Ammonium-N persistence and root nitrogen content of annual crops and perennial forage grasses following pig manure application
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Date
2016
Authors
Lasisi, Ahmed
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Abstract
Studies have shown that significant amounts of nitrate-N is leached beyond root zones of annual crops while small amounts of nitrate-N is leached beyond the root zones of perennial forage grasses. This study investigated short-term ammonium-N persistence and root nitrogen content of annual crop and perennial forage grasses following application of pig manure to a sandy loam soil at Carman, Manitoba. Results showed that ammonium-N in liquid pig manure (LPM) amended treatment peaked four days after manure application (DAM) in perennial cropping system (PCS; 50 - 74 kg ha-1) and annual cropping system (ACS; 18 - 29 kg ha-1) in 2014 and 2015. Ammonium-N persisted up to 7 DAM in LPM amended PCS, but did not persist beyond 4 DAM in LPM amended ACS. Ammonium-N measured in solid pig manure (SPM) amended ACS and PCS was low throughout the sampling days in both years. There was a greater percentage increase in accumulation of nitrate-N at 15 - 30 cm soil depth of LPM and SPM amended ACS than PCS. In both years, dry weight below-ground plant biomass ranged from 5,258 to 9,627 kg ha-1 at 0 - 60 cm depth in PCS while that of ACS ranged from 1,088 to 1,456 kg ha-1. Also, root N content in PCS ranged from 43 to 118 kg N ha-1 in both years while that of ACS ranged from 9 to 20 kg N ha-1.
In conclusion, ammonium-N persisted longer in PCS than ACS in the short-term and total plant N was greater in PCS than ACS. Greater total plant N in PCS than ACS was mainly due to its greater root N content rather than above-ground N uptake. The order of magnitude of the difference in root N content (34 to 98 kg N ha-1) between ACS and PCS was sufficient to account for the 20 to 60 kg N/ha of nitrate-N leached in ACS in previous study at the same site.
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Keywords
Root nitrogen, Ammonium-N, Annual cropping system, Perennial cropping system, Pig manure, Root biomass