Drip irrigation with saline water in North China Plain

Transcription

1 Drip irrigation with saline water in North China Plain KANG YAOHU, WAN SHUQIN, CHEN MING Key Laboratory of Water Cycle and Related Land Surface Processes Institute of Geographical Sciences and Natural Resource Research, Chinese Academy of Sciences 11A, Datun Road, Anwai, Beijing 111 China Abstract: - Field experiments were conducted in North China Plain, and saline water with salinity (EC iw ) from 1.1 to 1.9 ds/m was applied to irrigate tomato, cucumber, oleic sunflower and waxy corn under mulched drip irrigation. Throughout crops growing seasons, the soil matric potential at.2 m depth under emitters was kept higher than -2 kpa. The experimental results revealed when three seeds per hole were planted, rate of emergence > 8% can be obtained despite irrigation water salinity up to 1.9 ds/m; yield reduction was 1.4% and 1.7% for waxy corn and oleic sunflower for each unit of increase of EC iw above 1.6 ds/m, and was 7.5% for cucumber when EC iw was above 1.1 ds/m; irrigation water salinity lower than 4.9 ds/m didn t affect tomato yield, but yield reduced by 6.7% for each ds/m over 4.9 ds/m; tomato, waxy corn and oleic sunflower, a relatively salt-tolerant crops, showed a constant or slight increase WUE and IWUE, while cucumber, a relatively salt sensitive crop, showed a decrease of WUE and IWUE with increasing salinity; applying saline water under mulched drip irrigation with salinity as high as 4.9 ds/m didn t result in soil salinization, and when salinity up to 6.9~1.9 ds/m, soil salinity increased, but could maintain a balance and don t increase year-to-year. Therefore, saline water with salinity from 1.6 to 1.9 ds/m can be applied for crop production with drip irrigation when soil matric potential at.2 m depth under emitters is kept higher than -2 kpa. Key-Words: - Saline water; Drip Irrigation; Tomato; Cucumber; Oleic sunflower; Waxy corn; Seedling emergency; Yield, Water use efficiency, Irrigation water use efficiency 1 Introduction One of the major problems confronting irrigated agriculture nowadays throughout the world is the decreasing availability of fresh water. In many countries and regions, fresh water is relatively scarce, but there are considerable resources of saline water, which could be utilized for irrigation if proper crops, soil and water management practices were established [1,2]. In China, especially in North China, less and less freshwater is available for agriculture with increasing population and rapid economic growth. But there is much saline water widely available. Now, in China, saline water has been included as an important substitutable resource for fresh water. Drip irrigation system is flexible in scheduling water, can maintain high soil matric potential in the wetting zone, which can compensate low soil osmotic potential caused by salinity, as a result, relatively high total water potential can still maintain in the root zone and enable efficient root water uptake. In the meantime, salts are continuously leached away from the rhizosphere, and maintain a low salinity level in the root zone. Furthermore, possible damage to the foliage is prevented [3,4]. Therefore, drip irrigation has been recognized to be the best method for applying saline water to crops [5,6]. The objectives of this study were: (1) to assess the effects of drip irrigation with different salinity levels of irrigation water on emergence, yield and water use of the main crops grown in open-field in North China Plain, like tomato, cucumber, oleic sunflower and waxy corn; (2) to describe management strategies by establishing safe salinity levels of irrigation water to maintain crop productivity under drip irrigation system in North China Plain. 2 Methods and Materials 2.1 Experimental site Field experiments were carried out in successive years at two experimental stations in North China Plain. Experiments for the seasons were conducted at Tongzhou Experimental Station for Water Cycle and Modern Water-saving Irrigation Research (Tongzhou Experimental Station), Institute of Geographic Science and Natural Resource Research. The Station (Latitude: 39 36' N; Longitude: ' E; 2 m above sea level) is ISSN: ISBN:

