Effects of soil managements on surface runoff and soil

Catena 135 (2015) 193–201

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Effects of soil managements on surface runoff and soil water content in jujube orchard under simulated rainfalls Juan Wang a,b,g,1, Jun Huang c,d,1, Pute Wu a,e,f, Xining Zhao e,f,⁎, Xiaodong Gao e,f, Matthew Dumlao g, Bing Cheng Si a,h a

College of Water Resources and Architecture Engineering, Northwest A&F University, Yangling 712100, Shaanxi, China School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou, 225009, Jiangsu, China Pearl River Hydraulic Research Institute, Pearl River Water Resources Commission of the Ministry of Water Resources, 510611 Guangzhou, China d Soil and Water Conservation Monitoring Center of Pearl River Basin, Pearl River Water Resources Commission of the Ministry of Water Resources, Guangzhou 510611, China e Institute of Soil and Water Conservation, Northwest A & F University, Yangling 712100, Shaanxi, China f Institute of Soil and Water Conservation, Chinese Academy of Sciences & Ministry of Water Resources, Yangling 712100, Shaanxi, China g Department of Land, Air, and Water Resources, University of California Davis, Davis, CA 95616, USA h Department of Soil Science, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada b c

a r t i c l e

i n f o

Article history: Received 25 February 2015 Received in revised form 25 July 2015 Accepted 25 July 2015 Available online xxxx Keywords: Jujube tree Simulated rainfall Runoff and sediment Soil water content Soil management

a b s t r a c t Inappropriate soil management on the Chinese Loess plateau has induced significant soil erosion, and improvements were obtained with cover crops, whereas few studies were reported about orchard soil management. This study investigated effects of five soil management (SM) practices on surface runoff and soil water content, which were (i) full ground mulching with jujube branches (BM), (ii) strip tillage only (ST), (iii) jujube branch mulch + strip tillage (BMT), (iv) jujube branch mulch + strip white clover (Trifolium repens L.) cover (BMWC), and (v) no cover (NC) as a control. Six microplots (with a length of 200 cm, width of 80 cm and depth of 80 cm) were subjected to artificial rain during the growing seasons from 2011 to 2013. The variables about runoff and sediment evolution as well as soil water content were studied. Results showed that: (i) the time to runoff initiation was significantly shorter under NC than in other treatments, and the runoff plateau, total runoff volume and sediment yield were highest under NC. Compared with NC, there was over 60% reduction in runoff and 80% reduction in sediment load under other treatments, (ii) runoff and sediment discharge increased linearly under NC before reaching the peak value, while it increased step-wise in the other treatments, (iii) soil water content (θ) and soil water storage increase (SWI) were significantly greater under BM than others; The 2-year (growing season of 2011 and 2012) mean θ and SWI were the lowest under NC, (iv) overall, BM increased soil water content, and decreased runoff and sediment yield, and thus could potentially solve water shortage and soil erosion problems in rainfed jujube orchards on Chinese Loess Plateau. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Soil and water conservation has been an important topic since the 20th century in the USA (Helms, 2010). Soil management including ground cover and tillage has been regarded as an essential way to control soil and water losses as well as to modify the soil water content in arid and semiarid regions (Brevik et al., 2015). Since the initiation of the Grain for Green project in 1999, jujube trees have been extensively planted on the Chinese Loess Plateau (Wu et al., 2008, 2009), and the jujube orchard area will likely increase continuously in the future (Shao et al., 2004). Most jujube orchards are cultivated under rainfed ⁎ Corresponding author at: Institute of Soil and Water Conservation, Northwest A & F University, Yangling 712100, Shaanxi, China. E-mail address: [email protected] (X. Zhao). 1 These authors contributed equally to this work.

http://dx.doi.org/10.1016/j.catena.2015.07.025 0341-8162/© 2015 Elsevier B.V. All rights reserved.

conditions, and jujube orchards will suffer from severe drought due to limited water resource. Moreover, most jujube orchards were managed with traditional cultivation (clear cultivation), where growers remove plant residues from the soil surface. The traditional cultivation can induce more bare soil surface, higher evaporation, and severe soil degradation (Bravo-Espinosa et al., 2012; Ochoa-Cueva et al., 2013; Prokop and Poręba, 2012). Alternative soil managements, such as residual crop mulch and tillage reduce bulk density, increase soil organic matter, and improve soil water conditions by altering soil structure and the physical, chemical, and biological processes (Bhattacharyya et al., 2008; Brevik et al., 2015; Huang et al., 2014a,b; Xu et al., 2012). Various soil managements help in increasing water infiltration and soil water content (Aboudrare et al., 2006; Giménez-Morera et al., 2010; Hulugalle et al., 2010), and regulate surface runoff and soil erosion (Lee et al., 2013; Moreno-Ramón et al., 2014). Soil surface managements also reduced the impact of the

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J. Wang et al. / Catena 135 (2015) 193–201

kinetic energy of rain drops, and increased rainfall interception and storage. These beneficial effects are closely related to mulch application rates and diversity of materials (Adekalu et al., 2007; Jordán et al., 2010; Yang et al., 2012). Montenegro et al. (2013) conducted a simulated rainfall experiment by using 3 surface covers with different mulching applications, and observed 51% reduction in runoff peak value under a mulch cover of 4 t ha−1. In addition, high mulch rates increased soil water content and moderate soil temperature. The time to runoff initiation was also dramatically delayed and the runoff rate decreased with increased mulch weight (García-Moreno et al., 2013; Sadeghi et al., 2015). While low ground cover decreased most soil losses on a sloping field (Cerdà et al., 2009a), and Döring et al. (2005) noted that soil loss could be decreased by N97% on a potato field by using only 20% crop coverage. Soil surface features also play a great role in runoff generation and soil erosion. Previous studies on interactions of surface mulching and other soil management techniques reported the decrease in soil erosion following tillage abandonment without mulching change (Mchunu et al., 2011). The reduced water loss by soil management also attributed to decreased soil evaporation and moderated soil temperature (Austin, 2011). It is shown that increased water loss and more serious soil erosion occurred under adverse tillage as it facilitated evaporation demand and weakened soil structure (Dahiya et al., 2007; Moret and Arrúe, 2007; Xu et al., 2013). Vegetation cover is another popular soil management technique to control runoff and erosion, minimize leaching of nutrients and increase soil productivity (Durán Zuazo and Rodríguez Pleguezuelo, 2008; Podwojewski et al., 2011) by: (i) increasing hydraulic roughness, canopy and surface storage, (ii) improving soil profile storage capacity, and (iii) changing macropore geometry. Use of cover crops in California was suggested to increase infiltration, reduce runoff, and enhance the soil water-holding capacity in the root zone (Joyce et al., 2002). Cover crops can decrease nutrient leaching losses by transpiring water and depleting nutrients (Dabney, 1998). Many studies concerning mulching or tillage have been conducted on the Chinese Loess Plateau. These studies have contributed greatly to our understanding of soil management effects on soil properties, soil water content and nutrient status in croplands (Gao et al., 2011; Zhao et al., 2013a,b). However, there is limited information about surface runoff, and soil erosion under varying soil management in such orchards. In addition, there have been several studies based on effects of soil conservation managements on soil and water loss in orange, citrus, apricot and olive orchards (Abrisqueta et al., 2007; Cerdà et al., 2009a, b). However, it is still unknown if these management techniques also would be beneficial in rainfed jujube orchard for long-term production in Chinese Loess Plateau. Therefore, we conducted a rainfall simulation experiment to quantitatively study the effects of different soil management types on (i) surface runoff and sediment yield, both of which are severe environmental issues on the Chinese Loess Plateau, and (ii) soil water dynamics and distribution under simulated rainfall.

Table 1 Selected physical properties of the studied soil. Soil properties

Values Texture

Soil particle

Sand (2–0.02 mm) Silt (0.02–0.002 mm) Clay (b0.002 mm) Saturated hydraulic conductivity (mm min−1) 3 −3 Saturated moisture (cm cm ) Field capacity (cm3 cm−3) Wilting point (cm3 cm−3)

Content (%) 17.6 (1.3) 64.3 (1.8) 18.1 (2.6) 0.99 (0.15) 0.537 (0.019) 0.294 (0.009) 0.084 (0.013)

the 0–60 cm soil layer (Ma et al., 2012a,b). Apertures were drilled on the bottom of the soil bins to allow drainage. The slope gradient was set at 26.7%, which is typical for jujube plots on the Loess Plateau (Niu, 2009). 2.2. Treatments The study evaluated 5 treatments, each of which was applied to a 3-year-old jujube tree (cv. Lizao on Ziziphus rootstock) planted in the

2. Materials and methods 2.1. Test soil and soil bins The test loess soil was collected from farmland in Qingjian County (E 109°52′, N 37°03′), Yulin city in Shaanxi Province, China. The soil was passed through a sieve with 10 mm × 10 mm openings and then air-dried to about 6% of water content in mass. Finally, it was thoroughly mixed to minimize variability and packed into soil bins in seven 10-cm deep layers to achieve a natural bulk density of around 1.35 g cm − 3 . Each layer was lightly raked before packing the next layer to minimize discontinuities between layers. Table 1 gives selected physical properties of the test soil. The soil bins in this experiment measured 200 cm × 80 cm × 80 cm with four wheels to facilitate transportation (Fig. 1A). According to previous studies the roots of 3-year-old jujube trees are distributed mainly in

Fig. 1. The soil bin setup showing the size and the location of runoff collector (A) and the distribution of neutron tubes (B).


center of each soil bin. A treatment without cover and tillage was used as a control to simulate the standard local management practice (NC, no cover and no natural vegetation). The other 4 treatments were: (i) Full ground mulching (200 cm × 80 cm, 100%) with jujube branch (BM), (ii) Strip (60 cm × 80 cm strip at both ends of the soil bin, 60%) shallow tillage (ST) to 8–10 cm soil depth, (iii) Jujube branch mulch beneath the tree canopy (80 cm × 80 cm around the jujube tree's trunk, 40%) + strip shallow tillage (BMT), (iv) Jujube branches mulch beneath the tree canopy + strip white clover cover (BMWC). The detailed layouts of the five treatments are shown in Fig. 2. Three-year-old jujube trees from Qingjian County with a mean initial height of 24.5 ± 4.4 cm were transplanted on November 20th, 2009. The mulch used consisted of jujube branches cut into 5–8 cm long segments and uniformly applied to the soil surface to a thickness of approximately 5 cm on May 1st, 2010. White clover (Trifolium repens L.), widely planted on the Chinese Loess Plateau, was used as a cover crop and seeded at a rate of 15 g m−2 on March 5th, 2011. White clover was allowed to wither and die naturally without mowing, and the litter remained on the soil surface. It would regenerate from roots in the next growing season. Urea (55 g m−2) was applied with water onto each plot in June 2012. For the tillage management, a rake was used to manually till the soil surfaces to a depth of around 8–10 cm every 2 rainfall events.

2.3. Rainfall simulations A needle-type rainfall simulator was used in this study, which comprises three main components: (i) raindrop producer, (ii) rainfall intensity control apparatus, and (iii) water supply device. The details of rainfall simulator were described in previous publications (Huang et al., 2014a,b). Rainfall intensity was 0.5–2.8 mm min−1, and uniformity coefficient was over 85%. Rainfall area and the falling height were 6.0 m × 3.0 m and 4 m, respectively. Over the span of two years, 60 rainfall events were conducted at the Institute of Water Saving Agriculture in Arid Regions of China (E 108°4′ 7″, N 34°17′52″). The soil bins were moved indoors to conduct the artificial rainfall events and then moved outdoors immediately after. When natural rainfall occurred, the bins were moved under an awning to prevent them from receiving unscheduled water inputs. To partly simulate the field conditions in northern Shaanxi, the annual precipitation data for Qingjian County (around 500 mm) were used to design the rainfall. The specific information of rainfall simulation is given in Table 2. The rainfall intensity also mimicked the rainfall events during July to September in Qingjian County. The rainfall intensity was set around 40 mm h−1 and 68 mm h−1, and the rainfall duration was 90 min and 60 min in 2011 and 2012, respectively.

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Table 2 Rainfall information during 2-year study period. Year 2011

Month 7 8 9

2012

10 5 6 9 10

Day

Rainfall intensity (mm h−1)

Rainfall amount (mm)

18–22 1–2 18–20 10–11 24–25 17–19 26–28 8–10 24 2–3 22–23 13–14

39.72 (1.8) 33.54 (2.4) 33.01 (8.4) 36.54 (7.2) 38.1 (8.4) 38.4 (3) 76.86 (7.2) 73.56 (2.4) 72.54 (0.6) 72.36 (0.6) 71.94 (0.6) 72.12 (0.6)

59.6 (2.8) 50.3 (3.7) 49.5 (12.1) 54.8 (10.5) 57.2 (12.9) 57.6 (4.8) 98.0 (7.6) 75.4 (2.5) 79.5 (4.8) 76.5 (2.8) 75.1 (3.9) 72.5 (6.3)

Numbers between brackets are the standard deviation (the same below).

2.4. Measurements The bin was covered by a water-resistant cloth and moved under the rainfall needles, the cloth was removed at the same time as the stopwatch started. Once uninterrupted runoff was observed, the time was noted and recorded as the time to runoff initiation. A 1000 mL graduated cylinder was used to measure runoff volume. The turbid water was oven-dried and weighed to determine the sediment yield. A hydra probe soil sensor (Stevens Water Monitoring System, Inc., Portland, Oregon, USA) and a CS830 Neutron Probe (Nanjing ChiShun Technology Development Co., Ltd., Nanjing, China) were used to determine the soil water content at every 10 cm. The neutron probe was calibrated twice in 2011 and 2012 against field volumetric soil water contents determined by the oven drying method. Soil water content was determined at 21 points (3 locations in the box × 7 soil depths) (Fig. 1B), and was measured right before and after each rainfall event. The soil water storage increase (SWI) after rainfall event was calculated as follows: SWI ¼ ðθb −θa Þ DE: Here θb is the soil water content (cm3 cm−3) right after the rainfall event, θa is the antecedent soil water content (cm3 cm−3), DE is the depth of soil profile (700 mm). In order to evaluate the effects of soil managements (SMs, including BM, BMWC, BMT and ST) on surface runoff and sediment reduction in comparison to NC, we calculated the runoff reduction (RR) and sediment reduction (SR) under the studied SM treatments by (Zhao et al., 2013c): RR ¼ ðRV NC −RV ct Þ=RV NC SR ¼ ðSY NC −SY ct Þ=SY NC : Here RVNC and SYNC are the runoff volume (L) and sediment yield (g) under NC, while RVct and SYct are the runoff volume (L) and sediment yield (g) under the calculated SM treatment. The leaf area index (LAI) of each soil bin at different growth stage was measured by the ACCUPAR LP-80 ceptometer (Decagon Devices, Inc., Pullman, WA, USA). 2.5. Statistical analysis

Fig. 2. The layout of soil managements (‘*’ indicates the runoff collector, units: cm).

The difference in the observational variable across the 5 treatments was explored using one-way ANOVA, the least significant difference (LSD) method and t-test were used to conduct multiple comparisons between any two treatments. The differences between treatments were considered as statistically significant at the 95% confidence level. Microsoft Excel 2010 and the SAS 9.1 package were used for statistical comparisons. Origin Pro 8.0 package was used to draw the figures.

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3. Results 3.1. Vegetation cover dynamics According to Boer and Puigdefábregas (2005), the averaged LAI data was converted to vegetation coverage (VC) (Fageria et al., 2005), as shown in Fig. 3. Vegetation coverage was relatively large from June to August, the period of vigorous growth stage for both white clover and jujube tree. The largest and lowest vegetation coverage was seen under BMWC and NC, with mean values of 63.1 ± 10.8% and 48.4 ± 14.7%, respectively. The vegetation coverage under BMWC was significantly greater than that under ST and NC. 3.2. Surface runoff, sediment and their relationship The time to runoff initiation (TTI), runoff peak value (RP), total runoff volume (RVtotal) and total sediment yield (SYtotal) in 2012 under all treatments are presented in Table 3. Compared to NC, the BMWC showed the best effects with shortest TTI and least RP, RV and SY. Although vegetation coverage under BM was not the largest, the whole jujube branch mulch also ranked 2nd in regulating runoff and sediment. Surprisingly, the runoff volume and sediment yield under ST were also small. TTI under NC was the shortest, and significantly shorter than that under SMs; RP, RVtotal and SYtotal under NC were significantly greater (several to dozens of times) than those under SMs. The mean RP under BMWC was the least of all treatments, while the BM performed very well in reducing RVtotal. TTI under BM and BMWC was significantly longer than that under ST and BMT. No significant differences in RP, RVtotal and SYtotal were found among SMs. In order to illustrate the effects of vegetation growth stage on runoff, sediment and soil water storage increase, we selected data in 2012 and plot their variations in Fig. 4. Overall, with increasing vegetation cover, RVtotal and SYtotal decreased slightly and were steady until the vegetation was fully in maturity at the end of August (García-Estringana et al., 2013; Tian et al., 2008). The SYtotal decreased from 200 g at the beginning to around 75 g at the end of this study under NC, even though NC had the largest RVtotal and SYtotal among all treatments. It is worth noting that the RVtotal under all treatments showed a gentle increase in September. It can be seen that, when RVtotal decreased, the soil water storage increase did not go up as expected, but even decreased dramatically in May. RR and SR under all SMs ranged from 60% to 75% and 80% to 90% (Fig. 5). The largest RR and SR were found under BMWC and BM, respectively. These results indicated that whole jujube branches mulch played the best role on decreasing runoff, and such mulch was also efficient in

