Evapotranspiration , Grain Yield , and Water Productivity of Spring Oat ( Avena sativa L . ) under Semiarid Climate

Spring oat (Avena sativa) is produced for grain, hay, and green manure and can be integrated into a cropping system as a cover crop. Twenty-eight oat genotypes (G1, G2, G3, ...., G28), selected for their adaptability to the Southwestern United States, were evaluated for their yield performance under sprinkler irrigation during four growing seasons (2005-2008) at the Agricultural Science Center at Farmington, New Mexico State University. The genotypes were arranged in randomized complete blocs design with four replications. Irrigation scheduling was based on evapotranspiration and the depletion criterion of 40% to 45% total available water (TAW) was practiced to prevent the plants from experiencing any water stress. Crop evapotranspiration estimated by the FAO crop coefficient and reference evapotranspiration approach was low about 2 mm/day during crop initial stage and increased with plant growth and reached the maximum during crop mid-season or reproductive stage. It decreased during crop late season. Daily crop evapotranspiration varied from 0.5 to 12.6 mm in 2008 and the seasonal Spring oat evapotranspiration varied from 535.8 to 591 mm. Averaged across the four growing seasons, oat evapotranspiration was 570.4 mm. The results showed that Spring oat plant height varied significantly with genotypes and ranged from 59.1 to 100.8 cm. Oat grain yield significantly varied with years and genotypes. Grain yield varied from 3386 to 6498 kg/ha and average yield was 4245, 4265, 5477, and 4025 kg/ha during the 2005, 2006, 2007 and 2008, respectively. The best performing genotypes were G1, G2, G7, G19, G20, G21 and G23 with average yield greater than 4800 kg/ha while G3, G13, G17 and G27 showed the lowest yield among the genotypes. Oat crop water use efficiency (CWUE) varied with genotype and years and ranged from 0.53 to 1.07 How to cite this paper: Djaman, K., O’Neill, M., Owen, C., Koudahe, K. and Lombard, K. (2018) Evapotranspiration, Grain Yield, and Water Productivity of Spring Oat (Avena sativa L.) under Semiarid Climate. Agricultural Sciences, 9, 1188-1204. https://doi.org/10.4236/as.2018.99083 Received: August 22, 2018 Accepted: September 25, 2018 Published: September 28, 2018 Copyright © 2018 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access


Introduction
Oat (Avena sativa L.) hold many opportunities for development as foods, industrial and pharmaceutical products, which all add value to the oat crop [1] [2] [3].
Oat is mostly used for animal feeding and human health food [4]; however, the use of oat as animal feed has declined steadily and is replaced by other types of forage.Oat is also a health crop for human nutrition that provides the consumer with B-glucans and dietary fiber components, high tocopherol and natural antioxidant [5].Oat grain are rich with biologically significant substances and their consumption in human diet is beneficial for human well-being [3] [6].
Oat production is showing decreasing trends with total worldwide cultivated area that varied from 38,260,751 to 9,433,141 ha and the grain yield showing increasing trend from 1296.07 to 2437.34 kg/ha during the 1961-2016 period [7].
During the same period, oat cultivated area across the United States also showed decreasing trends at the expense of wheat, barley or maize and varied from 9,666,550 to 397,000 ha with increasing trends in grain yield ranging from 1411.08 to 2516.75 kg/ha [7].Consequently, oat production is decreasing despite the crop has great nutritional and therapeutic values.Gorash et al. [8] reported that oat crop traditionally has been neglected in a number of respects, cultivated in non-optimal cropping areas as wheat, barley or maize.Lin et al. [9] reported oat actual evapotranspiration (ETc) range of 227 -305 mm and water productivity that varied from 1.03 to 1.2 kg/m 3 under conventional irrigation and alternative partial root zone irrigation in Baicheng city, Jilin province of China.Zute et al. [10] reported average oat yield that varied from 3560 to 6620 kg/ha with the oat varieties Stmara and Laima showing the more stable yield of 5350 and 5830 kg/ha, respectively.Oat has great importance in animal production because of its high yielding potential to be produced as green fodder for forage.Singh and Singh [11] reported that oat cultivar produced green folder as high as 55,000 kg/ha while Naeem et al. [12] found oat green fodder yield of 81,170 kg/ha.Forsberg and Reeves [13] and Tamm [14] in-dicated that numerous biological, genetics, management strategies and climatic conditions impact high yields of high quality oat production.Forsberg and Reeves [13] pointed that cool and moist climate are considered the best for oat production and reported 14 oat varieties grain yield varietal and season dependent varying from 2753 to 7680 kg/ha.Tamm [15] reported variation in grain yield of some oat varieties from 3288 to 5824 kg/ha with environmental impact on the yield in Estonia.Sandhu and Horton [15] indicated that water shortage can cause serious loss of oat grain yield.Karing et al. [16] pointed that yield limiting factors in field crops can be divided into several groups: variety efficiency, soil fertility, agrotechnics, and meteorological conditions.South Dakota is the most oat production State followed by North Dakota, Wisconsin, Minnesota, Iowa, Pennsylvania, New York, Texas, Michigan and Maine [17].While oat is produced in the Northern, Midwest and Eastern United States, very limited data and information exist on Spring oat productivity across the Southwestern US under semiarid and arid climatic conditions.In the Southwestern United States, oat is a very secondary crop and is produced by only 27 farmers over 64 ha in New Mexico basically in Mora, Rio Arriba and Sandoval counties [18].Therefore, the objectives of this study were to evaluate grain yield of some Spring oat genotypes, and to determine their water productivity under semiarid climates and high elevation at Farmington, New Mexico.Wind speed (U 2 ), minimum temperature (T min ), maximum temperature (T max ), average temperature (T mean ), relative humidity (RH mean ), and solar radiation (R s )

