|Weil, Ray - UNIVERSITY OF MARYLAND|
Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 27, 2005
Publication Date: November 1, 2006
Citation: Waddell, J.T., Weil, R.R. 2006. Effects of fertilizer placement on solute leaching under ridge tillage and no till. International Journal of Soil and Tillage Research. 90(1-2):194-204. Interpretive Summary: This paper discusses the fate of nitrate under different tillage systems due to placement of nitrogenous fertilizer. In addition to nitrate, a surrogate tracer, bromide, was applied to the soil. A unique approach to take a snapshot of nitrate and bromide concentrations in a 2-dimensional framework was obtained with the use of suction lysimeters. Although the majority of discussion revolves around bromide movement in soil and plants, the author compares measurements of nitrate against bromide. Results are presented and conclusions made for fertilizer application under ridge tillage near the ridge top, in the furrow, and center-row in no-till. The usefulness of bromide as a nitrate tracer is also discussed.
Technical Abstract: Elevated nitrate concentrations in ground water can be a problem in agricultural areas, especially where soils are sandy. Tillage operations such a ridge tillage (RT) and no-tillage (NT) can reduce runoff and erosion but leaching of soluble nutrients can adversely impact groundwater. In a two year study, bromide was used to trace the effects of fertilizer placement on solute movement under corn (Zea mays L.) in RT and NT systems on a Monmouth fine sandy loam (typic Hapludult) located 12 km southeast of Washington, DC. Treatments included 120 kg ha-1 of Br- or NO3--N applied in a narrow band near the ridge top (RT-RA) or in the furrow (RT-FA) in ridge tillage , or in the interrow of no-tillage (NT). Two dimensional arrays of tensiometers and suction lysimeters were used to follow the movement of water and solutes during and after the corn growing season. Tillage and fertilizer placement did not significantly affect nitrogen uptake when averaged over both years. A pronounced argillic horizon beginning at 60 cm depth caused lateral movement of Br. It appears that Br leaching in the RT-RA treatment was slightly increased due to the crop canopy funneling rain towards the ridge top. Therefore, when fertilizer is applied near the row, rain occurring after full corn canopy may cause greater solute leaching in RT-RA compared to other treatments. Rain during the beginning of the growing season or after harvest caused less leaching in the RT-RA treatment. The research suggest that corn yield can be maximized and N leaching minimized by applying fertilizer to the upper portion of the ridge in RT, but not too near the corn rows.