Soil Quality Assessment of Long-Term Direct Seed to Optimize Production

Soil Quality Assessment of Long-Term Direct Seed to Optimize Production

Summary

Producers in the Pacific Northwest, the United States and worldwide are adopting direct seed farming to reduce soil erosion, improve soil quality, increase water infiltration and reduce number of passes with farm equipment. Direct seed farming creates the physical conditions of surface-managed residues and undisturbed soil that leave soil less susceptible to wind and water erosion which keeps more soil on the land. Direct seed producers are concerned about not reaching the yield and profit potential that was expected with long-term direct seed. This may be due to unique soil stratification caused by lack of soil disturbance that makes nutrients unavailable for plant uptake due to pH, electrical conductivity (EC) or banding of nutrients, or present at potentially toxic levels.

We are investigating the soil quality of thirteen long-term direct seed sites and three sites farmed with conventional or conservation tillage to identify those characteristics that play a part in limiting yield potential. Sites were selected to represent low, intermediate and high rainfall zones of the dryland farming region of eastern Washington and northern Idaho. The pH values on these soils range from 5.0 to 7.4, and EC ranges from 91.2 to 247.2 µs/cm³. Overall, native/undisturbed soils were higher in β-glucosidase and dehydrogenase enzyme activity, pH, EC, K, NO₃-N, Ca, P, Zn, B and NH₄-N than cultivated soils. Bottomland soils were higher in dehydrogenase, EC, K, NO₃-N, P, S, Fe, Mn and B than ridgetop and mid-slope soils. Ridgetop soils had lower pH and B and higher Al, Mg, CEC, Na and Cu than either mid-slope or bottomland soils. There were no differences detected in levels of CEC, Mg, Ca, Cd, Mo, Ni, Fe or B with sampling depth. Levels of β-glucosidase and dehydrogenase enzyme activity, EC, K, NO₃-N, NH₄-N, P, S, Zn and Mn were highest in the zero-to-one inch samples and decreased with depth to six to eight inches. Aluminum levels were highest in the two to three and three to four inches depths and lowest at six to eight inches. Averaged over all the farmed sites, pH was highest at the six to eight inches depth and did not differ significantly from the zero to one inch depth. The depth increments from two to three inches and three to four inches were significantly lower in pH than the zero to one inch depth but did not differ from the one to two inches and four to six inches depths. With these factors identified, management options can be investigated and strategies developed to obtain sustainable systems.

Objectives/Performance Targets

Objective 1: Evaluate, incrementally with depth, soil quality of long-term direct seed fields across landscape in relation to crop yield parameters.

Eastern Washington and northern Idaho experienced an extremely dry fall in 2012, and many producers planted their winter wheat crops later than usual. Because of this obstacle, we determined that it would be most beneficial to delay the full sampling of multiple landscape positions and multiple sites at each grower’s location until the conditions were more optimal in the spring. We elected instead to collect a smaller number of samples from a single field and a single landscape position in fall 2012. Samples were collected at each of the sixteen grower/cooperator’s locations in spring and fall 2013 (Table 1) from fields seeded to winter wheat. At each location, three landscape positions were sampled: ridgetop, mid-slope and bottomland. Three replications were collected from each landscape position, with each replication the composite of five cores collected using a king tube (5 cm diameter). The samples were collected at increments of zero to one inch, one to two inches, two to three inches, three to four inches, four to six inches and six to eight inches. Additionally, three replicate soil samples were collected using the same depth increments from a native or undisturbed site in close proximity to twelve of the thirteen direct seed locations. Soil samples were stored at 4^oC until analysis. In addition to the enzyme, pH, EC and nutrient analyses that have been performed, we will be conducting phospholipid fatty acid analysis (PLFA) and total C and N analyses. Nematode and aggregate distribution analyses are ongoing. Additional soil samples will be collected in spring and fall 2014 from the same grower/cooperators using different fields that are in the winter wheat phase of the crop rotation. The goals are to investigate the soil quality parameters which may be contributing to direct seeders’ inability to reach yield potential and provide an outlet to disseminate new information, while allowing experienced producers to share the skills and understanding they have gained from years of direct seeding.

Objective 2: Evaluate management options to remedy the yield-limiting soil characteristics.

