Ceres Trust Research Grant
Authors: Dr. Patrick M. Carr, Dr. Greta Gramig, Dr. Kevin McPhee, Dr. Frank Kutka, Mr. Steve Zwinger, Karri Stroh
Over 15 vetch and winter pea cover crop treatments, 15 spring pea cultivars, and 19 potato cultivars, were evaluated over a 3-yr period in certified organic fields at research facilities in east central (Carrington) and southwest (Dickinson) North Dakota. Late-summer seeding of in-state, on-farm sources of ‘common’ vetch seed resulted in cover crops that overwintered successfully and produced between 5420 and 8394 lb/acre of dry matter the following summer. Conversely, seedlings of winter pea and vetch cultivars developed outside the region failed to survive the winter. Grain yield of spring-seeded field pea ranged from 8 to 78 bu/acre, depending on cultivar, location, and year. The pea cultivar Spider produced grain yields that were equal or superior to those produced by other pea cultivars in 5 or 6 field experiments (P<0.05), indicating good adaptation of this cultivar to both low- and high-yield, certified organic environments, with one exception. Likewise, the potato cultivar Red Pontiac produced tuber yeilds that were comparable or greater than those of other cultivars in all but one environment. Results of a pea-weed competition study suggested that cultivars Cooper and CDC Golden may be preferred to three other cultivars in weedy environments, although adverse weather confounded interpretation of the study’s results. Potato cultivar trials in non-replicated strips or rows on certified organic farms failed to identify a cultivar that demonstrated superiority in yield and in certain quality factors (e.g., visual attractiveness to consumer) in all instances. Similarly, the relative rank changed across organic farms where spring-seeded field pea cultivars (DS Admiral, Majorety, CDC Striker) were evaluated. Results of this project demonstrate that cultivar selection must be matched to local conditions on certified organic farms for optimum crop performance. Ranking of pea and potato cultivars for photosynthetically active radiation (PAR) intercepted by the crop canopy reflected the relative rank for yield in some environments. Future evaluations of crop cultivars for adaptation to organic environments should consider measurements of crop canopy interception of PAR as a possible screening tool.