Fertilizer or Salt Leaching as Affected by Surface Shaping and Placement of Fertilizer and Irrigation Water
1975
Kemper, W. D. | Olsen, John | Hodgdon, Alan
Irrigation in furrows and placement of fertilizer in bands in ridges was evaluated as a means for allowing overirrigation to bypass nitrate and reduce leaching losses. In a loamy sand, placement of band 0 to 5 cm higher than the surface of water in the furrow allowed over 120 cm of overirrigation before the salt began to leave the root zone. In the clay loam a similar delay of nitrate removal was not achieved until the band was 10 cm higher than the water surface. This difference appeared to be associated with a perched water table that developed in the “cultivated” layer of the clay loam soil due to higher hydraulic conductivity in cultivated than in the lower soil. Downward movement of relatively concentrated salt solution near the band, due to its greater density, was a factor that allowed fertilizer bands at lower levels to enter the mainstream of the leaching water. Leaching of fertilizer from a soil can be delayed by placing it in ridges and irrigating in furrows rather than broadcasting fertilizer followed by flood irrigation. The practical significance of nitrate staying in the root zone longer as a function of such water and fertilizer management should be tested in the field.
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