Station Area
were measured at the site by an automated weather station on a daily basis and averaged on the seasonal basis (April -August) (Table 1).

Crop Actual Evapotranspiration Estimation (ETc)
Spring oat actual evapotranspiration was estimated according to the equation proposed by Jensen [19] and Allen et al. [20].

Reference Evapotranspiration Model: ASCE-EWRI (2005)
Daily grass-reference ET was computed using the standardized American Society of Civil Engineering (ASCE) form of the Penman-Monteith (PM-ETo) equation: ) where: ETo is the reference evapotranspiration (mm•day −1 ), Δ is the slope of saturation vapor pressure versus air temperature curve (kPa•˚C −1 ), Rn is the net radiation at the crop surface (MJ•m −2 •d −1 ), G is the soil heat flux density at the soil surface (MJ•m −2 •d −1 ), T is the mean daily air temperature at 1.5 -2.5 m height (˚C), u 2 is the mean daily wind speed at 2 m height (m•s −1 ), es is the saturation vapor pressure at 1.5 -2.5 m height (kPa), ea is the actual vapor pressure at 1.5 -2.5 m height (kPa), es − ea is the saturation vapor pressure deficit (kPa), γ is the psychrometric constant (kPa•˚C −1 ).The procedure developed by Allen et al. [20] was used to compute the needed parameters and the trend in the daily ETo for the 2005-2008 period is presented in Figure 1.

Crop Coefficients (Kc)
Spring oat was grown under non-limiting water and fertilizer conditions, and the standard FAO crop coefficients were used for crop actual evapotranspiration estimation.Spring oat crop Kc is affected by climate conditions, soil moisture status and crop growth stages.As the crop develops, the ground coverage, crop height and leaf area change.Due to differences in evapotranspiration during various growth stages, the Kc values for a given crop vary over the growing period.Oat growing period consists of the initial stage, crop development stage, mid-season stage, and late-season stage.Spring oat crop coefficients developed under a standard climatic condition by Allen et al. [20], as 0.
where Kc stage is the adjusted daily Kc during the mid and late seasons, Kc stage (tab) where CWUE, ETWUE and IWUE are in kg/m 3 , Yield in kg/ha, Spring oat seasonal ETc is the seasonal cumulative ETc (mm), the seasonal irrigation amount is the sum of the irrigation amounts throughout the season (mm), and seasonal water supply is the sum of seasonal precipitation and seasonal irrigation amount (mm).

