| dc.description | Nutrient management is a challenge in organic potato production. A potato rotation experiment was established to determine effects of forages and livestock manures on soil nutrient levels, plant nutrient uptake, and tuber yield in the first cycle of four-year rotations established on long-term pasture. The experiment was a two-stage nested design, with three soil amendments (composted poultry manure, composted beef manure, and alfalfa meal) nested under three forage levels (0-, 1-, and 2-year forage levels represented by wheat/soybean/barley/potato, wheat/barley/forage/potato, and wheat/forage/forage/potato, respectively). In order to equalize soil available nitrogen (N), soil amendments were applied according to their assumed N availability and soil test recommendations. In year four, all plots were seeded with potatoes and split into amended and unamended subplots. Applications of soil amendments increased soil nutrient levels, plant nutrient uptake, and tuber yield compared with residual effects of soil amendments. At the end of year four, soil organic matter was significantly different among treatments; soil mineral N was significantly higher in the 1- and 2-year than in the 0-year forage rotation because of both forage and soil amendment effects. Alfalfa meal had a larger positive effect on soil microbial biomass carbon, and released more mineral N compared with the two composts. Composted poultry and beef manures significantly increased soil P2O5 and K2O levels, respectively, through cumulative compost additions. Plant N uptake was not significantly different, while plant P and K uptake and tuber yield were significantly higher in the 0-year than in the 1-year forage rotation because of possible pest infestations in the forage rotations, and were highest under composted beef manure. Principal component analysis indicated that the 1- and 2-year forage rotations shared similarities, but were separated from the 0-year forage rotation, and that forage and soil amendment combinations shared both similarities and differences, depending on forage levels, types and application rates of soil amendments. Overall, soil isonitrogeneity was not achieved, while plant isonitrogeneity was achieved. Forages improved soil N, but were detrimental to potato production under these specific conditions. Composted beef manure was preferred for nutrient management and potato yield. | en_US |
