Jujube Plantations Research Articles

Optimized Extraction Method of Fruit Planting Distribution Based on Spectral and Radar Data Fusion of Key Time Phase

With China’s fruit tree industry becoming the largest in the world, accurately understanding the spatial distribution of fruit tree growing areas is crucial for promoting socio-economic development and rural revitalization. Remote sensing offers unprecedented opportunities for fruit tree monitoring. However, previous research has mainly focused on UAV and near-ground remote sensing, with limited accuracy in obtaining fruit tree distribution information through satellite remote sensing. In this study, we utilized the Google Earth Engine (GEE) remote sensing cloud platform and integrated data from Sentinel-1, Sentinel-2, and SRTM sources. We constructed a feature space by extracting original band features, vegetation index features, polarization features, terrain features, and texture features. The sequential forward selection (SFS) algorithm was employed for feature optimization, and a combined machine learning and object-oriented classification model was used to accurately extract fruit tree crop distributions by comparing key temporal phases of fruit trees. The results revealed that the backscatter coefficient features from Sentinel-1 had the highest contribution to the classification, followed by the original band features and vegetation index features from Sentinel-2, while the terrain features had a relatively smaller contribution. The highest classification accuracy for jujube plantation areas was observed in November (99.1% for user accuracy and 96.6% for producer accuracy), whereas the lowest accuracy was found for pear tree plantation areas in the same month (93.4% for user accuracy and 89.0% for producer accuracy). Among the four different classification methods, the combined random forest and object-oriented (RF + OO) model exhibited the highest accuracy (OA = 0.94, Kappa = 0.92), while the support vector machine (SVM) classification method had the lowest accuracy (OA = 0.52, Kappa = 0.31). The total fruit tree plantation area in Aksu City in 2022 was estimated to be 64,000 hectares, with walnut, jujube, pear, and apple trees accounting for 42.5%, 20.6%, 19.3%, and 17.5% of the total fruit tree area, respectively (27,200 hectares, 13,200 hectares, 12,400 hectares, and 11,200 hectares, respectively). The SFS feature optimization and RF + OO-combined classification model algorithm selected in this study effectively mapped the fruit tree planting areas, enabling the estimation of fruit tree planting areas based on remote sensing satellite image data. This approach facilitates accurate fruit tree industry and real-time crop monitoring and provides valuable support for fruit tree planting management by the relevant departments.

Synergistic effects of biochar and carboxymethyl cellulose sodium (CMC) applications on improving water retention and aggregate stability in desert soils

Making improvements to the water-holding characteristics and water-erosion resistance of desert soils, particularly in inland extremely arid areas, is vital for achieving both sustainable water resource utilisation and food security. The aim of this study is to evaluate the effects of the co-application of biochar and carboxymethyl cellulose sodium (CMC) on the physical properties of sandy desert soil, including infiltration rate, saturated water conductivity, field water-holding capacity and aggregate stability. Sandy desert soil samples were collected from jujube plantations on the southern edge of the Taklimakan Desert in the Hotan Prefecture, Xinjiang, China. Five CMC application ratios (C0:0, C1:0.01 g/kg, C2:0.02 g/kg, C3:0.04 g/kg and C4:0.08 g/kg) and five biochar application ratios (B0:0, B1:1.0 g/kg, B2:2.0 g/kg, B3:4.0 g/kg and B4:8.0 g/kg) were designed and a total of 11 experimental treatments were performed, which were labelled as CK (control group), B2C0, B2C1, B2C2, B2C3, B2C4, B4C4, B0C2, B1C2, B3C2 and B4C2. Compared with CK, the combined application of biochar and CMC reduced the soil bulk density (BD) by 1.29–9.41% and the saturated hydraulic conductivity (Ks) by 29.64–94.98%, and increased the soil saturated water content (SSWC) by 8.81–30.74% and the water holding capacity (WHC) by 13.91–36.87%. Similarly, the water-stable aggregates that were co-applied with biochar and CMC increased by 29.10–256.86%. This resulted in significant improvement in the stability of sandy desert soil against water erosion. The principal component analysis (PCA) results found B4C4 to have the best comprehensive improvement effect. Therefore, 0.08 g/kg of CMC and 8.0 g/kg of biochar were used as recommended for improving the hydraulic properties of desert soils. Generally, CMC and biochar have a mutually complementary effect on improving sandy desert soil, providing new ideas and approaches for the improvement of soil and the sustainable development of agriculture in desert areas.