Statistical Analysis
The effects of oat genotypes and the seasons and their potential interaction on Spring oat yield, evapotranspiration, CWUE, IWUE and ETWUE were analyzed using analysis of variance (ANOVA) in PROC MIXED in SAS [27].Separation of means was determined with the least significant difference (LSD) statement at the 5% significance level to identify any potential significant differences between the genotypes.

Spring Oat Evapotranspiration
The variation in the spring oat daily actual evapotranspiration is presented in and Hargreaves [28] and Jensen et al. [19] was successfully used by Allen et al. [20] and Djaman et al. [29] [30].Hobbs and Krogman [31] reported Spring oat seasonal ETc ranging from 409 to 542 mm at the Agriculture Canada Irrigation Substation at Vauxhall, Alberta.Lower oat ETc values were reported by Knaggs [32] who reported oat seasonal ETc ranged from 388 to 433 mm in western Canada.Lin et al. [16] found oat seasonal ETc that varied from 227 to 305 mm in Jilin province of China.

Oat Plant Height
Oat plant height varied with genotypes and ranged from 75.Higher oat plant height values were reported for the wild and early maturing group of oat in Brazil [33].Plant height is a trait strongly related to plant lodging and yield.Federizzi and Qualset [34] indicated that the introduction of a gene for low plant height was limited due to the multipurpose use of the cereals for forage and seed yield in addition to the low soil fertility that limits plant height.Carvalho and Federizzi [35] reported that improvement in oat grain yield is related to plant breeding for plant height reduction, earliness and fertility enhancement.Tumino et al. [36] reported that plant height was correlated to lodging severity and indicated that GWAS analyses detected six significant associations for lodging and two for plant height among a broad collection of European hexaploid oat genotypes.Berry and Berry [37] showed that plant height is the main trait affecting plant lodging in cereals and Marshall et al. [38] indicated that lodging causes significant yield losses.Breeding for high yield oat genotypes should involve plant height and yield components as the primary traits to improve oat yield.

Oat Grain Yield
Oat grain yield significantly varied with years (P = 0.023) and genotypes (Table 3).[40].Knaggs [32] found oat grain yield dependence on cultivar, nitrogen rates and the previous crop before oat production and varied from 4878 to 5309 kg/ha.Doehlert et al. [41] reported oat grain yield that varied with genotype and ranged from 3140 to 4110 kg/ha at Carrington, Edgeley, Minot and Prosper, ND.Tamm [14] reported inter-annual variation in oat grain yield at the Jogeva Plant breeding Institute in Estonia during the 1998-2002 period.From the evaluation of 21 oat genotypes in South Australian, Zaheri and Bahraminejad [42] reported oat grain yield that varied from 3580 to 9700 kg/ha under full irrigation and from 3188 to 7011 kg/ha under rainfed conditions and the genotypes Brusher, Tarahumara and Potoroo showed better performance than the rest of oat genotypes.Hisir et al. [43] reported the highest oat grain yield achieved by Checota cultivar from 17 oat genotypes evaluated for their yield performance at Kahramanmaras in Turkey.the average grain yield (R 2 > 0.98) (Figure 5) and decreased linearly with seasonal evapotranspiration (R 2 > 0.65) (Figure 6).There were strong linear relationships between CWUE, IWUE, and ETWE with R 2 close to unity (Figure 7).

Water Productivity of Oat
Yuan et al. [44] reported oat water productivity (WP) to vary from 1.1 to 1.3 kg/m 3 in China while Lin et al. [16] reported oat ETWUE as function of applied nitrogen fertilizer rate and ranged from 1.02 to 1.24 kg/m 3 .The environment, management practices, sowing date, and the genotype might have strong effect on the variability of water use efficiency [16] [45] [46] [47].

