Problem: Dryland agriculture in the Northcentral Great Plains is limited by low precipitation, cool
temperatures, and poor soil fertility. Because of this, there are few cash crops that consistently perform
well in the region and most dryland producers rely on winter wheat for their major cash crop. When
market prices for winter wheat fluctuate producers have very few alternative crop options to rotate into. In
addition to single market dependence, the most widely used cropping rotation of winter wheat-fallow
reduces landscape diversity and degrades soil health, making it unsustainable.
Research Question: Are pulses a sustainable crop option for dryland producers in the Northcentral Great
Plains? Incorporating pulse crops into the current wheat-fallow rotation will offer new cash crop options
for farmers in the region while also providing much needed soil health benefits from having a legume in
the rotation. Crops of chickpea, lentil, guar, and dry peas will be evaluated for their agronomic production
potential and the sustainable value of these crops will be assessed by measuring soil fertility parameters as
well as soil moisture. The results of this work have the potential to not only diversify crop production but
also improve the health of the overall system.
Expected outcomes: As the result of this project we expect to be able to provide producers information
1. Maximum yield expectation for each pulse crop and the potential profitability of each.
2. Soil nitrogen contribution of each pulse crop into current rotations.
3. Pulse crop water use and soil water recharge rate compared to fallow and how to maximize water
use efficiency for the cropping system.
4. Strategies to manage termination of pulse crops to maximize soil moisture and nitrogen
availability under variable environmental conditions.
1. Identify maximum yield expectation for lentil, chickpea, grain pea, and guar.
2. Measure soil nitrogen contribution of each pulse crop.
3. Measure crop water use and soil water recharge of each pulse crop compared to fallow.
4. Determine how timing of termination of pulse crops affects soil moisture and soil
This project was conducted at the University of Wyoming Sustainable Agricultural Research and Extension Center (SAREC) near Lingle, WY (42.09° N, 104.38° W, 1272 ASL). The trial was started in the spring of 2018 and will be repeated in the spring of 2019. Five main crop treatments consisting of lentil, chickpea, grain pea, guar, and a fallow control were planted on three planting dates, (early, standard, late) all within a four-week period. Two varieties of each crop were grown, one conventional variety and one short season. Varieties planted were: lentil- Maxim & Richlea, chickpea- Orion & Frontier, grain pea- Carver & EarlyStar, guar- Monument & Kinman. In total, there were 25 unique treatments replicated three times. Plots were split into two subplots, with half of the plot being terminated at peak biomass and half the plot taken to grain to allow for comparison of each pulse crop as a seed crop or cover crop.
General agronomic data was collected on all plots including stand establishment, date of first flower, date of first pod formation, date of last flower, biomass at first flower, peak biomass, nodule numbers, canopy development, plant height and total yield.
Identify maximum yield expectation for each pulse crop:
Knowing yield outcomes for each pulse crop is essential to gauging the profitability of each crop. To identify the maximum yield expectation for each pulse crop, we did a Normalized Difference Vegetation Index (NDVI) measurement to determine the rate of canopy establishment. A faster canopy establishment leads to a higher amount of sunlight being absorbed by the crop and less reaching to shorter plants, like weeds, that compete for resources. Less competition for resources leads to a higher potential yield for the crop. NDVI measurements were taken weekly using a RapidSCAN CS-45 handheld crop sensor. Planting at three different planting dates allows us to determine the optimal planting date to get the maximum yield. The cool season crops (lentil, chickpea, grain pea) were planted late March to early April. The warm season guar was planted late May to early April. At the end of the growing season, grain was harvested from each crop to determine yield that they produced. Grain was harvested with plot combine as well as hand samples of two one-meter rows.
Measure soil nitrogen contribution of each pulse crop:
In these low input wheat-fallow systems, any additional nitrogen for the crop following these pulse crops is a benefit. The nitrogen fixing ability of pulse crops creates a possibility for this additional nitrogen to be available. Because of this, it is important to determine the amount of nitrogen added to the soil by each pulse crop. In order to measure this, soil samples were taken before planting in the spring of 2018 before planting pulses and before planting wheat in the fall. Samples were taken at depths of 0-10, 10-30, and 30-60 cm. Soil was tested for nitrogen, nitrate, potentially mineralizable nitrogen, and organic matter.
Measure crop water use and soil water recharge rate of each pulse crop compared to fallow:
In a dryland system, water can be scarce which is why one of the main justifications for leaving fields fallow is to conserve water for the following crop. The ability of pulse crops to use water from a shallower depth than wheat allows for a quicker soil recharge rate and available water to remain in the deeper soil for wheat to use. To measure this soil moisture, three methods were used. Before planting pulses and after pulse harvest gravimetric water balance (GWB) cores were taken at depths of 0-10, 10-30, 30-60, and 60-90 cm. Before planting wheat, GWB cores were taken at depths of 0-10 and 10-30 cm. PR2 access tubes from Dynamax were installed to a depth of one meter. Soil moisture readings at depths of 10, 20, 30, 40, 60, 100 cm were measured once a week from the time of emergence through harvest using a PR2 multi depth soil moisture probe. Watermark sensors from Irrometer were also installed in one complete rep at depths of 30 and 60 cm. These sensors were set to take readings every hour from emergence to harvest. These three methods helped to give us a complete picture of the soil moisture profile and crop water use which can be used to determine which rotation has a better soil water recharge rate for the winter wheat crop.
Determine how timing of termination of pulses affects soil moisture and soil nitrogen availability:
With frequent drought and variable rainfall in the high plains, management flexibility can be a great tool for producers to mitigate risk. By treating each pulse crop as a grain crop and a cover crop we will be able to learn how the different management decisions affect soil moisture and nitrogen. To determine this, we split each plot in two with half being taken to grain and half terminated as a cover crop at peak flower. Soil moisture measurements were taken at the time of termination to see how much water can be saved through cover cropping.
Hand harvest yields for each crop were analyzed using a general linear model. The average yield for lentils was 504.14 kg/ha. There were no significant differences seen between the varieties (p= 0.72) or planting dates (p= 0.50). The average yield for guar was 335.83 kg/ha. There were no significant differences seen between the varieties (p= 0.69) or planting date (p= 0.21). For dry peas, the average yield was 1867.8 kg/ha with no significant difference in the varieties (p= 0.39) or planting date (p= 0.36). The average yield for chickpeas was 1552.19 kg/ha with no significant differences in variety (p= 0.83) or planting date (p= 0.51). There were significant differences seen in the variety by planting date interaction (p= 0.03). A Least Significant Differences test showed that yields increased with earlier planting dates in the Frontier variety and with later planting dates in the Orion variety. The results from this test are shown below.
|Average Yield kg/ha|
|Frontier||1706.1 ± 250.51||1674.5 ± 293.12||1338.0 ± 259.02|
|Orion||1148.8 ± 629.54||1441.4 ± 182.28||2016.3 ± 378.06|
Soil Water Recharge:
Gravimetric water balance (GWB) cores were taken before wheat planting to determine the amount of water available to the following wheat crop. Cores were separated into four depths: 0-10, 10-30, 30-60, and 60-90 cm. A general linear model was used to find significant differences between crop types as well as between treatments within crops.
Significant differences were seen between all crop types (p=<0.0001). The average soil moisture amounts are shown in the table below.
|Crop||Average Percent Soil Moisture|
|Fallow||17.9 ± 4.81|
|Dry Pea||15.7 ± 8.28|
|Chickpea||12.4 ± 3.32|
|Lentil||13.9 ± 3.84|
|Guar||20.8 ± 2.93|
Within crop types, significant differences varied. The treatments considered were planting date (early, mid, late) and termination treatment (cover crop, grain, fallow). Depth was significant (<0.0001) with moisture concentrations higher at deeper depths. In samples taken after pulse crop harvest, no significant differences were seen between varieties of crops, because of this, only one variety of each crop was sampled before wheat planting.
In guar, no significant differences were seen in the planting date (p=0.3793) or termination treatment (p=0.1159). The termination treatments for guar included only grain and fallow because the guar matured very late in the season and did not have a good cover crop treatment window.
There were also no significant differences seen in grain pea treatments; planting date (p=0.5100), termination treatment (p=0.3596). The termination treatments for grain pea included only grain and fallow because the cover crop treatment window was missed due to unforeseen circumstances.
Within lentils, planting date (p=0.2393) was not significant. Termination treatment (p=<0.0001) was considered significant. An LSD t-test showed that all termination treatments (cover crop, grain, fallow) were significantly different. A table of the averages is shown below.
|Lentil Termination Treatment||Average Percent Soil Moisture|
|Fallow||16.9 ± 4.33|
|Cover Crop||15.0 ± 4.01|
|Grain||12.2 ± 2.90|
Within chickpeas, planting date (p=0.3364) was not significant. Termination treatment was significant (p= <0.0001). Within this, an LSD t-test showed that cover crop and fallow were not significantly different, and grain was significantly different than both cover crop and fallow. Averages of this can be seen in the table below.
|Chickpea Termination Treatment||Average Percent Soil Moisture||Comparisons Significant at 0.05 Level|
|Fallow||15.1 ± 2.94||A|
|Cover Crop||14.1 ± 3.54||A|
|Grain||10.62 ± 1.89||B|
In chickpeas, the interaction between termination treatment and depth was also significant (p= 0.0098). In this LSD t-test, it was determined that the grain termination treatment had significantly lower soil moisture than both fallow and cover crop. Grain also had a more severe moisture dry down at deeper depths. Moisture averages from this are shown in the table below.
|Average Percent Soil Moisture|
|Chickpea Termination Treatment||Depth 1 (0-10 cm)||Depth 2 (10-30 cm)||Depth 3 (30-60 cm)||Depth 4 (60-90 cm)|
|Fallow||11.6 ± 1.20||13.9 ± 1.06||17.1 ±1.81||17.8 ± 1.96|
|Cover Crop||10.3 ± 1.29||13.2 ± 1.21||15.3 ± 1.59||17.7 ± 3.93|
|Grain||8.0 ± 0.78||11.1 ± 0.54||12.1 ± 0.94||11.3 ± 1.66|
Soil Nitrogen Additions:
Soil fertility cores were taken at 3 depths (0-10, 10-30, 30-60 cm) before wheat planting. Soil nitrate concentrations at these depths were analyzed using a general linear model.
Between crop types, termination treatment (grain, cover crop, fallow) were not significant (p=0.9001). Depth was a significant factor (p= <0.0001) with higher concentrations of nitrate at shallower depths. Crop type (p= 0.0363) and crop type by termination treatment (p= 0.0036) were significant with the results shown below.
|Crop Type||NO3 Average Concentration (ppm)||Comparisons Significant at 0.05 Level|
|Chickpea||6.3 ± 5.56||ABCD|
|Grain Pea||4.2 ± 3.23||C|
|Fallow||7.5 ± 5.49||AB|
|Guar||5.5 ± 3.56||ACD|
|Lentil||6.0 ± 5.30||ABC|
|NO3 Average Concentration (ppm)
|Crop Type/Termination Treatment||Cover Crop||Grain|
|Chickpea||5.4 ± 4.88||7.3 ± 6.07|
|Grain Pea||4.2 ± 3.23|
|Guar||5.5 ± 3.56|
|Lentil||6.6 ± 5.27||5.5 ± 3.56|
|Fallow||7.5 ± 5.49||7.5 ± 5.49|
Within crop types, significant differences varied, with depth (p=<0.0001) being significant in all crop types with higher nitrate concentrations at shallower depths. Factors analyzed within each crop included termination treatment (cover crop, grain, fallow), crop variety, planting date (early, mid, late), and depth.
Within chickpeas, varieties of Frontier and Orion (p= 0.1689) and planting date (p= 0.4010) were not significant. Termination treatment (p= 0.0121) was considered significant, an LSD test showed the following results.
|Chickpea Termination Treatment||NO3 Average Concentration (ppm)||Comparisons Significant at 0.05 Level|
|Cover Crop||5.4 ± 4.88||B|
|Fallow||8.2 ± 6.76||A|
|Grain||7.3 ± 6.07||A|
Within lentils, termination treatments (p= 0.2924) and varieties of Maxim and Richlea (p= 0.9582) were not considered significant. Planting date (p= 0.0313) was significant, an LSD t-test revealed the following results.
|Lentil Planting Date||NO3 Average Concentration (ppm)||Comparisons Significant at 0.05 Level|
|Early||7.6 ± 5.86||B|
|Mid||5.6 ± 4.63||A|
|Late||4.1 ± 4.51||A|
Within guar, termination treatment was not considered because of late maturation and all of the crop being taken to grain. Varieties of Kinman and Monument (p=0.2514) and planting date (p= 0.1224) were not found to be significant.
Within grain pea, termination treatment was not considered due to all of the crop being taken to grain due to unforeseen circumstances. Planting date (p=0.9316) was not found to be significant. Varieties of EarlyStar and Carver (p= 0.0191) were significantly different than fallow with results shown below.
|Guar Varieties||NO3 Average Concentration (ppm)||Comparisons Significant at 0.05 Level|
|Carver||4.6 ± 3.48||A|
|EarlyStar||3.8 ± 2.97||A|
|Fallow||8.2 ± 6.50||B|
Educational & Outreach Activities
Of the 4 consultations done, 3 were producers looking for information on how to look for nodules, the 4th was information about chickpea nodulation for a science fair project. 2 articles were published. One was an article about guar published in the Scottsbluff Star-Herald. Another article about introducing pulse crops into the wheat fallow system was published in the Wyoming Livestock Roundup. 2 poster presentations were given, one at the SAREC field day and the other at the Western Society of Crop Science annual meeting. There was also a radio talk given about guar and chickpeas were talked about at the local farmers market.
The number of farmers/ranchers who participated was estimated to be 520 with 20 of those being direct from the farmers market, consultations, and SAREC field day and 500 indirect through the radio and newspaper. The number of agricultural professionals who participated was estimated to be 120 with 20 being direct through farmers market and the Western Society of Crop Science meeting and 100 indirect through the radio and newspaper.
For outreach in progress, a newspaper article has been written and will be published when an appropriate newspaper is found. A meeting with local producers to discuss pulse crop production is being planned as well as a pulse crops field day at SAREC planned for the summer of 2019.