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Title: The Effect of Subsurface Drip and Furrow Irrigation on the Movement of Salts and Nitrate in the Root Zone.

Author
item BERRADA, ABDEL - CSU-AVRC, ROCKY FORD, CO
item Halvorson, Ardell
item BARTOLO, MICHAEL - CSU-AVRC, ROCKY FORD, CO
item VALLIANT, J - CSU-AVRC, ROCKY FORD, CO

Submitted to: Irrigation Associations Exposition and Technical Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/11/2006
Publication Date: 11/5/2006
Citation: Berrada, A., Halvorson, A.D., Bartolo, M., Valliant, J. 2006. The Effect of Subsurface Drip and Furrow Irrigation on the Movement of Salts and Nitrate in the Root Zone.. Irrigation Associations Exposition and Technical Conference Proceedings. P. 1-13.

Interpretive Summary: A field experiment was conducted at the Arkansas Valley Research Center (AVRC) in 2005 to evaluate the effects of irrigation type and scheduling and fertilizer rate on corn yield and salts and NO3-N movement in the soil profile. Four N fertilizer rates (0, 60, 120, and 180 lb N/a) and four manure rates (10, 20, and 30 t/a) under subsurface drip irrigation (SDI) and furrow irrigation (FrI) with two irrigation scheduling regimes (full and deficit irrigation) were compared. The results show no significant difference in corn yield between SDI and FrI, even though nearly twice as much water was applied with FrI than with SDI. Deficit irrigation decreased corn yields when water was withheld during two critical growth stages, silking and milk. Corn did not respond to N fertilizer rates beyond 60 lb N/a under deficit irrigation, while 30 t manure/a depressed the yield due to stand loss. Under full irrigation, the highest yield was obtained with 180 lb N/a which was more than the recommended rate of 120 lb N/a. Manure application increased soil salinity levels, which contributed to a decrease in plant population with increasing manure rate. Salinity issues need to be investigated further. Higher ECe values were observed at the 4- to 6-ft. depth under SDI than under FrI, probably because of greater leaching with the FrI system.

Technical Abstract: Water quality issues coupled with diminishing water supplies have led to increased acreage in drip irrigation in the Arkansas River Valley (Ark Valley) of southeastern Colorado. A field experiment was conducted at the Arkansas Valley Research Center (AVRC) in 2005 to determine the effects of irrigation type and scheduling and fertilizer rate on corn yield and salt and nitrate-nitrogen (NO3-N) concentration in the root zone. Four N fertilizer rates (0, 60, 120, and 180 lb N/acre) and four manure rates (0, 10, 20, and 30 t/acre) were tested under subsurface drip irrigation (SDI) and furrow irrigation (FrI) with full (FI) and deficit (DI) irrigation regimes. The results show no significant difference in corn yield between SDI and FrI, even though nearly twice as much water was applied with FrI than with SDI. Deficit irrigation decreased corn yield by 20 bu/acre on average. Corn yield generally increased with increasing N fertilizer rate, reaching a high of 233 bu/acre with FI and 180 lb N/acre. Corn produced the lowest yield with 30 tons of manure/acre under DI or SDI, similar to the no N fertilizer treatment. The high manure application rates increased soil salinity early in the season, which may have contributed to the lower corn population, compared to the non-manure treatments. After corn harvest, the difference in soil salinity between the manure (20 t/acre) and non-manure (120 lb N/acre) treatments was negligible. Subsurface drip irrigation had higher ECe in the furrow compared to FrI, which had higher ECe in the middle of the bed. There appeared to be salt build-up at the 4- to 6-ft depth under SDI compared to FrI, possibly due to leaching of salts with FrI. Soil NO3-N concentration was higher under SDI than under FrI, but the difference was only significant in the top foot. There was much more NO3-N in the top 4 ft. of soil in the spring of 2006, prior to fertilizer application, than in the fall of 2005; with no significant difference between FrI and SDI. The high manure-rate treatments had significantly more residual NO3-N than the other treatments. More results will be available in 2006.