Effect of water regime on evapotranspiration, grain and protein yields of pea, lentil, barley, spring wheat followed by winter wheat crop sequence

Principal Investigator: Gadi V.P. Reddy

Investigators: Etone Kenedy and John H. Miller

Project Personnel: Phillip Hammermeister and Alysia Miller

Western Triangle Agricultural Research Center,

Montana State University, 9546 Old Shelby Rd.,

P.O. Box 656, Conrad, MT 59425, USA

Background

Primarily due to low annual quantity and poor distribution of precipitation, the risk of crop production in dryland Montana is high. Available water in dryland agriculture is the most important factor controlling crop function and a decline in available water increases the physiological stress and vulnerability of plants (Guoju et al. 2013). There is no doubt that increasing soil moisture will favor crop productivity. Winter wheat-fallow agricultural systems have been widely adopted to reduce the risk of crop failure. Montana farmers believe that leaving land fallow after a cropping season is required to store soil moisture rather than continuously growing crops. This perception stems from cases of pulse failure across the state attributed to severe drought conditions. Based on soil water dynamics, farmers may predict when to skip fallow and adopt a pulse-winter wheat and barley-winter wheat cropping systems to increase profitability of their farmlands. In addition, this research examines the role of evapotranspiration and water use efficiency as related to yields and protein content. Considering the urgent need to develop a sustainable dryland cropping system, the Montana Wheat and Barley Committee renewed the funding of this research project in January 2017.

Objectives

The overall goals of this project were to determine the effect of soil water regime on evapotranspiration, grain yields and protein contents of lentil, pea, barley, spring wheat and the profitability of following these crops with winter wheat crop sequence.

Materials and Methods

Field trial was established in spring 2017 at the Western Triangle Agricultural Research Center. Soils in this area are described as Scobey clay loam with a soil surface pH of 7.7 and an organic matter content of 2.4%. Because of their yields and market popularity in North Central Montana, Vida, Hockett, Richlea and Banner varieties were respectively chosen for spring wheat, barley, lentil and pea. After initial soil testing, seeding was done with a total soil N (residual + fertilizer) rate of 50 lbs per acre. Fertilization was based on recommendations and expected yields and was kept to a minimum to avoid dilution and the masking of water regime effect on the crops. Four water regime treatments were set up through a differential line irrigation system aimed at providing 18 (high), 12 (medium), 6 (low) and zero (only precipitation) inches of water from seeding to flowering. Irrigation treatments were assigned to the main plots of 75 x 50 feet and crops and a fallow plot were randomly assigned to the sub plots with four replications in a randomized complete block design. Weeds were effectively controlled using appropriate herbicides.

Soil samples were collected at 1-3 ft depths before seeding and after harvesting in each plot to determine change in soil water content. Evapotranspiration or water use was calculated by adding total precipitation and change in soil water content. Water loss through drainage was assumed as negligible. Water use efficiency (WUE) was computed as the ratio of yield to evapotranspiration.

After harvest, grain yield was determined. Protein content and test weight was analyzed by Perten NIR. Data was subjected to analysis of variance and Pearson’s correlation and significance of means was determined at 5% level of probability using Tukey b test.

Research results, Significance and Recommendations

Results showed water regime significantly influenced evapotranspiration and water use efficiency of the crops (Table 1-4). Evapotranspiration increased with increasing water application throughout the growing season. Grain or seed yields of lentil, barley and spring wheat were significantly influenced by water regime. Grain or seed protein content of pea, barley and spring wheat generally increased with increasing water application but test weights were not significantly affected (Table 2-4). Except lentils, the crops used water more efficiently at lower water applications and evapotranspiration. Evapotranspiration generally had significant correlation with yield and water use efficiency (Table 5). Grain or seed yields showed significant positive correlation with evapotranspiration and WUE in lentil. WUE was positively correlated with grain or seed yields in pea, barley and spring wheat but significantly so only in barley.

