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34 1 j b TA HLNPV 2j4 k W = ( ? bW% A TD aa L= PrT#Byp 9 !7?4 Ib 1oM 9 !9 j j25 3 71HDF eN 26-309 H 71EE a ? Sa8la 11NL 3 71D7 O+Y ? 3#p+Y ? /b V V A “ -9 9 (1 A b+ E1| 9 /Z7 O $V9 n b E9 b,E1-7 O s,Yb Ea 6 E !8 vbHDE1NL 3 71Di O #pb 9/ L P ?v Pj m 2cbVV 3Z UsT PT A v HLNPVrT 1 z7 O TArT 1z FTAb TA 5QT ka55 HLNPV Pr 4 Kk HLNPV ? ? 3 CA9 Ah TA H ? b V 3 HLNPVsT9 P f Table 3 Application of HLNPV on some crops under (negative pressure irrigation) T Crop Site 9 HWIrrigation duration HLNPV # Pressure and number of HLNPV A Cover liquidHLNPV HLNPV running state l 2014-12-27 2015-02-26 5a7.5a10 kPa 6 F z F Ah 6 2 2014-06-13 08-10 5a10a15a20 kPa 4 F z F Ah ( 2014-08-29 10-30 5a10a15a20 kPa 4 F 5 kPa 25j30 d Ma 45j50 d j 5 10 kPa 45j50 d MB ? e 15a20 kPa zbl 2015-11-07 2016-01-23 5a10a15 kPa 6 F z F Ah o 6 2 2015-05-05 07-15 5a10a15 kPa 3 F z F Ah 2015-06-20 09-14 5a10a20a30 kPa 4 F 5a10 kPa50j55 d M 5 kPaa60-65d j 5 10 kPaB? e 20a30 kPa zb 3 6 2 2015-7-08 09-25 5a10a15 kPa 4 F z F Ah 6 2 2016-04-18 06-20 5a10a15a20 kPa 3 F z F Ah 6 2 2016-06-25 09-30 5a10a15a20 kPa 3 F 5 kPa9 20i25 MB ? e 10a15a20 kPa z k 2016-09-09 11-01 4a8a12 kPa 3 z Ah 2016-09-09 11-01 4a8a12 kPa 3 z Ah ( v i 2017-05-20 08-05 5 kPa10 z Ah K 2017-05-20 09-30 5a10a15 kPa 5 z Ah r - 2017-08-01 11-12 10a15a20 kPa 4 z Ah 9 HW 9 HWy1T s) 1Ml b Note: Irrigation duration refers to the negative pressure irrigation time, inorder to ensure the crop was surving. It begins some days later than sowing or transp lanting. F TA HLNPV PrT1 0 TA HLNPV 9QT k 3Q ks HLNPV ? 3M . j 57 P ? b Ma HLNPV ? HWM7 OV?C? 3 1 5 kPa 10 kPaHLNPVb2014 M( k 5 kPa HLNPV 25-30? Ma 45j50 d j5 10 kPaHLNPV 45j50 d Mk e ? b 2015 M k 5a10 kPaHLNPV 50j55 d M 5 kPaHLNPV 60-65? j 510 kPa HLNPV ? ? kb7 2016 M6 2 k k 90?P 5 kPa 7 SM7 O ? ? k b B? / b ? 3QHLNPV ? 3MC V ? F ? 3 Q9 V ? t k HLNPV s; P % s;v 7 3 V H( b bL N F A LVPV V L= PV 3 ZU 9 QT ka 129 F ALVPV 20a 15.5%HLNPV? 3 CK 8 a 6.2% HLNPV y 7 ? b a. z k H MCA Ah ba kV 3 MC ? ? k ca kV 3 V ? 57 ? . a. The LNPV running very well, no oxide precipitate generated at the whole experiment duration; b. Some black oxide precipitate generated, but can continuously maintained the proper native pressure; c. Lots of black oxide precipitate generated, maybe block up the tube and lose to maintained the proper native pressure. m 2 BW k A TD Fig.2 Photographs of HLNPV when field experiments were over 1 C9A TD !9 k 89 ) A TD ZE1 !9A TDHLNPV 1 !9 8 4 D V ? ?b f 9b T TA ? 3C B? TT 3 1 V?1QFTA 9F byN1sB?l b a ? 3QAb 3 “ - HLNPV ? !“db HLNPV e5 e % T1T 3!AHLNPVtZLb T| e5 ! a VA vv4ZL !“db 4NM U j 5a S j 5a bj o# ? W 9“d !9 A TDHLNPV F A ?b k i HLNPV e _BW HLNPV erT 41s HLNPV 9“dC ?S | / 1HLNPV sO q sO q 0.1 kPa 30 kPa =/Ml 5%b 2vs HLNPV L=BWHq/ ? b TA 5T 55 HLNPV 2j4 k W = ( ? b F TA 9 T 129 LVPV 2j3 k W = 15.5%? 3 MC 6.2%y 57Y ?b 3HLNPV MCZE A1 b 5.0j20.0 kPa/ + Ea,Ea Ea 6 E 9.6j17.2%8a l Ea 6 aHD,aHD * “1 ?9+ *“ ? HW/b 98 HLNPV ?1 HW“d S“d a8la a keL V9CZEb ju l C . B aRr S J. j C . r K 3# +Y J. S S 201536(1) 3541. Xiao Haiqiang, Liu Xueyong, Long Huaiyu, et al. The effects of soil water potential on the growth and water consumption of flue-cured tobaccoJ. Chinese Tobacco Science, 2015, 36(1): 3541. (in Chinese with English abstract) 28 oZ #: . 9 K 3# g qY J. S . 201622(2) 5260. Xiao Haiqiang, Ding Yahui, Huang Chuyu, et al. Effect of negative pressure irrigation on water fertilizer utilization and flue-cured tobacco growthJ. Acta Tabacaria Sinica, 2016, 22(2): 5260. (in Chinese with English abstract) 29 u C c . 