No-till Seeding After Alfalfa Reduces Expenses

Chapter 9 — Irrigated Systems, No. 2, Summer 1986

Roger Veseth

Rotation-Tillage Considerations

No-till seeding of winter wheat, spring wheat and field corn after alfalfa can be more economical than under conventional tillage on furrow irrigated land. That was the preliminary conclusion of David Carter after the first year of the tillage system comparison in southern Idaho. Carter is a USDA-ARS soil scientist and STEEP researcher at theSnake River Conservation Research Center near Kimberly, ID.

The research results indicate not only a need for changes in tillage practices but also potential changes in crop rotation. In the southern Idaho irrigated region, dry beans are commonly grown after alfalfa in the rotation. However, since both crops are nitrogen (N)-fixing legumes, much of the N fixed by the alfalfa can be lost through leaching or denitrification. Besides the low use-efficiency of available N, this rotation sequence also involves high production costs. Typically 8 to12 field operations are required for conventional seeding of dry beans afler alfalfa.

Carter suggests that producers consider growing wheat or corn after alfalfa instead of beans. This would effectively utilize the N fixed by the alfalfa. Dry beans can then be seeded after wheat or corn with only 4 to 5 operations or less, instead of 8 to 12 after alfalfa. This change in rotation reduces production costsby reducing the number of field operations over the entire rotation and reducing the N fertilizer requirement for the cereal crop.

The Experiment

The Research Center experiment in the 1984-85 crop year consisted of no-till and conventional tillage seedings of the three crops into a 5-year old alfalfa stand. The alfalfa field, which contained some grass, was chemically killed with Roundup (glyphosate) and 2,4-D after the third cutting.

Half of the field was conventionally prepared using the operations shown in Tables 1 and 2. The other half wasno-till seeded into the chemically killed alfalfa stubble. Both tillage treatments were seeded to Stephens winter wheat October 15, Fieldwin spring wheat April 8 and Pioneer F 15-3901 field corn May 2. The wheat was planted with aconventional, double disk drill in both treatments. For the corn, a small, narrow shank called a bull tongue was added ahead of each seed opener on a standard corn planter.

Effective Use of Nitrogen

Following alfalfa with a non-N fixing crop (non legume), like wheat, barley or corn provides more efficient utilization of the N released by the alfalfa, reducing fertilizer costs. An irrigated alfalfa crop typically can fix from 300 to 400 pounds N per acre. If the alfalfa is killed in the fall, Carter’s research indicates that about 200 to 250 pounds N per acre will be available to the following year’s crop. Much of the remaining N fixed by the alfalfa crop would be available over the second year.

Table 1. Production oparationa and estimated coatal for winter wheat and aprlng wheat after alfalfa under conventional tillage and no-till, Kimberly, ID (Cattar, USDA-ARS).

Table 2. ProductIon operationa and aatimated coetal for field corn after alfalfa under conventional tillaga and no-till, Kimberly, ID (Carter, USDA-ARS).

Carter applied 100 pounds N per acre to test strips in each crop. Winter wheat yields were increased, but not sufficiently, to pay for the cost of the fertilizer and application costs. Spring wheat and corn yields were not in creased with additional N. Carter stressed that there may be some advantage of applying a small amount of N fertilizer with the winter wheat to promote adequate fall growth. This is because of the slow initial rate of mineralization and release of N from the rhizobium nodules on the alfalfa roots after the crop is killed in the fall. With the additional decomposition and N release time, there was less advantage in applying N fertilizer to spring crops.

Additional Advantage

There is an additional advantage of no-till seeding under furrow irrigation. No-till seeding permits use of the previous year’s irrigation furrows, so water infiltration into the soil is more uniform than under conventional tillage. In fact, the no-till seedings were also easier to irrigate and required only V3 as much water to complete the first irrigation. Alfalfa residue did not cause any problems in getting the water through the furrows.

Results

Tables 1 and 2 list field operations and estimated costs (custom rates) of growing wheat and corn under both conventional tillage and no-till. Carter points out that the herbicide costs would vary depending on whether the alfalfa field contained grass. If grass is not a problem, herbicide costs would be lower because Roundup would not be needed.

There was no significant difference in crop yields between conventional tillage and no-till treatments. To illustrate the differences in net profit per acre, Carter used average yields and compared expenses of the different tillage systems (Table 3). Lower production expenses in notill increased net profits/acre by $38 for wheat and $47 for corn. If no herbicide was used to kill the alfalfa ($2L/acre) under conventional tillage, there would still be an economic advantage for no-till seeding: $16/acre for wheat and $25/acre for corn. Reduced machinery and labor expenses would provide additional savings with notill. Timeliness of planting with no-till could also increase yield potential in some cases.

The results of this 1985 tillage system comparison after alfalfa look very promising for both yield and net profit. Carter is continuing the study in the 1985-86 crop year.

Table 3. Net profit/acre from winter wheat, spring wheat and field corn after alfalfa under conventional tillage and no-till, Kimberly, ID (Carter USDA-ARS).

Use of Trade Names

Research results are given for information only and are not to be construed as a recommendation for an unregistered use of a pesticide. Always read and follow label instructions carefully. To simplify the information, trade names have been used. Neither endorsement of named products is intended nor criticism implied of similar products not mentioned.