Soil Aggregates Are Governed by Spacing Configurations in Alfalfa-Jujube Tree Intercropping Systems

Soil aggregates play an important role in affecting the structural stability of the soil, and it is important to understand the relationship between soil aggregate stability and crop yield in herbage-fruit tree intercropping systems. In this study, we determined the optimal spacing configurations for improving aggregate stability while increasing crop yields in alfalfa-jujube intercropping systems. The treatments included three intercropping patterns, i.e., the distances between alfalfa and jujube at 0.5 m (IP0.5m), 1 m (IP1m), and 1.45 m (IP1.45m), along with monoculture alfalfa (CKAL) and jujube (CKJU). The results showed that IP0.5m, IP1m, IP1.45m, and CKJU effectively improved soil aggregate structure compared to CKAL. The IP1m spacing significantly increased the amounts of macro-aggregates (8.2%), and improved soil mechanical properties and aggregate stability among the other treatments, which was partly attributable to increased mean weight diameter (13.6%) and decreased soil aggregate destruction rate of water-stable aggregates (2.9%). The results of the principal component analysis showed that IP1m treatments had a positive effect on PC1. The one-meter spacing of jujube-to-alfalfa intercropping optimized the soil structure while improving the yield (8.3%); thus, it can be considered the most suitable intercropping spacing configuration for growing alfalfa in jujube plantations.

Plastic film mulching combined with sand tube irrigation improved yield, water use efficiency, and fruit quality of jujube in an arid desert area of Northwest China

Water scarcity and high evaporation are critical factors affecting crop growth and yield. Sustainable production of jujube (Ziziphus jujuba Mill.) plantations is essential for economic development and environmental protection in arid desert areas of Northwest China. However, few studies have investigated how plastic film mulching combined with sand tube irrigation (STI) affects soil surface wetted area, soil water indices, crop water consumption, yield, water use efficiency (WUE), and fruit quality in jujube plantations in arid desert areas. Therefore, a 2-year field experiment was conducted with three levels of STI (SW1, 300 m3 ha–1; SW2, 375 m3 ha–1; SW3, 450 m3 ha–1) and surface drip irrigation as a control (DW3, 450 m3 ha–1). Compared with surface drip irrigation, STI significantly decreased (p < 0.05) surface wetted area, and SW3 significantly increased soil water storage in the 60–100 cm layer as well as the 0–100 cm soil layer. Sand tube irrigation also alleviated the soil water deficit in the 60–100 cm soil layer and each soil layer before irrigation and increased yield by 0.6% and WUE by 27.3% on average. The highest yield and WUE were in SW3 in both years. Crop water consumption of jujube trees increased and then decreased during the growth period in both years and reached a maximum in the fruit swelling period. With STI, vitamin C content increased by 9.8%, soluble protein content by 15.6%, and the sugar to acid ratio by 12.2% in both years. Overall, application of STI increased jujube yields and WUE and improved fruit quality by increasing soil water storage and reducing soil water deficit. Thus, this study demonstrates STI can increase economic and ecological benefits, and also provides guidelines to apply STI and improve agricultural water productivity.

Response of dew and hydraulic redistribution to soil water in a rainfed dryland jujube plantation in China’s Hilly Loess Region

Soil desiccation occurs widely across China’s Loess Plateau due to long-term water demand in excess of water supply. Hydraulic redistribution (HR) - the movement of water from wet to dry soil via roots - and canopy dew (CD) are crucial to water replenishment in dryland ecosystems. However, much is still not known about the response of CD and HR to soil water deficits (including no deficit, slight deficit, moderate deficit, and severe deficit water conditions) in dryland jujube (Ziziphus jujuba Mill.) plantations in China’s Hilly Loess Region. To this end, the duration and intensity of dew were monitored using dielectric leaf wetness sensors to better understand the effects of soil water status on dew. Also, soil water content, sap flow, and meteorological variables were measured during the jujube growing seasons in 2017–2019. The results showed that the time of occurrence of CD under the no deficit condition came earlier than the time of occurrence of CD under slight, moderate, and severe soil water deficit conditions. Peak CD appeared at 5:00–6:30 am and ended at 6:30–9:00 am local time under the four soil water conditions. The amount, duration, and frequency of CD decreased with increasing soil water deficit. The amount and duration of CD under the no deficit condition were significantly higher than under the slight, moderate, and severe soil water deficit conditions (p < 0.05). The amount and frequency of HR (in the 20–60 cm soil layer) increased with increasing soil water deficit. Under the no deficit condition, HR was significantly lower than under the slight, moderate, and severe soil water deficit conditions (p < 0.05). While HR was influenced by CD, CD enhanced HR under the no deficit condition, but inhibited HR under slight, moderate, and severe soil water deficit conditions. For the growing season, the contribution of CD to total actual evapotranspiration (ETc act, CD/ ETc act ratio) was highest under the no deficit condition (maximum CD/ ETc act ratio of 0.21). The contribution of HR to ETc act (HR/ ETc act ratio) was higher under slight, moderate, and severe soil water deficit conditions (maximum of 0.11). The mutual effects of CD and HR lessened soil water deficit, making them important ecohydrological processes affecting the response of dryland jujube plantations to soil desiccation.

