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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #232561

Title: Effects of Tillage and Sampling Depth on the Distribution of Phosphorus and Nitrogen Forms in Manure Applied Soils

item Watts, Dexter

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/5/2008
Publication Date: 10/5/2008
Citation: Tazisong, I.A., Senwo, Z.N., Taylor, R.W., Watts, D.B. 2008. Effects of Tillage and Sampling Depth on the Distribution of Phosphorus and Nitrogen Forms in Manure Applied Soils. ASA-CSSA-SSSA Annual Meeting Abstracts. CDROM.

Interpretive Summary:

Technical Abstract: Estimating N and P forms in environmental and agricultural soils can be influenced by tillage practices and sampling depths. Historically, soil sampling depth used to estimate nutrients is about 15 cm because most plant roots grow to that depth. Under conventional tillage (CT) nutrients are mixed into the soil profile to about 15 cm depth. However, when sampling for soil nitrates, a sample down to a depth of 30 cm may provide a more accurate indication of the amount of nitrate available to the crops, since nitrate is normally leached more easily with soil water than most nutrients. Sampling at shallow depths may over estimate N and P availability likewise sampling to greater depth may underestimate N and P availability. Our objective was to investigate the effects of tillage and sampling depths (0-5, 0-15, and 5-15 cm) on N and P forms in manure applied soils. Soils were sampled from no-till and conventional plots, with or without manure (NTM or CTM) application. Phosphorus forms from soils were extracted using the chemical fractionation scheme of Golterman (1996) and Golterman et al. (1998). Ammonium and nitrate N were extracted using 2 M KCl. Result showed that Pi was mostly Fe-bound while Po was mostly organic matter bound at the 0-5 and 0-15 cm depth for NTM and CTM. Ammonium nitrogen (NH4+) was highest at the 0-5 cm than at 0-15 cm and 5-15 cm depth for NTM, but no difference was observed with CTM soils. Nitrate nitrogen (NO3-) concentration was also highest at the 0-5 than 0-15 and 5-15 cm depth in the NTM soils. In the CTM soils, NO3- concentration was lowest at 0-5 while 5-15 cm had the highest NO3- concentrations.