Conclusion
Field experiment was conducted to evaluate the performance of twenty-eight Spring oat genotypes under irrigation conditions during four growing seasons at the NMSU Agricultural Science Center, Farmington, NM.Seasonal irrigation amount varied from 488 to 591 mm and the Spring oat seasonal evapotranspiration varied from 535.8 to 591 mm.Oat plant height significantly varied with genotypes.Oat grain yield also significantly varied with years and genotypes and ranged from 3386 to 6498 kg/ha.The best performing genotypes at Farmington and which are suitable for Farmington, New Mexico, were G1, G2, G7, G19, G20, G21 and G23 with average yield greater than 4800 kg/ha while G3, G13, G17 and G27 showed the lowest yield among the genotypes.Oat CWUE, IWUE and ETWUE varied with genotype and years and ranged from 0.53 to 1.07 kg/m 3 , 0.57 to 1.20 kg/m 3 , and 0.57 to 1.21 kg/m 3 , and averaged 0.76, 0.83, and 0.81 kg/m 3 , respectively.The results of this study demonstrate the possible incorporation of oat production into the cropping systems in the Four Corners region for grain yield or forage production.However, additional research needs to be conducted to determine the best agricultural practices on oat, the optimum water and fertilizer requirements and application timing and the optimum planning window to cope with the late Spring and the early Fall freeze that usually occurs at the high elevation in the Four Corners region.
This study was conducted at the Agricultural Science Center at Farmington, New Mexico State University (NMSU) (Latitude 36.69'North, Longitude 108.31'West, elevation 1720 m) during the 2005, 2006, 2007 and 2008 growing seasons.

Figure 1 .
Figure 1.Seasonal course of distributions of the average daily reference evapotranspiration for the 2005-2008 period at the experimental station.

Figure 2 .Figure 2 .
Figure 2. Crop daily evapotranspiration was low during crop initial stage and increased with plant growth and reached the maximum values during crop mid-season or reproductive stage.It decreased during crop late season.Daily crop evapotranspiration varied from 0.5 to 10.9 mm in 2005, from 1.2 to 9.7 mm

Oat
CWUE varied with genotype and years and ranged from 0.53 to 0.75 kg/m 3 in 2005, from 0.65 to 0.96 kg/m 3 in 2006, from 0.76 to 1.07 kg/m 3 in 2007, and from 0.55 to 0.83 kg/m 3 in 2008 (Table 4).Overall average CWUE was 0.65, 0.78, 0.91 and 0.70 kg/m 3 in 2005, 2006, 2007 and 2008, respectively.For the study period, Genotype average CWUE was within the range of 0.65 -0.87 kg/m 3 and the overall average CWUE was 0.76 kg/m 3 .The highest CWUE was achieved by G19 and the lowest CWUE was obtained by G13.IWUE which represents the quantity of yield produced per cubic meter of water, varied from 0.57 to 1.20 kg/m 3 and was genotype dependent and average 0.70, 0.87, 1.01, and 0.68 kg/m 3 in 2005, 2006, 2007 and 2008, respectively (

Figure 4 .Figure 5 .
Figure 4. Relationship between (a) oat average seasonal evapotranspiration (ETc) and the seasonal reference evapotranspiration (ETo), and (b) seasonal reference evapotranspiration (ETo) and the growing season duration.

Table 2 .
Spring oat planting and harvesting date, applied fertilizer rate, precipitation and irrigation applied during the 2005-2008 period.

Table 3
3 to 89.3 cm in 2005, from 59.1 to 92.1 cm in 2006, from 71.1 to 98.4 cm in 2007 and from 61.8 to ).G11 obtained the lowest value in 2005 and G26 consistently obtained the shortest plant height in 2006, 2007 and 2008.G13 obtained the highest plant height value of 89.3 cm in 2005 while the G17 was the highest in 2006 and 2008 as 92.1 and 100.8 cm, respectively, and G27 obtained the highest plant height value of 98.4 cm in 2007.The results of this study are in agreement with Matiello et al. [33] who reported similar plant height values during their experiment in 1994 in Brazil.

Table 3 .
Variation in Spring oat plat height and grain yield as function on oat genotype and growing season during the 2005-2008 period.Pecio and Bichoński [39] reported that oat grain yield averaged 5198, 3600 and 3253 kg/ha during the 2005, 2006 and 2007 seasons and significantly varied with year, applied nitrogen and pesticide rates in the Grabów Experimental Station of the Institute of Soil Science and Plant Cultivation in Puławy, Poland.Oat grain yield was 2915 kg/ha in Manitoba