Farmers in semiarid environments are struggling to sustain fallow year in their rotation due to rapid evolution of herbicide-resistant weeds and declines in soil health caused by a lack of plant biomass production. Planting cover crops to address these issues may not be economically justified in water-limiting environments (unless grazed or harvested for hay) as they use water, which can reduce yield of subsequent cash crop. Field pea may be a solution to this problem as it may provide ecosystem services similar to cover crops, while still being a profitable crop in the rotation. Field pea may also be a viable alternative to corn-soybean rotation in humid environments. Farmers in humid environments of NC SARE region may want to consider diversifying their crop rotations to spread financial risks associated with low market prices of corn and soybean and high prices of farm inputs. Research objectives are to: (1) Quantify the rotational costs and benefits of field pea vs fallow (Rotation study); (2) Evaluate the response of field pea to 3 planting dates and 5 seeding rates (Agronomic study); (3) Test varieties of field pea and short-season sorghum suitable for double cropping in humid environments (Double cropping study). Rotation and Agronomic studies will be conducted in different precipitation zones throughout the semiarid western Nebraska to capture a variety of scenarios for growing field pea in semiarid environment; several parameters including water use, soil health, biodiversity, effects on succeeding wheat crop, and profit will be measured. Double cropping study will be conducted in humid eastern Nebraska. Project outcomes. Farmers will be able to: (1) identify the circumstances upon which replacing fallow with field pea will generate profit, better utilize available soil water and off-season precipitation, and improve soil health and environmental quality ; (2) use optimal seeding rates and planting dates to maximize grain yield potential; (3) select best-matching field pea and grain sorghum cultivars for double cropping to diversify their corn-soybean crop rotation and spread production risks; (4) improve their economic well-being, quality of life, and professional inquiry of issues related to environmental stewardship and long-term sustainability. Project summary table
Farmers in semiarid environments will be able to identify the circumstances upon which replacing fallow with field pea will generate profit, better utilization of available soil water and off-season precipitation, and improvement in soil health and environmental quality. Farmers will utilize optimal seeding rates and planting dates to maximize grain yield potential. Farmers in humid regions will able to select best-matching field pea and grain sorghum cultivars for double cropping, diversify their crop rotation and spread production risks. Farmers will improve their economic well-being, quality of life, and professional inquiry of issues related to environmental stewardship and long-term sustainability.
Field peas can be successfully used to replace fallow in dry regions or as a double crop in more humid regions while having a beneficial impact on the soil, and increasing the profitability and sustainability of producers.
Study locations and timeline
Rotation studies will be conducted on two University research farms and one farmer’s field, thereby covering three different annual precipitation zones throughout the semiarid region of west-central Nebraska: (1) North Platte, NE (22 inches) – West Central Research and Extension Center (University); (2) Enders, NE (19 inches) – farmer’s field (Chris Pursley); and (3) Sidney, NE (17 inches) – High Plains Agricultural Lab (University).
Small-plot studies at the two University farms will be done as part of larger long-term rotation studies that will be established in 2017 to evaluate 6-10 crop rotations (4 replications). Experimental plots under rotations that include a fallow year will be divided and one half will be planted to field pea to enable side by side comparison with fallow. The first year of rotation (2017), field pea will be planted in the spring (mid-March, 2017) and harvested in the summer (mid-July, 2017), while fallow will only be sprayed for weed control. The same year in the fall (mid-September, 2017), wheat will be planted across both treatments. Wheat will be harvested for yield in the summer of the following year (mid-July, 2018) completing the field pea vs. fallow study.
A large-scale strip trial located at a farmer’s field was initiated in 2015 and it was historically operated under a no-till system in a wheat-corn-fallow crop rotation. The study at this location has been set as pairwise (side-by-side) comparison of field pea vs fallow with 9 replications (total of 18 strips, each being 45 ft wide and 2,650 ft long). Preliminary results after 1st rotational year have been published; evaluations of 2nd rotational year will be done after wheat harvest in July 2016 (Stepanovic et al., 2016). As part of this grant, we will utilize this study to do a 3rd year (2017-corn), 4th year (2018-fallow/field pea), and 5th year (2019-wheat) evaluation.
Measurements and data collection (What, How, When, and Where)
- Water utilization:
- Actual evapotranspiration (ET, i.e. water use) will be estimated using the soil water balance method: ET = Rain + Soil water at beginning – Soil water at end – Runoff – Deep percolation. Changes in soil water status will be measured in 3 replications every 12 inches to a depth of 60 inches using neutron attenuation on a bi-weekly basis (Rudnick et al., 2016). Watermark granular matrix sensors (Irrometer Co., Inc., Riverside, CA), will be installed in 2 replications to monitor hourly soil water dynamics for estimation of deep percolation (Rudnick and Irmak, 2014). The sensors will be installed in representative areas in the field pea and fallow plots and water use will be monitored from emergence until after wheat harvest.
- Crop water productivity will be calculated for field pea by dividing grain yield by seasonal ET.
- Precipitation storage efficiency (PSE) is the fraction of precipitation that is stored in the soil profile over a period of time and will be quantified by measuring the change in soil water status via neutron attenuation and watermark sensors and dividing it by precipitation amount collected on-site.
- Soil parameters:
- Soil nutrient cycling and soil microbial activity will be evaluated by taking soil samples for each treatment at different periods (4 periods between planting field pea and wheat harvest) and different depths (3 depths – 1st, 2nd, and 3rd foot) and having them tested for nitrate (NO3-N), phosphorous (P), potassium (K), organic matter (OM), and microbial activity (Solvita test).
