water use efficiency and physiological responses of oat under alternate partial root-zone irrigation...

Procedia Engineering 28 (2012) 33 – 42

1877-7058 © 2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Society for Resources, Environment and Engineering doi:10.1016/j.proeng.2012.01.679

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Procedia

Engineering Procedia Engineering 00 (2011) 000–000

www.elsevier.com/locate/procedia

2012 International Conference on Modern Hydraulic Engineering

Water use Efficiency and Physiological Responses of Oat under Alternate Partial Root-zone Irrigation in the Semiarid

Areas of Northeast China LIN Yechuna, ZENG Zhaohaia, REN Changzhongb, HU Yuegaoa, a*

aCollege of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China bBaicheng Academy of Agricultural Sciences, Baicheng City, Jilin 137000, China

Abstract

Water use efficiency (WUE) and some crop physiological responses were studied when oat (Avena nuda L.) was applied with alternate partial root-zone irrigation (APRI). A field experiment was carried out with two organic fertilizer levels (e.g. 0 and 240 kg hm-2) and three irrigation levels (i.e. 60, 90 and 120 mm). The irrigation methods included the conventional irrigation (CI) and APRI. Compared with CI, APRI under the moderate water stress reduced water consumption by 9.97-12.46%, and improved WUE by 0-9.09%, but the grain yield was slightly reduced by 2.1-12.76%. APRI under the severe water stress would significantly (P<0.05) reduce the plant height than CI. APRI with organic fertilizer could increase the root shoot ratio by 18.18-45.45% after the grain filling stage. Under the severe water stress APRI significantly reduced the net photosynthetic rate (Pn), and these treatments with organic fertilizer generally had much higher Pn than those without organic fertilizer. Our results indicate that APRI under the moderate water stress improves WUE and root shoot ratio, and slightly reduce grain yield and Pn with applied organic fertilizer. © 2011 Published by Elsevier Ltd. Keywords: Water use efficiency; Alternative irrigation; Organic fertilizer; Photosynthesis; Avena nuda

1. Introduction

Irrigated agriculture is the main consumer of the available water resources in the world. According to FAO (2000), about 60% of total water resources all over the world are expended in agricultural irrigation.

* Corresponding author: HU Yuegao. Tel.:+86 10 62733847; fax: +86 10 62732441. E-mail address: [email protected].

© 2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Society for Resources, Environment and Engineering

34 LIN Yechun et al. / Procedia Engineering 28 (2012) 33 – 42 Author name / Procedia Engineering 00 (2011) 000–000

In 2008, the total water consumption was 54 billion m3 in Northeast China; however, agriculture consumed about 70% of it. Since the irrigated agriculture usually get much more crop yield than rainfed does, Lascano et al.[1] indicated that the irrigated area should be increased by more than 20% and the irrigated crop yield should be increased by 40% by 2025 to secure the food for 8 billion populations. Therefore, it is critically important to improve the water use efficiency in agriculture.

On the other hand, the intensive cultivation resulted in decrease of soil organic matter (SOM) and degradation of framing land quality, thus cropland showed poor capacity for water and nutrient conservation[2]. Qiu et al.[3] reported that total soil organic carbon (SOC) storage in crop lands in Northeast China was about 1243.48 × 106 t (0-30 cm soil layer); under the current cultivation systems, SOC was in a negative balance with organic carbon losing at a high rate of 31.22 × 106 t and 2.05 t hm-2 a-

1. This situation was more severe in Heilongjiang and Jilin provinces. Soil in paddy fields and vegetable fields had higher SOC concentrations than those in dry farming land[4]. It is necessary that an amount of organic fertilizer is applied in dry farming land for the agricultural sustainable development.

Alternative partial root-zone irrigation (APRI) is novel water saving irrigation method and can improve WUE of crop production without much yield reduction[5-6]. APRI requires that approximately half of the root system of the crop is always exposed to drying soil while the remaining half is irrigated as in normal irrigation. And irrigation would be exchanged between the wetted zone and dried zone in a frequency according to crops, growing stages and soil water balance[6]. When soil water content was maintained 55-65% of its capacity, compared to the full-irrigated maize, APRI reduced water consumption and total dry mass accumulation by 34.4-36.8% and 6-11%, respectively, thus leading to significantly increase in canopy WUE[7]. There are a large number of studies on WUE and physiological responses of field crops and fruit trees by APRI technique[7-10], but few studies assessed the effect of APRI on the grain-grass crop such as oat in the farming-grazing transitional zone. This study assess if APRI can improve WUE and if some physiological responses are severely affected by water stress.