We have been speaking with growers individually about various options. As additional soil samples are collected and analyses are completed, we will be evaluating the data for each individual grower to provide information on soil characteristics by depth increment and landscape position so that growers may adjust their management practices if needed. Management options will be discussed in a February 19, 2014 meeting with grower/cooperators.

Objective 3: Compute the effects on profitability of management remedies to sustain long-term direct seed yields.

Prior to collecting soil samples in spring 2014, we will meet with the grower/cooperators to identify direct seed and adjacent conventional fields for sampling, and we will obtain information on current and historical management practices. Enterprise budgeting will be used to compute treatment effects on profitability based on average yield responses and the total and variable costs of the management treatments.

Objective 4: Inform producers, land managers, agribusiness personnel and landlords about the agronomic and economic benefits of direct seed cropping systems and also the management options to remedy soil quality and yield potential concerns.

A grower/cooperator meeting is scheduled for February 19, 2014 in conjunction with the Palouse Direct Seeders breakfast meeting in Colfax, WA. Additional meetings will be scheduled as needed, and presentations will be given to growers and agribusiness personnel as opportunities arise. We will participate in winter meetings of the Palouse Direct Seeders, the Clearwater Direct Seeders and the Pacific Northwest Direct Seed Association. As additional data are collected, we will present the results at grower field days. Upon completion of the project, results will be published in industry publications as well as scientific journals.

• Table 1. Long-term direct seed project grower/cooperators, locations, and current rotations on winter wheat fields sampled in spring, 2013.

Accomplishments/Milestones

Soil quality analyses of direct seed and conventionally farmed fields

The study sites were selected to represent low, intermediate and high rainfall zones of the dryland farming region of eastern Washington and northern Idaho. After the dry fall and limited soil sampling in 2012, soil sampling progressed according to plan in spring and fall 2013. The soil quality analyses completed thus far include soil moisture, pH, electrical conductivity (EC), dehydrogenase enzyme assay, β-glucosidase assay, macro- and micronutrient analyses. The mean values from spring 2013 for soil quality analyses (Table 2), macronutrients (Table 3) and micronutrients (Table 4) are listed for each grower/cooperator. The highest β-glucosidase level of 21.28 ρ-nitrophenol g^-1 soil hr^-1 was found at the Stubbs (LaCrosse, WA) site, and the lowest levels of 9.67 and 9.85 were found at the two Wilbur, WA sites (Sorensen and Sheffels) (Table 2). Dehydrogenase enzyme activity was highest at the Odberg (Genesee, ID) location with 3.29 µg TPF g^-1 soil hour^-1 and lowest at another Genesee, ID site (0.79 µg TPF g^-1 soil hour^-1; Jensen). The pH values on these soils ranged from 5.2 at the Schultheis (Colton, WA) site to 7.4 at the Sorensen (Wilbur, WA) conventional site. Electrical conductivity ranged from 91.2 at the Cochran (Colfax, WA) site to 247.2 µs cm^-3 at the Schultheis location. Cation exchange capacity ranged from a high of 24.8 meq at the Druffel conventional location (Pullman, WA) to a low value of 9.0 meq at the Koch direct seed site at Ritzville, WA.

The Jirava conventional site at Ritzville, WA had the lowest NO₃-N (22.4 mg kg^-1), NH₄-N (3.2 mg kg^-1) and Olsen P (P; 13.7 mg kg^-1) values (Table 3). Highest NO₃-N was found at the Schultheis site (79.6 mg kg^-1), highest NH₄-N at the Bailey (St. John, WA) site (18.6 mg kg^-1), and highest P at the Thorn (Dayton, WA) site (51.2 mg kg^-1). Highest K was found at the Hutchens (Dayton, WA) site (751.3 mg kg^-1), and lowest K at the Druffel conventional site (258.7 mg kg^-1). Sulfur ranged from 4.1 mg kg^-1 at the Sorensen conventional site (Wilbur, WA) to 34.8 mg kg^-1 at the Schultheis farm. Calcium was also highest at the Sorensen location (13.9 mg kg^-1), but lowest and the Koch direct seed site (Ritzville, WA; 5.9 mg kg^-1). Magnesium content ranged from 1.6 mg kg^-1 at the Sheffels Wilbur, WA site to 4.0 mg kg^-1 at the Druffel site. Micronutrient analyses were conducted for Al, Cd, Mo, Ni, Na, Zn, Fe, Mn, Cu and B (Table 4). The Schultheis location at Colton, WA was highest in Al, Cd, Mo, Zn and Fe. Several sites had no measurable Mo or Na. Regression analysis showed no correlation between pH and micronutrient concentration (R²<0.49) across all of the farmed sites.  

