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NE MO & W IL | Pfarms, that is good thinking but in actuality, soybeans are net users of nitrogen, meaning they use every lb of N they produce (around 4 lbs/bu). The rhizobium or nodules actually only produce about 75% of the total N needed in a typical crop and the rest is obtained through soil N usually from mineralization. So really, there is no hot pocket of available nitrate or ammonium in nodules the next spring, unless they were in a very accelerated rate of decay and mineralization. The "soybean credit" comes from the fact that soybeans, in comparison to corn or wheat, have much lower Carbon to Nitrogen ratios. Soybean residue above and below ground is broken down much quicker and requires much less energy for microbes to mineralize the residue back into available forms of N. This is why soybeans get a "N credit" the next year. Corn or wheat residue takes so much more time to "cycle" and it actually takes soil N away from the subsequent crop, initially, to feed the microbes.
So, if you are planting over the old rows to aquire more N, you are just as effecient planting right next or even in the middle of the old rows. The corn roots will grow and branch out to aquire any available N that is mineralized that season. Now, I have heard of the theory that planting over the old soybeans rows would allow the corn roots to follow the old soybean taproot channel and get better root penatration. I think that would highly depend on your corn hybrid's genetics and rooting capibilities. Some hybrids may respond, others would not.
Edited by agger802 11/25/2009 00:36
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Planting on soybean row...no-till/Nitrogen credit
