Post-CRP Land Management and Sustainable Production Alternatives for Highly Erodible Land in the Southern Great Plains
1.) Develop best-management plans to prepare CRP grasslands for grazing or haying,
2.) Determine the productivity and profitability of land management systems to revert successfully and environmentally sound to winter wheat and cotton production on highly-erodible lands in the Southern Plains.
The majority of contracts on 1.2 million acres of CRP lands in Oklahoma will expire in 1996, 1997, and 1998. A general lack of integrated management guidelines exists on how highly erodible lands (HEL) should be used for grazing livestock production or how to revert to annual cropping while meeting conservation compliance. Under USDA-ARS coordination, a collaborative project was conducted on two CRP fields under contract since 1987 and 1989.
The project objectives were to assess, on the field-scale, environmentally sound grazing-crop options for highly erodible CRP lands. One study site is near Forgan, OK in a 450-mm precipitation zone of NW Oklahoma. The other is near Duke, OK in a 750-mm precipitation zone in the SW. Both sites were seeded to Old World bluestem (Bothriochlora ischaemum L.).
Field-scale comparisons of management systems for OWB, conservation- and no-tillage wheat (Triticum aestivum L.), and conservation-tillage cotton (Gossypium hirsutum L.) production systems were made to evaluate the productivity and the optimal management of HEL after the CRP. Each of the project years, we implemented the grass and wheat recrop options in a new area of the CRP field and re-established the Year 1 (first established in 1994) and Year 2 (first established in 1995) treatments. This approach allowed us to assess the options’ performance for the first time out of CRP grass and producing second and third-year crops under weather conditions of each year during the 1994-1997 period.
Small-plot experiments were also conducted to evaluate herbicides and fertilizer requirements for killing the sod and preparing the fields for reverting CRP lands to crop production. Rainfall simulations were conducted to measure runoff and soil erosion characteristics the first year following conversion of CRP to winter wheat production during 1996. During the project, we found that:
1. CRP lands planted to OWB require improvements before they are used in hay or grazing livestock production. Greatest limitations are inadequate N, P, stand density, and forage quality. After the initial removal of the old growth, baseline unfertilized OWB production in 1994 averaged 3,200 and 3,600 kg /ha at Forgan and Duke, respectively. In 1995, an application of 67 kg N/ha resulted in no significant increase in forage production at Forgan.
In contrast, the application of urea-N tripled OWB dry matter production over the unfertilized plots at Duke, equaling 81% of the biomass accumulated over the seven years that the field was enrolled in the CRP.
In 1996, applications of 67 kg N and 22 kg P/ha resulted in an average 1.7-fold increase in OWB forage production at both locations. In 1997, OWB forage production tripled and quadrupled by improved management and fertilizers at Forgan and Duke, respectively. Therefore, management actions are needed at the end of the contract period to convert CRP fields into productive grasslands.
Overall, minimal management action such as removing the dead grass litter in early spring stimulated forage production. Fertilizers enhanced production and forage quality for both stands. However, optimal use of OWB still depended upon a delicate balance between forage yield and peak nutritive value of the forage.
2. Our results showed the need to move back the time line that CRP landowner or operator would be permitted to work on the grass cover, if provisions for soil erosion control are in place. Timing of suppression of a warm-season grass is critical for conserving stored soil water that is vital to the success of producing a wheat crop in the year a CRP contract expires. Otherwise a year of production would be lost.
In nutrient-depleted CRP fields, fertilization was necessary to achieve agronomic yields; unfertilized plots yielded only 34 and 60% of plots receiving 112 kg N/ha at Forgan and Duke, respectively. The amount of old dry matter removed and new regrowth is critical to how well we can perform reduced tillage, kill the growing cover, and establish a uniform crop stand.
In 1994, dryland wheat yields averaged 890 and 1,660 kg ha-1 at Forgan and Duke, respectively. NT wheat yields were equal to or 21% higher than CT wheat at both CRP sites, because of higher soil water storage attained with surface residues and the absence of tillage. Without prior removal of old growth, MT and burial of the sod had highest wheat yields, followed by DT, and NT at both locations, due to uniform stand, higher plant density in the clean tilled surface.
In 1995, wheat yields ranged from 190 to 880 kg ha-1 due to the extremely dry weather. NT was significantly better during the drought of 1995 when the crop was produced mainly from stored water and no significant rains fell between October 1995 and June 1996.
