The Advanced Research Projects Agency of the Department of Defense did a study titled, "Magnetic Treatment of Water" , in 1973 (I have a copy of the entire report). In it, it says, and I quote, "In general, there are two features characteristic of magnetic treatment: the poor reproducibility of experimental results (especially under laboratory conditions), and the "memory" of its magnetization which water seems to show, i.e., the persistence of the magnetization effects for several hours or even days, if the temperature of the water system is sufficiently low (1)."
In the study they did not take into account the differences of the North and South poles, and this would certainly give mixed results. The report also states, "In practice, however, no one argues whether magnetic treatment is effective or not; in the Soviet Union the magnetic treatment of water is used extensively and with great economic effect. The only argument is on how to explain the observed phenomena correctly: by the changes which take place within the water itself, or solely by the influence of the impurities present in the water (2)."
Seeds are alive too, they're just dormant until planted. Every living thing has bioelectric (or electromagnetic) currents flowing through it. And we do see differences in the Northern and Southern hemispheres. The magnetic field of the earth is very weak now (1/2 of one gauss), and alternating magnetic polarities are showing up all over the earth in both hemispheres right now. The magnetic poles of the earth are nearing a reversal. If the magnetic fields were much more powerful (and stable), the contrast of the Northern and Southern hemispheres would be much more obvious.