Phosphorus drawdown rate following cessation of repeated manure application to annual crops

• Published in: Nutrient cycling in agroecosystems Vol. 125; no. 1; pp. 63 - 75
• Main Authors: Lasisi, Ahmed A., Akinremi, Olalekan O., Kumaragamage, Darshani, Racz, Geza
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 2023; Springer Nature B.V
• Subjects: Agriculture; Aquatic environment; Biomedical and Life Sciences; Crops; Drawdown; Dry matter; Life Sciences; Manures; Nitrogen; Oilseed crops; Original Article; Phosphorus; Pig manure; Soil testing; Soils; Urea; N-based manure; Phosphorus uptake; Phosphorus drawdown; STP
• ISSN: 1385-1314; 1573-0867
• DOI: 10.1007/s10705-022-10255-9

Repeated nitrogen (N)-based manure application to meet crop N requirements could result in phosphorus (P) accumulation to potentially detrimental levels in aquatic environment. A 3-year (2016–2018) field study was conducted to evaluate the rate of P drawdown from cereal-oilseed rotation plots that previously received annual applications of N-based rates of solid (SP–N) or liquid (LP–N) pig manure for 7 years (2009–2015). Plots were fertilized with urea at 91–141 kg N ha
−1
with no additional P. At harvest, crop above-ground biomass was sampled to assess yields and P uptake. Soil was sampled each spring and fall to determine Olsen soil test P (STP). During the 3 years of cropping, cumulative dry matter yield was similar in SP–N (24.4 Mg ha
−1
) and LP–N (24.2 Mg ha
−1
) plots. However, cumulative P uptake was significantly greater in SP–N (64.4 kg P ha
−1
) than LP–N (49.0 kg P ha
−1
) plots. A first-order decay equation showed similar P drawdown rates in SP–N (15%) and LP–N (12%) plots but absolute STP decline was greater in SP–N (35.3 mg kg
−1
) than LP–N (16.3 mg kg
−1
) plots. Based on the P drawdown rate, it would require 9 and 6 years to reduce elevated STP levels in SP–N and LP–N plots, respectively to the level prior to manure application (23.8 mg kg
−1
). Greater soil P buildup with SP–N than LP–N plots, with similar P drawdown rates after cessation of manure application, requires a longer period to bring the STP to an accepted level from SP–N than LP–N soils.