Jinan Small Qinghe Sewage Irrigation On Corn Early Growth And Some Of Its Physiological Indicators

Sewage has been used for an age. For example, Athens had used sewage to irrigatecrops B.C. and it is almost a hundred years to sewage for large acreage over the world. Inour country, sewage was also used to irrigate crops from forties or fifties in the lastcentury, and sewage irrigation gets a rapid development due to the shortage of waterresource. At present, Tianjin, Beijing, Shijiazhuang, Jinan and Shenyang are the famoussewage irrigation regions.It is an effective method to make use of the municipal sewage which has beentreated to some extent for the irrigation of agricultural land. For one side, it can depurateand detoxicate the remains of poisons and diminish the pollution of sewage due toedaphic clarifying capacity. For another, it also promotes agricultural production as aresult of nutritious substance contained in the sewage absorbed by plants, and thismethod can also relieve the problem of water resource scarcity by recycle. But sewageirrigation in our country lags in technology, and corresponding policies and codes are notenough healthy, especially requisition of water quality is not rigorous in sewage irrigation,which usually bring about a series of problem. The main problem among them is theadverse effect of sewage irrigation on the growth and development of crops.Sewage used directly to irrigate crops without any treatment certainly will affectcrop's growth and development, physiologic index and character. Some researches havebeen reported about that both here and abroad. But the researches are different from eachother, perhaps it is due to the different water quality in different regions, which givedifferent effects on the crops.It is about fifty years since sewage irrigation from Jinan Xiaoqing river began in1956, and now becomes very common along the river. Recently, however, Xiaoqing riveris somewhat severely polluted because of domestic sewage and industrial wastewater.Farmers directly draw water from the river without any treatment to irrigate their cropsso that the development and physiological metabolism of crops may be affected to someextent. This study is to research and discuss the effects of sewage irrigation formXiaoqing river on the crops.The former researches about the effect of sewage irrigation mainly focused on twocrops, that are wheat and rice, however, there are few reports on maize. We use maize asresearch materials and, though potted method, systematically study the effect of differentconcentration sewage of Jinan Xiaoqing river on the early growth, physiologicalmetabolism index and root tip cells of maize. The main results are followed:1. Light concentration sewage can promote the sprouting of maize and 100%concentration sewage can inhibit the sprouting of maize, but final sprouting ratio is lessaffected.2. All concentration sewage can promote maize's growth and development. But with theincrease of sewage's concentration, the promotion enhances at first and then descendsgradually. But it works as inhibitor when we irrigate maize with high concentrationsewage from the Xiaoqing river.3. The chlorophylla content of maize leaf descends gradually when maize are irrigatedwith sewage and the chlorophylla a is especially sensitive. The value of chlorophylla band chlorophylla a/b descends gradually when maize are irrigated with pure sewage,and it is harmful to the photosynthesis of maize.4. They are significant signs about whether plants are destroyed or the damaged degreethat permeability of plasma membrane and content of MDA. Our researches indicate thatthe content of MDA obviously increased in leaves of maize and the plasma membranepermeability augmented, and we draw a conclusion that maize's physiological functionsare damaged when maize are treated with sewage.5. POD in the active oxygen elimination system of maize leaves descend after 50%concentration sewage irrigation from Xiaoqing river, but CAT does not descendapparently. Both descend gradually when irrigated with pure sewage. Active oxygenelimination system is damaged due to POD activity descending, which leads toaccumulation of active oxygen and do harm to maize.6. micronucleus tests of maize's root tip indicate that sewage irrigation can obviouslyincrease maize's root tip micronucleus ratio, which have genetical toxicity to maize.Analytic results on water quality contamination index show that 50% concentrationsewage from Xiaoqing river belongs to light contamination and 100% concentrationsewage belongs to heavy contamination.Thus it can be seen, water in Xiaoqing river is polluted severely and can not be useddirectly to irrigate agricultural lands. Sewage from Xiaoqing river without any treatmentdoes little harm to maize's early growth and development seen from exterior figure, butits physiological function is damaged obviously, which must affect the maize's laterdevelopment, output and quality of production. Low concentration water from Xiaoqingriver is less contaminated and its harm to maize's physiology is little, which to someextent can promote growth and development. So we suggest that sewage from Xiaoqingriver should be combined with clear water to irrigate crops or rotation irrigation be taken.