2 located in the southeast region of Beijing. It is a temperate semi-humid monsoon climate, with mean annual temperature 11.3 C and mean annual global radiation 5.24 GJ/m 2. Mean annual precipitation is 62 mm, mainly concentrated from July to September. The dominant soil is a silt loam. In -3 cm plow layer, the average bulk density is 1.35 g/cm 3, the soil organic matter is about 1.3%, and the average soil salinity and ph of 1:5 soil: water solution is.9% and 7.8, respectively. In 27 and 28, field experiments were conducted at Jinghai Experimental Station for Efficient Water Use of Agriculture in Coast Zone (Jinghai Experimental Station), Institute of Geographic Science and Natural Resource Research. The station (Latitude: 38 53' N; Longitude: ' E) is located in the southwest region of Tianjin. It is a temperate semi-humid monsoon climate. Mean annual temperature is 12 C with an average of 27 sunshine hours a year. Mean annual precipitation is 57 mm, mainly concentrated from June to August. The soil is predominantly silt. In -3 cm plow layer, the average bulk density is 1.22 g/cm 3, and the average soil salinity of 1:5 soil: water solution is.95%. 2.2 Experimental design In 23-25, artificial saline water was produced by adding industrial-grade NaHCO 3, Na 2 SO 4, MgSO 4, MgCl 2 and CaCl 2 to local groundwater of Tongzhou in molar proportion of.5:.5:.24:.9:.1, similar to the ionic compositions of the aquifer in Cangzhou area, one of the large areas with rich saline water (2-5 ds/m) resource in North China Plain. The experiment consisted of five salinity levels, and the average EC iw (electrical conductivity of irrigation water) were 1.1 (local groundwater), 2.2, 2.9, 3.5 and 4.2 ds/m in 23 and 24, and were 1.1 (local groundwater), 2.2, 3.5, 4.2 and 4.9 ds/m in 25. Ionic composition for local groundwater and saline water is given in Table 1. All of the treatments were replicated three times followed a complete randomized block design. Tomato (Lycopersicon esculentum Mill cv. L-2) and cucumber (Cucumis sativus L. cv. Zhongnong) were tested in this experiment. Table 1: Ionic composition of local groundwater and saline water at Tongzhou and Jinghai Experimental Stations Stations EC Ionic concentration (mmol/l) iw 2- - (ds/m) CO 3 HCO 3 Cl - 2- SO 4 Ca 2+ Mg 2+ K + Na + SAR* Tongzhou Jinghai *SAR means sodium adsorption ratio. In 27-28, field experiment was conducted at Jinghai Experimental Station, where is rich in saline water resource. There were two irrigation wells in the station. During the growing seasons in 27 and 28, groundwater pumping from the two wells with salinity averaged 1.6 and 11.9 ds/m, respectively. Ionic composition for groundwater pumping from the two irrigation wells is given in Table 1. Intermediate levels of salinity for the experiments were obtained by mixing the water from both wells in the required proportion. Tomato (Lycopersicon esculentum M. cv. Baiguo), cucumber (Cucumis sativus L. cv. Zhongnong), oleic sunflower (Helianthus annuus L. cv. G11) and waxy corn (Zea mays L. sinesis Kulesh cv. Zhongnuo) were used in this experiment. The experiment consisted of five salinity levels, the average EC iw were 1.6, 3.9, 6.3, 8.6, and 1.9 ds/m for oleic sunflower and waxy corn, and were 4.7, 6.3, 7.8, 9.4 and 1.9 ds/m for tomato and cucumber. All of the treatments were replicated three times followed a complete randomized block design. 2.3 Agronomic practices Every plot consisted of three raised beds, with 1.4 m between bed centers. The beds were.6 m wide, 4.4 m long and.15 m high. The area of each plot was m 2. Seedlings (tomato) and seeds (cucumber, oleic sunflower and waxy corn) were transplanted and sown in double rows (spaced.3 m apart) in a zigzag pattern in the middle of spring. Black polyethylene mulches were applied before or during the experiments to prevent the accumulation of salts on the soil surface. The cultural, diseases and pest management practices for different crops were ISSN: ISBN:

3 similar to local commercial crop production. 2.4 Irrigation Every plot was a single unit of gravity drip irrigation system. In the front of each plot, a tank, with volume about 12 L, was installed at 1 m high and used to contain irrigation water. Drip tubes with emitters spacing.2 m were placed on the center of each raised beds. Kang et al (24, 25) recommend a drip irrigation schedule by controlling the soil matric potential at.2 m depth immediately under drip emitters [7-9], and suggested the irrigation threshold -35 kpa for radish, -25 kpa for potato, -2 kpa for unheated greenhouse tomato and -5 kpa for field tomato in North China Plain [1-13]. Based on these studies, during crops growing periods in 23-28, irrigation was applied only when the soil matric potential at.2 m depth immediately under drip emitters was close to -2 kpa, except in seeding stage, when required more water. At Tongzhou experimental station, fresh water was applied in tomato and cucumber seedling stage, and thereafter saline water was applied. When saline water was applied, surplus water was added to provide a leaching fraction, which was calculated according to NRCS National Engineering Handbook (section 15) [14]. When the EC iw was ds/m, the amount of water applied was 5.1, 5.4, 5.7, 6., 6.3 and 6.3 mm for tomato, and 4.8, 5.2, 5.6, 6., 6.3 and 6.3 mm for cucumber, respectively. At Jinghai experimental station, saline water was used for irrigation throughout crops growing seasons. The irrigation amount applied per time was the same, 6.9 mm, for different EC iw treatments and different crops. 2.5 Observation Water use At Tongzhou experimental station, tomato and cucumber water use were measured by weighing lysimeter installed in the center of each treatment. The lysimeters were weighed at 8: every day in 23 and 25, and every two days in Seedling emergence At Jinghai experimental station, cucumber, oleic sunflower and waxy corn seeds were sown at the rate of 3 seeds per hole. Seedling emergence was recorded daily after sowing till thinning, based on total percent emergence and rate of emergence. Total percent emergence was the percentage emergence of the actual number of seeds sown, and rate of emergence was the percentage emergence of the number of hole Yield For tomato and cucumber, fruits were picked by hand at 2 to 4 days interval. The fruit number and the total weight per plot were checked on each harvest time. For oleic sunflower and waxy corn, ten plants in each plot were chosen to determine the yield Soil salinity Soil samples were obtained on soil cores from each plot with an auger (2. cm in diameter and 15 cm high). The three plot samples were composited into one sample per treatment. In 23 and 24, the distances to drip tapes for sampling were, 17.5, 35, 52.5 and 7 cm, and sample depths were -2, 2-1, 1-2, 2-, - and -9 cm. In 25, the sampling locations were located, 7, 14, 21, 28, 35, 42, 49, 56, 63 and 7 cm from the center of the beds, and sample depths were the same as before. In 27 and 28, the distances to drip tapes for sampling were, 14, 28, 42, 56, 7 cm, and sample depths were -1, 1-2, 2-3, 3-, -, -8, 8-1 and 1-12 cm. All soil samples were air-dried and sieved through a 1 mm sieve. Soluble salt estimates were based on extracts of 1 part soil to 5 parts water by weight. Soil salinity was determined by analyzing the Na +, K +, Ca 2+, Mg 2+, CO 2-3, HCO - 3, Cl - 2- and SO 4 in 2- - laboratory. The concentration of CO 3 and HCO 3 were determined by titration with acid, Cl - was determined by titration with silver nitrate, SO 2-4, Ca 2+ and Mg 2+ were determined by titration with EDTA, Na + and K + were determined by flame photometer. Salinity units (%) were expressed as quantity of soluble salts in dry soil Weather Daily values of the climatic variables (air temperature, relative humidity, evaporation and precipitation) were collected from automatic weather stations installed close to the experimental fields. 2.6 Statistical analysis The treatments were run as a single-factor analysis of variance (ANOVA). The ANOVA was performed at significance levels of α=.5 and.1 to determine if significant differences existed among treatment means. ISSN: ISBN:

4 3 Results and Discussion 3.1 Weather At Tongzhou experimental station in 23-25, during tomato and cucumber growing seasons, the total rainfall was 224.8, and mm, and the ratio of seasonal evaporation to rainfall was 2.6, 1.4 and 2. in 23, 24 and 25. The weather in 24 and 25 was relatively more humid than that in 23, especially in the late growth period, with the average relative humidity values higher than 8%. While, due to heavy wind in the first few weeks of tomato and cucumber growing season in 25, evaporation was obviously higher than that in the corresponding period in 24 and 23. At Jinghai experimental station in 27 and 28, during crops growing seasons, the total rainfall was 31.7 and mm, and the ratio of seasonal evaporation to rainfall was 1.5 and 2. in 27 and 28, respectively. The weather in 27 was wetter than that in Irrigation amount At Tongzhou experimental station in 23-25, fresh water was applied in tomato and cucumber seedling stage. Because of the windy weather in 25, much more fresh water was applied to enable seedlings to survive bad weather successfully. It is clear that the total irrigation times and depths decreased when saline water was applied, and the higher the salinity level of irrigation water was, the less irrigation times and depths were needed, especially in 23, the relatively dry year (Table 2). Table 2: The irrigation amount for different salinity treatments during tomato and cucumber growing-period in Years Treatments (ds/m) Tomato Cucumber Fresh water (mm) Saline water (mm) Fresh water (mm) Saline water (mm) Table 3: The irrigation amount for different salinity treatments during tomato, cucumber, oleic sunflower and waxy corn growing-period in 27 and 28 Crops Tomato Cucumber Treatments Water depths (mm) Water depths (mm) Crops Treatments Oleic sunflower Waxy corn At Jinghai experimental station in 27 and 28, similarly, the higher the salinity level of irrigation water was, the less irrigation amount was applied, especially in 28, the relatively dry year (Table 3). ISSN: ISBN:

5 In conclusion, applying saline water in crops planting not only can save valuable fresh water, but also can decrease irrigation times and depths, especially in the dry year. 3.3 Seedling emergence In 27 and 28, saline water was applied immediately after sowing. The increasing salinity ranging ds/m had significant effect on cucumber germination. Water salinity exceeding 1.6 ds/m not only delayed emergence but also reduced the total percent emergence (Fig.1). The total percent emergence of cucumber was decreasing by a rate of 3.5% for each unit increase of EC iw above 1.6 ds/m. The salinity of irrigation water didn t affect the total percent emergence of waxy corn 6 days after sowing (Fig.1), but had some effects on oleic sunflower in 28. Compared to the relatively low salinity (1.6, 3.9 and 6.9 ds/m) of irrigation water, the high salinity (8.6 and 1.9 ds/m) caused a delay in emergence, and decreased the total percent emergence by 18% (Fig.1) Cucumber total percent emergence (%) dS/m 6.3dS/m 7.8dS/m 9.4dS/m 1.9dS/m Cucumber total percent emergence (%) dS/m 4.7dS/m 6.3dS/m 7.8dS/m 9.4dS/m 1.9dS/m Day after sowing Day after sowing 1 Oleic sunflower total percent emergence (%) Oleic sunflower total percent emergence (%) ds/m 1.6dS/m 3.9 ds/m 3.9dS/m 6.3 ds/m 6.3dS/m 8.6 ds/m 2 8.6dS/m 1.9 ds/m 1.9dS/m Days after sowing Day after sowing 1 Waxy corn total percent emergence (%) ds/m 3.9 ds/m 6.3 ds/m 8.6 ds/m 1.9 ds/m Waxy corn total percent emergence (%) ds/m 3.9 ds/m 6.3 ds/m 8.6 ds/m 1.9 ds/m Days after sowing Day after sowing Fig.1: The change of total percent emergence of cucumber, oleic sunflower and waxy corn for different salinity treatments after sowing in 27 and 28 ISSN: ISBN:

6 The average rates of emergence before seedling thinning were 84% and 93% for oleic sunflower, and 88% and 91% for waxy corn in 27 and 28 (Table 4), which averaged 1.2 times of the total percent emergence of the two crops. The rate of emergence for cucumber was missing, but according to the field observation, it was also over 8%. Table 4: The rate of emergence of oleic sunflower and waxy corn for different salinity treatments t before thinning in 27 and 28 Crops Oleic sunflower Waxy corn Treatments Rate of emergence(%) (ds/m) a 97.7a a 97.1a a 93.7ab a 87.6b a 89.5b a 95.4a a 93.7a a 89.7a a 88.6a a 89.7a The different small letters are significantly different at.5 level. Table 6: The yield of oleic sunflower and waxy corn for different salinity treatments in 27 and 28 Years Treatments Yield* (Mg/hm 2 ) Oleic sunflower Waxy corn a 9.1a ab 9.1a ab 9.1a b 8.8a ab 9.a a 9.9a b 9.8a b 9.4ab b 9.ab b 8.6b The different small letters are significantly different at.5 level. It is dry seed yield for oleic sunflower, and fresh corn yield for waxy corn Table 5: Yield and seasonal water use of tomato and cucumber for different salinity treatments at Tongzhou and Jinghai stations in 23~28 Years Yield* (Mg/hm 2 Seasonal water use Treatments ) Treatments Yield* (Mg/hm 2 ) (mm) Years (ds/m) (ds/m) Tomato Cucumber Tomato Cucumber Tomato Cucumber a 128.9A a 25.6a a 122.2AB bc 21.1b a 111.4BC b 12.c a 14.8C d 1.2cd a 13.1C cd 9.5d a 49.9A a 42.3b a 44.AB b 29.8c a 41.8B c 26.5d a.8B bc 19.9e a 38.4B a 2.7e a 31.1A a 28.5AB 36.9, a 26.9AB a 24.AB a 2.9B The same small letters are not significantly different at.5 level, and different capital letters mean significant difference at.1 level. It is fresh fruit yield for tomato and cucumber. Overall, when saline water with salinity up to 1.9 ds/m was applied in the emergence stages of cucumber, oleic sunflower and waxy corn, the rate of emergence higher than 8% can be obtained when three seeds per hole were planted. 3.4 Crops yield At Tongzhou experimental station in 23-25, statistical analysis showed that irrigation water salinity ranging from 1.1 to 4.9 ds/m had no obvious effect on average fruit weight, fruit number per plant and yield of tomato [15], but had a significant (P<.1) effect on cucumber yield (Table 5), and it decreased linearly with the increasing of EC iw in the three years. The relationship between the correlated magnitudes was quite linear, and same slope coefficients can be distinguished in the three years, ISSN: ISBN:

7 relative yield of cucumber decreased 7.4% for 1 ds/m increase in EC iw. At Jinghai experimental station in 27 and 28, salinity of irrigation water ranging ds/m had some effect on yield of oleic sunflower and waxy corn (Table 6), and salinity higher than 4.7 ds/m significantly affected tomato and cucumber yield (Table 5). 1 of EC iw above 1.3 ds/m [17]. However in this experiment, cucumber yield decreased only by 7.5% for 1 ds/m increase in EC iw. The main reason was that cucumbers were planted in open field, and the frequency rainfall during cucumbers growing stages would dilute the salinity in the root zone. From the results of the experiment, it is obvious that waxy corn and oleic sunflower belong to relatively salt-tolerant crops, whereas cucumber is a relatively salt sensitive crop. 9 Relative yield (%) Y rc = -7.7EC iw + 11 R 2 =.91 Y rt = -6.7EC iw R 2 =.73 Y ro = -1.7EC iw + 98 R 2 =.66 Y rw = -1.4EC iw + 15 R 2 =.72 Cucumber Tomato Oleic sunflower Waxy corn Fig.2: Relative yield of cucumber, tomato, oleic sunflower and waxy corn response to different salinity levels of irrigation water in 27 and 28 The relative yield of different crops response to salinity of irrigation water is illustrated in Fig.2. For waxy corn and oleic sunflower, yield reduction was only 1.4% and 1.7% for each unit of increase of EC iw above 1.6 ds/m, but for cucumber, yield reduction was high to 7.7% for a 1 ds/m increase in EC iw. From the results obtained from Tongzhou experimental station, irrigation water with salinity lower than 4.9 ds/m didn t affect the yield of tomato, but when salinity was higher than 4.9 ds/m, the relative yield of tomato reduced by 6.7% for each ds/m. Considering together the results in Tongzhou and Jinghai experimental station, when irrigation water salinity ranging from 1.1 to 1.9 ds/m, the relative yield of cucumber reduced by 7.5% for each unit of increase of EC iw above 1.1 ds/m. According to the results reported by Sonneveld and Voogt (1978), greenhouse cucumber yields decreased linearly as EC iw increased, and the yield reduction was about 17% for a 1 ds/m increase in EC iw [16]. In Chartzoulakis s experiment (1992), also achieved in greenhouse, the relative yield of cucumber (cv. Pepinex) reduced by 15.9% for each unit of increase 3.5 Seasonal water use At the end of the experiment, it is clear that tomato and cucumber seasonal accumulative water use decreased as irrigation water salinity increased (Table 5). For tomato, every 1 ds/m increase in EC iw resulted in 7.8%, 6.1% and 6.4% decrease of seasonal accumulative water use in 23, 24 and 25, averaged 6.8% in the three years (Fig.3). Whereas, for cucumber, three quite different slope coefficients were noticeable in the three years, with 8.8%, 1.9% and 6.3% in 23, 24 and 25, respectively (Fig.3). The relatively low decreasing rate in 24 may be due to mulch. In 24, black polyethylene mulches were applied over the beds two days before sowing, however in 23 and 25, mulches were applied about one month after sowing. So crop water use was affected by time of mulch application. 3.6 Water use efficiency (WUE) Water use efficiency (WUE) is defined as the ratio of crop yield to its seasonal accumulative water use. The relationships between tomato and cucumber WUE and irrigation water salinity in 23, 24 and 25 are illustrated in Fig.4. For tomato, the general tendency of the curves was similar in the three years, i.e., tomato WUE increased slightly (logarithmically) as salinity of irrigation water increased. For cucumber, WUE decreased linearly with the increase of EC iw in 24 and 25, whereas the relationship between WUE and EC iw in 23 was unclear. Katerji et al. (23) had pointed out that the classification of plant salt tolerance corresponds with a difference in water use efficiency. The tolerant crops show a more or less constant water use efficiency, and the sensitive crops show a decrease of water use efficiency with increasing salinity, for the yield of sensitive crops decreases more than the evapotranspiration [18]. ISSN: ISBN:

8 1 1 Relative water use of tomato(wurt) (%) WU rt23 = -7.75EC iw + 15 R 2 =.72 WU rt24 = -6.14EC iw + 14 R 2 =.74 WU rt25 = -6.36EC iw + 11 R 2 = Relative water use of cucumber (WUrc) (%) WU rc23 = -8.8EC iw R 2 =.78 WU rc24 = -1.88EC iw + 13 R 2 =.85 WU rc25 = -6.26EC iw R 2 = Fig.3: Relative water use of tomato and cucumber response to different salinity levels of irrigation water in 23, 24 and WUE 23 =.11EC iw +.55 WUE for tomato (Mg/hm 2 /mm) WUE 23 =.64Ln(EC iw ) +.21 R 2 =.81 WUE 24 =.41Ln(EC iw ) +.23 R 2 =.79 WUE 25 =.21Ln(EC iw ) +.14 R 2 =.67 WUE for cucumber (Mg/hm 2 /mm) R 2 =.2 24 WUE 24 = -.18EC iw +.31 R 2 = WUE 25 = -.62EC iw +.16 R 2 = Fig.4: Relationship between water use efficiency (WUE) of tomato, cucumber and different salinity levels of irrigation water in 23, 24 and Irrigation water use efficiency (IWUE) Irrigation water use efficiency (IWUE) is computed based on crops yield dividing by the total irrigation water. Considering together the results in Tongzhou and Jinghai experimental stations, the relationships between IWUE and EC iw for different crops are illustrated in Fig.5. When irrigation water salinity ranged from 1.1 to 1.9 ds/m, cucumber IWUE decreased sharply from.8 Mg/hm 2 /mm to.15 Mg/hm 2 /mm as irrigation water salinity increased, whereas for waxy corn, IWUE increased linearly and slightly from.8 Mg/hm 2 /mm to.14 Mg/hm 2 /mm with increase salinity of irrigation water. For tomato and oleic sunflower, IWUE increased logarithmically with the increase of EC iw, but the increase tendency for oleic sunflower was too slight to notice. The IWUE values for cucumber and tomato were relatively high, while the values for oleic sunflower were much low, it was because fresh fruits were harvested for cucumber and tomato, but dry seeds were harvested for sunflower. So it can be concluded that the relatively tolerant crops show a constant or slight increase irrigation water use efficiency, and the sensitive crops show a decrease of irrigation water use efficiency with increasing salinity. ISSN: ISBN:

9 IWUE for crops (Mg/hm 2 /mm) IWUE c = -.66EC iw +.87 R 2 =. IWUE t =.787Ln(EC iw ) +.35 R 2 =.44 IWUE o =.41Ln(EC iw ) +.11 R 2 =.61 IWUE w =.55EC iw +.78 R 2 = Cucumber Tomato Oleic sunflower Waxy corn Fig.5: Relationship between irrigation water use efficiency (IWUE) of tomato, cucumber, oleic sunflower, waxy corn and different salinity levels of irrigation water in 27 and Soil salinity In the end of the experiment in 25, the average salinity in the whole soil for each treatment was no higher than.9%, and compared soil salinity values before treatment in 23 (Table 7), it is obviously salt did not accumulate in soil profile from to 9 cm depth after three years of saline water irrigation. Before saline water irrigation experiment at Jinghai station, no crop was grown in the experimental plots, except some weeds. The soil salinity had a tendency to increase with increasing salinity level of saline water (Table 8), and salts also tended to build up on the edge of bed. The average salinity values close to drip tapes (within 35 cm from emitters) at -1 cm depth for high saline water treatments 6.3, 8.6 and 1.9 ds/m were.22%,.23% and.32%, much higher than the values in the corresponding places of 1.6 and 3.9 ds/m treatments and the values in the furrow (35-7 cm away from emitters). However comparing the values in the end of experiment in 27 and 28, soil salinity did not increase significantly after two years of saline water irrigation. So, though high salinity level ( ds/m) water was used for irrigation, soil salinity in profile from to 12 cm depth didn t increase year after year and maintain in a state of equilibrium. If we adjust irrigation schedule, and increase the soil matric potential value from -2 kpa to -1 kpa or higher, the soil salinity may not increase in soil profile. Table 7: Soil salinity in profile -9 cm depth for different salinity treatments in the beginning and the end of the experiment in 23, and the end of the experiment in 25 Year Treatments (ds/m) Before treatment Soil Depths salinity (cm) (%) So in North China Plain, a semi-humid area, applying saline water under mulched drip irrigation with salinity as high as 4.9 ds/m didn t seem to result in soil salinization, and when salinity up to 1.9 ds/m, soil salinity increased, but could maintain a balance and don t increase year-to-year. Table 8: Soil salinity in profile -12 cm depth in the vertical transect perpendicular to the drip tape for different salinity treatments in 27 and 28 ISSN: ISBN:

10 Treatments (ds/m) Depths (cm) Soil salinity (%) Before experiment Distance from drip tape (cm) ~35 35~7 ~35 35~7 ~35 35~ Conclusion Because of the increasing water competition between human, industry and agriculture, use of saline water for irrigation gain more and more interests. In order to make a good use of saline water, five-year open field experiments were conducted in two experimental stations in North China Plain, saline water with salinity from 1.1 to 1.9 ds/m was applied to irrigate tomato, cucumber, oleic sunflower and waxy corn. Throughout crops growing seasons, the soil matric potential at.2 m depth under emitters was kept higher than -2 kpa. Despite that irrigation water salinity was up to 1.9 ds/m, rate of emergence > 8% can be obtained for cucumber, oleic sunflower and waxy corn when three seeds per hole were planted, For waxy corn and oleic sunflower, the relatively tolerant crops, yield reduction was only 1.4% and 1.7% for each unit of increase of EC iw above 1.6 ds/m, and was 7.5% for cucumber (the relatively sensitive crop) when EC iw was above 1.1 ds/m. Irrigation water with salinity lower than 4.9 ds/m didn t affect tomato yield, but the relative yield of tomato reduced by 6.7% for each ds/m over 4.9 ds/m. Applying saline water in crops planting not only can save valuable fresh water, but also can decrease irrigation times and depths, especially in the dry year. The relatively tolerant crops, such as tomato, waxy corn and oleic sunflower, showed a constant or slight increase WUE and IWUE, while the sensitive crops, like cucumber, showed a decrease of WUE and IWUE with increasing salinity. Applying saline water under mulched drip irrigation with salinity as high as 4.9 ds/m didn t result in soil salinization, and when salinity up to 6.9 ds/m, soil salinity in profile from to 12 cm depth did increased, but didn t increase year after year and maintain in a state of equilibrium. So in North China Plain, or similar semi-humid area, when there were no enough fresh water for irrigation, after adopting some appropriate farming and management practices, such as mulching, using drip irrigation and keeping soil matric potential at.2 m depth under emitters higher than -2 kpa, saline water with salinity from 1.6 to 1.9 ds/m can be applied to irrigate crops, like oleic sunflower and waxy corn, and if some yield depression is acceptable, tomato and cucumber can also be irrigated. Acknowledgements This study was supported by the Chinese Academy of Sciences (CAS) Knowledge Innovation project (KSCX2-YW-N-3), the Chinese Academy of Sciences Action Plan for the Development of Western China (KZCX2-XB2-13), the Key Technologies R&D program (6YFGZNC1) supported by Tianjin Municipal Science and Technology Commission, and the Project for 1 Outstanding Young Scientists supported by Chinese Academy of Sciences. References: [1] Mantell A., Frenkel H., Meiri A., Drip irrigation of cotton with saline-sodic water, Irrigation Science, 6, 1985, ISSN: ISBN:

11 [2] Oster J.D., Irrigation with poor quality water, Agricultural Water Management, 25, 1994, [3] Elfving D.C., Crop response to trickle irrigation, Horticultural Reviews, 4, 1982, [4] Meiri A., Plaut Z., Crop production and management under saline conditions, Plant Soil, 89, 1985, [5] Rhoades J.D., Kandiah A., Mashali A.M., The Use of Saline Waters for Crop Production, FAO Irrigation and Drainage paper 48, FAO, United Nations, Rome, [6] Shalhevet J., Using water of marginal quality for crop production: major issues, Agricultural Water Management, 25, 1994, [7] Kang Y., Wang F.X., Liu H.J., Yuan B.Z., Potato evapotranspiration and yield under different drip irrigation regimes, Irrigation Science, 23, 24, [8] Kang Y., Applied method for drip irrigation scheduling, Water Saving Irrigation, 3, 24, (in Chinese with English abstract) [9] Wang F.X., Kang Y., Methods of soil water regulation for potato under drip irrigation, Agricultural Research in the Arid Areas, 23, 25, (in Chinese with English abstract) [1] Yuan B. Z., Kang Y., Nishiyama. S., Drip irrigation scheduling for tomatoes in unheated greenhouse, Irrigation Science, 2, 21, [11] Kang Y., Wan S., Effect of soil water potential on radish (Raphanus sativus L.) growth and water use under drip irrigation, Scientia Horticultura, 16, 25, [12] Wang F.X., Kang Y., Liu S.P., Hou X.Y, Effects of soil matric potential on potato growth under drip irrigation in the North China Plain, Agricultural Water Management, 88, 27, [13] Wang D., Kang Y., Wan S., Effects of soil matric potential on tomato yield and water use under drip irrigation condition. Agricultural Water Management, 87, 27, [14] USDA-NRCS., National Engineering Handbook, Irrigation Section 15, Chapter 7, Trickle Irrigation, Washington D.C., US Dept. of Agriculture, Natural Resource and Conservation Service, [15] Wan S., Kang Y., Wang D., Liu S.P., Feng L.P., Effect of drip irrigation with saline water on tomato (Lycopersicon esculentum Mill) yield and water use in semi-humid area, Agricultural Water Management, 9, 27, [16] Sonneveld C., Voogt S.J., Effects of saline irrigation water on glasshouse cucumbers, Plant and Soil, 49, 1978, [17] Chartzoulakis K.S., Effects of NaCl salinity on germination, growth and yield of greenhouse cucumber, The Journal of Horticultural Science, 67, 1992, [18] Katerji N., van Hoorn J.W., Hamdy A., Mastrorilli M., Salinity effect on crop development and yield, analysis of salt tolerance according to several classification methods, Agricultural Water Management, 62, 23, ISSN: ISBN: