Soil Nitrogen Status within an Integrated Crop and Livestock System in Western North Dakota, USA.

Protecting natural resources while maintaining or maximizing crop yield potential is of utmost importance for sustainable crop and livestock production systems. Integrated crop-livestock systems research at the North Dakota State University Dickinson Research Extension Center is evaluating seasonal soil nitrogen fertility within an integrated crop and livestock production system. The 5-year diverse crop rotation is: sunflower (SF) - hard red spring wheat (HRSW)  - fall seeded winter triticale-hairy vetch (THV) spring harvested for hay/spring seeded 7-species cover crop (CC)  - Corn (C) (85-90 day var.) - field  pea-barley intercrop (PBY). The HRSW and SF are harvested as cash crops and the PBY, C, and CC are harvested by grazing cattle. In the system, yearling beef steers graze the PBY and C before feedlot entry and after weaning, gestating beef cows graze the CC. Since rotation establishment, four crop years have been harvested from the crop rotation.  Seasonal soil nitrogen status (NO₃-N, NH₄-N, NO₃-N + NH₄-N) was monitored throughout the growing season from June to October in 3 replicated non-fertilized field plot areas within each 10.6 ha triple replicated crop fields. Within each plot area, 6 – 20.3 cm x 0.61 m aluminum irrigation pipes were pressed into the soil as enclosures to restrict root access to soil nitrogen. Soil samples were at approximately 2-week intervals from both inside and outside the enclosures. The crop rotation N values were also compared to triple replicated perennial native grassland plot areas dominated by western wheatgrass (Pascopyrum smithii), blue grama (Bouteloua gracilis), little bluestem (Schizachyrium scoparium), and switchgrass (Panicum virgatum). NH₄-N and NO₃-N showed similar trends across the 2014 growing season. There was a greater amount of soil nitrogen accumulation inside the enclosures than outside the enclosures.  Seasonally, when comparing the cropping system crops, NO₃-N declined by mid-July and then rebounded by mid-August and continued to increase until leveling off in September. In the corn plots, however, NO₃-N did not follow this pattern, but increased from early June to the end of June and remained high until the first of September. The impacts of the previous CC on corn production as well as, proposed explanations for the mid-summer nitrogen decline will be presented and implications for reduced fertilizer application will be discussed.

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 [L1] The > symbol usually means that the first value is greater than the second value.  In this case a dash (-) is more appropriate because you are not assigning any values to the cropping systems but are trying to separate one system from another.  Not a big deal but could be mis-interpreted by some readers.

See more from this Division: SSSA Division: Nutrient Management & Soil & Plant Analysis
See more from this Session: Nutrient Management & Soil & Plant Analysis Poster Session

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