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 to keep more soil on the land. However, the continual application of fertilizers in the same soil depth has resulted in zones of low pH which interferes with micronutrient chemistry. 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 conservation tillage to identify those characteristics that play a part in limiting yield potential (Table 1). 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 7.5, and EC ranges from 90 to 250 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. As expected, 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 0-1 inch samples and decreased with depth to 6-8 inch. Aluminum levels were highest in the 2-3 and 3-4 inch depths, and lowest at 6-8 inch depths. Averaged over all the farmed sites, pH was highest at the 6-8 inch depth and did not differ significantly from the 0-1 inch depth. Of greatest concern were the depth increments from 2-3 inch and 3-4 inches, as they were significantly lower in pH than the other depths. The sites sampled in 2013 had lower pH in these two depths than the sites sampled in 2014.

For the sites with low pH and elevated Al in the 2 to 4 inch depths, four management options were presented to the growers. Options included broadcast lime applications, shank or spoked-wheel lime application, surface tillage, subsurface/wide spaced shank tillage, and no action. A combination of these options were applied to strips in each field at several sites.  With these factors identified, these management options will be investigated to determine which management practice increases the pH and reduces the available Al. From these data, strategies will be developed to obtain sustainable systems.

• Table 1. Long-term direct seed project grower/cooperators, locations, and current rotations on winter wheat fields sampled in spring, 2014.

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. 

Samples were collected at each of the sixteen grower/cooperator’s sites in the fall of 2012 (2012 report), spring and fall of 2013 (2013 report, Table 1), and 2014 (Table 1) from fields seeded to winter wheat. We sampled from different fields each year that were in the winter wheat phase of the crop rotation. At each site, 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 dia.). The samples were collected at increments of 0-1 inch, 1-2 inch, 2-3 inch, 3-4 inch, 4-6 inch, and 6-8 inch. 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 sites. Soil samples were stored at 4^oC until analysis. In addition to the enzyme, pH, EC, and nutrient analyses that have been performed, we are conducting phospholipid fatty acid analysis (PLFA), and total C and N analyses. The goal is 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.

Various different management options were discussed with the growers to increase the pH of those low pH soil zones. These management options were broadcast lime, lime applied with spoke wheel or shanked into the soil at the 2 to 4 inch depth; surface tillage and space shake tillage, and no action. 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 were discussed at February 2014 meetings with grower/cooperators. Additional meetings in 2015 are scheduled in February and March, as well as individual discussions with each cooperator throughout the year.

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

We will continue to meet with the grower/cooperators to identify direct seed and adjacent conservation-tilled fields for sampling, and we will obtain information on current and historical management practices. Management practices to be investigated will also be discussed. 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.

Several meetings with growers as a group (Palouse Direct Seeders breakfast meetings in Colfax, WA (February 19, 2014) were held. Individual growers were contacted in the winter of 2013 and results discussed to them for their land. A grower/cooperator meeting is scheduled for February and March 2015 in conjunction with the Palouse Direct Seeders breakfast meetings in Colfax, WA and Lewiston, ID. Additional meetings will be scheduled as needed, and presentations will be given to growers and agribusiness personnel as opportunities arise. We participated in winter meetings of the Palouse Direct Seeders, the Clearwater Direct Seeders, and the Pacific Northwest Direct Seed Association in 2012, 2013, 2014, and again in 2015. As additional management 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. 

Accomplishments/Milestones

Soil quality analyses of direct seed and conventionally farmed fields:

The study sites represented low, intermediate, and high rainfall zones of the dryland farming region of eastern Washington and northern Idaho. The soil quality analyses completed are soil moisture, pH, electrical conductivity (EC), dehydrogenase enzyme assay, β-glucosidase assay, macro- and micronutrient analyses. The mean values from spring 2014 for soil quality analyses (Table 2), macronutrients (Table 3), and micronutrients (Table 4) are listed for each grower/cooperator. Values varied with year and site. The spring 2014 enzyme activities were less than those for spring 2013.The highest β-glucosidase level of 20.2 mg ρ-nitrophenol g^-1 soil hr^-1 was found at the Cochran (Colfax, WA) site, and the lowest level of 9.7 was found at the Juris site (Bickleton, WA) (Table 2). Dehydrogenase enzyme activity was highest at the Scheffels (Wilbur, WA) site with 2.0 µg TPF g^-1 soil hour^-1 and lowest at the Druffel site (0.5 µg TPF g^-1 soil hour^-1; Pullman, WA). The pH values of these soils ranged from 5.2 at the Druffel (Pullman, WA) site to 7.3 at the Sorensen (Wilbur, WA) conventional site, as they had in 2013. Electrical conductivity ranged from 88 µs cm^-3 at the Jensen (Genesee, ID) site to 513 µs cm^-3 at the Zenner site, also near Genesee, ID. Cation exchange capacity ranged from a high of 22.2 meq at the Jensen site (Genesee, ID) to a low value of 10.1 meq at the Jirava site at Ritzville, WA.

As in spring 2013, the Jirava conventional site at Ritzville, WA in spring 2014 had the lowest NO₃-N (6.0 parts per million (ppm)), NH₄-N (2.0 ppm), and Olsen P (P; 17.7 ppm) values (Table 3). Highest NO₃-N was found at the Wilke site (43.4 ppm), highest NH₄-N at the Cochran (Colfax, WA) site (8.8. ppm), and highest P at the Hutchens site (Dayton, WA) site (46 ppm). Highest K was found at the Hutchens (Dayton, WA) site (618 ppm) and lowest K at the Schultheis site (313 ppm). Sulfur ranged from 32 ppm at the Druffel site (Pullman, WA) to 10 ppm at the Koch site (Ritzville, WA). Calcium was also highest at the Zenner site (15.2 ppm) but lowest at the Koch direct seed site (Ritzville, WA; 5.6 ppm). Magnesium content ranged from 1.6 ppm at the Sheffels (Wilbur, WA) site to 3.6 ppmph. The actual sites were different in 2014 from those in 2013. The pH values and Al differed among the sites and years.

Landscape position:

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 2014 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 0-1 inch samples and decreased with depth to 6-8 inch; however, the differences among depth increments were not significantly different in all cases (data not shown). Aluminum levels were highest in the 2-3 and 3-4 inch depths and lowest at 6-8 inch. The depth increments from 2-3 inch and 3-4 inch were significantly lower in pH than the 0-1 inch depth but did not differ from the 1-2 inch and 4-6 inch depths.

Comparison of direct seed and conservation-tillage 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 few differences in β-glucosidase, N, P, or K between the direct seed and conservation-tilled soils. In contrast to other data, β-glucosidase, dehydrogenase enzyme activity, CEC, N, P, K, and Cd were not different between the direct seed site and the conservation-tillage site. pH was higher in the direct seed site. EC, S, and Al were lower 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 conservation-tilled soils, while P, K, S, and Cd were higher in the direct seed soils. At the Ritzville, WA direct seed and conservation-tilled sites there were no differences in β-glucosidase, pH, or NH₄-N.  In the conservation-tilled, low rainfall site, dehydrogenase, EC, and CEC were higher, and all other means across depth and landscape were higher in the direct seed soils. 

Comparison of direct seed and native/undisturbed soils:

At twelve of the direct seed sites, a native or undisturbed area was sampled for comparison. At the majority of sites, dehydrogenase enzyme activity and pH were significantly higher in the undisturbed soils compared to the direct seed sites (Table 6). At more than half of the sites, there were no differences in the mean across all landscape and depths the β-glucosidase, CEC, NO₃-N, K, S, or Al between the direct seed and undisturbed soils.  Electrical conductivity, NH₄-N, and P were higher in the undisturbed soils at ten of the twelve sites, 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 sites.

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 and 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, 2013, and 2014 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 3. Results of soil macronutrient analyses for the 16 direct seed and conventional/conservation tillage study locations in spring, 2014. Values are means across landscape positions and depths.
• Table 4. Results of soil micronutrient analyses for the 16 direct seed and conventional study locations in spring, 2014. Values are means across landscape positions and depths.
• Table 2. Results of soil quality analyses for the 16 direct seed and conventional study locations in spring, 2014. Values are means across landscape positions and depths.
• Table 5. Comparison of select soil characteristics between direct seed and conservation tillage sites from each of the three rainfall zones, averaged across all landscape positions and depth increments for Spring 2014. 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 from spring 2014, 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.

Impacts and Contributions/Outcomes

From these analyses, and the management practices implemented, we are developing a greater understanding of the soil characteristics that influence plant growth to be included in management recommendations. Soil pH and micronutrients are deviating from the norm due to long-term zone application of nutrients. These changes are now affecting resiliency in direct seed systems and management efforts are being studied 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 site, 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 conservation-tilled cropping systems to direct seeding is risky and requires long-term commitment; however, change in direct seeding management is needed to resolve this decrease in pH. 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 and negatives of direct seeding and continue to educate both producers and the general public, while addressing the obstacles to adoption and the downfalls of long-term direct seed that limits net farm profit.

To date, ten 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. Meetings were held during February, 2014 for the grower/cooperators on this project to present the results of the soil quality analyses and to solicit suggestions and feedback on the project and interest in slight changes in management to mitigate the decrease in pH in the 2 to 4 inch soil depth. This research will further our knowledge of soil quality and assist in developing profitable best management practices for direct seed systems.

Collaborators: