Effect of cover-cultivation on soil temperature and growth of Ziziphus jujuba Mill. ‘Lingwu Changzao’

L.H. Song and B. Cao School of Agriculture, Ningxia University, No. 489, Helan Mountain West Road, Xixia District, Yinchuan, China.

Abstract Ziziphus jujuba Mill. ‘Lingwu Changzao’ (Lingwu long jujube) is one of the important economic forestry trees in Ningxia, China. It is also the main component of agriculture industry in Ningxia because of its great ecological, social and economical benefits. As Lingwu long jujube plantation has been increasing, the water requirement for jujube irrigation has been increasing, but the water resource is limited in Ningxia. In order to select water-saving and labour-saving cultivation techniques, grey-blue fibre film (GBF), black plastic film (BPF), black-silver fibre film (BSF), and wheat straw (WS) were used to cover the soil of jujube plantation for one growing season; the soil moisture and temperature, shots and leaf growth, photosynthesis, single-fruit-weight etc. were tested to analyse the cover effect and to find the best cover material. The results showed that different cover materials showed different soil water holding and soil temperature keeping effect, thus made a different growth effect. When covered by black plastic, soil moisture in 10-20 cm depth was 75.56% which was more than that of control group. The soil temperature in 0-10 and 10-20 cm depths was higher than that of control group by 18.89 and 15.06% respectively, and leaf chlorophyll content increased by 21.95%, enhancing the photosynthesis process. All of this indicated that black-plastic-cover cultivation was more effective for Lingwu long jujube.

Keywords: jujube, black plastic, soil moisture content, leaf chlorophyll content, net photosynthetic rate, single fruit weight

INTRODUCTION Ningxia province is located at northwest region of China, and the middle and upper part ranges the Yellow River. The total land area of Ningxia is 66,400 km2, and the population is 6.64 million, of which 57% is farm population. The climate type here belongs to temperate zone and continental climate; annual precipitation is about 200‐500 mm from north to south in Ningxia, annual sunshine duration is 2194.9‐3082.2 h, and annual mean temperature is 5‐ 10°C. So this is one of the best places to grow temperate fruit trees. In order to increase farmers’ income, local government supported farmers and private companies for planting fruit trees to develop economic forestry, such as grape (Vitis vinifera), apple (Malus pomila), Chinese wolf berry (Lycium barbarum), and jujube (Ziziphus jujuba) (Yang et al., 2013). Ziziphus jujuba Mill ‘Lingwu Changzao’ (Lingwu long jujube) is one of the important economic forestry tree cultivars in Ningxia because of its excellent flavour and good nutrient value in fruit (Li et al., 2013). The plantation area of Lingwu long jujube is now about 9,334 hm2, so the Lingwu long jujube industry is becoming a main agriculture industry for local region, Lingwu County (Wan et al., 2013). As Lingwu long jujube plantation has been increasing, the water requirement for jujube plantation irrigation has been increasing, but the water resource is limited in Ningxia (Li et al., 2013; Wei et al., 2011). So it is necessary to conduct and select water‐save cultivation techniques. Mulching is a perfect method for saving water and reducing labour cost for plantation management, but it has not been done in Lingwu long jujube plantation. In order to select optimal mulching materials for local jujube plantation, we use plastic, fibre or straw staff to cover the plantation soil surface.

Acta Hortic. 1116. ISHS 2016. DOI 10.17660/ActaHortic.2016.1116.15 89 XXIX IHC – Proc. III Int. Jujube Symp. Eds.: Mengjun Liu et al.