Table 3 Runoff and sediment measurements in 2012 in all treatments. Treatments

TTI (min)

RP (L)

RVtotal (L)

SYtotal (g)

NC BM BMWC ST BMT

10.1 (2.1)c 19.8 (1.4)a 20.9 (4.6)a 16.3 (1.6)b 14.0 (2.8)b

11.8 (4.6)a 2.2 (0.9)b 1.9 (0.5)b 7.4 (4.5)b 5.3 (3.3)b

51.9 (22.9)a 10.8 (3.5)b 11.5 (3.8)b 17.8 (5)b 18.4 (2.5)b

133.5 (58.5)a 13.0 (5)b 15.9 (4.6)b 20.9 (4.5)b 18.1 (4.9)b

Same letters in a column indicate no significant differences (P b 0.05), the same below.

sediment reduction when combined with white clover cover. No significant differences in RR and SR were detected among SMs. In each treatment, SR was always greater than RR, which indicates that SMs were more efficient in decreasing soil loss than reducing runoff. A scatter diagram of SYtotal versus RVtotal under all treatments is shown in Fig. 6. Apparently, SYtotal increased with increasing RVtotal, although the type of increase varied with different treatments. According to the increased rate of sediment yield with increasing runoff volume, the data are better divided into two groups: (i) the no cover cultivation — NC, (ii) the four SMs. The equations describing these relationships are given in Fig. 6. Line ① is steeper than line ②, which indicates that with the same increase in runoff volume, more sediment was generated under group (i) than under group (ii). 3.3. Runoff volume and sediment yield Release of sediment was similar for each rainfall event in each individual treatment. We therefore investigated five rainfall events at the beginning of June 2012 to study the surface runoff and sediment release (Fig. 7). The runoff and sediment increased rapidly and linearly under NC. The load under ST was similar, but the rate of increase was far less. The sediment release curve under other treatments resembled a step-shaped increase before reaching a plateau stage, which was in accordance to the results from strip vegetation covers (Huang et al., 2013). Once the rainfall stopped, the runoff volume and sediment yield under all treatments sharply decreased and approached zero. The time to reach the peak value for both runoff volume and sediment yield under NC (approximately 45 min) were slightly greater than those under SMs (around 40 min). The durations of both under NC (25–30 min) were a bit shorter than those under SMs (30–40 min). These results indicated that: (i) SMs delayed the commencing of runoff and sediment, and (ii) SMs extended the time to reach the peak value. In a special case of ST, the time to reach sediment yield plateau was around 50 min, and the duration of plateau was relative short (approximately 18 min). 3.4. Soil water content variation and soil water storage increase after rainfall

Fig. 3. Variation in vegetation cover during the study period (same letters at the end of the lines indicate no significant differences).

We used the entire profile (0–70 cm) data from 2011 to 2012 to depict temporal changes in soil water content (Fig. 8). Soil water content variation among the four SM treatments was similar throughout the 2-year period, except under BM. It fluctuated, with a general decline from late July 2011 until middle April 2012. During this time, which corresponds to the main growing season for white clover and jujube, a larger quantity of soil water was required for growth. Soil water content under BM continuously increased after that time, and was far larger than that under other treatments. This is because a full mulch cover of jujube branches can substantially decrease soil evaporation and retain soil water. Additionally, we observed that the topsoil under BM remained wetter during the whole experiment period. Soil water content under BMWC from August 2011 to May 2012 was far less than that under NC, often approaching the wilting point. Soil water content continuously decreased until the first rainfall event in 2012, and then fluctuated with water input and output. We installed micro-lysimeters in the soil bins in March 2013 to determine the soil


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Fig. 4. Variation of total runoff volume (RVtotal), total sediment yield (SYtotal) and soil water increase.

evaporation (Fig. 9). During the key growth stage of the jujube tree from July to October 2013, the daily soil evaporation under BM and NC were 1.0 mm and 1.4 mm, respectively. It was 33% greater under NC than with BM. It should be highlighted that soil water content under BMWC increased sharply at the end of year 2012, while no obvious change was found under the remaining treatments. Table 4 listed the soil water content and soil water storage increase after rainfall. Compared to NC, soil water content was higher under all SMs (except BMWC) in 2011, with a significant difference between BM and other treatments. Soil water content and soil water storage increase following rainfall under both BM and BMWC were significantly higher than those under other treatments in 2012. Overall, the 2-year mean soil water content under SMs treatments was higher than that under NC, but no obvious difference appeared among treatments (except BM). The lowest soil water content in 2011 and 2012 was observed under BMWC and ST, respectively. Soil water storage increase after rainfall under BM was also significantly higher than under the other treatments (except ST in 2011);

around 2 times larger compared to NC. The increases in soil water content under all SM treatments were relatively similar in both years. The smallest soil water storage increase was under NC, and it was significantly lower than that of other treatments (except ST in 2011). The BM treatment showed not only the highest soil water content, but also the greatest infiltration following rainfall, which indicated that the whole ground mulch with jujube branches can help maintaining soil water and promote the greatest infiltration. This is particularly relevant in arid and semiarid regional orchards. 4. Discussion It is well known that soil surface management including mulching and tillage, will affect runoff and sediment as well as soil water conditions. Similar results were also reported by previous studies (Montenegro et al., 2013; Singer and Blackard, 1978). However, there is still some controversy on the effects of living vegetation cover, especially with regard to soil water content (Li et al., 2007).

Fig. 5. Runoff and sediment reduction in all SMs relative to control (error bars here are the standard deviation between repeated rainfall events).

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Fig. 6. Relationship between total sediment yield and runoff volume.

Compared to NC, the SMs in our study showed great effects in reducing the runoff amount and sediment yield, which is in accordance with most of previous studies (Cerdà et al., 2014; Huang et al., 2014a,b; Zhao et al., 2014). The positive effects of SMs on runoff and sediment can be explained by that mulching and tillage increased the slope surface resistance, and then delayed the runoff initiation (Rodríguez-Caballero et al., 2012). Besides, the jujube branch and living white clover covered the whole soil surface, which significantly reduced the impact of raindrops on the soil surface (Singer and Blackard, 1978), thereby maintaining high infiltration rates and reducing runoff amounts and runoff values (Jordán et al., 2010). This was also reported by Sadeghi et al. (2015) who showed that mulching had significant benefits on the time to runoff initiation, runoff coefficient and sediment loss.

Fig. 8. Variations in soil water content in all treatments from 2011 to 2012 (Error bars in “A” represent standard deviation of rainfall amount between different treatments).

Fig. 7. Runoff volume and sediment yield during a typical rainfall event.


Fig. 9. Diagram showing layout of a typical soil bin (photo shown here is BM bin).

We also noticed that the runoff and sediment yield under ST were relatively small, which differed from previous field observations (Turkelboom et al., 1997). This difference can be attributed to the effect of distinct study scales (Chaplot and Poesen, 2012; Raclot et al., 2009; Smets et al., 2008; Wei et al., 2012). It is also reported that the benefits of ground management would be different with plot size. Li et al. (2005) reported the increased runoff volume increment with increasing plot size. Besides, the duration of mulching and vegetation growing stage also influenced the soil structure and hydrological process (Huang et al., 2014b; Liu et al., 2012). The decrease of SY total from 200 g to around 75 g under NC might be due to soil crusting formation on the slope after several rainfall events (Moore and Singer, 1990; Wu and Fan, 2005). Soil crusts can reduce soil infiltration and promote runoff (Bissonnais and Singer, 1992, 1993). Sediment loss under NC was more than that under SMs with the same runoff increase. The reason may be that the sediment concentration (amount per runoff volume) under NC was greater than that under other treatments. The similar research were also studied and reported by Loch (2000). The runoff reduction and sediment reduction under all SMs was 60% to 75% and 80% to 90%, respectively, which indicates SMs are more efficient in decreasing soil loss than reducing runoff. The same results were also reported by Maetens et al. (2012), Vásquez-Méndez et al. (2010), Zhao et al. (2013c) and Huang et al. (2013). That may be because a small reduction in runoff may lead to a proportionately large reduction in sediment. This was explained by that overland flow does not reach the necessary energy for detaching soil particles at fine scales under a rainfall simulation (Lasanta et al., 2000). The soil water content under BM continuously increased and was higher than that of other treatments. This is because a full mulch cover of jujube branches can significantly decrease soil evaporation and retain soil water. Similar results were found in the research of Turk and Partridge (1947). However, the soil water content situation under BMWC was lower than that under BM although the soil surface was also fully covered. The water consumption by white clover may

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be to blame. Further, there was an obvious increase in soil water content under BMWC in the end of 2012, but not under other treatment. This could be because the wilting of white clover at the end, not only led to dramatically decreased transpiration but also became a dry surface mulching. These results are supported by Anderson et al. (1992), Hogue and Neilsen (1987), Li et al. (2007) who revealed that vegetation cover, may greatly reduce soil water content. Therefore, the BMWC performed better than BM in delaying runoff initiation and reducing the runoff amount. With the vegetation water consumption, soil water content was drier under BMWC, which facilitates more soil infiltration during rainfall events. Previous studies also discussed the effects of antecedent soil water content on runoff regulation (Gao et al., 2013; Giudice et al., 2012; Hu et al., 2014). The soil water content under BMWC was lower in 2011, but much higher in 2012. At various study scale further investigation is still needed to figure out whether strip vegetation cover will be a threat in jujube orchards because of competition for soil water and nutrients. Nevertheless, BM treatment can be considered as a realistic soil management in rainfed jujube orchards as it maintains a satisfying soil water condition for jujube tree growth, and efficiently regulates runoff and sediment. Further, it is worth noting that the jujube tree branches were obtained from on-site annual pruning, which promotes nutrients cycling, and reduces the labor and capital costs related to management in this hilly region.

5. Conclusions Soil managements can significantly alter surface runoff and sediment, and improve soil water content. TTI under NC was significantly shorter than that under SMs. RP, RVtotal and SYtotal under NC were larger than that under SMs, but no significant difference existed among SMs. The runoff and sediment release curves under NC and ST was linear before the plateau value, while these parameters increased stepwise in other treatments. Mulching the whole ground with Jujube branches (100% coverage) showed the best soil water conditions among all treatments. Both the average soil water content and soil water storage increase under BM were significantly greater than those under the other treatments. The 2-year mean soil water content under NC was the lowest among all treatment. Among SMs, soil water content was lowest under BMWC and ST in 2011 and 2012, respectively. Therefore, whole jujube branches mulching as the best soil management practice. All of the jujube trees in the study area were subjected to traditional management with shoot pruning during the sprouting leaves period, which can help to prevent over-flourishing and reduce water consumption. Mulching using the chopped-up branches will further reduce soil water runoff and soil erosion, enhance rainfall water infiltration and suppress evaporation. Therefore, integrating shoot pruning with whole jujube branches mulching is effective in regulating transpiration, increasing rainfall water infiltration, reducing evaporation, and consequently increasing soil water use efficiency for a jujube orchard. This could potentially lead to improved soil water shortage and reduced soil erosion in rainfed jujube orchards on the Chinese Loess Plateau.

