Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/7/2004
Publication Date: 10/1/2004
Citation: Davis, J.R., Huisman, O.C., Westermann, D.T., Everson, D.O., Schneider, A., Sorensen, L.H. 2004. Some unique benefits with Sudangrass for improved U.S. #1 yields and size of Russet Burbank potato. American Journal of Potato Research. 81:403-413. Interpretive Summary: Among cropping practices, green manures can be highly effective for both the control of Verticillium wilt, caused by Verticillium dahliae, and the improvement of yield and quality of potatoes. Benefits of a sudangrass green manure crop appear to go beyond that obtained by normal disease suppression. The purpose of our study was to attempt to identify and define these effects. Green manure crops of sudangrass, sweet corn, Austrian winter pea, and barley were grown during the summer months at Aberdeen, ID and all plant biomass incorporated by a rotovator by the end of August. In addition, a plot was also treated with metan-sodium (Vapam HL) to reduce soil Verticillium populations. Russet Burbank potatoes were grown on all plots the following year. Potato tuber yields and quality improved from the incorporation of only the sudangrass green manure crop over and above that from just disease suppression. While the cause of this benefit was not positivity identified, it appears that combinations of increased soil biological activity and improved plant nutrient availabilities after the incorporated crop were responsible. This research emphasis our lack of completely understanding the unique effects of selected plant residues on the dynamics of the soil-water-plant biological system.
Technical Abstract: Three studies provided additional knowledge of beneficial effects of sudangrass for yield and quality increases of the Russet Burbank potato. Two of these studies showed significant increases of both U.S. #1 and smooth tubers >280 g following green manures of sudangrass. These sudangrass (HS-33) effects did not differ from a sorghum-sudan hybrid (Trudan-8). When a sudangrass green manure was compared with a fallow treatment, results of the first study showed mean yield increases of 36% for U.S. #1 tubers >280 g and yields of a second study by 34% for U.S. #1 tubers. This same sudangrass treatment outperformed green manures of either Austrian winter pea, barley, or sweet corn by increased U.S. #1 yields that ranged from 27% to 61%. By several lines of evidence, these benefits were found to extend beyond the effect of Verticillium suppression. Soil N was significantly increased following green manures of sudangrass, and these increases were in turn negatively correlated with wilt incidence and positively correlated with yields of both U.S. #1 tubers and tubers >280g. Additional benefits also included significant increases of tuber grade percentages for marketable tubers and of smooth tubers >280g. Benefits from sudangrass green manures beyond the effects of Verticillium suppression became further evident following a greenhouse study that involved field soil and sudangrass that had been grown in the same field. This study corroborated both field experiments by showing increased yields with green manures of sudangrass that approximated 5.5 t/ha dry wt. As with the field studies, these yield benefits also extended beyond the effects of Verticillium suppression and were closely associated with significant increases of Fusarium equiseti, F. oxysporum, and F. solani. Throughout all studies, sudangrass green manures significantly increased microbial activities with increased populations of Fusarium spp. and increased concentrations in soil of mineralizable N, organic P, K, Mn, along with the percent organic matter-all factors that could have contributed to significant increases of yield and quality.