Submitted to: Methyl Bromide Alternatives and Emissions Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/12/2005
Publication Date: 11/6/2005
Citation: Trout, T.J., Skaggs, T.H., Rothfuss, Y. 2005. Irrigation practices that improve drip fumigation.. Methyl Bromide Alternatives and Emissions Research Conference Proceedings. Annual International Research Conference on Methyl Bromide Alternatives And Emissions Reductions Conference 2005, pp 35-1 - 35-3. Interpretive Summary: Fumigants are being applied through drip irrigation systems. Drip fumigation has become an increasingly popular alternative in California where about 8000 acres of strawberries, melons, and peppers were drip fumigated with 1,3-D or chloropicrin in 2003. A limitation to drip fumigation is how far horizontally the water and fumigant can be spread from a drip tape emitter. Management techniques have been proposed to increase the horizontal spread of water from drip tape, including pre-irrigation to wet the beds, high application rates, and pulsing the water. The objective of this study is to test these techniques to determine application practices that can maximize the relative horizontal-to-vertical water movement from a drip tape. Field measurements and computer modeling showed that pre-wetting soil decreased the horizontal spread of water and any substances dissolved in the water. Application rate and sequence had little effect on water distribution. Soil texture and water content are the primary factors in determining water distribution.
Technical Abstract: Horizontal water movement from drip irrigation emitters is important to store water in the root zone, and for treating soil with water-applied fumigants. Field measurements and computer modeling were used to quantify the effects of irrigation practices on horizontal water movement. Hydrus 2-D predicted that, for sandy loam soils, water application rate or sequence does not significantly affect water distribution. Field measurements supported that conclusion. The model predicted that wet soil near field capacity caused less horizontal movement of water and solutes in the water. This is expected since high water content decreases capillary forces that move water horizontally. Water contents from 50% available water to wilting point did not significantly affect relative horizontal-to-vertical water movement. The results indicate that, for a given soil type, little can be done to increase horizontal water movement.