- Soil aggregate stability and soil infiltration rates will be evaluated after wheat harvest at the end of the rotation. Bulk soil will be sampled at the following depth intervals: 0-4 and 4-8inch depths. Ten samples will be collected from each plot and composited by soil depth. Samples will be air-dried for 72 h and passed through 8 mm sieves. Fifty grams of the sieved soil will be sieved in water using 0.25, 2, and 4.75 mm sieves in a wet sieving machine to determine percent water-stable aggregates. Water infiltration will be measured using double ring infiltrometers for 2 h. Two measurements per plot will be done to reduce variability. Infiltration rate and cumulative infiltration will be computed.
- Potential biological control Bacillus species will be targeted for isolation from the roots of mid-season field pea samples by plating on Tryptic soy agar after heat treatment (Adesemoye and Wei, unpublished). Isolation will also be done from wheat roots and microbial populations in wheat roots following pea will be compared to the population in wheat roots following fallow. Isolates of the microbial biocontrol agents will be identified through 16S rDNA.
- Isolation and characterization of mycorrhizal fungi will be done through a modified method of Senoo et al (2007). Isolates will be recovered from pea roots as well as from the subsequent wheat crop. As widely reported in the literature (Senoo et al., 2007), mycorrhiza is able to take up nutrients, for example, phosphate through extraradical hyphae via a phosphate transporter to the intraradical hyphae and help make more phosphate available to plants. Thus, analyses will be conducted to compare the interactions of mycorrhiza and roots of wheat following fallow or pea as indication of the effects of planting pea. Additionally, isolation from roots of wheat will target soilborne fungal pathogens to detect any effect of the treatments on the incidence of pathogens. Recovered mycorrhiza isolates and soilborne fungal pathogens will be identified through morphology and sequencing of the internal transcribed spacer (ITS) and β-tubulin regions, which are highly conserved across all fungi (Adesemoye et al., 2014).
- Abundance and diversity of beneficial and pest arthropods will be measured by collecting insects from pitfall traps (two traps per plot) that capture insects that move along the ground and sweep nets (one sample of 30 sweeps per plot) that capture insects from plant foliage three times during the field pea/fallow growing period and two times during the growing cycle of the succeeding wheat crop.
- Crop Yield
- Yield will be collected from field pea plots and test weight and moisture will be recorded. Yield and quality effects on the succeeding wheat crop the following year will also be collected at harvest.
- System profitability
- Estimations of both rotations (field pea-wheat vs fallow-wheat) will be based on market price of field pea, actual costs of farm inputs (seed, fertilizer, herbicides, etc.), and cost of farm operations (planting, spraying, harvest)
To evaluate the effects of seeding rates and planting date on field pea yield in semiarid environments and to minimize production risk through better understanding of biological response (yield components) of field pea to different agronomic practices.
Study locations and timeline
This study will be conducted in 2017 and 2018 in conjunction with an established field pea statewide variety testing at 4 different locations through western Nebraska; thus, cost of planting and harvesting this study will be partially funded by field pea industry. Locations will include: Hemingford, NE (farmer’s field – Brad Hansen); Sidney, NE (University farm); Venango, NE (farmer’s field – Steve Tucker); North Platte, NE (University farm).
Experimental design and data collection
There will be 3 different planting dates and 5 seeding rates arranged in a split-plot design with 4 replications, with planting date being main plot, and seeding rates sub-plots. Planting populations will include the rate commonly used by many growers in the area, 310,000 live seeds/a, and two populations over and under that recommendation. Yield responses will be plotted against the actual number of plants/ac, taken from mid-season stand counts, using the non-linear asymptotic regression model. Yield components including number of plants per acre, pods per plant, seeds per pod, and seed size will also be collected and analyzed using Pearson correlation analysis.
Double cropping field pea and grain sorghum
A variety study will be conducted in 2018 and 2019 at UNL’s Southeast Research and Extension Center (SEREC) near Mead, NE (32 inches of annual precipitation). Ten or more field pea cultivars will be planted in the spring (mid-March) and harvested in summer (mid-July). Five or more short-season sorghum varieties will be planted following harvest of field pea and harvested in early November. Yield data will be collected and analyzed to recommend the best yielding cultivars for double cropping field pea and grain sorghum. In 2019 an organic farmer will be identified to test this concept on the large scale.
Poor seed germination derailed experiments in 2017. Will be completed again in 2018 and 2019. During 2017, emergence of the crop was around 20% despite having high germination tests. After collecting emergence data and soil moisture data, it was determined that the data would have minimal importance and would not hold up to peer review due to the poor stand. Therefore, it was determined that resources would be preserved to conduct the experiment in 2018 and 2019. The early planting date at two locations of the agronomic study were just planted on March 8 and March 9.
Educational & Outreach Activities
This SARE project supported numerous field days and workshops. Field days were held in North Platte, Venago, Sidney, and Hemingford to allow growers to see field pea varieties and weed control options. During these meetings, growers were able to interact with pulse crop representatives and ask production questions.
Winter meetings were held in Bridgeport and Grant in January. Attendance was at capacity at both meetings and was well supported by industry partners. Information was presented on varieties, production, pest management, and end use.
Publications have been submitted through CropWatch online that discuss crop rotations, water use, and populations. Some of these articles were picked up by popular press or had other popular press articles written about the research.
- Yellow field pea production
- Weed management
- Soil water management