Seedbed Preparation in Rhizoma Peanut for Millet and Sorghum.

Rhizoma peanut (Arachis glabrata Benth.; RP) is used as a perennial warm-season forage, ornamental ground cover, and cover crop in areas with minimal freezing temperatures, although at least one cultivar, Latitude 34, survives prolonged freezing temperatures. It is being experimentally incorporated as perennial living mulch in annual cereal grain production systems as well.  We measured the effects of seedbed preparation method (control, tillage, mowing and glyphosate) of an established rhizoma peanut field on weed mass (WM) and RP plant number regeneration under millet and sorghum during early (T1) and late (T2) season. Time was a factor (P≤0.05) in seedbed preparation for rhizoma peanut (RP) living mulch, regardless of soil preparation. Time 2 date lends itself to better reemergence of RP peanut relative to T1. A later date may foster greater CHO reserves in rhizomes which results in healthier plant numbers at 45 DAP. Mowing seedbeds yielded the greatest (P≤0.05) number of RP shoot reemergence out of all treatments at both times although there was no difference with the control at T1. Rhizoma peanut reemergence in herbicide plots was much greater (P≤0.05) than in control plots at T1 than in T2. This could be due to the stage of peanut physiological maturity. The earlier in the season that seedbeds are prepped, the more vulnerable the RP living mulch is to herbicide whereas the opposite appears to be the case for tillage. Tillage and herbicide resulted in greater (P≤0.05) weed mass (WM) in T1 than in T2.  This could be due to more aggressive weed development vis-à-vis greater RP setback at T1. This is a mirror reflection of RP plant numbers. At T1, till and herbicide treatments were the least effective (P≤0.05) at suppressing WM compared to the control or mowing.  This difference disappeared (P>0.05) by T2. Weed mass in mowing and control plots did not differ (P>0.05) at either time and resulted in lower WM at T1. Time was not a factor (P>0.05) in WM for either cereal species. The presence of cereal decreased WM 57 to 63% (P≤0.05) vis-à-vis control at T1. Weed mass was 3.1 times greater (P≤0.05) in T1 control compared to T2 indicating that WM was suppressed in plots with no grain as temperatures increased.  This could be due to the weeds advanced maturity when the second trial was tilled. Perhaps since the weeds were more mature, regrowth was much harder than in the earlier trial. Cereal species did not affect (P>0.05) WM at either time. Seedbed preparation methods had no impact (P>0.05) on WM in millet plots. Mowing seedbeds prior to seeding both cereal species did not have an effect on weed mass compared to the control. Herbicide application resulted in greater (P≤0.05) WM in sorghum and control plots compared to mowed plots but this was not the case for millet. Spraying herbicide in millet seedbeds lowered (P≤0.05) WM compared to control plots, indicating that millet canopy was essential for weed suppression. Seedbed tilling decreased (P≤0.05) WM in both millet and sorghum plots compared to the control. There was no difference (P>0.05) in WM in plots of sorghum or millet as a result of seed bed preparation. Millet plots had lower (P≤0.05) WM than control plots when tilled or sprayed with herbicide.  Rhizoma peanut shows some promise as a living mulch for warm-season grain production but further research is necessary.