Nitrogen Credits from Peanut to Wheat.

Cooperative Extension generally recommends 22-45 kg N/ha reduction in mineral fertilizer application to crops after peanut production. However, recent research has reported that these are overestimated. Field experiments were conducted over five site-years in Florida to quantify N availability from peanut to a subsequent wheat crop. The experiment was a randomized complete block split-plot design with four replications, with main plots as summer crop (cotton, peanut and fallow) and subplots as four levels of mineral N applied to a subsequent wheat crop. Most site years showed no wheat yield differences due to previous crop. However, when previous crop did make a difference in wheat yields, previous peanut was not different from the previous fallow treatment, indicating that peanut production was not different from a fallow control. Furthermore, wheat yields were reduced after cotton production compared to both peanut and fallow as previous crops. In those cases, results indicate a yield reduction after cotton rather than a yield increase after peanut – a result that would not be observed without a summer fallow treatment. This result would ordinarily appear as a N credit after peanut if a fallow control was not employed. It is possible that the yield reduction after cotton may a result of N immobilization by cotton residues. Further research is needed to determine peanut N environmental fate.