Exploratory research on negative-pressure soaking technology for peanut pods

Transcription

1 Fu, Xiong, Xing, Min, Zhu, He and Feng (2018). Seed Science and Technology, 46, 1, Research Note Exploratory research on negative-pressure soaking technology for peanut pods Xiaoji Fu, Huiwei Xiong, Shengping Xing, Hua Min, Xuejing Zhu, Jialin He and Jianxiong Feng* Institute of Food Science and Technology, Jiangxi Academy of Agricultural Sciences, Nanchang, , Jiangxi, China ( *Author for correspondence. (Submitted September 2017; Accepted November 2017; Published online December 2017) Abstract Here, a rapid liquid soaking technology for peanut pods is discussed. The vacuum pressure and treatment time significantly influenced the germination of peanuts. After pretreatment, the highest germination of two kinds of peanuts, TianFu No.18 and GanHua No.7, increased 8.7 and 4.9%, respectively, compared with the regularly soaked samples. Germination increased with processing time at MPa. However, it decreased with processing time at and -0.1 MPa, while the electric conductance increased at the same time. The optimum technological conditions for the pretreatment of pod-sowing was 15 minutes at MPa. A field experiment showed that the emergence rate and times of pod-sowing samples were comparable to those of seed-sowing and the regularly soaked samples. Additionally, the number of effective branches and yield were superior to those of the control group. Keywords: peanut, pod sowing, rapid soaking technology, vacuum soaking Experimental and discussion Pod-sowing is an important technology in peanut cultivation and is widely used in southern and northern China (Yu, 2004; Chen et al., 2009; Chang et al., 2013). In the peanut producing areas of north China, there are droughts in spring, making it difficult for peanuts to germinate in the suitable season. If farmers wait for a spring rain, then they miss the best time for peanut cultivation. However, the use of pod-sowing and mulching film technology alleviates issues of low temperature and drought, conditions that are not suitable for planting (Fu, 2009; Na, 2010). In the peanut producing areas of south China, it is cold and rainy in spring, resulting in peanut seeds becoming mildewed and rotting in the soil, which reduces peanut yield significantly. However, germination can be guaranteed through the use of pod-sowing technology because of the protection provided 2017 Feng et al. This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: 65

2 XIAOJI FU, HUIWEI XIONG, SHENGPING XING, HUA MIN, XUEJING ZHU, JIALIN HE AND JIANXIONG FENG by the shell (Sun et al., 2007; Lu et al., 2011). There are many other advantages of podsowing, such as reduced costs to remove peanut shells and shorter sowing times. Peanut pods should be dipped in soaking liquid directly for hours before sowing (Li, 1993). However, there are disadvantages of using this soaking method, such as the long soaking time and durations of seedling emergence (Dong, 2003). Thus, a highly efficient, easily operable pod-soaking technology is necessary to solve current production issues and increase the efficiency of the peanut production industry. The peanut varieties GanHua No.7 and TianFu No.18 were used as raw materials to research negative-pressure soaking technology. The selected peanut pods were put into mesh bags (100 g per bag) and the bags were placed into a container of soaking liquid with the peanut pods below the liquid s surface. Then, the container was put into the vacuum equipment under negative pressure. The soaking liquid filled the peanut pods rapidly after pressure release. The influence of the processing pressure (0, -0.06, and -0.1 MPa) and time (5, 10 and 15 minutes) on water absorption, electrical conductance and germination rate were studied. Five parallel experiments were performed and the optimum processing conditions determined. Water absorption rate: Samples consisted of 100 g of dry peanut-pods of the same size. After the liquid-soaking treatment, the surface water was removed and the samples were re-weighed to determine the amount of water absorbed. Electrical conductance: After liquid-soaking, the peanut seeds were removed and 10 peanut seeds were randomly selected as a group. Three parallel experiments were performed. The seeds were washed twice with regular water and once with deionised water. The water on the surface was removed using filter paper. Then, the seeds were put into a clean beaker and 150 ml of deionised water added. The electrical conductance was detected using a DDS-12D (Lida Inc., Shanghai, China) conductivity meter, measuring every two hours for 24 hours at 25 C. G ermination rate: Three samples of 100 p eanut p ods were removed after liquid soaking. The pods were bathed in a 1% bleach solution for 10 minutes and then rinsed three times under running tap water. Each sample was sown in wet sand and placed in a climate incubator (28 C). After one week, th e samples were removed and the number of peanuts breaking through the shell and the peanut kernels inside that had at least part of the radical breaking through the seed coat were counted. D ata were recorded as the percentages of the number of successfully germinated peanut pods out of the total number of peanuts sampled. Wa ter absorption rate, electrical conductance and germination percentage were assessed using ANOVA. Post-hoc comparisons were made between groups using LSD. Significant values were reported at the α = 0.05 level. Wat er absorption of the pods reached more than 60% (tables 1 and 2), the regular soaking treatment (0 MPa) took 2,880 minutes, while the MPa vacuum pressure treatment only required five minutes. The water absorption of peanut pods was more dependent on the negative pressure than the processing time. Thus, the wat er absorption rate was close to the maximum after only five minutes at -0.1 MPa, while the rate did not change much as the processing time increased at MPa. 66

