Longevity of shallow subsurface drip irrigation tubing under three tillage practices

Authors: Sorensen, Ronald - Ron; Lamb, Marshall

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2014
Publication Date: 5/15/2015
Publication URL: http://dx.doi.org/10.2134/CFtm2014.0097
Citation: Sorensen, R.B., Lamb, M.C. 2015. Longevity of Shallow Subsurface Drip Irrigation Tubing Under Three Tillage Practices. American Society of Agronomy. doi: 10.2134/cftm2014.0097.

Interpretive Summary: Crop yield response to S3DI has been documented but crop yield using S3DI and associated with strip- or no-till system is unknown. Additionally, the useful life of the drip tubing installed near the soil surface (S3DI) where it is vulnerable to biological and mechanical damage is unknown. Similarly, the economic cost or benefit of using a more expensive, i.e., thicker wall tubing in these tillage situations has not been determined. The objectives of this research were to determine: 1) crop yield when using S3DI in conjunction with conventional, strip and no tillage, 2) longevity of drip tubing with various wall thicknesses to biological or mechanical damage, and 3) economic viability of S3DI with conservation tillage techniques. Conventional tillage consisted of the following practices in order after the first year described previously: 1) disk harrow (fall), 2) chisel plow (fall), 3) row bedding (spring), and 4) field cultivate (spring) to incorporate fertilizer and/or pre-plant herbicides. Drip tubing was installed on the conventionally tilled area immediately following plant emergence. Following cotton and corn harvest, drip tubing in the conventional tilled area was removed from the soil, rolled, and stored on spools using experimental equipment. Strip tillage was performed in early spring creating a 8-in wide planting bed. Tillage occurred following additions of lime and fertilizers to get as much soil mixing as possible in the crop root zone. There was no tillage operations performed in the no-till area prior to planting. There was no yield difference within irrigation or tillage treatment for cotton, corn, or peanut. Yield in all three crops were greater with irrigation compared with non-irrigation in all treatments tested. There were significantly less repairs in the conventional tillage treatment than other treatments probably due to less exposure time in the field. There were more repairs in the thinner wall tubing than thicker tubing probably due to mechanical damage from mowing crop debris and operator error of lowering the “bush-hog” too close to the soil surface. The cost of tillage was significantly greater for the conventional tillage compared with strip tillage or no tillage. The cost of tillage may have been less for strip and no tillage but the extra cost of tubing repairs brought the total expenditure to values similar to conventional tillage. The cost of yearly tubing removal and installation was greater for conventional tillage such that the partial net return to the grower was numerically less compared with strip or no tillage operation system. Overall, there was less expense with strip and no tillage with S3DI compared with conventional tillage with the yearly removing and reinstalling the same drip tubing. Overall, the use of S3DI is recommended for strip and no till situations with cotton, corn and peanut for best yields and economic returns. The average time for tube replacement across all tillage regimes with a cotton-corn-peanut rotation would be about 6 years provided cotton and corn was raised in the first 5 years and peanut in the last year of the rotation.

Technical Abstract: Shallow Sub-Surface drip irrigation (S3DI) has drip tubing buried about 2-in below the soil surface. It is unknown how long drip tubing would be viable at this shallow soil depth using strip- or no-tillage systems. The objectives were to determine drip tube longevity, resultant crop yield, and partial net revenue when using conventional, strip- and no-tillage. Drip tubing (8, 10, and 15 mil) was buried 1.5-in in 2006 and left in the field for 5 years under strip- and no-till areas and removed and reinstalled in conventional-tilled areas. Crop rotation was cotton the first year (Gossypium hirsutum L.), corn the next three years (Zea mays L.), and peanut (Arachis hypogaea L.) in the final year. There was no difference in cotton lint yield by tillage treatment and irrigated lint yield was 2.4 times greater than nonirrigated. There was no difference in irrigated corn yield across year or tillage practice. Irrigated corn yield was 5.8 times greater than nonirrigated yield. Irrigated peanut yield was the same across tillage treatments but was 2.6 times greater compared with nonirrigated yield. For tube longevity, conventional tilled areas had less tube repairs compared with strip- or no-tilled practices. Thinner wall tubing (8 mil) had 3.5 times more holes compared with thicker wall tubing (15 mil). The “cost-to-repair” versus “cost-to-replace” tubing indicates average replacement time at about 5.4 years. There was less production expenses for strip- and no- till compared with conventional tillage. Both strip- and no-tillage systems are recommended when installing S3DI.