Study on water-saving irrigation of rape (Brassica rapa) and pak-choi (Brassica rapa var. chinensis)

• Main Authors: Bie-Chuan Chu, 朱百川
• Other Authors: Hsiao-Feng Lo
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/xc7ahz

碩士 === 國立臺灣大學 === 園藝暨景觀學系 === 106 === In Taiwan, 70% of all consumed water was agriculture irrigation water, in which 60% was used in surface irrigation during 2015. However, water use efficiency of surface irrigation is low due to the irrigation water applied is more than plant requirement. In present study, rape ‘Qing Long’ (Brassica rapa) and pak-choi ‘Feng-Jing’ (Brassica rapa var. chinensis) were used as the materials for experiments of (1) water dis-supply and (2) re-water after water dis-supply, for 3 replications. In water dis-supply experiment, non-destructive physiological characters including SPAD, chlorophyll fluorescence FV/FM, NDVI and PRI, and destructive physiological characters including fresh weight, dry weight and dry matter ratio of shoots, leaf water potential and antioxidant enzymes activities, as well as volumetric water content (VWC) of peat medium were investigated after water dis-supply to select suitable character as irrigation indicator. In re-water after water dis-supply experiment, shoot fresh weight and dry weight of 2 crops were investigated under different irrigation treatments. Peat VWC was also measured to select suitable indicator for re-watering. In rape experiment replication I, the suitable non-destructive physiological character is chlorophyll fluorescence FV/FM. The recommended peat VWC for harvest is 30% and for re-watering 38%. In rape experiment replication II, any non-destructive physiological character was not suitable as an irrigation indicator. The recommend peat VWC for harvest is 20% and for re-watering 18%. In rape experiment replication III, the plants did not face drought stress. In pak-choi experiment replication I, no non-destructive physiological character was suitable as an irrigation indicator. The recommended peat VWC for harvest is 20% and for re-watering 39%. In pak-choi experiment replication II, the suitable irrigation indicator for non-destructive physiological character is chlorophyll fluorescence FV/FM and NDVI. The recommended peat VWC for harvest is 20%, and for re-watering 22%. In pak-choi experiment replication III, no non-destructive physiological character was suitable as an irrigation indicator. The recommend peat VWC for harvest is 20%, and for re-watering 18%. In conclusion, chlorophyll fluorescence FV/FM has the potential to be an irrigation indicator, but is still not stable. The recommended peat VWC for irrigation is 30% during sunny days or unstable weather, and 20% during rainy days. Peat VWC never below 40% is conservatively suggested. Artificial neural network was also used to predict classification of pak-choi yield. The accuracy rate is 31%. More experimental units are needed to increase the accuracy of predicting the classification of pak-choi yield and reach intelligence agriculture.