Table 4 Soil water content and soil water storage increase after rainfall under all treatments. Treatments

NC BM BMWC ST BMT

Soil water content (cm3 cm−3)

Soil water increment (mm)

2011

2012

2-year mean

2011

2012

2-year mean

0.120 (0.010)bc 0.166 (0.020)a 0.101 (0.010)c 0.138 (0.020)b 0.139 (0.020)b

0.133 (0.020)c 0.238 (0.019)a 0.180 (0.060)b 0.127 (0.013)c 0.129 (0.021)c

0.126 (0.021)b 0.202 (0.039)a 0.140 (0.059)b 0.133 (0.020)b 0.134 (0.018)b

34.1 (10)b 49.2 (3.9)a 45.1 (9.7)a 41.5 (8.3)ab 47.2 (4.9)a

34.2 (12.5)b 61.4 (9)a 60.2 (11)a 61 (9.9)a 58.4 (6)a

34.1 (10.8)b 55.3 (9.2)a 52.7 (12.6)a 51.3 (13.4)a 52.8 (7.8)a

200


Acknowledgments We would like to thank Jing Zilong, Li Hongbin and Chen Xiaoli for their help in accomplishing these experiments. Give special thanks to Timothy A. Doane for revising the Language. This work is jointly supported by the Special Foundation of the National Natural Science Foundation of China (41401315, 31172039), the “111” Project (No. B12007), the Supporting Project of Resources Leading Key Technology in Agriculture of Shaanxi Province (2015KTCL02-25), the Supporting Plan of Young Elites and the Chinese Scholarship Council (CSC), the Natural Science Foundation of Shannxi Province of China (2014JQ5179). Special thanks to both reviewers for their valuable comments on this manuscript. References Aboudrare, A., Debaeke, P., Bouaziz, A., Chekli, H., 2006. Effects of soil tillage and fallow management on soil water storage and sunflower production in a semi-arid Mediterranean climate. Agric. Water Manag. 83, 183–196. Abrisqueta, J., Plana, V., Mounzer, O.H., Mendez, J., Ruiz-Sanchez, M., 2007. Effects of soil tillage on runoff generation in a Mediterranean apricot orchard. Agric. Water Manag. 93 (1), 11–18. Adekalu, K., Olorunfemi, I., Osunbitan, J., 2007. Grass mulching effect on infiltration, surface runoff and soil loss of three agricultural soils in Nigeria. Bioresour. Technol. 98, 912–917. Anderson, J., Bingham, G., Hill, R., 1992. Effects of permanent cover crop competition on sour cherry tree evapotranspiration, growth and productivity. Acta Hort. 313, 135–142. Austin, A.T., 2011. Has water limited our imagination for aridland biogeochemistry? Trends Ecol. Evol. 26, 229–235. Bhattacharyya, R., Kundu, S., Pandey, S., Singh, K., Gupta, H., 2008. Tillage and irrigation effects on crop yields and soil properties under the rice–wheat system in the Indian Himalayas. Agric. Water Manag. 95, 993–1002. Bissonnais, Y.L., Singer, M.J., 1992. Crusting, runoff, and erosion response to soil water content and successive rainfalls. Soil Sci. Soc. Am. J. 56, 1898–1903. Bissonnais, Y.L., Singer, M.J., 1993. Seal formation, runoff, and interrill erosion from seventeen California soils. Soil Sci. Soc. Am. J. 57, 224–229. Boer, M., Puigdefábregas, J., 2005. Effects of spatially structured vegetation patterns on hillslope erosion in a semiarid Mediterranean environment: a simulation study. Earth Surf. Process. Landf. 30, 149–167. Bravo-Espinosa, M., Mendoza, M., Carlón Allende, T., Medina, L., Sáenz-Reyes, J., Páez, R., 2012. Effects of converting forest to avocado orchards on topsoil properties in the trans-Mexican volcanic system, Mexico. Land Degrad. Dev. http://dx.doi.org/10. 1002/ldr.2163. Brevik, E.C., Cerdà, A., Mataix-Solera, J., Pereg, L., Quinton, J.N., Six, J., Van Oost, K., 2015. The interdisciplinary nature of SOIL. Soil 1, 117–129. http://dx.doi.org/10.5194/soil1-117-2015. Cerdà, A., Morera, A.G., Bodí, M.B., 2009a. Soil and water losses from new citrus orchards growing on sloped soils in the western Mediterranean basin. Earth Surf. Process. Landf. 34, 1822–1830. Cerdà, A., Jurgensen, M.F., Bodí, M.B., 2009b. Effects of ants on water and soil losses from organically-managed citrus orchards in eastern Spain. Biologia 64, 527–531. Cerdà, A., Jordán, A., Zavala, L., José Marqués, M., Novara, A., 2014. The contribution of mulches to control high soil erosion rates in vineyards in Eastern Spain. EGU General Assembly Conference Abstracts. 16, p. 16127. Chaplot, V., Poesen, J., 2012. Sediment, soil organic carbon and runoff delivery at various spatial scales. Catena 88, 46–56. Dabney, S.M., 1998. Cover crop impacts on watershed hydrology. J. Soil Water Conserv. 53, 207–213. Dahiya, R., Ingwersen, J., Streck, T., 2007. The effect of mulching and tillage on the water and temperature regimes of a loess soil: experimental findings and modeling. Soil Tillage Res. 96, 52–63. Döring, T.F., Brandt, M., Heß, J., Finckh, M.R., Saucke, H., 2005. Effects of straw mulch on soil nitrate dynamics, weeds, yield and soil erosion in organically grown potatoes. Field Crop Res. 94, 238–249. Durán Zuazo, V.H., Rodríguez Pleguezuelo, C.R., 2008. Soil-erosion and runoff prevention by plant covers. A review. Agron. Sustain. Dev. 28, 65–86. Fageria, N., Baligar, V., Bailey, B., 2005. Role of cover crops in improving soil and row crop productivity. Commun. Soil Sci. Plant 36, 2733–2757. Gao, X., Wu, P., Zhao, X., Shi, Y., Wang, J., Zhang, B., 2011. Soil moisture variability along transects over a well-developed gully in the Loess Plateau, China. Catena 87, 357–367. Gao, X.D., Wu, P.T., Zhao, X.N., Zhang, B.Q., Shi, Y.G., Wang, J.W., 2013. Estimating the spatial means and variability of root-zone soil moisture in gullies using measurements from nearby uplands. J. Hydrol. 476, 28–41. García-Estringana, P., Alonso-Blázquez, N., Marques, M., Bienes, R., González-Andrés, F., Alegre, J., 2013. Use of Mediterranean legume shrubs to control soil erosion and runoff in central Spain. A large-plot assessment under natural rainfall conducted during the stages of shrub establishment and subsequent colonisation. Catena 102, 3–12. García-Moreno, J., Gordillo-Rivero, Á.J., Zavala, L.M., Jordán, A., Pereira, P., 2013. Mulch application in fruit orchards increases the persistence of soil water repellency during a 15-years period. Soil Tillage Res. 130, 62–68.

Giménez-Morera, A., Sinoga, J., Cerdà, A., 2010. The impact of cotton geotextiles on soil and water losses from Mediterranean rainfed agricultural land. Land Degrad. Dev. 21, 210–217. Giudice, G.D., Padulano, R., Rasulo, G., 2012. Factors affecting the runoff coefficient. Hydrol. Earth Syst. Sci. Discuss. 9, 4919–4941. Helms, D., 2010. Hugh Hammond Bennett and the creation of the Soil Conservation Service. J. Soil Water Conserv. 65, 37A–47A. Hogue, E.J., Neilsen, D.H., 1987. Orchard floor vegetation management. Hortic. Rev. 9, 377–403. Hu, W., She, D., Shao, M., Chun, K., Si, B., 2014. Effects of initial soil water content and saturated hydraulic conductivity variability on small watershed runoff simulation using LISEM. Hydrol. Sci. J. http://dx.doi.org/10.1080/02626667.2014.903332. Huang, J., Zhao, X., Wu, P., 2013. Surface runoff volumes from vegetated slopes during simulated rainfall events. J. Soil Water Conserv. 68, 283–295. Huang, J., Wang, J., Zhao, X., Li, H., Jing, Z., Gao, X., Chen, X., Wu, P., 2014a. Simulation study of the impact of permanent groundcover on soil and water changes in jujube orchards on sloping ground. Land Degrad. Dev. http://dx.doi.org/10.1002/ldr.2281. Huang, J., Wang, J., Zhao, X., Wu, P., Qi, Z., Li, H., 2014b. Effects of permanent ground cover on soil moisture in jujube orchards under sloping ground: a simulation study. Agric. Water Manag. 138, 68–77. Hulugalle, N., Weaver, T., Finlay, L., 2010. Soil water storage and drainage under cottonbased cropping systems in a furrow-irrigated Vertisol. Agric. Water Manag. 97, 1703–1710. Jordán, A., Zavala, L.M., Gil, J., 2010. Effects of mulching on soil physical properties and runoff under semi-arid conditions in southern Spain. Catena 81, 77–85. Joyce, B., Wallender, W., Mitchell, J., Huyck, L., Temple, S., Brostrom, P., Hsiao, T., 2002. Infiltration and soil water storage under winter cover cropping in California's Sacramento Valley. Trans. ASAE 45, 315–326. Lasanta, T., Garcıa-Ruiz, J., Pérez-Rontomé, C., Sancho-Marcén, C., 2000. Runoff and sediment yield in a semi-arid environment: the effect of land management after farmland abandonment. Catena 38, 265–278. Lee, J.W., Park, C.M., Rhee, H., 2013. Revegetation of decomposed granite roadcuts in Korea: developing digger, evaluating cost effectiveness, and determining dimensions of drilling holes, revegetation species, and mulching treatment. Land Degrad. Dev. 24, 591–604. Li, X., Liu, L., Gao, S., Shi, P., Zou, X., Zhang, C., 2005. Microcatchment water harvesting for growing Tamarix ramosissima in the semiarid loess region of China. For. Ecol. Manag. 214, 111–117. Li, H., Zhang, G., Zhao, Z., Li, K., 2007. Effects of growing different herbages on soil waterholding of a non-irrigated apple orchard in the Weibei area of the Loess Plateau. Acta Agrestia Sin. 15, 76–81 (in Chinese with English abstract). Liu, Y., Fu, B., Lü, Y., Wang, Z., Gao, G., 2012. Hydrological responses and soil erosion potential of abandoned cropland in the Loess Plateau, China. Geomorphology 138, 404–414. Loch, R., 2000. Effects of vegetation cover on runoff and erosion under simulated rain and overland flow on a rehabilitated site on the Meandu Mine, Tarong, Queensland. Soil Res. 38, 299–312. Ma, L., Wu, P., Wang, Y., 2012a. Spatial distribution of roots in a dense jujube plantation in the semiarid hilly region of the Chinese Loess Plateau. Plant Soil 354, 57–68. Ma, L., Wu, P., Wang, Y., 2012b. Spatial pattern of root systems of dense jujube plantation with jujube age in the semiarid loess hilly region of China. Chin. J. Plant Ecol. 36, 292–301 (in Chinese with English abstract). Maetens, W., Poesen, J., Vanmaercke, M., 2012. How effective are soil conservation techniques in reducing plot runoff and soil loss in Europe and the Mediterranean? Earth-Sci. Rev. 115, 21–36. Mchunu, C.N., Lorentz, S., Jewitt, G., Manson, A., Chaplot, V., 2011. No-till impact on soil and soil organic carbon erosion under crop residue scarcity in Africa. Soil Sci. Soc. Am. J. 75, 1503–1512. Montenegro, A., Abrantes, J., de Lima, J., Singh, V., Santos, T., 2013. Impact of mulching on soil and water dynamics under intermittent simulated rainfall. Catena 109, 139–149. Moore, D.C., Singer, M.J., 1990. Crust formation effects on soil erosion processes. Soil Sci. Soc. Am. J. 54, 1117–1123. Moreno-Ramón, H., Quizembe, S., Ibáñez-Asensio, S., 2014. Coffee husk mulch on soil erosion and runoff: experiences under rainfall simulation experiment. Solid Earth 5, 851–862. Moret, D., Arrúe, J., 2007. Dynamics of soil hydraulic properties during fallow as affected by tillage. Soil Tillage Res. 96, 103–113. Niu, J., 2009. Calculate and Evaluate the Utilization Potential of Regulable Runoff in a Small Watershed of the Loess Plateau Based on GIS. Northwest A&F University, Yangling, Shaanxi, China (in Chinese with English abstract). Ochoa-Cueva, P., Fries, A., Montesinos, P., Rodríguez-Díaz, J.A., Boll, J., 2013. Spatial estimation of soil erosion risk by land-cover change in the Andes of southern Ecuador. Land Degrad. Dev. http://dx.doi.org/10.1002/ldr.2219. Podwojewski, P., Janeau, J.L., Grellier, S., Valentin, C., Lorentz, S., Chaplot, V., 2011. Influence of grass soil cover on water runoff and soil detachment under rainfall simulation in a sub‐humid South African degraded rangeland. Earth Surf. Process. Landf. 36, 911–922. Prokop, P., Poręba, G., 2012. Soil erosion associated with an upland farming system under population pressure in northeast India. Land Degrad. Dev. 23, 310–321. Raclot, D., Le Bissonnais, Y., Louchart, X., Andrieux, P., Moussa, R., Voltz, M., 2009. Soil tillage and scale effects on erosion from fields to catchment in a Mediterranean vineyard area. Agric. Ecosyst. Environ. 134, 201–210. Rodríguez-Caballero, E., Cantón, Y., Chamizo, S., Afana, A., Solé-Benet, A., 2012. Effects of biological soil crusts on surface roughness and implications for runoff and erosion. Geomorphology 145, 81–89.