Quality Control System of Red Jujube by Hybrid Model: Development of an Efficient Framework.

Food traceability is very important for the quality and safety of agricultural products, which is related to the people’s livelihood and national economy and has drawn great attention from governments and scientists around the world. The existing studies have not yet overcome the crisis characteristics comprehensively and systematically. A traceability system of red jujube is constructed by a hybrid mode of blockchain and the Internet of Things (IoTs). The system integrates the blockchain and the IoT technologies with characteristics of tamper-proof, decentralization, and distributed storage and solves the problem of date quality traceability by designing the technical process and architecture of date quality traceability and the big data of red jujube, jujube plantation, processing enterprise, commercial enterprises, and market administration. The whole process from planting to processing and sales of red jujube are recorded in the block to ensure the realization of quality traceability of red dates in the process. Through the whole process of big data processing, the key information collected in each process is stored in the database to ensure the realization of quality traceability of red dates in the framework. The system can help to minimize the production and distribution of unsafe or poor-quality products, thereby minimizing the potential for bad publicity, liability, and recalls.

The comparison of different irrigation methods on yield and water use efficiency of the jujube

Water shortage restricts the development of jujube plantation in southern Xinjiang, and the application of water–saving irrigation technology is the key to solve this problem. This study investigated the response of irrigation water use efficiency to various irrigation technologies (vertical tube irrigation and surface drip irrigation) and jujube yield and quality, and to choose a suitable irrigation method for Hui–jujube trees planting. The field experiment was conducted over 2 years. Vertical tube irrigation was implemented with three levels of water pressure by using water pressure heads 0.8, 1.0, and 1.2 m. Additionally, surface drip irrigation was used as a control, and four treatments were used in total. The results indicated that vertical tube irrigation helped save approximately 37–70% of water, and its water use efficiency was 1.4–4.3 times that of surface drip irrigation. Compared with Hui–jujube trees watered by drip irrigation, those watered by vertical tube irrigation had slightly higher yield and decreased fruit cracking (25–83%). Moreover, the sugar–acid ratio increased significantly (P < 0.05). Besides, the continuous water supply used in vertical tube irrigation allowed the maintenance of relatively stable SWC in the main root layer (20–60 cm), can provided a good soil–water–air environment for jujube growth. Vertical tube irrigation saved water primarily because it sends water directly to the main root layer through the emitters buried in the soil, reducing the evaporation of water in the upper soil layer. The irrigation water amount of vertical tube irrigation was proportional to the water supply pressure head. Water use efficiency was the highest under the lowest water supply pressure (water pressure head 0.8 m). The present findings provide a scientific basis for the application of vertical tube irrigation in arid areas.

Comparison of the performance of leaf wetness duration models for rainfed jujube (Ziziphus jujuba Mill.) plantations in the loess hilly region of China using machine learning

AbstractLeaf wetness duration (LWD) affects the ability of tree canopy to regulate eco‐hydrological processes. Jujube (Ziziphus jujuba Mill.) is one of the main plants with significant impact on water cycle process and flux characteristics in the Loess Plateau region of China. However, little is known about LWD in rainfed jujube plantations in the loess hilly region of China. For the causes of leaf wetness in rainfed jujube plantations, dew‐only, rain and the combined scenario were investigated in terms of LWD and meteorological variables for the 2012, 2013, 2017 and 2018 jujube growing seasons. The results were as follows: The leaf wetness events occurred frequently, and the days of leaf wetness driven by dew‐only and rain accounted for 88.3% of the total number of days in a regular jujube growing season. LWD driven by dew‐only was significantly lower than that driven by rain (p &lt; 0.05). The correlation between LWD and meteorological factors varied with different scenarios. In dew‐only scenario, the four calibrated models (RH, DPD, CART and NN) accurately predicted LWD. In rain scenario, only the calibrated NN model performed well. In the combined scenario, the calibrated RH, CART and NN empirical models performed nearly equally; all well estimated LWD. On the basis of accuracy, practicability and variable count, the calibrated RH, NN and RH models for dew‐only, rain and the combined scenario can reliably estimate LWD in rainfed jujube plantations in the loess hilly region of China.

Transcriptome Analysis of Differentially Expressed Genes in Wild Jujube Seedlings under Salt Stress

Wild jujube (Ziziphus acidojujuba) and cultivated jujube (Ziziphus jujuba) belong to the family Rhamnaceae. Jujubes have marked drought- and salt-tolerant properties. After salt stress, wild jujube seedling growth was inhibited and photosynthetic efficiency was reduced. A bioinformatics approach was used to analyze the transcriptomics data from wild jujube seedlings grown under salt stress, and the genes differentially expressed under the salt stress were identified to provide a theoretical basis for the development and use of wild jujube plantations in salinized soil. The transcriptome sequencing from leaves of wild jujube seedlings was carried out using second-generation sequencing technology. The effects of salt stress on the differential expression of photosynthesis-related genes in wild jujube seedlings were analyzed. Transcriptome sequencing revealed a total of 5269 differentially expressed genes (DEGs), of which 2729 were up-regulated and 2540 were down-regulated. DEGs were mainly enriched with respect to photosynthesis, photosynthetic antenna proteins, glyoxylic acid and dicarboxylic acid metabolism, linolenic acid metabolism, cysteine and methionine metabolism, and porphyrin and chlorophyll metabolism. Among them, the photosynthesis pathway-related DEGs were most highly enriched. Further analysis of porphyrin and chlorophyll synthesis and photosynthesis-related pathways revealed that they were significantly enriched by 97 photosynthesis-related DEGs. The DEGs in the photosynthesis and photosynthetic antenna protein pathways were down-regulated, whereas the DEGs glutamyl-tRNA reductase (HEMA), ferrochelatase (HEMH), and pheophorbide a oxygenase (PAO) in the porphyrin and chlorophyll synthesis pathways were up-regulated, with the remainder being down-regulated. The nuclear gene encoding Rubisco, the key enzyme in the photosynthetic carbon fixation pathway, was also down-regulated. The results showed that the photosynthetic rate of wild jujube seedlings decreased following exposure to salinity stress, an effect that was related to the increased synthesis of 5-aminolevulinic acid and heme, and the up-regulation of expression of a gene encoding a chlorophyll-degrading enzyme, and was related to the down-regulation of gene expression in photosynthesis-related pathways such as light energy capture and carbon fixation. Selection of nine DEGs related to photosynthesis and chlorophyll biosynthesis by quantitative real-time-PCR confirmed that expression changes of these nine DEGs were consistent with the transcriptome sequencing results.

Bayesian analysis of jujube canopy transpiration models: Does embedding the key environmental factor in Jarvis canopy resistance sub-model always associate with improving transpiration modeling?

The Jarvis canopy resistance sub-model is commonly used in transpiration modelling, although its optimal structure is rarely studied. It is still not fully clear that to what extent transpiration modeling may differ if using different constraint function forms for key environmental variable in Jarvis sub-model. In this study, various Jarvis canopy resistance sub-model configurations were embedded in the Penman-Monteith model to compare their ability to model daily transpiration of rain-fed jujube (Ziziphus jujuba Mill.) plantations where soil moisture is a key factor of tree water use. Parameters were calibrated using the Bayesian Markov Chain Monte Carlo (MCMC) simulation technique and model comparison was quantified using Deviance Information Criterion (DIC). The results showed significant differences in model performance between the constraint function forms of soil water content. The difference in DIC between the model with the best constraint function form and the other two forms reached 37.66–50.94, much higher than the evaluation criteria for significance (larger than 7). When the best constraint function form was used, the performance of the transpiration model improved. The model performance worsened when the other constraint function forms were used, even worse than those without consideration for soil water content. However, only slight differences in model performance were detected for the constraint function forms of temperature, vapor pressure deficit and photosynthetically active radiation. Using the best configuration of Jarvis canopy resistance sub-model, daily transpiration of jujube plantation was well estimated with overall good accuracy and acceptable uncertainty. The predictions and observations were highly correlated (R2 = 0.87 for calibration and R2 = 0.80 for validation). The results suggested that different constraint function forms of an environmental factor contributed differently to transpiration model performance, and the situation was different for different environmental factors. Including the key environmental factor in the Jarvis canopy resistance sub-model will not always improve the performance of transpiration models.

Non-rainfall water contributions to dryland jujube plantation evapotranspiration in the Hilly Loess Region of China

Non-rainfall water inputs (NRWIs) provide crucial water resources for dryland ecosystems in arid and semi-arid regions. However, little is known about the quantitative characteristics and formation of NRWIs, and the relative importance of NRWIs as water sources in a dryland jujube (Ziziphus jujuba Mill.) plantation in the Hilly Loess Region of China. The objectives of this study were to determine the characteristics of NRWIs during the jujube growing season with regard to amount, duration, and contributions to transpiration, evaporation, and evapotranspiration. Dew intensity and duration were monitored using dielectric leaf wetness sensors, Also sap flow, soil water content, soil temperature, and meteorological variables were measured during the 2017 and 2018 growing seasons. NRWIs were found to be composed of canopy dew (CD) and water vapor adsorption (WVAS) in the 0–5 cm soil layer, amounting to 75.218 mm in 2017 and 75.309 mm in 2018 (CD accounted for about 81% of NRWI). Daily average CD was significantly greater than WVAS (P < 0.05), and CD duration was 2.09–9.14 h more than WVAS duration (P < 0.05). The CD rate and frequency generally exceeded that of WVAS. CD occurred from 19:00 to 9:00. WVAS mainly occurred from 6:30 to 9:00. CD reduced nocturnal sap flow by 7.36–55.64%, but increased soil water storage (in the 5–100 cm root zone) by 0.274–0.717 mm. WVAS had no effect on soil water evaporation. Over the entire growing season, the ratio of CD to total transpiration was 0.218 in 2017 and 0.258 in 2018, and the ratio of WVAS to soil water evaporation was 0.082 in both years. NRWIs occurred more frequently and were quantitatively more stable than rainfall events. Their contributions to evapotranspiration reached a maximum value of 0.184 in 2018. NRWIs are important components of the hydrological cycle in this region, and probably have potential positive ecological effects on dryland jujube plantations in the Hilly Loess Region of China.

