SB estimations from pre- and Early CNS volcanic bodies emplaced at low paleolatitudes (λ<20˚). This observation suggests that the emergence of the superchron was not accompanied by a change in the behavior of the geomagnetic PSV. Finally, our results, together with previous paleo-equatorial observations, show that the middle part of the superchron had lower angular dispersion (i.e., lower SB) compared to the scatter that prevailed during the beginning of the superchron. This observation suggests that the geomagnetic field transitioned into a more axial dipole dominance state toward the middle part of the superchron. Altogether, our analysis indicates that the superchron cannot be treated as a period characterized by a steady-state field behavior.

Groundwater recharge is an essential component of the water cycle. The total recharge is often divided into several components, including diffuse recharge, focus recharge, and agricultural recharge (