Switching To No-till and Controlled Wheel Traffic Can Save Irrigation Water

Switching To No-till and Controlled Wheel Traffic Can Save Irrigation Water

January 7, 2009

Water is the lifeblood of agriculture, but increasingly producers are facing pressures to conserve its use. In Nebraska, some Natural Resource Districts have implemented irrigation water restrictions. Switching to no-till and controlled wheel traffic can conserve groundwater and surface water used for irrigation and reduce irrigation-related costs.

UNL field trials have shown that using center pivot irrigation and no-till practices instead of furrow irrigation and conventional tillage can reduce irrigation need by up to half. Switching to no-till and center pivot irrigation conserves groundwater and surface water and gives farmers the maximum benefit when they irrigate.

No-till Benefits

Years ago farmers were taught that tillage was needed to prepare a seedbed. Today farming has proven this is a myth and current soils research has actually shown how tillage can break down soil structure and cause increased soil crusting and agricultural runoff during irrigation and rainfall events. With conventional tillage and cultivation, crop residue is destroyed, which leaves soil exposed to wind and water erosion. No-till leaves crop residue on the soil surface, which provides for better water infiltration into the soil and greatly decreases evaporation.

Conventional tillage dries the soil before planting to the depth of the tillage layer. Typically 1/3 to 3/4 inch of moisture is lost per tillage pass. In a no-till system, seeding depth can usually be adjusted so seed is placed into moist soil, thus avoiding an early season irrigation to ensure good germination.

Seasonal crop water use is a combination of evaporation from the soil surface and water transpired through the crop. With a center pivot, soil is constantly wetted at the surface, causing additional evaporation. Leaving crop residue on the soil surface can reduce evaporation significantly.

No-till Saves Water

Past field trials have found that when producers switch from conventional tillage to no-till under center pivot irrigation, they can save 3 to 5 inches of water annually. Studies of continuous no-till corn by former UNL Extension Engineer Norm Klocke in west central Nebraska have proven a combined growing season and non-growing season savings of 4-5 inches. This water savings reduces pumping costs and is a direct savings to the operator. No-till farming also saves labor, fuel, and farming equipment costs. In areas of declining water supply, this is not only a dollar savings but a water resource savings.

Table 1 is a review of typical irrigation application depth for corn, comparing furrow irrigation and pivot irrigation with or without no-till. No-till farming under a pivot can save 3 to 5 inches of irrigation water applied using best management practices compared to conventional tillage with a pivot. There is a large water savings switching from furrow to center pivot irrigation.

Table 1. Effect of management practices and no-till on irrigation application–average inches of irrigation water applied for central Nebraska.
Avg. Management
Best Management Practices
Irrigation Type or Practice
20"
18"
Furrow Irrigation with Tillage
15"
13"
Center Pivot with Tillage
12"
9"
Center Pivot with No-till
Table 2. Effect on water intake in soils depending on management practice.*
Management Practice
Wheel Track Row (in/hr)
Soft Rows (in/hr)
Conventional Tillage
0.2
0.4
No-Till
0.5
> 4.0
*Research data from Paul Jasa, UNL Extension Engineer

Nebraska is subject to thunderstorm events where rainfall intensities of 1 to 2 inches per hour are common. It is important to maintain high soil infiltration rates to minimize runoff and take maximum advantage of rainfall. Water intake rates of soils are influenced greatly depending on whether the soil is tilled or the field is in long-term continuous no-till. Farming practices can greatly influence soil water infiltration by affecting changes in soil structure. Soil compaction from wheel traffic will greatly reduce water intake. Tillage breaks down soil structure and keeps water intake rates low. Table 2 is a summary of how water intake changes depending on management practice and wheel traffic pattern.

Estimate Your No-Till Cost Savings

To estimate the cost of pumping irrigation water, download a computer spreadsheet from UNL Extension's Lancaster County Web site at lancaster.unl.edu/ag/crops/irrigate.shtml. The spreadsheet named Irrigcost.xls was used to calculate an average cost of center pivot irrigation with 130 acres, pumping water 125 feet using a system pressure of 35 psi, diesel fuel at $2.47 per gallon, drip oil cost at $3.47 per gallon and operator labor at $12.00 per hour.

In this example, under center pivot irrigation the annual operating cost (repairs, operator labor and energy) for each inch of water applied is $6.70 an acre. With no-till farming and a savings of 3 to 5 acre inches of irrigation water, the annual operating cost savings range is $20.10 per acre to $33.50 per acre. (Energy cost alone in this example for each inch of water applied is $4.62 per acre). This is a direct irrigation energy savings range of $13.86 per acre to $23.10 per acre when switching to no-till farming practices.

This author observed no-till crops being raised under center pivot at the Dakota Lakes Research Farm near Pierre, S.D. in 2002. Duane Beck, no-till farmer and researcher, demonstrated applying 2 inches of water in 12 minutes over the same spot in long-term, no-till fields under crop rotation. This was with a 40-acre lateral pivot pumping 1000 gpm out of the Missouri River. The author observed little to no runoff under irrigation with the long-term no-till. Long-term no-till and crop rotation can have a significant impact on soil properties, as demonstrated by Beck's high yields for irrigated no-till corn and soybean in South Dakota.

Tips for Adopting No-Till

In Nebraska, the use of no-till under irrigation in a corn-bean rotation in increasing. Rather than tilling after the combine in the fall, no-tillers are making combine adjustments before harvest, eliminating an operation, and allowing winterization to break down the residue.

Adopting and using no-till means making some adjustments, in your practices and in your outlook; for example:

  • parking the anhydrous rig for a few hours to allow residue to dry,
  • eliminating soybean residue piles that can interfere with no-till planting the following year, or
  • explaining to your neighbors that your fields are planted and you are not sick after all.

You cannot underestimate the importance of good residue distribution with the combine. On some combines with the corn header, using tapered stock rollers, slowing down the gathering chains, and adding beveled stripper plates can provide more even crop residue distribution. The less residue run through the combine, the better.

Under heavy residue situations, placing a starter fertilizer in furrow with the seed is recommended. Do not exceed recommended amounts to avoid salt injury.

Summary

Today the technology, machinery, and herbicides are available for no-till and the dollar savings are documented. Yes, there may be challenges with handling heavy residue, but one of the biggest challenges is a shift in attitude. For those farmers who can achieve the same yields or higher yields with no-till (compared to their neighbors who are tilling), there are real and significant savings that can be taken directly to the bank.

Randy Pryor
Extension Educator