Effect of pruning intensity on soil moisture and water use efficiency in jujube (Ziziphus jujube Mill.) plantations in the hilly Loess Plateau Region, China

Jujube (Ziziphus jujube Mill.) is a traditional economic forest crop and is widely cultivated in hilly areas of the Loess Plateau, China. However, soil desiccation was discovered in jujube plantations. Pruning is recognized as a water-saving method that can reduces soil water consumption. In this study, we monitored the jujube plots with control (CK), light (C1), medium (C2) and high (C3) pruning intensities during the jujube growing period of 2012–2015 to explore the effect of pruning intensity on soil moisture and water use efficiency (WUE) of jujube plantations in the hilly Loess Plateau Region. The results showed that pruning is an effective method for soil water conservation in jujube plantations. Soil moisture increased with increasing pruning intensity during the jujube growing period of 2012–2015. C1, C2 and C3 pruning intensities increased soil water storage by 6.1–18.3, 14.4–40.0 and 24.3–63.3 mm, respectively, compared to CK pruning intensity. Pruning promoted soil moisture infiltration to deeper soil layer. Soil moisture infiltrated to soil depths of 240, 280 and >300 cm under C3 pruning intensity, 220, 260 and 260 cm under C2 pruning intensity, 200, 240 and 220 cm under C1 pruning intensity, and 180, 200 and 160 cm under CK pruning intensity in 2013, 2014 and 2015, respectively. Soil water deficit was alleviated by higher pruning intensity. In 2013–2015, soil water change was positive under C2 (6.4 mm) and C3 (26.8 mm) pruning intensities but negative under C1 (−20.5 mm) and CK (−40.6 mm) pruning intensities. Moreover, pruning significantly improved fresh fruit yield and WUE of jujube plants. Fresh fruit yields were highest under C1 pruning intensity with the values of 6897.1–13,059.3 kg/hm2, which were 2758.4–4712.8, 385.7–1432.1 and 802.8–2331.5 kg/hm2 higher than those under CK, C2, and C3 pruning intensities during the jujube growing period of 2012–2015, respectively. However, C3 pruning intensity had the highest WUE values of 2.92–3.13 kg/m3, which were 1.6–2.0, 1.1–1.2 and 1.0–1.1 times greater than those under CK, C1 and C2 pruning intensities, respectively. Therefore, C3 pruning intensity is recommended to jujube plantations for its economic and ecological benefits. These results provide an alternative strategy to mitigate soil desiccation in jujube plantations in the hilly Loess Plateau Region, which is critical for sustainable cultivation of economic forest trees in this region.

Canopy pruning as a strategy for saving water in a dry land jujube plantation in a loess hilly region of China

AimsSoil drying has occurred widely in artificial plantations in the semiarid loess region because the water consumption exceeds the rainfall. Jujube (Ziziphus jujube Mill. CV. Lizao) plantations have been planted to improve the economic income since 2000. In order to prevent soil drying and sustain artificial plantation development, we examined the relationships between the canopy size, water consumption, and water use efficiency in a dry land jujube plantation. MethodsSeven treatments were tested comprising native jujube with no pruning and dwarfing jujube under different pruning levels ranging from 1 to 6. Jujube is a popular dwarfing canopy type in this region with a tree height of 2.2 m and this comprised level 1. Jujube received increased intensities of pruning as well as decreases in tree height and canopy size for levels 2–4. Jujube received severe pruning to a tree height of only 1.1 m at level 5, and the canopy was removed with only 30–40 cm of the trunk left for level 6. Soil water was detected using CNC100 neutron tubes. A thermal diffusion probe was used to monitor the sap flow in jujube trees throughout the whole growth period. ResultsDuring our study period, 2014 was a wet year with rainfall of 460.4 mm and 2015 was a dry year with rainfall of only 380.8 mm. Transpiration and water consumption by jujube decreased significantly whereas the soil water content increased as the pruning intensity increased in these two years. Compared with 15-year-old native jujube, the annual soil water consumption by 15-year-old dwarfing jujube (pruned at level 1) was 6.54 mm less and the soil water consumption depth moved upward by 2.2 m. The soil water recovered faster for jujube at level 6 and the soil water restoration depth reached 4.6 m after 3 years, with an annual restoration depth of 153.3 cm. Compared with level 1 jujube, at level 5, the height was halved, the transpiration was about 22.1%, and the water use efficiency was significantly improved by 1.1 times, thereby demonstrating that the water consumption could be regulated by the canopy size. Level 2 jujube had the highest water use efficiency with the optimal pruning level in the local region. ConclusionsWe found that pruning could effectively decrease water consumption, relieve deep soil drying, and improve the water use efficiency in jujube. The pruning level should be determined based on the water consumption rate and average rainfall to obtain high yields.

Optimized Water and Fertilizer Management of Mature Jujube in Xinjiang Arid Area Using Drip Irrigation

Studying water–fertilizer coupling effects in a drip irrigation system is critical for sustainable agricultural development in arid areas, such as that of Xinjiang in China, to find out the optimized water and fertilizer management. Therefore, a two-year field experiment was conducted to find out how the combination of three levels of irrigation quotas and three levels of fertilizer amounts would affect the physiological and growth indexes of jujube, as well as ascertain the differences between drip irrigation and flood irrigation. The results showed that the interacted and coupled effects of irrigation and fertilization influenced most of the physiological indicators and growth indexes. On the other hand, the physiological and growth indexes were increased after transferring flood irrigation to drip irrigation, as the maximum chlorophyll content (CC) and photosynthetic nitrogen use efficiency (PNUE) values increased on average by 6.00%, and 11.39% in 2016, and 1.47% and 6.83% in 2017, respectively. Undoubtedly, inappropriate water and fertilizer management had negative impacts on jujube growth and yield. Based on the treatments and results in this paper, low fertilizer and moderate irrigation would be the best choice. The crop yield, irrigation water use efficiency (iWUE), and fertilizer partial productivity (PFP) increased by 6.77%, 29.48%, and 193.62% in 2016, and similar increments were also found in 2017 of 6.17%, 78.72%, and 133.06%, respectively. This indicated that fertilizer efficiency was promoted along with water use, and in turn, the water amounts were adjusted by the amount of fertilizer that was applied. Based on a comprehensive consideration of the physiological and growth indexes, a mathematical model was established, and the optimized irrigation and fertilizer amounts of jujube in northern Xinjiang area were found to be 815 mm and 400 kg ha−1 (with N–P2O5–K2O proportioned at 2–1–1.5). The results that were obtained in this paper would provide theoretical reference to the sustainable development of jujube plantation using drip irrigation in the arid areas.

Extreme natural drought enhances interspecific facilitation in semiarid agroforestry systems

Agroforestry is a widely advocated adaptation strategy for enhancing agricultural resilience to extreme climates. However, it is somewhat controversial and there is limited evidence regarding its efficacy in semiarid regions. Here we describe studies on jujube agroforestry regimes using two different cash crops: the annual fodder species rape (Brassica napus) and the perennial daylily (Hemerocallis fulva). The jujube agroforestry systems were characterized with respect to their interspecific water interactions and their responses to extreme natural drought using stable isotopic techniques and in situ soil water observations in China’s semiarid Loess Plateau region. We found that agroforestry altered the jujube trees’ water sources but its impact depended on soil wetness: compared to monocultures, jujube trees in agroforestry systems generally shifted to deeper water under dry conditions but to shallower water under wet conditions. Complementary water use between jujube trees and crops was observed on most sampling dates, but there was clear evidence of water competition in the shallow layer under relatively wet conditions. Furthermore, a simple index, Relative Difference in Soil Water content (RDSW), was developed to indicate interspecific water interactions under various wetness conditions. It was found that facilitative interspecific interactions were clearly enhanced in both agroforestry systems during extreme drought. In addition, jujube yields in agroforestry systems were clearly higher than in monoculture. These findings demonstrate that agroforestry is a climate-smart agricultural system and can increase the resilience of semiarid jujube plantations to extreme real-world drought.

Effects of pruning and mulching measures on annual soil moisture, yield, and water use efficiency in jujube (Ziziphus jujube Mill.) plantations