2. Materials and methods

2.1. Experimental site and materials

The field experiment was conducted in the arid and semiarid areas at the experimental station of Baicheng academy of agricultural sciences, Baicheng city, Jilin province of China (latitude 45°37ˊN, longitude 122°48ˊE, 152 m altitude). This station is within a continental monsoon climate area in the northwestern part of Jilin province, with the average annual sunshine duration 2 919 h, average annual temperature 4.9°C. The frost-free period is 157 days, and average annual precipitation is 380 mm (the precipitation during June-September accounts for 83% of the annual precipitation). Average annual evaporation was 1 914 mm, which exceeded more 5 times of mean annual precipitation. The experimental soil type is chernozem, and the physical and chemical characters of different depth of the soil can be found in Table 1. Oat (Baiyan No. 2, a local dominant naked oat variety) was selected for this study.

Table 1. Physical and chemical parameters of the experimental field.

Soil depth (cm)

Bulk density (g cm-3)

Organic matter (g kg-1)

Total nitrogen (g kg-1)

Available phosphorus (mg kg-1)

Available potassium (mg kg-1)

pH

0-20 1.23 15.03 0.146 14.17 48.57 6.64 20-40 1.48 14.44 0.796 2.61 43.30 6.91 40-60 1.49 7.21 0.279 1.72 45.26 6.76 60-80 1.56 2.86 0.147 1.06 40.36 8.25 80-100 1.60 1.43 0.119 1.18 41.78 7.00 100-120 1.54 0.72 0.046 1.12 41.44 7.35

35LIN Yechun et al. / Procedia Engineering 28 (2012) 33 – 42 Author name / Procedia Engineering 00 (2011) 000–000

2.2. Experimental design

Treatments were three levels of irrigation quantity and two organic fertilizer levels with two irrigation methods. Three irrigation quantity levels either 60 mm or 90 mm and 120 mm was irrigated with conventional irrigation (CI, soil was evenly irrigated with Ф32 cm pipe in each watering), alternative partial root-zone irrigation (APRI, watering was alternately applied to two sides of one row by drip irrigation as the method specified in Fig. 1) at the stages of jointing, heading and grain filling. The 120 mm irrigation level was popular irrigation quantity. Two organic fertilizer levels include 0 kg hm-2 (A1, organic fertilizer is usually not used for oat at local areas) and 240 kg hm-2 (A2, organic matter content ≥ 40%). The recommended inorganic fertilizers were 37.5 kg N, 37.5 kg P2O5 and 18 kg K2O per hectare. The details of these treatments are showed in Table 2.

Table 2. Experimental design for the field experiment. CI: conventional irrigation by flooding, APRI: alternative partial root-zone irrigation by drip irrigation.

Treatments Organic fertilizer levels Irrigation methods with different amounts of irrigation water

CI120 mm 0 kg hm-2 (A1) CI (CK1) with 120 mm during all growing season

APRI60 mm APRI with 60 mm during all growing season



CI120 mm 240 kg hm-2 (A2) CI (CK2) with 120 mm during all growing season




The field experiment had 24 plots in total, arranged in a randomized block design with three replicates per treatment. Each plot size used in this experiment was 10 m × 4 m, with a 50 cm wide space ridging mulched 50 cm deep plastic film between two plots to prevent the effect of lateral soil water movement. Except controls, thin-wall drip tapes with drippers 30 cm apart and a flow rate of 2.7 L h-1 0.15 MP working pressure were used. The space between drip lines was 60 cm.

Fig. 1. Alternate partial root zone irrigation was laid out in field. T-1 and T-2 indicate the places of PVC tubes, which were used to measure soil moisture by TDR.


2.3. Field management

The field experiment was ploughed in the winter of 2009. Seeds were sown on the April 10th, 2010. The distance between the rows was 30 cm, and sowing rate was 200 kg hm-2. During the growing season, three times of irrigation were at the stages of jointing (55 days after sowing, DAS), heading (66 DAS) and grain filling (74 DAS), respectively. All plots were applied with urea at a rate of 75 kg hm-2 as top dressing at the heading stage of oat. The date of harvest was July 18th, 2010, for oat, i.e. 100 DAS.

2.4. Plant sampling and measurement

Soil water content: Two TRIME access tubes in each plot were installed vertically into the soil to the depth of 1.2 m before oat sowing. The position of TRIME access tubes are found in Fig. 1. During the oat growing season, volumetric soil water content (cm3/ cm3) was periodically measured by a time domain reflectometry (TDR) tube probe (IMKO, Germany, TRIME-FM/T3) from 5 cm to 85 cm depth at an increment of 10 cm.

Photosynthetic characteristics: The photosynthesis photon flux densities (PPFD) were measured from 9:00 am to 11:00 am on sunny day at the late grain filling stage (83 DAS) of oat. These expanded and intact flag leaves in each treatment were selected, and a portable open gas exchange system was employed; LED (model 6400-02B, LI-COR Inc.) was chosen as the light source of a portable open gas exchange system. The gas entry was connected to a gas pole 4 m aboveground. The temperature, relative humidity, flux and CO2 concentration were set at 25°C, 60-70%, 500 μmol s-1 and 400 μmol mol-1, respectively. The photosynthetic curves were made against the PPFD of 1500, 1200, 1000, 800, 600, 400, 200, 150, 100, 50, 20 and 0 μmol m-2 s-1.

Dry biomass: 0.5 m successive plants of each plot were selected for their dry biomass accumulation between jointing and ripening stages. Roots and shoots were separated to calculate root shoot ratio. Root shoot ratio is the root dry weight over the shoot dry weight. Fresh plant material was firstly dried at 105°C for 30 min, and then dried at 80°C to constant weight.

Yield and water use efficiency: The total grain yield of one plot was determined by hand harvesting 1 m2 in each plot at maturity.

Crop evapotranspiration (ETc) was estimated using the water balance equation as follows:

ETc = I + P – R – D ± ΔS (1)

where I is the irrigation amount (mm), P is the precipitation in growing season (mm), R is the surface runoff (mm), D is the drainage below crop, and ΔS is the change of soil water storage. Each plot was considered to have received the same amount of rainfall. To get ΔS, T3 probe (TDR) was used to measure verticality soil water content (cm3/ cm3) in the soil profile from 5 cm to 115 cm depth by 10 cm increments just when sowing and harvesting. As there were ridges separating the plots to block runoff, the surface runoff was neglected. The drainage was supposed to be negligible because drip irrigation hardly affected the soil water content below 1 m depth[11].

Water use efficiency (WUE) was calculated using this formula as follows:

WUE = Y / ETc (2)

where Y is the total grain yield (oven dry) of each plot (kg hm-2), ETc is the total crop evapotranspiration over the entire season (mm).

2.5. Statistical analysis


The data were analyzed by F-test using Statistical Analysis Software (SAS 8.2, SAS Institute Inc., USA). The significance of the treatment effect was determined using the F-test, and to determine the significance of the means, least significant differences (LSD) was used with 5% probability level, and Duncan’s multiple range test was used for comparing treatments.

Fig. 2. Mean daily air temperature, 0-20 cm soil temperature and precipitation during the whole growing season of oat.

3. Results and discussion

3.1. Temperature and precipitation

Weather data would be obtained from the meteorological station of Baicheng Weather Bureau, which is close to experimental field within 1 km. Mean daily air temperature, 0-20 cm soil temperature and precipitation during the whole growing season are shown in Fig. 2. Mean daily air temperature ranged from -1 to 30.4°C, and average temperature during the whole growing season was 17.7°C. Daily maximum air temperature ranged from 1.7 to 37.3°C, and minimum air temperature from -9.4 to 22.7°C. Before three-leaf stage (41 DAS), mean daily air temperature was 9.2°C, which was much lower than the optimum growth temperature (15°C) for oat[12]. Soil temperature and mean air temperature had similar trend in changing, as a result, lower soil temperature delayed the date of seeding, about a 20-day extension. Low temperature affected the vegetative growth of oat at earlier stages, and high temperatures impacted the reproductive growth of oat at later stages. High temperatures mainly occurred from booting (59 DAS) to filling stage (74 DAS). Some reports indicated that high temperatures between panicle initiation and anthesis caused floret abortion, reduced fertile tillers and consequently reduced grain yield[13-14]. During the growing season, total effective precipitation (>5 mm) was 164 mm, and primarily occurred at May and July. Drip irrigation was carried out in June, when there were only a few showers.

3.2. Total water received and consumed in field

Total water received and consumed of different treatments during the whole growing season is shown in Table 3. Precipitation in the growing season was 195 mm; however, effective precipitation (>5 mm) was cut down to 164 mm. The change of soil water storage (ΔS) was the lowest for APRI60 mm treatments, but it increased as the irrigated quantity increased more than 60 mm, which was comparable to some early reports[15-17]. CI120 mm had the highest evapotranspiration, and APRI60 mm got the lowest evapotran-


spiration. Whether there was organic fertilizer applied or not, under the same irrigation the change of soil water storage and evapotranspiration tended to be similar.

Table 3. Total water received and consumed of different treatments during the whole growing season.

Treatment I (mm) P (mm) ΔS (mm) D (mm) ETc (mm) 0 kg hm-2 Organic fertilizer

CI120 mm 120 164 -17 0 301 APRI60 mm 60 164 -3 0 227 APRI90 mm 90 164 -17 0 271 APRI120 mm 120 164 -18 0 302

240 kg hm-2 Organic fertilizer CI120 mm 120 164 -22 0 305 APRI60 mm 60 164 -5 0 229 APRI90 mm 90 164 -13 0 267 APRI120 mm 120 164 -17 0 301

3.3. Physiological responses

3.3.1. Plant height The differences in early season plant height of each treatment were much lower than those in late

season, and there was the similar trend between treatments with organic fertilizer and without (Fig. 3). During the early growing season (before June 11), each treatment had the similar plant height and the differences among these treatments were not significant according to F-test (P>0.05). This could be explained by the irrigation schedule not to be carried out. When the irrigation schedule was put into effect, the differences between treatments began to be significant (P<0.05). The result showed that at A1 (without organic fertilizer) condition, APRI60 mm significantly reduced the height by 7.43-11.04% compared with CI120 mm, but the differences among other treatments were not significant except at milk ripening stage. At A2 (240 kg hm-2 organic fertilizer) condition, APRI60 mm significantly reduced the height by 7.30-8.87% compared with CI120 mm, and the differences among other treatments were not significant. The lowest amount of irrigation significantly reduced the height of oat plant compared with others, and organic fertilizer seemly reduced the differences among these treatments[18].

Fig. 3. Oat plant heights of different treatments during the growing season.

3.3.2. Root shoot ratio As shown in Fig. 4, compared with conventional irrigation (CI), at A1 (without organic fertilizer)

condition, alternate partial root zone irrigation (APRI) reduced root shoot ratio of oat by 13.16-37.5%

A1 A2


before the flowering stage (70 DAS). At A2 (240 kg hm-2 organic fertilizer) condition, APRI reduced it by 14.29-42.86% at the booting (59 DAS) and flowering stages but increased it by 18.18-45.45% during the flowering and filling stages (74 DAS). The results showed that differences were not significant among these treatments with or without organic fertilizer at the other stages. The result also indicated that dry mass accumulation was increasing but root shoot ratio was decreasing during the growing season.

When the irrigation schedule was applied, there were some differences among these treatments with or without organic fertilizer, but differences were being reduced in the late growing season. Ben-Asher et al.[19] and Gallardo et al.[20] considered that plant roots tended to proliferate in the area of high available water, so root and shoot of a plant (i.e. oat) would be restricted by water stress. Under the lower irrigation, a root shoot ratio was not always higher than the higher irrigation.

Fig. 4. Root shoot ratios of different treatments during the growing season of oat.

3.3.3. Photosynthesis Photosynthetic light response curves of different treatments are shown in Fig. 5. The net

photosynthetic rate (Pn) firstly increased quickly with the increasing photosynthetic photon flux density (PPFD), and then reduced slowly when the PPFD reached the light saturation point, which were similar for treatments with or without organic fertilizer. When the PPFD ranged within 0-200 μmol photons m−2 s−1, the Pn was most rapidly improved. Studies of Wei et al.[21] on soil water for Cyclobalanopsis glauca, Zhou et al.[22] on oat varieties, and Guan et al.[23] on planting density for oat had the similar photosynthetic light response curves within 0-200 μmol photons m−2 s−1. When the PPFD ranged within 1000-1600 μmol photons m−2 s−1, however, the Pn was slightly reduced. This could be explained by that high light intensity usually causes high leaf temperature, but high temperature would force stomata to close, and then Pn is reduced[24].

Fig. 5. Photosynthetic light response curves of different treatments with or without organic fertilizer during the late grain filling of oat. PPFD and Pn in the figures mean photosynthetic photon flux density and net photosynthetic rate.

A1 A2

A1 A2


The result displayed that at A1 (without organic fertilizer) condition, the maximum net photosynthetic rate (Pmax) of these treatments were 13.68 (CI120 mm), 4.11 (APRI60 mm), 12.19 (APRI90 mm) and 11.99 μmol CO2 m−2 s−1 (APRI120 mm), respectively. Compared with CI120 mm, APRI reduced Pmax by 69.96% (APRI60 mm), 10.89% (APRI90 mm) and 12.35% (APRI120 mm). At A2 (240 kg hm-2 organic fertilizer) condition, the maximum net photosynthetic rate of these treatments were 10.97 (CI120 mm), 8.17 (APRI60

mm), 13.53 (APRI90 mm) and 11.85 (APRI120 mm) μmol CO2 m−2 s−1, respectively. APRI60 mm was lower than CI120 mm by 25.52%, but APRI90 mm and APRI120 mm were much higher than CI120 mm than 23.34% and 8.02%. The result indicated that severe water stress (i.e. only 60 mm) would significantly reduce Pn[25-26], and these treatments with organic fertilizer generally had much higher Pn than those without organic fertilizer[27].

3.3.4. Yield and water use efficiency The grain yields by APRI under the two levels of organic fertilizer were a little lower than CI (Control),

and almost as much as the local average grain yield of naked oats (3000 kg hm-2)[14]. It always seemed that application of organic fertilizer helped to increase grain yield under the same amount of irrigation.

Table 4. Total water received and consumed of different treatments during the whole growing season.

Treatment ETc (mm) Yield (kg hm-2) WUE (kg hm-2 mm-1) 0 kg hm-2 Organic fertilizer

CI120 mm 301 3231.75 aa 10.74 ba APRI60 mm 227 2755.13 b 12.14 a APRI90 mm 271 3163.88 a 11.67 a APRI120 mm 302 3094.13 a 10.25 b

240 kg hm-2 Organic fertilizer

CI120 mm 305 3413.25 aa 11.19 ba APRI60 mm 229 2845.73 c 12.43 a APRI90 mm 267 2977.88 bc 11.15 b APRI120 mm 301 3168.75 ab 10.53 b

a Differences among different treatments are significant by F-test (P<0.05). Means in a column with the same letter are not significantly different according to Fisher’s LSD (P>0.05).

The result (Table 4) showed that at A1 (without organic fertilizer) condition, CI120 mm (CK1) had the highest grain yield compared with APRI60 mm or APRI90 mm or APRI120 mm, but only significantly (P<0.05) increased production by 14.75% compared with APRI60 mm; besides, compared with APRI90 mm and APRI120 mm, APRI60 mm significantly reduced grain production by 14.84% and 12.30%, respectively. At A2 (240 kg hm-2 organic fertilizer) condition, compared with CI120 mm (CK2), alternate partial root-zone irrigation (APRI) significantly (P>0.05) reduced yield by 16.63% (APRI60 mm) or 12.76% (APRI90 mm) or 7.16% (APRI120 mm), respectively. Lesser irrigation water (i.e. 60 mm) always significantly reduced grain yield compared with more irrigation water whether organic fertilizer was applied or not.

On the other hand, APRI60 mm always obtained the highest WUE under the two levels of organic fertilizer (Table 4). Compared with the CI120 mm treatment, at A1, APRI60 mm and APRI90 mm significantly improved WUE by 13.29% and 9.09%, respectively. There was no significant difference between APRI120

mm and CI120 mm; at A2, compared with the CI120 mm treatment, only APRI60 mm treatment significantly reduced water consumption of oat by 11.41%. Both the grain yield and WUE suggest that less irrigation and higher production was beneficial, and APRI90 mm seemed to be the favorable for oat in this area.


4. Conclusion

Compared with CI, APRI slightly reduced the grain yield of oat but water consumption substantially, under water stress, especially. Thus, WUE was improved by this irrigation method (APRI). APRI under the severe water deficit would significantly (P<0.05) reduce the height of oat plant than CI. APRI with organic fertilizer could increase the root shoot ratio by 18.18-45.45% after the grain filling stage. Under the severe water stress (i.e. only 60 mm) APRI significantly reduced the net photosynthetic rate (Pn), and these treatments with organic fertilizer generally had much higher Pn than those without organic fertilizer. Our results indicate that APRI under the moderate water stress improves WUE and root shoot ratio, and slightly reduce grain yield and Pn with applied organic fertilizer, however, it is necessary to check these preliminary results in field conditions.

Acknowledgements

We are grateful to the study grants from the Special Fund for Agro-scientific Research in the Public Interest (nyhyzx07-009-2) and China Agriculture Research System (CARS-08-B-1). We would also like to thank anybody for their assistance with this experimental work.

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