Maintaining soil quality and fertility is of worldwide importance. Any changes in the factors influencing soil quality and soil processes can take decades to have any measurable effect. Similarly, the effects of agriculture on the wider environment may take years to become obvious. Long-term experiments with their contrasting treatments and management are an invaluable resource, which we can use to examine these effects in greater detail.
Dr. Amir started a long-term field experiment in 1975 at the Gilat Research Center, located in the south of Israel (31°20’ N, 34°41’ E) to determine best managements for semi-arid and arid wheat dominated cropping system. The site is characterized by an average annual precipitation of 230 mm and sandy loam loess–Calcic Xerosol soil. An irrigation-rotation-tillage-fertilization long-term study was conducted, and the main objects were to measure the effects on crop yields of inorganic nitrogen and phosphorus, clean fallow and supplemental irrigation. Like the classical oldest long-term experiment in Rothamsted UK, the experiment has been modified on occasion. The main treatments that were managed by conventional tillage were established in 1975, while no-tillage treatment was initiated in 1994 and minimum tillage in 1998. Water and fertilization have been kept almost without modification; one field examined in non-irrigated conditions and another one with supplemental irrigation. Fertilization treatments include 4 nitrogen and 2 phosphorus levels. Rotation include continues wheat vs. clean fallow or other fallow crop. Hence, high variation exists each year between the harvested 384 subplots. Moreover, according to environmental conditions, mainly rain, there is a high variation between years too.