Soil desiccation and water shortage are major challenges of rain-fed crop production in the semi-arid areas of the Loess Plateau of China. Mulching and pruning were considered effective strategies to improve harvest by reducing soil water evaporation and plant transpiration rates. In the present study, the possible synergistic effects of the combination of mulching and pruning on soil water status, growth, yield, and water use efficiency were explored in the jujube plant. Field experiments were conducted in a typical hilly semi-arid region over three growing seasons and two dormancy seasons in 2015–2017. The three treatments applied to mountain jujube plantations throughout the year were grassland (CK), regular pruning (PR), and pruning and mulching (PM). Soil water storage (0–200 cm) was higher in the PM than the PR treatment but lower than that of the CK in all three growing seasons. Relative to PR and CK, PM significantly decreased soil water loss during the dormancy season. The soil moisture infiltration depths were 300 cm, 160 cm, and 420 cm in 2016 and 420 cm, 280 cm, and 460 cm in 2017 for PM, PR, and CK, respectively. Soil desiccation was substantially reduced under the PM treatment in the deep soil layer but was less effectively mitigated under the PR treatment. In the CK treatment, soil desiccation appeared at 0–200 cm but was alleviated by heavy rainfall. Fresh fruit yield ranged from 6643–11,056 kg ha−1 for the PM treatment in 2015–2017. This range was 1221–2628 kg ha−1 higher than that for the PR treatment. Water use efficiency was 2.28 kg m−3, 2.05 kg m−3, and 2.22 kg m−3 under the PM treatment in 2015, 2016, and 2017, respectively. These rates were 1.27 × , 1.26 × , and 1.39 × higher, respectively, than those for the PR treatment. These results suggest that the combination of mulching and pruning is an alternative strategy for mitigating soil desiccation in the hilly regions of the Loess Plateau of China. This alternative land management system may be critical for the sustainable cultivation of economically important forest trees in the Loess Plateau region and elsewhere.

Spatial configuration drives complementary capture of light of the understory cotton in young jujube plantations

In intercropping systems (growing >1 species in a field), interactions between species affect the performance of plants and the overall yield. These interactions lead to plastic responses in plant traits due to the specific environmental conditions typical for intercrops, especially in agroforestry in which the understory crop is strongly shaded by the trees. To quantify the extent to how physiological plasticity is driven by inter-specific competition, field experiments with mixtures of cotton and jujube trees grown in strips were conducted in 2012 and 2013 in Hetian, Xinjiang, China. Cotton was grown at three levels of inter-specific competition, represented by the distance between the adjacent cotton and tree rows without change in plant density. The highest cotton yield was attained farthest away from the trees, i.e. at the lowest level of inter-specific competition, with a higher proportion of fiber in the bolls as well as a higher boll density compared to plants grown at higher inter-specific competition. Low inter-specific competition also increased maximum leaf area index (LAI), total light interception and dry matter accumulation. However, light-use efficiency was higher at high levels of inter-specific competition especially in the rows close to the tree line, associated with a higher fraction of diffuse radiation. These results aid in the optimization of the spatial pattern of crops in agroforestry system.

Effects of pruning intensity on jujube transpiration and soil moisture of plantation in the Loess Plateau

In order to ease soil desiccation and prevent ecological deterioration in the Loess Plateau, where jujube (Zizyphus jujube MIll) is widely cultivated as a drought tolerant plant, four pruning intensities (PI), from PI-1 (light) to PI-4 (heavy) were set up based on total length of secondary branches to study the effects of pruning on transpiration and soil moisture in jujube plantations. Furthermore, growth indexes were regularly monitored to estimate jujubes biomass. Sap flow, meteorological and soil moisture conditions were monitored using thermal dissipation probes (TDP), weather station (RR-9100) and the combination of time domain transmission (TDT) technology and neutron moisture gauges (CNC503B), respectively. The results showed that daily actual transpiration of jujube was positively correlated with leaf biomass. Compared with PI-1, jujube transpiration during growth period under PI-2, PI-3, and PI-4 dropped by 11.1%, 29.2%, and 47.9%, respectively. On the contrary, annual water storage under PI-2, PI-3, and PI-4 increased by 6.29 mm, 25.78 mm and 34.74 mm while water use efficiency increased by 5.1%, 15.7% and 24.2%, respectively. Overall, increase in pruning intensity could significantly reduce water consumption of jujube and improve soil moisture in jujube plantations.

黄土丘陵区枣林土壤水分调控技术研究

针对黄土丘陵半干旱区大面积人工林草地土壤干化严重问题，而有关专门进行土壤水分亏缺的恢复试验研究缺乏的问题。本研究在陕北12龄山地密植枣林对秸秆覆盖、保水剂、聚水沟、少量补灌、矮化密植、缩小树体修剪措施下的土壤水分进行了定位试验观测，并结合林地根系调查，研究了几种措施对枣林土壤水分的调控作用。结果表明：秸秆覆盖、保水剂、聚水沟措施可分别影响0~260 cm、0~160 cm、0~300 cm土层的土壤水分含量，聚水沟措施具有更强的土壤水分调控功能；稀植枣林由于根系深度超过矮化密植枣林根系，从而增加了林地土壤深层水分亏缺；小量补充灌水会促进树木生长，而对土壤水分的恢复没有明显作用；通过修剪控制树体规格降低叶面积指数可以较好地减小枣树蒸腾耗水量，有利于土壤水分的调控，是土壤水分调控的新途径；研究认为在黄土丘陵半干旱区，可以尝试在矮化密植枣林结合应用聚水沟技术以及根据当地降雨调控枣树产量的节水型修剪技术，达到恢复土壤水分为目的的调控土壤水分手段。该研究对半干旱区旱作林草地土壤水分调控及可持续发展具有十分重要的意义。 There are many researches on soil moisture deficit of artificial forest and grass in Semiarid Loess Hilly Area, but a few studies are focused on the recovery of soil moisture deficit in this region. In this study, 12 old mountain in Northern Shaanxi jujube forest planting of straw mulch and water retaining agent, a small amount of irrigation ditch, poly, dwarfing close planting, soil moisture reduced tree pruning measures under the experiment observation, combined with forest root investigation, study the controlling effect of several measures on soil moisture in jujube forest. Results showed that the soil water content depths under straw mulching, water-retaining agent and rainwater harvesting ditch treatments can reach 260 cm, 160 cm, and 300 cm, respectively, but the rainwater harvesting ditch has stronger effect on soil moisture regulation. Dwarf and dense planting jujube can shoal the rooting depths and reduce deep soil water deficit, while sparse planting jujube plantations have deeper root system. A little supplemental irrigation would promote jujube growth, but has little effect on soil moisture restoration. Transpiration water consumption of jujube can be effectively reduced by pruning trees to control specifications and lowering leaf area index, which is beneficial to soil water regulation. Combined applied water-saved pruning and rainwater harvesting ditch technique, dwarfed dense Jujube plantations would effectively regulate soil moisture in Semiarid Loess Hilly Areas. The study is significant to soil moisture ecological restoration as well as sustainable development of forestry.

Effects of branch removal on water use of rain-fed jujube (Ziziphus jujuba Mill.) plantations in Chinese semiarid Loess Plateau region

As a drought tolerant plant, jujube (Ziziphus jujuba Mill.) is commonly planted in Chinese semiarid Loess Plateau Region under rain-fed conditions. To evaluated the effectiveness of branch removal to conserve water resources in rain-fed jujube plantations in the region, two degrees of branch removal treatments (T1–two main branches removed; T2–one main branch removed) were compared with control treatment (none of the three main branches removed) and the effects on water use in Jujube plantations were analyzed. Sap flow was monitored (using the Granier-type thermal dissipation probes) along with meteorological factors, soil water content, vessel diameter, crown projection area and leaf area index, with soil moisture condition divided into water stress and non-water stress. Results showed that branch removal was an efficient way of conserving water resources in jujube plantations. a) It improved soil water content by reducing water loss via total evapotranspiration (ET) during jujube growth period. Total ET values were 452, 463 and 478mm respectively for T1, T2 and the control treatments during jujube growth period in 2012; 408, 426 and 451mm respectively for T1, T2 and the control treatments during jujube growth period in 2013 and 374, 381 and 392mm respectively for T1, T2 and the control treatments during jujube growth period in 2014. b) Branch removal not only decreased transpiration per unit ground area (stand transpiration: Tg), but also increased the sensitivity of Tg to environmental variables. In contrast, the removal of two (out of three) branches increased transpiration per unit leaf area (leaf transpiration: Tl), making it less sensitive to soil water content. c) Treatment T1 significantly increased the sensitivity of canopy conductance (Gc) to vapor pressure deficit (VPD), which effect was not significant under T2. Isohydric regulation of water loss through Gc response to VPD was the same for the three treatments, regardless of the different tree canopy sizes and soil water conditions, but reference canopy conductance (Gcref: canopy conductance at VPD=1kPa) was treatment-specific. d) Branch removal improved the tolerant of jujube tree to negative water potential and xylem cavitation by decreasing average vessel lumen diameters. Compared with the control, both branch removal treatments (T1 and T2) resulted in a significant decrease in average vessel lumen diameter at 15mm below the cambium (40.74, 42.53 and 46.81μm respectively for T1, T2 and the control treatments). Similarly, T1 and T2 reduced mean vessel lumen diameter at 5mm below the cambium (43.20, 47.44 and 48.39μm respectively for T1, T2 and the control treatments). e) Branch removal significantly decreased the fresh fruit yield and water use efficiency except in 2013, during which differences were not significant. Fresh fruit yield values were 8082, 8964 and 11293kgha−1 respectively for T1, T2 and the control treatments in 2012; 5691, 5426 and 6000kgha−1 respectively for T1, T2 and the control treatments in 2013; 6804, 8341 and 10589kgha−1 respectively for T1, T2 and the control treatments in 2014. WUE values were 1.79, 1.94 and 2.36kgm−3 in 2012; 1.40, 1.28 and 1.33kgm−3 in 2013; 1.82, 2.19 and 2.70kgm−3 in 2014. T1 treatment was recommended in terms of improving soil water storage as well as maintaining a certain amount of productivity in jujube plantations in Chinese semiarid Loess Plateau Region. The result of the study is critical for the development of effective water management strategies in jujube plantations ensure that the fragile ecology of the Loess Plateau is sustained.