Landscape position

Averaged over all sites and all sampling depths, the native/undisturbed soils had higher β-glucosidase and dehydrogenase enzyme activity, pH, EC, K, NO₃-N, Ca, P, Zn, B and NH₄-N than the ridgetop, mid-slope or bottomland soils (data not shown). The undisturbed soils were lowest in Al, Na, Ni, Mn, Fe and Cu, although the differences were not significant in many cases (data not shown). Bottomland soils were higher in dehydrogenase, EC, K, NO₃-N, P, S, Fe, Mn and B than ridgetop and mid-slope soils. Ridgetop soils had lower pH and B and higher Al, Mg, CEC, Na and Cu than either mid-slope or bottomland soils. There were no differences in concentration of the micronutrients Cd and Mo among any landscape position.

Soil depth

In spring 2013 soil samples there were no differences detected in levels of CEC, Mg, Ca, Cd, Mo, Ni, Fe or B with sampling depth when averaged across all sample sites and landscape positions (data not shown). Levels of β-glucosidase and dehydrogenase enzyme activity, EC, K, NO₃-N, NH₄-N, P, S, Zn and Mn were highest in the zero to one inch samples and decreased with depth to six to eight inches; however, the differences among depth increments were not significantly different in all cases (data not shown). Aluminum levels were highest in the two to three and three to four inches depths and lowest at six to eight inches. Averaged over all the farmed sites, pH was highest at the six to eight inches depth and did not differ significantly from the zero to one inch depth. The depth increments from two to three inches and three to four inches were significantly lower in pH than the zero to one inch depth but did not differ from the one to two inches and four to six inches depths.  

Comparison of direct seed and conventionally farmed sites

One conventional or conservation tilled site was selected in each of the rainfall zones for comparison to a direct seed site. The result of this comparison with select soil quality analyses is shown in Table 5. In comparing the high rainfall sites near Colton and Pullman, WA, we found no differences in β-glucosidase, N, P or K between the direct seed and conventional farms. Dehydrogenase enzyme activity, pH and CEC were higher in the conventional site, and EC, S, Al and Cd were higher in the direct seed site. In the intermediate rainfall comparison of farms near Wilbur, WA, there were no differences in β-glucosidase, dehydrogenase, N or Al between direct seed and conventional. pH, EC and CEC were higher in the conventional soils, while P, K, S and Cd were higher in the direct seed soils. At the Ritzville, WA direct seed and conventional sites there were no differences in β-glucosidase or NO₃-N. In the conventional, low rainfall site, dehydrogenase, pH, EC and CEC were higher and NH₄-N, P, K, S, Al and Cd were higher in the direct seed soils.

Comparison of direct seed and native/undisturbed soils

At twelve of the direct seed locations, a native or undisturbed area was sampled for comparison. At half or fewer of the locations there were no differences in β-glucosidase, CEC, NO₃-N, K, S or Al between the direct seed and undisturbed soils (Table 6). At the majority of sites, dehydrogenase enzyme activity and pH were significantly higher in the undisturbed soils. Electrical conductivity, NH₄-N and P were higher in the undisturbed soils at ten of the twelve locations, although those differences were not always significant (Table 6). Cadmium concentration was higher in the direct seed soils than the undisturbed soils at eight of the locations.  

Field operation costs

Remedial management by farmers to improve, maintain or restore soil quality will depend considerably upon their efficiency in carrying out field operations. Past research has confirmed that some of the most efficient machinery managers in eastern Washington are found in the Horse Heaven Hills (HHH) in Benton County, who grow winter wheat in the driest rainfed area of the world (Schillinger and Young, 2004). One HHH grower with over 10,000 acres in direct seeded winter wheat, and known for efficient machinery management, recently shared his superb records with the project economist. The costs in Table 7 were computed from these records using machinery costs software (University of Idaho, 2013). Table 7 presents five-year average variable and fixed costs by field operation. Most of the direct seed grower/cooperators in this study are located in the annual cropping area of the eastern Palouse. However, the project economist has found it useful to compare field operation costs among growers and across regions. The variable and fixed costs in Table 7 will serve as a useful efficiency benchmark for the farm cooperators in this study.

