Effect The Condition Of Soil Water And Fertilizer On The Physiological Characteristics Of Plant And Soil Environments Of Cucumber And Tomato In Greenhouse

With the development of economy and people's living standard, vegetable consumption increased gradually; at the same time, vegetable production in greenhouse was developed rapidly in the north of China. In order to get more benefits from vegetable production, farmers preferred to input water and fertilizer as much as possible. In vegetable production, improper fertilization and watering cause undesirable effects on fruit yield and quality, as well as on soil. In this paper, with cucumber (Cucumis sativus L.) and tomato (Lycopersicon esculentum Mill) in the greenhouse as samples, a total of six treatments with three relative water content(RWC) levels (Wh: 90%-100% RWC, Wm: 70%-80% RWC, Wl: 50%-60% RWC) and two fertilization levels (Fh: 600kgN?hm-2+420 kgP2O5?hm-2, Fl: 420 kgN?hm-2 +294 kgP2O5?hm-2) were established to be used in the investigation of their coupling effects on the basis of previous studies. Carried out were continuous studies in 2007 and 2008 of coupling effects on plant growth, fruit yield and quality, soil nutrients and temperature, and biological environment. The following results were obtained.Different soil water and fertilizer influenced the growth and production of cucumber and tomato. When the soil relative water content (SRWC) was at the same level, several indexes including SOD activity, POD activity, net photosynthetic rate(Pn), leaf area and expansion rate at early fruit stage and fruit stage at the Fh level were increased over that at the F1 level, while MDA content and the ability to resist dehydration of leaves were reduced. And higher yield, less water consumption, increased water use efficiency (WUE) and fruit quality indicated by the contents of glucose, amino acid, nitrate and protein were achieved for cucumber under Fh treatment, meanwhile fruit quality of tomato indicated by the contents of glucose, organic acid, amino acid, Vc, and soluble protein decreased comparing with Fl level. With the increase of SRWC, leaf area and expansion rate at the early-fruit stage and fruit stage were increased, while the leaf ability to resist dehydration at fruit stage was reduced, and while yield and water consumption of cucumber and tomato enhanced, their WUE decreased. When SRWC reached 70%-80%, leaf's CAT and leaf ability to resist dehydration at early-fruit and later-fruit stage of cucumber were the strongest; and the leaf's CAT, POD, SOD activity is strong while MDA content low, which indicated that the plant grew healthily. Stepwise linear regression analysis was used to reveal the effect of leaf physiological characters on yield. The data showed that POD activity, leaf expansion rate, the ability to resist water, and net photosynthetic rate had a significant influence on cucumber yield. The same approach was used for tomato and the data showed that SOD activity, leaf area, leaf expansion rate, the ability to resist water had a significant influence on tomato yield.Different soil water and fertilizer treatments influenced the distribution of N, P in plant and in soil. The increase of SRWC resulted in an increasing irrigation level, and led to higher efficiency in the use of nitrogen and phosphorous. When SRWC was the same level, additional fertilization would result in low efficiency in the use of nitrogen and phosphorous. After two years'coupling treatments of water and fertilization, several soil nutrients indexes including organic matter, total nitrogen, available nitrogen(NO3--N, NH4+-N), total phosphorous, available phosphorous were increased. When SRWC was the same, soil organic matter, total N and NO3--N, total phosphorous, available phosphorous were increased with the fertilizer supply increased. With the increase of SRWC, plants grew stronger and absorbed more N, P nutrition from the soil, as result that soil total phosphorous, available phosphorous, total N and NO3--N declined.The coupling treatments of water and fertilizer changed the environment of soil water level, temperature and fertility. Researches on dynamic change and diurnal variation of soil temperature in 2007 and 2008 indicated that, the increase of SRWC led to lower soil temperature at 5cm, 10cm, 20cm, 30cm. At the same level of SRWC, soil temperature was lower at the Fh level than at the F1 level. While the fertilizer supply increase, there was enough C/N nutrition for microbial reproduction, and soil micro-diversity index, evenness index, soil respiration and active Carbon, activity of Suc, Pho, Ure were increased. With the increase of SRWC, the activity of Suc, Ure and Pho were increased. The soil microbial features, such as, soil enzymes, soil microbial diversity, soil respiration and soil active carbon, were closely related and they together influenced the soil microbial environment. Grey rational analysis indicated that the best soil microbial environment was achieved under the treatment of SRWC 70%-80% and 600kgN?hm-2+420 kgP2O5?hm-2 fertilization.Grey rational analysis indicated that the most comprehensively evaluated plant grew healthily, with high quality and more benefit; sustainable development of cucumber and tomato production was achieved under the treatment of SRWC 70%-80% and 600kgN?hm-2+420 kgP2O5?hm-2 fertilization.