3 EXPLORATORY RESEARCH ON SOAKING TECHNOLOGY Seed germination requires the absorption of water to reach 40 60% of seed weight (Wang, 2008). After liquid-soaking for five minutes, water absorption reached more than 60%, which met the requirement for germination. Pod-sowing requires a higher water content to support seed germination from the pods, the optimum water absorption for pod-sowing was 69 79%. The germination of the two kinds of peanuts increased with treatment time when the vacuum was MPa. When the pressure was -0.1 MPa, the germination decreased with treatment time. Processing at MPa for 15 minutes and at MPa for five minutes produced reasonable results. The processing time had little influence on the electrical conductance of seeds at 0 and MPa, and the electrical conductance increased with treatment time at -0.1 MPa (tables 1 and 2). Higher vacuum pressures could injure the peanut s cytomembrane, therefore, causing the electrical conductance to increase rapidly at -0.1 MPa. In accordance with the observations of peanut seed dissection (data not provided), there was no water between peanut cotyledons at and MPa, and there was water between the cotyledons at -0.1 MPa. The appearance showed that the soaking liquid could enter the peanut shell at lower negative pressures only. However, the soaking liquid could enter the peanut ker nels at higher negative pressures because of the extraction of air from the interspaces of the kernels. The liquid absorption of peanut seeds at negative pressure is a rapid passive water absorption process. The process could injure the peanut s cytomembrane and have a negative effect on germination (Bramlage et al., 1978). Thus, the ger mination at a lower negative pressure is better than the higher negative pressure. Table 1. Effect of vacuum pressure and time on the water absorption, germination and relative conductance of Tianfu No.18 peanut kernels. Different letters represent significant differences between treatments at P < Pressure (MPa) Time (minutes) Pod weight Wet weight Water absorption Germination Relative conductance ± 1.88d c 7.04 ± 0.56c ± 2.08d c 7.62 ± 0.48c ± 1.15e b 7.65 ± 0.63c ± 2.08d a 7.66 ± 0.71c ± 2.00c a 8.64 ± 0.91c ± 2.31b bc 8.88 ± 0.86c ± 1.20b c ± 0.91b ± 2.08a c ± 1.3b ± 2.51a d ± 1.55ab ± 2.08a d ± 1.41a 67

4 XIAOJI FU, HUIWEI XIONG, SHENGPING XING, HUA MIN, XUEJING ZHU, JIALIN HE AND JIANXIONG FENG Table 2. Effect of vacuum pressure and time on the water absorption, germination and relative conductance of Ganhua No.7 peanut kernels. Different letters represent significant differences between treatments at P < Pressure (MPa) Time (minutes) Pod weight Wet weight Water absorption Germination Relative conductance ± 1.96e b 6.12 ± 0.5d ± 2.08e b 6.49 ± 0.7d ± 1.52d b 6.96 ± 0.6cd ± 2.54d a 7.26 ± 0.75cd ± 2.38c b 7.60 ± 0.65cd ± 3.01ab c 7.93 ± 0.89cd ± 3.21b d 9.67 ± 0.87bc ± 1.52a d ± 1.5b ± 3.00ab e ± 1.2a ± 2.65a e ± 1.6a Field experiments were conducted in the test field of Jiangxi Academy of Agricultural Sciences. The field has sandy loam and medium fertility. There were three modes of sowing: seed-sowing (control), regular soaking (soaking 48 hours) and vac uum pressure (pod liquid-soaking conditions: MPa for 15 minutes). Three parallel experiments were performed. Seed-sowing used two seeds per hole and pod-sowing used one pod per hole. The space between each plant was 135 mm. The emergence was counted 12 days after sowing. The time when germination reached 90% was also recorded and the peanut yield was estimated after seed selection. Emergence after vacuum-pressure treatment was nearly the same as that of the control while the regular-soaking treatment resulted in relatively low emergence for the two peanut varieties (table 3). For TianFu No.18, the seed-sowing samples (control) and the pod-sowing samples (vacuum pressure) required 6 and 5 days, respectively, to reach germination, while th e regular-soaking treatment required seven days. For GanHua No.7, both the control and vacuum-pressure samples required nine days, and the regular-soaking treatment required 10 days. Thus, the vacuum-pressure samples were as productive as the control samples, and more productive than the regular-soaking samples. This indicated that soaking the peanut seeds in water for a long period may not be a good pretreatment and may lead to low germination rates. Compared with the control samples, the podsowing treatment (vacuum pressure and regular soaking) produced more compact plants with lower stem heights, but they produced more branches, although the differences were not statistically significant. The pod-sowing samples had slightly higher yields than the seed-sowing samples (table 3). Pod -sowing is an important technology in peanut cultivation and it is widely used in China. However, there are some application problems, s uch as longer soaking 68

5 EXPLORATORY RESEARCH ON SOAKING TECHNOLOGY Table 3. Effect of vacuum pressure on the emergence rate, economical characteristics and yields of peanut pods. Variety Treatment Emergence Time to 90% emergence (days) Plant height (mm) Number of branches per plant Yield (kg 666 m -2 ) Tianfu NO. 18 Control 96a ± 8.5a 6.6 ± 0.6a 289 ± 5.0a Regular soaking 92a ± 7.3a 7.1 ± 0.49a 292 ± 7.5a Vacuum pressure 96a ± 5.6a 7.4 ± 0.37a 293 ± 6.5a Ganhua NO. 7 Control 98a ± 18.9a 5.95 ± 0.47a 227 ± 8.6a Regular soaking 91a ± 17.4a 6.69 ± 0.55a 236 ± 4.8a Vacuum pressure 97a ± 12.3a 6.47 ± 0.79a 238 ± 8.0a time and irregular emergence. The use of negative pressure liquid pod-sowing tec hnology can solve these problems, and the optimum parameters were obtained. Field experiments were also carried out to verify the feasibility of applying this technology. Acknowledgements This work was supported by the National Natural Science Foundation of China ( ). Ref erences Bra mlage, W.J., Leopold, A.C. and Parish, D.J. (1978). Chilling stress to soybeans during imbibition. Plant Physiology, 61, Chang, M. and Zheng, Y. (2 013). Effects of coated peanut sowing on germination of peanut s seedlings. Journal of Anhui Agricultural.Science, 41, [In Chinese.] Chen, Z., Zou, X. and Song, L. (2009). The study on peanut pod sowing technique. Acta Agriculturae Jiangxi, 2, [In Chinese.] Dong, D., Jiang, L. and Zhang, P. (2003). Effects of pod-sowing and chemical regulation on physiological characteristics and yield of peanut. Journal of South China Agricultural University, 24, [In Chinese.] Fu, X. (2009). The seeding technique of peanut with peanut shell in northern China. Rain Fed Crops, 29, [ In Chinese.] Li, B. (1993). The study on peanut pod sowing technique. Journal of Peanut Science, 3, [In Chinese.] Lu, S., Wu, J. and Qiu, L. (2011). Advances in high-yield cultivation of peanut and high-yield method for peanut planting in southern China. Hunan Agricultural Sciences, 11, [In Chinese.] Na, Y. (2010). Preliminary report on early sowing of shell-peanut covered with plastic film in Shenyang. Ra in Fed Crops, 30, [In Chinese.] Sun, Y., Li, L. and Liu, D. (2007). Study on reasonable close planting technology of peanut in hilly and arid areas in middle reaches of the Yangtze. H unan Agricultural Sciences, 6, [In Chinese.] Wan, S. (2008). Variety Improvement and High Yield and Quality Cultivation in Peanut, China Agriculture Press. [In Chinese.] Yu, W. (2004). Study on the yield increasing mechanism of peanut Pod-sowing and film mulching cultivation. Crops, 6, [In Chinese.] 69