Water And Nitrogen Interactions On Tomato Growing In Eco-organic Type Soilless Culture

The experiment on effects of water and nitrogen interaction on yield, quality and water use efficiency as well as fertilizer use efficiency of tomato in Greenhouse was carried out with D-saturation optimum design under the Eco-organic type soilless culture in Greenhouse. The proper ratio of water and nitrogen application was suggested for higher yield, better quality of tomato, and the major results were as followed:1. The regression equation between the tomato yield(Y) and substrates water content(X1), nitrogen rate (X₂) was: Y=1543.54+527.70X1* -227.13X2 +83.28X₁²-309.03X₂². Tomato yield was significantly depended on substrates water content. The average yield in high water level treatments (substrates water content of 90%) was 150% significantly higher than that in the low water level treatments (substrates water content of 50%). The nitrogen was negatively correlated to the yield, but not significant. The highest yield did not occurred in the high nitrogen high water level treatment (substrates water content of 90%, pure nitrogen rate of 1.50g/pot/time), which meant that it was not the proper way to over water and fertilizer for getting high yield. Base on the regression equation, the optimum levels of water and nitrogen for the highest yield (2196.24g/pot) under the study condition were substrates water content of 90%, pure nitrogen rate of 0.58g/pot/time.2. The substrates water content had negative correlations to the soluble sugar, total acid, solid matter as well as the nitrate content of tomato fruit, but not distinct. However it did have significant negative effect on the Vitamin C content. Under the same nitrogen level, compare to the high water level (substrates water content of 90%) treatments, low water level (substrates water content of 50%) treatments'Vitamin C, total acid and solid matter content increased by 25.70%,36.60%,28.03% respectively. The nitrogen had positive effects on all those quality indexes but not significant. Under the same water level, the high nitrogen level (pure nitrogen rate of 1.50g/pot/time) treatments'total acid, soluble solid matter content were significantly increased by 43.43%,29.30% respectively as compared with low nitrogen level (pure nitrogen rate of 0.15g/pot/time)treatments. The sugar/acid ratio was an important index to evaluate the taste of tomato, and it was shown that the middle levels of substrates water content and nitrogen (substrates water content of 66%, pure nitrogen rate of 0.74g/pot/time) treatment had the highest sugar/acid ratio of 8.34.3. The water consumption of tomato had close relation to the water irrigation, the more it irrigated, the more it consumed. The water consumption in high water level (substrates water content of 90%) treatments was 53.06L/plant average, which was 1.34 times higher than that in the low level (substrates water content of 50%) treatments. However with the nitrogen increased, water consumption decreased. The water consumption in high nitrogen level (pure nitrogen rate of 1.50g/pot/time) treatments was 20.98% less than that in the low nitrogen level (pure nitrogen rate of 0.15g/pot/time) treatments. Through the stepwise regression we had the regression equation between tomato water use efficiency ( Y ) and the substrates water content ( X1 ) , nitrogen ( X2 ) : Y=32.58+1.49X1+4.12X₁²-0.89X₂²+2.02X1X2, the regression equation indicated that the substrates water content had the positive correlation to water use efficiency. There was a positive correlation between water and nitrogen coupling on water use efficiency which meant that the right proportion of water and nitrogen could increase water use efficiency.4. The regression equations between the nitrogen use efficiency(YN), phosphorus use efficiency (YP), potassium use efficiency (YK) and substrates water content(X₁), nitrogen (X₂) were: YN=154.63+181.79X₁-434.67X₂^*-345.83X₂²-147.85X₁X₂;YP=246.18+84.16X₁^*-36.22X₂ +13.28X₁²-49.29X₂²;YK=161.29+55.14X₁^*-23.73X₂+8.69X₁²-32.29X₂². The substrates water content had significant positive effects on phosphorus use efficiency and potassium use efficiency, it also had positive effect on nitrogen use efficiency but not significant. Nitrogen use efficiency significantly decreased with the nitrogen fertilizer increasing. The nitrogen had negative correlations on phosphorus use efficiency and potassium use efficiency but not significant. Base on the regression equations that the optimum levels of substrates water content and nitrogen for the highest nitrogen use efficiency( 1264.75g/gN ) , phosphorus use efficiency (350.28g/gP) and potassium use efficiency (229.49g/gK)under the study condition were substrates water content level of 90%, pure nitrogen rate of 0.15g/pot/time, 0.58g/pot/time,0.58g/pot/time respectively.5. Base on the analysis of yield regression equation, TOPSIS of fruit quality and the Grey Relational analysis, the best substrates water content and nitrogen levels for the high yield, good quality under the study condition were substrates water content of 90%, pure nitrogen rate of 0.58⁰.74g/pot/time.