咸淡水交替灌溉对滨海垦区夏玉米生理生长的影响

Effect of Alternate Irrigation with Fresh and Slight Saline Water on Physiological Growth of Summer Maize in Coastal Reclamation Area

我国东部滨海地区拥有大量滩涂和微咸水资源,但土壤含盐量高、淡水资源缺乏,探究合理的咸淡水交替灌溉方法,可以促进滨海垦区土地资源的高效利用。选取江苏省滨海垦区典型土壤,使用3种不同矿化度(1、3、5 g/L)的微咸水在夏玉米3个不同生育期(壮苗期、拔节抽雄期、灌浆成熟期)进行咸淡交替灌溉("咸淡淡"、"淡咸淡"、"淡淡咸")盆栽试验。结果表明,微咸水灌溉后土壤上层积盐明显,夏玉米叶片的净光合速率(Pn)、气孔导度(Gs)减小,胞间CO2浓度(Ci)由于气孔限制而减小,但随着矿化度的增大,非气孔限制引起Ci增大。微咸水灌溉后夏玉米叶片中过氧化氢(H2O2)和丙二醛(MDA)含量增加,同时伴随着超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)酶活性的增强。高矿化度咸淡水交替灌溉抑制了玉米的生长和生产,拔节抽雄期夏玉米耗水量大幅增加,导致微咸水灌溉量增加,盐分胁迫最强烈,致使"淡咸淡"的灌溉方式表现最差。夏玉米在灌浆成熟期的抗性增强,此时微咸水灌溉对各生理指标影响较弱。在滨海垦区进行夏玉米种植,可在壮苗期采用较低矿化度的微咸水进行灌溉,而较高矿化度的微咸水仅适合在灌浆成熟期进行。

Coastal areas in eastern China have a large amount of reclaimed land and slight saline water resources. In order to exploit the reasonable and sustainable utilization of them, a pot experiment was carried out to investigate the characteristics of soil salinity, photosynthesis parameters, oxidation parameters, antioxidant enzymes activities, growth, yield and water use efficiency of summer maize ( Zea mays L.) subjected to three alternate sequences (i.e., BFF: in which maize was irrigated with saline water at the seedling stage and fresh water at other stages; FBF: in which saline water was irrigated at the jointing stage and fresh water at other stages; FFB: in which plants were watered with saline water at the reproductive stage and fresh water at other stages) with three levels (i.e., 1 was 1 g/L NaCl; 3 was 3 g/L NaCl; 5 was 5 g/L NaCl). The result showed that under the same salinity of saline water irrigation, the descending order of soil salt content distribution in upper layer was FBF,FFB and BFF. Net photosynthetic rate ( P n ) and stomatal conductance ( G s ) of summer maize leaves under slight saline water irrigation were decreased compared with that under fresh water irrigation throughout the whole growth period (CK). Under the same salinity irrigation, the descending order of P n and G s was FFB, BFF and FBF. Intercellular carbon dioxide concentration ( C i ) was decreased due to stomatal limitation, but with the increase of irrigation water salinity, non-stomatal limitation caused C i to increase in 5 g/L treatment. FBF5 had a maximum increase of 19.44% at 81 d and FFB5 had a minimum increase of 1.38% at 108 d. Hydrogen peroxide and malondialdehyde (MDA) in maize leaves under saline irrigation was higher than those under freshwater irrigation. At the same time, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were also increased. However, limitation of the activities of POD and CAT was observed in FBF5 treatment, but it was still higher than those of CK by 37.67% and 13.71%. Compared with CK, alternate irrigation with fresh and slight saline water inhibited the growth and production of maize, resulting in the reduction of plant height, leaf area, growth, yield and water use efficiency. In addition, these adverse effects were more evident in BFF and FBF, because the salt resistance of summer maize was not fully developed and it was more sensitive to salt stress caused by brackish water irrigation. Maize suffered from the most deleterious impact due to saline irrigation during the jointing stage, leading to the most loss of growth and yield. It was confirmed that although maize became more tolerance as crops developing, enhanced crop evapotranspiration also caused more intense salt stress at the jointing stage. Its increasing salt resistance was still insufficient to overcome the corresponding salt stress. In all alternate sequences,the order of water use efficiency (WUE) of summer maize from high to low was FBF,BFF and FFB. As the degree of salinity was increased, the WUE of FBF5 was the lowest, which was decreased by 38.04% compared with that of CK. Based on the analysis of the experimental results, 1 g/L and 3 g/L salinity water irrigation can be applied at the seedling stage with negligent negative impacts on maize production, and higher salinity irrigation can be used at the reproductive stage, while freshwater irrigation was more appropriate during the jointing stage.