9/K l 3Y J. S j S 201750(4)689697. Zhao Xiujuan, Song Yanyan, Yue Xianlu, et al. Effect of different potassium levels on the growth of bok choy under negative pressureJ. Scientia Agricultura Sinica, 2017, 50(4): 689697. (in Chinese with English abstract) 30 3 C . gB89( a r qY J. !g 201723 (2) 416426. Li Shengping, Wu Xueping, Long Huaiyu, et al. Water and nitrogen use efficiencies of cucumber under negatively pressurized fertigationJ. Journal of Plant Nutrition and Fertilizer, 2017, 23 (2): 416426. (in Chinese with English abstract) Design and experiment of heavy liquid-type negative pressure valve used for negative pressure irrigation Long Huaiyu, Zhang Huaizhi, Yue Xianlu, Zhang Renlian (Institute of Agriculture Resources and Regional Planning, Chinese Academy of Agriculture Science, Beijing 100081, China) Abstract: Negative pressure irrigation (NPI) is a high efficient irrigation technology which has attracted great concern from some Chinese scholars in the past decade. To produce and maintain a steady negative pressure is an essential key point for NPI, and at present there are mainly 5 methods, namely hanging water column (HWC), static water column (SWC), climbing water column (CWC), electromagnetic valve (EMV) and negative pressure water circulation (NPWC). However, due to some inherent shortcomings, those methods are not convenient to practically operate. The HWC is easily to fail due to the air embolus, the EMV and NPWC are energy-consuming, and too large heights of HWC, SWC, CWC and NPWC make them very cumbersome and not easy to install. In fact, the negative pressure results in the soil water sopping, which is always continuous, slow and unidirectional, and the function of the negative pressure maintaining device is similar to negative pressure limiting valve which does not need to act continuously or high frequently. Therefore, the heavy liquid static pressure should be theoretically used to control the negative pressure in the NPI system. It is known that 1 mmHg which can be easily determined with naked eyes can generate 0.133 kPa static pressure. Moreover, the negative pressure in actual NPI is seldom set under -30 kPa which is equivalent to 22.5 mmHg. Obviously, the negative pressure maintaining device using the static pressure of mercy whose density is the largest in the world to control the negative pressure in NPI should have high precision and small size, and be easily to operate. Accordingly, a heavy liquid-type negative pressure valve (HLNPV) was designed. The HLNPV consists of 3 basic interconnected parts, i.e., a U-shaped tube, an S-shaped pressure maintaining tube and a hollow ball, together with a certain amount of mercury which can be poured into them and cyclically flow in them. The negative pressure is maintained by the static pressure of the mercury in the S-shaped tube. Additionally, a device to slow down the air entering was installed between HLNPV and atmosphere, and the mercury in the hollow ball was overlapped by paraffin oil or water to prevent the evaporation of mercury. Laboratory test showed that the precision of HLNPV could reach 0.1 kPa, which is too enough for NPI, and the relative error of HLNPV with the theoretical control pressure from -5 to -30 kPa was less than 5%, which is satisfactory for NPI. In the field, most paraffin oil overlapping HLNPV could steadily run for the whole experiment period of 2-3 months, while the mercury in 15.5% of the HLNPV was oxidized after running for 1-3 months, and that in 6.2% of the HLNPV was blocked up by the oxide precipitate, which caused their failure to maintain negative pressure. Water-overlapping HLNPV could steadily run for the whole experiment period of 2-4 months, while water is a theoretic volatile liquid, if the runtime is more than 4 months, the overlapping water maybe need to be complemented. In one word, the HLNPV can overcome many disadvantages of the present negative pressure maintaining methods, and has the advantages of larger negative pressure, no energy consumption, small size, high accuracy, easy to install and debug, as well as more security. The mechanism, structure, application effect and suggestions for improvement of the HLNPV are described explicitly in this paper, thereby providing a reference for its further application, innovation and improvement. Keywords: irrigation; design; agriculture; heavy liquidtype negative valve; negative pressure irrigation; negative pressure maintaining
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