Significance in correlation is an indication that two variables have a strong association. A change in one variable can be used to predict the response of the associated variable with some degree of certainty.

There was wide variation in yields of the crops compared to the average yields for Montana in 2015. According to the USDA (2016) average yields for lentil, dry pea, barley and spring wheat for Montana State in 2015 was 1100 lb ac-1, 1450 lb ac-1, 52 bu ac-1 and 31 bu ac-1 respectively. Lentils and spring wheat responded well with high yields in increased irrigation plots compared to pea and barley. Barley and pea proved to be sensitive to soil moisture by yielding more in dryer conditions. These results indicate that genotypic differences exists between these crops in their response to different water regime conditions. This study proves that there is need to continue to look into better and more accurate understanding of different crops and their response to soil water dynamics in semi-arid agri-systems and Montana farmers must continue to be prudent in making soil and crop management decisions in this era when rainfall is erratic and unpredictable. The information from this study could be used to help farmers formulate strategies for ensuring effective and efficient use of stored soil water for sustainable production of irrigated lentil, pea, barley and spring wheat in dryland agro-ecological environment. Under irrigated conditions, the highly mobile nitrates move out of the root zone before plants can take them up (Inskeep et al. 1992). Therefore, further studies are necessary to investigate these crops at different water regimes and N fertilizer rates to determine a proper combination of applied water and fertilizer N that will meet a realistic yield goal while minimizing leaching of fertilizers.

Table 1. Effect of water regimes on evapotranspiration, seed yield and water use efficiency of lentil. Values are means of 4 replicates.

*,*** P<0.001, P<0.05 respectively. ns not significant. Means followed by different letters are significantly different.

Table 2. Effect of water regimes on evapotranspiration, test weight, protein content, seed yield and water use efficiency of pea. Values are means of 4 replicates.

***, *, P<0.001, P<0.05 respectively. ns not significant. Means followed by different letters are significantly different.

Table 3. Effect of water regimes on evapotranspiration, test weight, protein content, plumps, seed yield and water use efficiency of barley. Values are means of 4 replicates.

***,** P<0.001, P<0.01 respectively. ns not significant. Means followed by different letters are significantly different.

Table 4. Effect of water regimes on evapotranspiration, test weight, protein content, seed yield and water use efficiency of spring wheat. Values are means of 4 replicates.

***,* P<0.001, P<0.05 respectively. ns not significant. Means followed by different letters are significantly different.

Table 5. Pearson correlation coefficients between evapotranspiration (ET), water use efficiency (WUE) and grain or seed yield (Y) and associated P values of lentil, pea, barley and spring wheat.

Project Challenges and problems

Water for irrigation was released into the canal (source) at the end of May 2017. For this reason, there was delay in irrigation initially planned to start as early as seeding. Therefore, instead of eight weeks planned irrigation, plots received six weeks of irrigation water. Yields of pea and barley were severely affected by the feeding damage of a swarm of birds at the juicy dough stage of the pods and grains respectively.

Next phase of the project into 2018

In September 2017, winter wheat was seeded into previously cropped and fallowed plots and grains will be harvested in summer 2018. The benefits of pulse-winter wheat rotation and profitability will be determined taking into consideration the yields and estimated fertilizer cost of each cropping sequence.

Acknowledgments

This study was supported by Montana Wheat and Barley Committee. The support of the MSU- Western Triangle Agricultural Research Center staff was highly appreciated.

References

Guoju X, Fengju Z, Zhengji Q, Yubi Y. 2013. Impact of climate change on water use efficiency by wheat, potato and corn in semiarid areas of China. Agriculture, Ecosystem and Environment 118: 108-113.

Inskeep B, Hengel D, Jacobsen J. 1992. Nitrogen utilization by malting barley under varying moisture regimes. Fertilizer Facts: September 1992, Number 2.

USDA 2016. United States Department of Agriculture, National Agricultural Statistic Service, Montana Annual Crop Summary 2015.