MATERIALS AND METHODS This study was conducted in Machanghu jujube plantation (E 106°20’07”, N 38°07’45”, elevation 1184 m) in Lingcu County during April to September in 2012. The seven‐year‐old Lingwu long jujube plantation was selected, and grey‐blue fibre film (GBF), black plastic film (BPF), black‐silver fibre film (BSF), and wheat straw (WS) were used as mulching materials. Single factor randomized block design with three replications was used. Four treatments (mulching with GBF, BPF, BSF, WS), and a control group (CK, no mulching), each replication including five Lingwu long jujube trees (spacing in the row and between the row 2×4 m, H = 3.09 m, Droot collar = 67.62 mm). Two meters of the soil surface between the rows were mulched (including the row, and one meter of each side of the row). Two depths (0‐10 cm, 10‐20 cm) of soil temperature and moisture content were tested every seven to ten days by digital thermometer and soil moisture meter (TSC‐II, China). The length of new fruit shot was measured every seven to ten days, and leaf chlorophyll content and photosynthesis were tested every month during fast growing season by chlorophyll meter (SPAD‐502, Japan) and portable photosynthesis monitor (LCI, UK). Thirty fruits were collected from each replication after mature to measure single fruit weight with electronic scale. All collecting data were analyzed with ANOVA, and LSD for multiple comparisons.

RESULTS AND DISCUSSION

Soil moisture and temperature Environment factors affected the growth and development of plant, epically soil water condition and temperature. The mean soil moisture contents of Lingwu long jujube plantation mulched by grey‐blue fibre film (GBF), black plastic film (BPF), black‐silver fibre film (BSF)mulching, or wheat straw (WS) mulching were 25.07, 26.18, 24.83, 13.71% respectively during the whole growth season, but for the CK, it was just 14.91% (Figure 1). So the moisture condition mulched by BPF was better than that of others. The soil temperatures of the jujube plantation for 0‐10 cm depth and 10‐20 cm depth under different mulching treatment were different (Figures 2 and 3), and higher than that of control group’s except the WS mulching treatment. When mulched by BPF, the soil temperatures of two depths were 25.49 and 20.95°C respectively, which were higher than that of CK’s by 20.58 and 20.05%.

Figure 1. Soil moisture content (10‐20 cm) comparison under different mulching treatments.

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Figure 2. Soil temperature (0‐10 cm) comparison under different mulching treatments.

Figure 3. Soil temperature (10‐20 cm) comparisons under different mulching treatments.

Photosynthesis and single fruit weight The leaf chlorophyll content had close relationship with plant photosynthesis. The leaf chlorophyll content of jujube with BPF mulching was higher than that of control group by 45.98% in May, and 3.98% in September (Figure 4), and the net photosynthetic rate (Pn) of BPF mulching treatment accounted for 137.3% of CK, and higher that of other mulching treatments (Table 1). The weight of single fruit for the BPF mulching treatment was also higher than that of other treatments (Figure 5), but there were no significant differences (p = 0.213>0.05).

Figure 4. Comparisons of leaf chlorophyll content in Lingwu long jujube comparisons under different mulching treatments.

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Table 1. The photosynthesis comparison of Lingwu long jujube under different mulching treatments. Mulching treatments CK GBF BPF BSF WS Pn (µmol m-2 s-1) 14.14c1 18.99a 19.41a 18.55a 16.46b Gs (mmol m-2 s-1) 0.24c 0.52a 0.51a 0.56a 0.36b Ci (µmol mol-1) 212.06c 236.69a 230.5a 240.44a 224.63b E (mmol m-2 s-1) 4.89c 7.24a 7.27a 7.64a 6.7b WUE (µmol mmol-1) 2.89 2.63 2.69 2.43 2.5 1The values of every index under different treatments with same low case letters means no difference at α=0.05 level.

Figure 5. Comparisons of single fruit weight in Lingwu long jujube comparisons under different mulching treatments.

CONCLUSIONS According to the test result, the four different materials that were used – grey‐blue fibre film (GBF), black plastic film (BPF), black‐silver fibre film (BSF), and wheat straw (WS) – to cover the soil of jujube plantation for one growing season, showed different soil water holding and soil temperature keeping effect, thus made a different growth effect. Black‐ plastic‐cover cultivation was more effective for Lingwu long jujube plantation. Because this is just a one year testing result, the long term effect of black‐plastic‐cover effect, optimal cover duration and cover patterns would be study next.

ACKNOWLEDGEMENTS This work was funded by National Natural Science Foundation of China (No. 31260171).

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