J. Wang et al. / Catena 135 (2015) 193–201 Sadeghi, S.H.R., Gholami, L., Sharifi, E., Khaledi Darvishan, A., Homaee, M., 2015. Scale effect on runoff and soil loss control using rice straw mulch under laboratory conditions. Solid Earth 6, 1–8. Shao, X., Yan, C., Xu, Z., 2004. Progress in monitoring and simulation of soil moisture. Prog. Geogr. 23, 58–66 (in Chinese with English abstract). Singer, M.J., Blackard, J., 1978. Effect of mulching on sediment in runoff from simulated rainfall. Soil Sci. Soc. Am. J. 42, 481–486. Smets, T., Poesen, J., Knapen, A., 2008. Spatial scale effects on the effectiveness of organic mulches in reducing soil erosion by water. Earth-Sci. Rev. 89, 1–12. Tian, D., Yan, W., Chen, X., Deng, X., Peng, Y., Kang, W., Peng, C., 2008. Variation in runoff with age of Chinese fir plantations in Central South China. Hydrol. Process. 22, 4870–4876. Turk, L.M., Partridge, N.L., 1947. Effect of various mulching materials on orchard soils. Soil Sci. 64, 111–126. Turkelboom, F., Poesen, J., Ohler, I., Van Keer, K., Ongprasert, S., Vlassak, K., 1997. Assessment of tillage erosion rates on steep slopes in northern Thailand. Catena 29, 29–44. Vásquez-Méndez, R., Ventura-Ramos, E., Oleschko, K., Hernández-Sandoval, L., Parrot, J.F., Nearing, M.A., 2010. Soil erosion and runoff in different vegetation patches from semiarid Central Mexico. Catena 80, 162–169. Wei, W., Chen, L., Yang, L., Fu, B., Sun, R., 2012. Spatial scale effects of water erosion dynamics: complexities, variabilities, and uncertainties. Chin. Geogr. Sci. 22, 127–143. Wu, F., Fan, W., 2005. Effects of soil encrustation on rainfall infiltration, runoff and sediment generation. Sci. Soil Water Conserv. 3, 97–101 (in Chinese with English abstract).

201

Wu, P., Wang, Y., Xin, X., Zhu, D., 2008. Integration and demonstration of the date microirrigation technology in the hilly of Shanbei. Agric. Res. Arid Areas 26, 1–6 (in Chinese with English abstract, 12). Wu, P., Wang, Y., Ma, L., 2009. Chinese Loess Plateau ecological research and practice of modern agriculture. Manag. Res. Sci. Technol. Achievements 31–34 (in Chinese with English abstract). Xu, Q., Wang, T., Cai, C., Li, Z., Shi, Z., 2012. Effects of soil conservation on soil properties of citrus orchards in the Three‐Gorges Area, China. Land Degrad. Dev. 23, 34–42. Xu, Q., Wang, T., Cai, C., Li, Z., Shi, Z., Fang, R., 2013. Responses of runoff and soil erosion to vegetation removal and tillage on steep lands. Pedosphere 23, 532–541. Yang, Y., Gray, J.L., Furlong, E.T., Davis, J.G., ReVello, R.C., Borch, T., 2012. Steroid hormone runoff from agricultural test plots applied with municipal biosolids. Environ. Sci. Technol. 46, 2746–2754. Zhao, X., Wu, P., Gao, X., Tian, L., Li, H., 2013a. Changes of soil hydraulic properties under early-stage natural vegetation recovering on the Loess Plateau of China. Catena 113, 386–391. Zhao, X., Wu, P., Gao, X., Persaud, N., 2013b. Soil quality indicators in relation to land use and topography in a small catchment on the loess plateau of China. Land Degrad. Dev. http://dx.doi.org/10.1002/ldr.2199. Zhao, X., Chen, X., Huang, J., Wu, P., Helmers, M.J., 2013c. Effects of vegetation cover of natural grassland on runoff and sediment yield on loess hilly region of China. J. Sci. Food Agric. 94, 497–503. Zhao, L., Liang, X., Wu, F., 2014. Soil surface roughness change and its effect on runoff and erosion on the Loess Plateau of China. J. Arid Land 6, 400–409.