| The failure treatments of water and fertilizer have limited sustainable development of agriculture and improvement of ecological environment. How to resolve this problem was also a key point to improve yield and quality of vegetable. So researches on water-requirement-rule of vegetables and effects of soil-fertility on vegetables have been one of the hotspots on vegetable cultivation of agricultural facility. There were many researches on fertilizer and water of vegetables for fruit vegetables, such as cucumber, tomato and so on, while few of them were on leafy vegetables. Lactuca Sativa L. is the typical representative of leafy vegetables. There were few reports about the relationship between lettuce and water-fertilizer coupling presently. The works in this paper were supported by the key project of science and technology in Jilin Province"The key technologies and demonstration of modern facility agriculture in cold region (20080246)". In this experiment, Lactuca was as sample in the greenhouse to be measured by four factors (nitrogen fertilizer(N), phosphate fertilizer(P), potash fertilizer(K) and irrigation amount(W)) and five levels of general rotation (1/2 implementation) combination design in 2008 at biological and agricultural engineering school of Jilin University. Effects on growth, yield, quality, economic effect of lettuce and soil environment that which were studies, and multiple objective comprehensive evaluation that which were used with principal component analysis method and grey relational analysis method. Through the experiment obtained the following results:(1)The effects of different water and fertilizer on yield of lettuce were studies, mathematical regression models were established between yield and water and fertilizer factors. The results show that, contribution of P on yield is maximum (2.612), secondly W(2.186), N(2.102), and K(1.762). When N, P, K and W are 473.6～583.0kg·hm-2, 529.7～626.3kg·hm-2, 150.6～212.8kg·hm-2, 537.2～655.6m3·hm-2, yield of Lettuce is higher than 50000kg·hm-2.(2)The effects of different water and fertilizer on quality of lettuce were studies, mathematical regression models were established between quality(vitamin C content and soluble sugar content of lettuce) and water and fertilizer factors. The results show that,①water and fertilizer combined with vitamin C content of lettuce was a significant relationship. In which, contribution of P on vitamin C(2.258) is maximum, secondly W(1.766), N(1.424) and K(1.399); When N, P, K and W were 518.3～648.8kg·hm-2, 536.1～655.7kg·hm-2, 100.5～176.8kg·hm-2, 427.3～585.6m3·hm-2 respectively, vitamin C content of lettuce was higher than 35.000mg·(100g)-1;②Soluble sugar content of lettuce was positively correlated with the four factor, and the effect of order was P>N>K>W. When N, P, K and W were 510.7～617.9kg·hm-2, 530.4～629.4kg·hm-2, 92.4～154.5kg·hm-2, 416.2～545.9m3·hm-2 respectively, soluble sugar content of lettuce was higher than 80.000%.(3)Through analysis on economic benefit of different water and fertilizer treatment of lettuce were done, more investment could bring more output and more profit, but could not necessarily with more benefit, and would destroy the ecological environment security.(4)Based on the physiological characteristics of lettuce, some analysis were made. During the growth progress of lettuce, the leaf net photosynthesis rate ( Pn ), transpiration rate (Tr ), stomatal conductance (Gs ) and intercellular CO2 concentration (Ci ) are increased firstly and then decreased, but the leaf water use efficiency is decreased firstly and then increased. Analysis on chlorophyll fluorescence kinetics parameters showed that Fo and Fv were higher in low level of water and fertilizer treatment, but Fv Fm and Fv Fo are lower in low level of water and fertilizer treatment in different growth period. In early, middle and late growth period, Fo and Fv have not significant changes, and Fv /Fm, Fv /Fo are higher in the middle than early and late.(5)Soil environment was changed by different water and fertilizer treatment. Soil pH was decreased in each unit. The average value was 6.3. In which, soil pH value (6.0) of unit 10 was minimum. Soil aggregate structure was also changed in different units. Soil aggregate gross was maximum in unit 8(50.9%), secondly unit 10(49.8%), unit 16(49.1%), but soil aggregate gross was minimum in unit 1(37.8%). The variation of soil moisture was different that soil moisture of unit 8, unit 10 and unit 16 was higher in growth period, but soil moisture of treatment1 was the lowest. And soil moisture content of all of the treatment at later growth stage was higher than the growth of early and mid. Soil organic matter, available nitrogen, available phosphorus and available potassium had the same variation. For same kind of water and fertilizer treatment, contents of soil available nitrogen (available N), available phosphorus (available P) and available potassium (available K) at high level treatment were higher. Structure of soil aggregate were extremely significant positive correlated with soil organic matter, available N, available P at level 0.01, and with available K at level 0.05; significant positive correlation at level 0.05 between organic matter and soil available K were found; soil available N was significantly positive correlated to available P at level 0.05.(6)Principal component analysis and grey correlative degree analysis were used to evaluate physiological characteristics of lettuce, yield, quality and economic benefit and soil environment of different water and fertilizer treatment. The more benefit and sustainable development of lettuce production was achieved under the unit of 600 kg·hm-2 N+ 600 kg·hm-2 P+ 237.5kg·hm-2 K+ 680 m3·hm-2 W.The water and fertilizer coupling model in this paper was special and difficult to apply in protection ground of different soil-fertility. So we should construct a universal model of solar-greenhouse. These should be developed in the future.
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