In the third year, herbicide application and tillage (sweep and disk tillage) effectively control OWB. Early chemical suppression of OWB promoted early emergence and growth of wheat during 1996 and early 1997. However, night temperatures on April 12 and 13, 1997 dipped below 6 and 8o C at Forgan and 4.5 and -6.8oC at Duke, OK. Freeze damage was extensive for the Duke wheat crop that was in the grain-fill stage of development and had a yield potential in the 2800-3000 kg ha-1 range. The Forgan wheat crop was not as far along in development, in the early booting stage. That wheat crop partially recovered as excellent growing conditions existed following the cold spell.
Final yields averaged 715 and 1045 kg ha-1 at Forgan and 580 and 910 kg ha-1 at Duke for conservation-till and no-till treatments, respectively. Overall, NT practices were more effective at conserving and utilizing stored soil water for crop production on former CRP fields and wheat yields were significantly higher than CT yields at both locations between 1994 and 1997.
3. Conversion to dryland cotton was not as successful as yields averaged 100 kg ha-1 due poor weather conditions that existed at planting and during boll-setting stage in 1995. A 1996 crop was not planted due to the extremely dry conditions that prevailed at the site and throughout the region. In summary, climatic variability served as a constant reminder of the precarious environment and the high risk of agricultural production in the Great Plains while considering the conversion of CRP lands back to intensive cultivation of either summer- or winter-season crops.
4. No difference in cumulative runoff was found between grass and wheat treatments under simulated rainfall at an intensity of 65 mm hour-1. Significant differences in surface cover existed between undisturbed CRP, grass regrowth after burning, conservation disk-tilled, and no-till wheat treatments at Duke, OK on June 13-18, 1996. Surface coverage values ranged from 42, 71, 79, and 100% on disk-tilled, no-till, and OWB regrowth, and undisturbed OWB treatments, respectively.
The data suggested that conversion of this CRP site to winter wheat production using no-till and disk-till management practices did not enhance runoff or reduce water infiltration. However, soil loss in disk-tilled plots was 3 to 4 times greater than no-till wheat and OWB plots, averaging 210 kg ha-1, compared to 58 kg ha-1 for no-till and OWB treatments. Although differences in soil erodibility existed, conversion to wheat production would not result in excessive erosion during the first year of production using the disk-tillage practices to destroy the sod.
5. Using regional custom rates, the total variable costs for the first year following conversion were 122 and 131 dollars per acre for conservation-till (CT) and no-till (NT) wheat production, respectively.
Wheat breakeven price to cover these variable costs would be $2.50 and $2.76/bu at a yield goal of 35 bu/A for CT and NT, respectively. Potential income for grazing the wheat forage was not included and would reduce the total variable costs.
7. Outreach activities in 1995-1997 included field days at the study sites, producer metings, and technical conferences. The Duke tour was held on April 4, 1996 and the Forgan tour on April 11, 1996 to highlight crop growth under drought conditions and last year’s research results.
Field days were held at Duke, OK on April 11 and at Forgan, OK on April 17, 1997. These were the final tours to be organized at the study sites and attracted nearly 100 attendees from Oklahoma and Texas.
The study results were focused on Old World bluestem grass management and wheat production options. The CRP study results were also presented at SARE Sustainable Agriculture Field Day at Tyrone, OK on August 20, 1997. The event attracted 250 producers and agricultural industry and agency personnel.
A team of extension specialists from Colorado, Kansas, New Mexico, Oklahoma, and Texas conducted a series of day-long producer meetings to update CRP contract holders on proposed regulations and future land uses based on economic decisions from Sep 30 to October 10, 1996.
A national technical CRP conference was organized in Amarillo, TX to elaborate on research results and post-contract management options on October 22-23, 1996. The program targeted the message to NRCS and ES personnel in the Central and Southern Great Plains. In the final year of the project, a major effort was focused on the technology transfer and extension of the R&D results to producers, action agency personnel, and the general public.
Two major conferences were organized and held in conjunction with the All Oklahoma Chapter of the Soil and Water Conservation Society. The conferences titled The Future of CRP in Oklahoma-Alternatives and Planning Options were held in Altus and Woodward, OK on February 10-11, 1997. Over 200 producers, agency personnel, bankers, and businessmen attended.
Other outreach efforts were made to prepare publications and news articles for the local and regional farm press. Information from our studies was a major component of a 4-page insert in the Conservation Technology Information Center Partners newsletter. The insert CRP: Converting to Cropland offered practical assistance to growers who were planning to farm their CRP land in various region of the country. Two Production Technology information sheets also were prepared on the conversion of CRP to winter wheat production and livestock production on former