Yield and Water Use of Field Peas and Chickpeas Under Irrigation
In southwest Nebraska, irrigating corn and soybeans with limited water is challenging due to typically dry weather conditions and high crop water use (i.e., evapotranspiration or ET) in July and August. (Evapotranspiration is the water lost to the atmosphere from both evaporation from any surface and transpiration from green vegetation.) In addition, declining groundwater levels, water allocations, frequent droughts, limited irrigation well capacities, and light-textured soils often prevent southwest Nebraska farmers from irrigating summer crops to meet their full crop water requirements.
Implementing alternative spring-planted crops such as chickpeas and field peas in the irrigated crop rotations may provide benefits such as:
- more efficient use of spring precipitation;
- increased irrigation system capacity to meet peak ET demands of both winter and summer crops, especially if grown under the same irrigation system; and
- Increased overall cropping system water use efficiency (CWUE; grain produced per unit of water used) and profitability.
The objective of this project was to investigate the feasibility of field pea and chickpea production under irrigation and evaluate their potential for water conservation in irrigated cropping systems. Specifically, our goal was to quantify the grain yield and CWUE of field peas and chickpeas under different irrigation levels.
Study Approach and Treatments
The field experiment was conducted during the 2018 growing season at the Henry J. Stumpf International Wheat Center near Grant. The following irrigation treatments were applied to chickpeas and field peas:
- dryland (DRY, no-irrigation applied),
- deficit irrigation (DI), and
- full irrigation (FI).
Soil moisture sensors using neutron attenuation down to a 5-foot depth were used to schedule irrigation and quantify changes in stored soil water. These neutron readings were used for calculating water balance parameters, including
- precipitation (P),
- irrigation (I),
- runoff (RO),
- deep percolation (DP),
- evapotranspiration/crop water use (ET), and
- seasonal soil water change (DSW).
Field peas were planted March 14 and harvested July 16. Chickpeas were planted March 24 and harvested August 17. The soil was predominantly Kuma silt loam and had an approximate plant available water capacity of 2.2 inches per foot. The previous crop was wheat and soil moisture was near field capacity at the time of planting. Growing season precipitation (March-August) was 6.5 inches higher than the 30-year average.
Yield Response and Water Use
Dryland yield of chickpeas (53.5 bu/ac) and field peas (55.5 bu/ac) was well above average due to having a full soil water profile at planting and above average seasonal precipitation (Table 1; Figure 1). Although dryland yield was similar in both crops, chickpeas used 16.7 inches, which was 3 inches more than field peas (13.7 inches). Consequently, the crop water use efficiency of chickpeas (3.2 bu/ac-in) was 1.1 bu/ac-inch lower than field peas (4.3 bu/ac-in) under dryland conditions (Table 1; Figure 1).
Irrigating field peas resulted in increased crop water use and increased yield. Field peas grown under deficit irrigation (1.8 inches applied) used an additional 2.3 inches and out-yielded dryland by 5.7 bu/ac (2.5 bu/ac per inch of water used). Supplementing an additional 1.8 inches under full irrigation (3.6 inches total); however, caused an increase in deep percolation losses and minimal increase in crop water use (0.5 inches) and yield (0.9 bu/ac) over deficit irrigation (Table 1; Figure 1).
In contrary, irrigating chickpeas resulted in increased crop water use and yield decrease (Table 1, Figure 1). Chickpea yield under deficit (2.2 inches applied) and full irrigation (4.4 inches applied) was 16.5 bu/ac and 28.5 bu/ac yield less than dryland, respectively (Table 1; Figure 1). Negative yield response to irrigation is not common in plants, especially if it’s coupled with increase plant water use; however, it is possible for irrigation to influence other yield-limiting factors. In our study, such response may be attributed to the increased incidence of Ascochyta blight two weeks prior to harvest.
Patterns in Soil Water Extraction
Field peas effectively utilized soil water available in the profile, especially under dryland conditions where water extractions were observed up to a four-foot depth (Figure 2). Irrigating field peas with 3.8 inches (i.e., full irrigation treatment) resulted in recharge of water deeper in the soil profile (Figure 2).
Chickpea soil water extraction was similar under dryland and irrigation with most of the soil water depletion occurring in the top three feet of the soil profile (Figure 2). Soil water recharge below the three-foot depth occurred in both dryland and full irrigation treatments and can be attributed to combined effects of abundant precipitation and slow crop development early in the spring (Figure 2).
|Crop||Irrigation treatment||P (in)||I (in)||RO (in)||DP (in)||ET (in)||DSW (in)||Yield (bu/ac)||CWUE (bu/ac-in)|
This study highlighted the potential for field peas and chickpeas to be used in areas with limited irrigation. Both crops were able to efficiently utilize early season precipitation and produce very good dryland yields.
In a wet year, field peas may benefit from
- light irrigation amounts,
- careful consideration of current soil water levels, and
- a favorable 10 day-weather forecast (little rain and dry weather).
The potential development of Ascochyta blight also should be considered when deciding whether to irrigate chickpeas. More research is needed to evaluate the response of field peas and chickpeas in normal and drier-than-normal years.
Field peas had higher crop water use efficiency and a greater ability to extract soil water from deeper in the profile than chickpeas, demonstrating greater potential under limited irrigation. Field peas, due to the shorter season, also have an advantage over chickpeas in terms of opportunities to double crop forages and/or cover crops and gain additional income.
Our thanks to the Nebraska Environmental Trust who provided financial support for this research and to Justin Richardson, the UNL technician assisting with this project.