The importance of macropore flow in the loss of urea nitrogen from grazed dairy pastures
1989
Williams, P.H. (Canterbury Agriculture and Science Centre, Lincoln (New Zealand)) | Hedley, M.J. | Gregg, P.E.H. (Massey Univ., Palmerston North (New Zealand))
Measures have been made, both in growth chambers and in field studies, of the amount of nitrogen that is lost beyond the major plant rooting depth due to the physical movement of urine down soil macropores. Using intact cores of pasture soils in growth chamber studies 34-62% of the N applied in the urine appeared to leachate immediately via soil macropores. In field studies on seven different soil types the macropore flow resulted in up to 46% of the urine being lost beyond the effective plant root depth. The results suggest that on a dairy farm up to 30 kg N per cow may be lost annually in this way. Variations in loss depended on the physical condition of the soil surface rather than soil type or moisture content
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