Costs are typically divided into variable and fixed categories. The former vary by the number of acres cultivated. These include labor, fertilizer, herbicides, seed, fuel, machine rental and machine repairs and maintenance. Fixed costs include depreciation, interest, property taxes, housing and insurance on machinery. Land is also traditionally included as a fixed cost. Land cost equals the cash or share rent for land and property taxes.

In order to provide a forward perspective of the results for farmers in the region, 2012 and 2013 prices were utilized for fertilizer, herbicides, seed, fuel and labor. The HHH farmer reported that he broke even with respect to crop insurance premiums and indemnities, so no net charge was deducted for crop insurance.

References:

Schillinger, W.F. and D.L. Young. 2004. Cropping systems research in the world’s driest rainfed wheat region. Agronomy Journal 96:1182-1187.

University of Idaho. 2013. Crop Enterprise Budget Worksheet (CEBW) and Machinery Cost Worksheet (MACHOST), current versions, http://web.cals.uidaho.edu/idahoagbiz/management-tools/. Accessed September 9, 2013.

• Table 4. Results of soil micronutrient analyses for the 16 direct seed and conventional study locations in spring, 2013. Values are means across landscape positions and depths.
• Table 5. Comparison of select soil characteristics between direct seed and conventional/conservation tillage sites from each of the three rainfall zones, averaged across all landscape positions and depth increments. Different letters in the same section in the same column are significantly different at P<0.05.
• Table 6. Comparison of select soil characteristics between direct seed and native/undisturbed sites, averaged across all depth increments. Different letters in the same grower’s section in the same column are significantly different at P<0.05.
• Table 7. Average variable and fixed costs ($ ac-1) by field operation for an efficient eastern Washington machinery manager using a winter wheat-summer fallow rotation in the Horse Heaven Hills region.
• Table 2. Results of soil quality analyses for the 16 direct seed and conventional study locations in spring, 2013. Values are means across landscape positions and depths.
• Table 3. Results of soil macronutrient analyses for the 16 direct seed and conventional/conservation tillage study locations in spring, 2013. Values are means across landscape positions and depths.

Impacts and Contributions/Outcomes

From these analyses we will develop a greater understanding of the soil characteristics that influence plant growth to be included in management recommendations. For example, if pH, compaction or micronutrients are shown to be deviating from the norm or possibly affecting resiliency in direct seed systems, then management efforts will be directed to improve these factors. For each study, the impact of direct seed management options on plant growth will be determined, and the relationships among these data and the variables of location, soil characteristics and climate will be determined. The variability in topography and climate of this region make successful adoption of direct seeding challenging. Many producers in past decades failed at direct seeding, and these memories linger in the minds of non-farmers and many older generation farmers who are retired but maintain control of the land as landlords for younger farmers. Making the transition from conventionally tilled cropping systems to direct seeding is risky and requires long-term commitment. Additionally, the specialized equipment required to farm the landscape of the inland Pacific Northwest is expensive, with limited availability. The benefits of direct seeding on stopping soil erosion and reducing fuel costs through fewer trips over the field are well-documented; however, soils in most areas of the inland Northwest continue to remain productive in spite of high input costs and erosion. There seem to be few incentives for making the transition to direct seeding. There is a need to publicize the many benefits of direct seeding and continue to educate both producers and the general public, while addressing the obstacles to adoption.

To date, six student workers with interest in pursuing careers in agriculture have been employed to work on the soil analyses for this project and gain experience in their chosen field. We have presented hands-on soils experiments to local high school and middle school students. A meeting has been scheduled in February 2014 for the grower/cooperators on this project in order to present the results of the soil quality analyses, thus far, and to solicit suggestions and feedback on the project. This research will further our knowledge of soil quality and assist in developing profitable best management practices for direct seed systems.

Collaborators: